Chemistry Notes for NEET Chapter 26 - Alcohol, Phenol, and Ether Hydroxy Compounds PDF
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Summary
These notes cover the chemistry of alcohols, phenols, and ethers. They describe different types of alcohols and how they are prepared. The notes also outline the various reactions of these compounds.
Full Transcript
60 Chapter E3 26 Alcohol, Phenol and Ether Hydroxy compounds ID H 2O CH 3 CH CH 3 CH 3 CH CH 3 | Hydroxy compounds are those compounds in which the hydroxy group, – OH is directly linked with the aliphatic or aromatic carbon. Monohydric alcohols C 2 H 5 Br Bromoethan e Ethanol C 2 H 5...
60 Chapter E3 26 Alcohol, Phenol and Ether Hydroxy compounds ID H 2O CH 3 CH CH 3 CH 3 CH CH 3 | Hydroxy compounds are those compounds in which the hydroxy group, – OH is directly linked with the aliphatic or aromatic carbon. Monohydric alcohols C 2 H 5 Br Bromoethan e Ethanol C 2 H 5 OH AgBr AgOH Moist silver oxide Ethanol 1° alkyl halide gives good yield of alcohols. 2° alkyl halide gives mixture of alcohol and alkene. 3° alkyl halide gives alkenes due to dehydrohalogenation. CH 3 CH 3 | | U (Aqueous) D YG Bromoethan e CH 3 | 2-Methylpropene (Major product) CH 3 | U CH 3 C CH 3 | KBr H 2 O OH ST Direct process : Alkene | | CC | | | | OH H Alcohol Sulphuric acid Ethyl hydrogen sulphate H 2O Hg(OAc)2 Mercuric acetate | | | NaBH 4 C C Demercurat ion OH HgOAc | | OH H Alcohol This reaction is very fast and produces the alcohol in high yield. The alcohol obtained corresponds to Markownikoff’s addition of water to alkene. (c) Hydroboration oxidation (HBO) : (Antimarkownikoff’s orientation) | | | | | | H BH 2 | | H OH Alcohol Diborane is an electron defficient molecule. It acts as an electrophile reacting with alkenes to form alkyl boranes R 3 B. RCH CH 2 R CH CH 2 H BH 2 R CH C H 2 | H | B H2 Alkyl borane Ethanol In case of unsymmetrical alkenes CH 3 CH CH 2 HOSO 2OH Markowniko ff'' s Propene | C C H 2O CH 3 CH 2 OH H 2 SO 4 Boil Alcohol Oxymercura tion H O , OH C C H BH 2 C C 2 2 C C Indirect process : CH 2 CH 2 HOSO 2 OH CH 3 CH 2 OSO 2 OH Ethene OH (b) Oxymercuration-demercuration HOH C C dil H 2 SO 4 C CH 3 Tert. butyl alcohol(side product) (ii) From alkenes : (a) Hydration CC H 2O C CH 3 CH 3 | (Aqueous) | C CH 2 H H 2 SO 4 CH 3 C CH 3 KOH CH 3 C CH 2 Br OH Propan - 2 - ol CH 3 These are compound containing one hydroxyl group. Their general formula is Cn H 2n 2O (1) Preparation : (i) From alkyl halide C 2 H 5 Br KOH C 2 H 5 OH KBr | Boil OSO 2 OH rule RCH CH 2 (R CH 2 CH 2 )2 BH (RCH 2 CH 2 )3 B Dialkyl borane Trialkyl borane Carbocation are not the intermediate in HBO hence no rearrangement take place. (iii) By reduction of carbonyl compounds Pd RCHO H 2 RCH 2 OH Aldehyde LiAlH4 NaBH 4 RCO R H 2 R CH R Ketone O | or Ni / Pt H 2O RCH 2CH 2OH Mg(X )OH RCH 2CH 2 OMgX OH Secondary alcohol HO + 3 CH2 CH3 CH3 H2O CH3 CH3 HO OH (c) With carbonyl compounds : H || CH2OH HO – CH2 O Hydride selectively attacks the less alkylated carbon of the epoxide. CH 3 | CH 3 C CH 2 H H | OH O (iv) By reduction of carboxylic acids and their derivatives (i) LiAlH4 R COOH RCH 2 OH (ii)H 2 O H2 RCOOH RCOO R RCH 2 OH R OH | CH 3 2 | CH 3 U CH 3 C OCH 3 4[H ] 25 CH 3 CH 2 OH CH 3 OH Na / C H OH Reduction with aluminium isopropoxide is known as Meerwein- Ponndorff verley reduction (MPV) reduction. 2 Me 2 C O (CH 3 )2 CHOH Al(OCHMe ) Isopropyl alcohol Me 2 CHOH CH 3 CH 3 CO (v) By alkaline hydrolysis of ester O || R C O R HO Na (aq ) R C ONa R OH. U H CH 3 CH 2 CH 2 CHO Zn – Cu 2 (Major) Methanol D YG Ethanol Sod. salt of acid Alcohol (vi) From primary amines CH 3 CH 2 NH 2 HONO 2 NaNO / HCl Aminoethan e CH – CH – CH – CH – OH (2) Physical properties of monohydric alcoholsn- Butyl alcohol (i) Character : Alcohols are neutral substances. These have no effect on litmus paper. This is analytical test for alcohols. (ii) Physical state : The lower alcohols (upto C ) are colourless alcohol with characteristic smell and burning taste. The higher members with more than 12-carbon atoms are colourless and odourless solids. (iii) Polar character : Oxygen atom of the – OH group is more electronegative than both carbon and hydrogen. Thus the electron density near oxygen atom is slightly higher. Hydrogen bonding shown below H O- - - - H O- - - H O- - - - H O. This gives polar 3 Ethanol It is not a good method of preparation of alcohols because number of by product are formed like alkyl chloride alkenes and ethers. (vii) From Grignard reagent (a) With oxygen : | | | | R R R R 2 R Mg X O2 2 R O Mg X. Al2 O 3 2 HOH 2 ROH 2 Mg(X )OH 2 2 character to OH bond. (iv) Solubility : The lower alcohols are miscible in water. H O : - - - - - H O : Solubility | 1 Size of alkylgroups R H Increase in carbon-chain increases organic part hence solubility in water decreases. Isomeric 1°, 2°, 3° alcohols have solubility in order 1°> 2°> 3°. (v) Boiling points : Due to intermolecular hydrogen bonding boiling points of alcohols are higher than hydrocarbon and ethers. 1 ; B.P. follows the trends : No. of branche s 1° alcohol > 2° alcohol > 3° alcohol (vi) Density : Alcohols are lighter than water. B.P. 2 12 | CH 3 CH 2 OH N 2 H 2 O 3 Isobutyl alcohol (Minor) O ST CH – CH – CH OH 2 3 Esters are also reduced to alcohols (Bouveault Blanc reaction) (b) With ethylene oxide : H Zn – Cu CH – CH – CHO Catalyst || prepare every type of alcohols. (viii) The oxo process : It is also called carbonylation or ID primary alcohol Ester OH hydroformylation reaction. A mixture of alkene carbon monoxides and hydrogen. Under pressure and elevated temperature in the presence of catalyst forms aldehyde. Catalyst is cobalt carbonyl hydride [CoH (CO )4 ] product is a mixture of isomeric straight chain (major) and branched chain (minor) aldehydes. Aldehydes are reduced catalytically to the corresponding alcohols. 2CH 3 CH CH 2 2CO 2 H 2 | CH 3 C CH 3 LiAlH4 | OMgX E3 CH 3 || | If R = H, product will be 1°alcohol. If R = R, product will be 2°alcohol. If carbonyl compound is a ketone, product will be 3° alcohol. It is the best method for preparation of alcohol because we can CH 2 CH 2 LiAlH4 CH 3 CH 2 OH O H | | O LiAlH4 also reduces epoxides into alcohol : Methyl acetate (Ester) H 60 6 Carboxylic acid | H 2O R Mg X R C R C R R C R BH Carboxylic acid CH2 2 R Mg X CH 2 CH 2 Primary alcohol Density Molecular masses. (vii) In toxicating effects : Methanol is poisonous and is not good for drinking purposes. It may cause blindness and even death. Ethanol is used for drinking purposes. (3) Chemical properties : Characteristic reaction of alcohol are the reaction of the – OH group. The reactions of the hydroxyl group consists of either cleavage of C – O bond or the cleavage of O – H bond. O || CH 3 C Cl H O CH 2 CH 3 Ethanoyl chloride Ethanol O || CH 3 C OCH 2 CH 3 HCl Pyridine Ethyl ethanoate (Ethyl acetate) | C O H O O || || Acylation : CH 3 C O C CH 3 H OCH 2 CH 3 Aceticanhydride Ethanol O 60 | C – O bond is weaker in the case of tertiary alcohols due to +I effect bond weaker in primary alcohols as electron of alkyl groups while – OH bond isPolar density increase between O – H bond and hydrogen tends to separates as a proton. || | R R R C O H ; | H R R R CH OH ; Secondary Primary CH 3 C OCH 2 CH 3 CH 3 COOH Ethyl ethanoate C OH (d) Reaction with grignard reagents : CH 3 OH C2 H 5 MgBr C2 H 6 CH 3 OMgBr weaker bond Tertiary Acidic nature of alcohol decrease with increase of alkyl groups on – R R | H R C O H R C O R H H (a) Reaction with Na : (Active metals) | | 2 RO H 2 M 2 ROM H 2 (M = Na, K, Mg, Al, etc.) Evolution of H 2 shows the presence of –OH and reaction show that alcohols are acidic in nature. Alcohols acts as Bronsted acids because they donate a proton to a strong base (: B ). Example : U.... R O H : B R O : B H.... Conjugate acid Alcohol (acid) Base Alkoxide (conjugate base) Acid.. Conjugate acid OH Conjugate base Base This is the analytical test for alcohols. (b) Reaction with carboxylic acid [Esterification] : RCO OH H OR acid Conc. H2SO4 RCOO R H 2 O Ester Alcohol When HCl gas is used as catalyst, the reaction is called fischer-speier esterification. Presence of bulky group in alcohol or in acid decreases the rate of esterification. This is due to steric hindrance of bulky group. Reactivity of alcohol in this reaction is 1 2 3. (c) Reaction with acid derivatives : (Analytical test of alcohol) o o o R O H CH 2 C O CH 2 C O R CH 3 C O R | || H O O (Keto form) (enol form) (f) Reaction with isocyanic acid : R O H H N C H N C O R || | O OH H NH C O R || O amino ester (Urethane) (g) Reaction with ethylene oxide : ROH R O H CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 | O OH H 2O | OR | OR | OR 1, 2-dialkoxyethane (h) Reaction with diazomethane : R OH CH 2 N 2 R O CH 3 N 2 (Ether) (ii) Alkylation : ROH R 2 SO 4 ROR R HSO 4 (iii) Reaction involving cleavage of C OH with removal or | | substitution of –OH group.. ST.... (e) Reaction with ketene : | | On reaction of alkoxide with water, starting alcohol is obtained. H O H R O : R O H Ethane H D YG R C O Ethyl magnesium bromide U OH bonded carbon due to +I (inductive) effect of alkyl group. H Methyl alcohol ID Thus primary alcohols give the most of reaction by cleavage of O – H bond while tertiary alcohols are most reactive because of cleavage of C – O bond. Hence – O – H cleavage reactivity order : Primary > Secondary > Tertiary and C – O – cleavage reactivity order : Tertiary > Secondary > Primary alcohol (i) Reaction involving cleavage of with removal of ‘H’ as proton Alcohols are stronger acids than terminal acetylene but are not acidic enough to react with aqueous NaOH or KOH. Acidic nature is in the order HOH ROH CH CH NH 3 RH. E3 H weaker bond (a) Reaction with hydrogen halides : Alcohols give alkyl halide. The reactivity of HX is in the order of HI > HBr > HCl and the reactivity of ROH is in the order of benzyl > allyl > 3° > 2°> 1°. The reaction follows a nucleophilic substitution mechanism. Grove’s process Conc. H SO 2 4 2 ROH HX R X H 2O ZnCl anhydrous If alcohols react with HI and red phosphorus, alkane will be formed. Red P C 2 H 5 OH 2 HI C 2 H 6 I 2 H 2 O heat Primary alcohols follow S N 2 mechanism. R OH 2 X X - - - R - - - OH 2 R X H 2 O CH 3 CH 3 | Protonated 1o alcohol | CH 3 H CH 3 C CH CH 3 CH 3 C C | CH 3 In secondary and tertiary alcohols, the S N 1 mechanism operates H + R OH R OH 2 –H O CH 2 CH CH 2 CH 3 X R R X 2 | H+ H2SO4 – H2O OH (b) Reaction with PCl : ROH PX5 RX POX3 HX ; X = (Analytical test for alcohols) CH 2 CH CH 2 CH 3 5 Cl CH 3 2 - alkene (c) Reaction with PCl : 3 CH 2 CH CH CH 3 Alcohol Alkyl chloride Phosphorus trichloride 60 3 ROH PCl3 3 RCl H 3 PO3 Phosphorus acid (d) Reaction with thionyl chloride [SOCl ] : CH CH CH 2 CH 3 2 ROH SOCl 2 RCl SO 2 HCl Pyridine More amoun t (iv) General reaction of alcohols (a) Reduction : R OH 2 HI R H H 2 O I2 ROH NH 3 RNH 2 Al2 O 3 o 360 C Primary amine ROH ROH R 2 NH R 3 N Al2 O 3 Secondary amine Tertiary amine (f) Reaction with HNO : D YG 4 Conc. H SO 170 2 4 CH 3 CH 2 OH 2 CH = CH 4 2 H SO 2 4 5 4 Ethyl hydrogen sulphate 140°C CHO – CH 2 5 2 –(H ) U + ST | + | Tert. butyl alcohol (Tertiary) 4 [O ] CH 3 COOH CO 2 H 2 O (Under strong condition) Aceticacid (Lesser number of carbon atoms) 3° alcohols are resistant to oxidation, but on taking stronger oxidising agent they form ketone. (c) Catalytic oxidation/dehydrogenation H | H | 1° CH 3 C O H CH 3 C O H 2 Cu , 573 K | Ethanal (Acetaldehyde) H CH 3 | 2° CH 3 C O H CH 3 C O H 2 Cu , 573 K Propanone (Acetone) H CH 3 | | | OH CH 3 CH 3 | CH 3 C CH CH 3 CH 3 C CH CH 3 H 2 SO 4 CH 3 OH Acetone (Lesser number of carbon atoms) 2-Propanol (Sec. alcohol) OH | (Under strong condition) | Alcohol leading to conjugated alkene are dehydrated to a greater extent than those of alcohols leading to nonconjugated alkene. Thus dehydration is in order CH 2 CH CH CH 3 CH 3 CH 2 CH CH 3 | | CH 3 | Shifting CH 3 CH 3 CH 3 | | 3° CH 3 C OH CH 3 C O CH 3 + 4 CH 3 4 [O ] Ethanol (Pri. alcohol) CH 3 OH CH 3 2 O RCOOH CO 2 H 2 O Drastic conditions 5 Diethyl ether H /H SO | 2 C H HSO 2 || O CH 3 Ethylene 110° H SO | Carboxylic acid Secondary alcohol (g) Reaction with H SO [Dehydration of alcohol] : The elimination of water from a compound is known as dehydration. The order of ease dehydration is Tertiary > Secondary > primary alcohol. The products of dehydration of alcohols are depend upon the nature of dehydrating agents and temperature. CH 3 C C C CH 3 Aldehyde CrO 3 2° R CH R R C R U alkyl nitrate | | OH OH O H 2O O R OH conc.HNO 3 R O N | | H | 3 | (b) Oxidation : Difference between 1°, 2° and 3° alcohols. 1° RCH 2 OH R C O R C O ID Al2 O 3 2 E3 (e) Reaction with ammonia : H 2O | CH 3 CH 3 | 3° CH 3 C OH CH 3 C CH 2 H 2 O | CH 3 2-Methylpropan - 2-ol (Tert. alcohol) Cu , 573 K 2-Methylpropene (Alkene) Important reagents used for oxidation of alcohols PCC [Pyridinium chloro chromate (C 6 H 5 N H Cl CrO3 ) ] to oxidise 1° alcohols to aldehydes and 2° alcohols to ketones. PDC [Pyridinium di chromate (C5 H 5. NH )22 Cr2 O72 ] to oxidise 1° alcohols to aldehyde and 2° alcohol to ketones. CrO3 H 2 SO 4 / Acetone to oxidise 2° alcohol to ketones. Jones reagents (chromic acid in aqueous acetone solution) oxidise 1° alcohol to aldehyde and 2° alcohol to ketone without affecting (C = C) double bond. MnO2 selectively oxidises the –OH group of allylic and benzylic 1° and 2° alcohols to give aldehyde and ketone respectively. N 2 O 4 in CHCl 3 oxidises primary and secondary benzyl alcohol. (d) Self condensation : Guerbet’s reaction R CH 2 CH 2 OH H CH CH 2 OH | R Interconversion of monohydric alcohols (i) Primary alcohol into secondary alcohols SOCl 2 alc KOH C 3 H 7 OH C 3 H 7 Cl CH 3 CH CH 2 Propene Propan -1- ol (1 alcohol) HBr aq. KOH CH 3 CH CH 3 CH 3 CH CH 3 | (e) Reaction with cerric ammonium nitrate : Cerric ammonium nitrate ROH Red colour solution of complex. Yellowcolour || [O ] CH 3 CH CH 3 CH 3 C CH 3 Propan - 2- ol (Iso - propyl alcohol) (2 alcohol) Since reaction takes place with alkali solution as one of the reagents hence alkyl halide like CH 3 CH 2 Cl and CH 3 CH R will also give | K 2 Cr2 O7 / H OMgBr | OH | H , H 2O CH 3 C CH 3 CH 3 C CH 3 CH 3 MgBr | | CH 3 CH 3 2 - Methylpropan - 2 - ol (3 ) (tert. butyl alcohol) (iii) Primary alcohol into tertiary alcohol ID This is analytical test for alcohols. (f) Iodoform test : When a few drops of alcohol are warmed with iodine and NaOH yellow precipitate of iodoform with characteristic smell is obtained. Any alcohol consists CH 3 CHOH group give iodoform test. CH 3 | CH 3 | CH 3 CH CH 2 OH CH 3 C CH 2 HBr Cl D YG U ST H 2 SO 4 , Heat 2- Methylpropan -1- ol (1 ) (Iso butyl alcohol) U this test. (4) Uses of monohydric alcohol : (i) Uses of ethanol : It is used (a) In alcoholic beverages, (b) As a solvent in paints, varnishes, oils, perfumes etc., (c) In the preparation of chemical like chloroform, ether etc., (d) As a fuel in spirit lamps, (e) As an antifreeze for automobile radiators, (f) In the scientific apparatus like spirit levels, (g) As power alcohol. (ii) Uses of methanol : (a) Methanol is an important industrial starting material for preparing formaldehyde, acetic acid and other chemicals. (b) As a fuel (a petrol substitute). A 20% mixture of methyl alcohol and gasoline is a good motor fuel. (c) As an antifreeze or automobile radiators. (d) To denature ethyl alcohol. The mixture is called methylated spirit. (e) In the preparation of dyes, medicines and perfumes. Methyl salicylate and methyl anthra anilate are used in perfumery. Table : 26.1 Difference between methanol and ethanol Methanol Ethanol (i) When CH OH is heated on Cu coil it (i) It does not give formalin gives formalin like smell. like smell. (ii) When CH OH is heated with salicylic (ii) No such odour is given. acid in H SO (conc.) then methyl salicylate is formed which has odour like Distinguish between primary, secondary and tertiary monohydric alcohols Dehydratio n Markowniko ff's rule CH 3 | CH 3 | CH 3 C CH 3 CH 3 C CH 3 aq. KOH | | Br OH 2- Methylpropan - 2- ol (3 ) (tert. butyl alcohol) (iv) Lower alcohol into higher alcohol (ascent of series) HI KCN CH 3 OH CH 3 I CH 3 CN Methanol (1 carbon atom) 4 (H ) HONO CH 3 CH 2 NH 2 CH 3 CH 2 OH Reduction Ethanol (2 carbon atoms) (v) Higher alcohol into lower alcohol [Descent series] K Cr O , H NaOH 7 C2 H 5 OH 2 2 CH 3 COOH CH 3 COONa Ethanol (2 carbon atoms) [O ] Cl 2 NaOH CaO aq. KOH CH 4 CH 3 Cl CH 3 OH 3 Heat 3 4 (i) Lucas test : A mixture of anhydrous ZnCl 2 conc. HCl is called as Lucas reagent. R CH 2 OH 2 R CH 2 Cl ppt. appears after heating conc. HCl / ZnCl anhy. H 2O Secondary conc. HCl / ZnCl 2 anhy. R2 CH OH R2 CH Cl ppt. appears with in 5 minutes Tertiary R3 C OH R3 C Cl ppt. appears immediately H 2O ZnCl 2 / HCl OH Propan - 2- ol (2 alcohol) E3 higher alcohol Primary | Br | | R CH 2 CH 2 CH CH 2 OH 2 (iii) It gives haloform test (ii) Secondary alcohol into tertiary alcohol OH O R NaOC 2 H 5 , winter green oil. (iii) It does not give haloform or iodoform test. 60 H 2 CrO4 (chromic acid) to oxidise 1° alcohol to carboxylic acid. Methanol (one carbon atom) (ii) Victor mayer test : Also known as RBW test. RBW Red, Blue, White test. Primary PI HONO NaOH 2 2 C2 H 5 OH C2 H 5 I C2 H 5 NO 2 CH 3 C NO 2 CH 3 C NO 2 AgNO || || NOH NONa Nitrolic acid Secondary P I2 Sod. salt of nitrolicacid (Red colour) (CH 3 )2 CHOH (CH 3 )2 CHI (CH 3 )2 C NO 2 (CH 3 )2 C N O 2 No reaction (Blue colour) AgNO 2 HONO NaOH | | H Tertiary P I2 AgNO 2 HONO (CH 3 )3 COH (CH 3 )3 Cl (CH 3 )3 CNO 2 No reaction (colourless) These are compound containing two hydroxyl groups. These are dihydroxy derivatives of alkanes. Their general formula is Cn H 2n 2 O 2. The simplest and most important dihydric alcohol is ethylene glycol. They are classified as , , ….. glycols, according to the relative position of two hydroxyl groups. is 1, 2 glycol, is 1, 3 glycol. (1) Preparation (i) From ethylene : (a) Through cold dilute alkaline solution of Bayer’s reagent | | (i) dil. KMnO –C=C– – (ii) dil. OH | | OH RCO OH 2 | | 2 + (b) With O in presence of Ag : O Ethylene oxide NaHCO 3 E3 2 PBr | 2 1,2 Dichloroethane CH Br 2 | 3 CH OH CH Br 2 2 1, 2-dibromoethane CH I 2 CH I | 2 | 2 CH I CH 2 Ethylene iodide (Unstable) 2 Ethylene CH 2 OH | CH Cl 2 2 | | HCl 200°C CH OH 2 CH Cl 2 CH 2 OH NaCl CO 2 U Glycol (ii) From 1, 2 dibromo ethane [Lab method]: CH 2 OH CH 2 Br | Na 2 CO 3 H 2 O | 2 NaBr CO 2 CH 2 OH CH 2 Br CH 2 OOCCH 3 2CH 3 COOK | 2 KBr CH 2 Br CH 2 OOCCH 3 CH 3 COOH CH Cl Ethylene glycol CH 2 OH ST CH Br 3 HCl 160°C | dil. HCl Ethylene chlorohydr in | 2 | CH Cl 2 CH 2 OH H 2O (c) With HOCl followed by hydrolysis : (Industrial method) CH 2 CH 2 OH || | HOCl CH 2 Cl CH 2 CH 2 Br CH Cl 5 CH OH Chlorohydrin 3 D YG CH 2 1 Catalyst || O2 | Ag, 200 400 C CH CH 2 2 2 Ethylene PCl (Anti-hydroxylation) 2 CH 2 2 | 5 OH O 2 CH Cl PCl PI –C– C– | | HO H –C–C– | CH ONa Dialkoxide (Disodium glycollate) U | 2 | Na 160°C CH OH ID (Syn-hydroxylation) – C=C – CH ONa 2 | 2 PBr OH OH CH ONa Na 50°C 4 | 60 (3) Chemical properties Dihydric alcohols | NO CH OOCCH 2 CH COOH 3 | 3 CH COOH 3 CH OH CH OOCCH 2 3 | CH OOCCH 2 2 3 Glycoldiacetate CH2OH | CH ONO 2 Conc. HNO Conc. H SO CH2OH 2 2 | 3 CH ONO 2 4 2 Ethylene dinitrate Glycol CH2 – CH2 heat 600°C O Ethylene oxide COOH Conc. HNO [O] | 3 COOH Oxalic acid Glycol diacetate KMnO /H HCOOH + CH 2 OH | 2CH 3 COONa CH 2 OH NaOH 4 Formic acid HIO or (CH COO) Pb HCHO 4 (2) Physical properties (i) It is a colourless, syrupy liquid and sweet in taste. Its boiling point is 197°C. (ii) It is miscible in water and ethanol in all proportions but is insoluble in ether. (iii) It is toxic as methanol when taken orally. (iv) It is widely used as a solvent and as an antifreeze agent. 3 Formaldehyde 4 CH –CH –OH Conc. H SO 2 2 O 4 CH –CH –OH 2 CH –CH 2 2 O CH –CH 2 2 Diethylene glycol CH Dehydration ZnCl 2 CH OH 3 Unstable CH O 2 CH CHO (HCl) | 3 CH O CHCH 2 Cyclic acetal CH O=C 3 CH CHO Acetaldehyde 2 2 2 Dioxane Isomerisation | 2 3 O H2 CH 2 CHCHO CH 2 CHCH 2 OH catalyst 22 HOCH 2 CHOHCH 2 OH H O /OH 4 R CO R 2 HCHO Aldehyde is more reactive than ketone in dioxalane formation. HIO O O Glycerol (2) Physical properties (i) It is a colourless, odourless, viscous and hygroscopic liquid. (ii) It has high boiling point i.e., 290°C. The high viscosity and high boiling point of glycerol are due to association through hydrogen bonding. (iii) It is soluble in water and ethyl alcohol but insoluble in ether. (iv) It is sweet in taste and non toxic in nature. (3) Chemical properties (i) Reaction with sodium CH 2ONa CH 2 OH CH 2ONa 60 Dioxalane formation provides a path of protecting a carbonyl group in reaction studied in basic medium in which acetals are not affected. The carbonyl compound may be regenerated by the addition of periodic acid to aqueous solution of the dioxalane or by acidic hydrolysis. O CH 2 R R C H 2 OH | | C C O CH 2 OH O CH 2 R R | | + CH OH – CH OH O HC CH 3 CH – OH 2 | CH – OH 3 5 | O CH 3 | CH 2OH 3 (4) Uses (i) Used as an antifreeze in car radiators. (ii) Used in the manufacture of dacron, dioxane etc. (iii) As a solvent and as a preservatives. (iv) As a cooling agent in aeroplanes. (v) As an explosives in the form of dinitrate. | (b) CH OH | | CH OOCR 3 H 2 O CH OH 3 RCOOH | | steam CH 2 OOCR Oil or fat PBr3 | | CH 2 CH 2 I || | (c) CH OH PI3 CH I CH I 2 | | | CH 2OH CH 2 I CH 2 I | U CH 2 OOCR NaOH | CH OH CH OH CH 2 OH CH 2 OH HCl | CH 2 OH | ST Na 2 SO 3 Glucose Glycerol || CH 2 | Cl 2 CH o 600 C propene || 110 C CH 2 OH | HOCl CH Cl | CH 2 OH - monochloro hydrin (iv) From propenal : CH 2 || || CH 2 Cl , - dichlorohydrin | (b) CH Allylalcohol | CH 2 OH | aq. NaOH CH OH | CH 2 OH Glycerol CH 3 | HI CH I | | Glycerol , - dichlorohydrin (56%) Glycerol (44%) CH 2 || CH 2 I 1,2,3 - Tri-iodopropan e (Unstable) | CH OH CH 2 OH | CH 2OH | CH 2 I Warm | CH 2 OH CH 2 Cl | CH I (a) CH OH 3 HI CH 2 Allylchloride - Glycerol monochloro hydrin (34%) CH Cl o | NaOH (dil) CH CH 2 | CH 2 OH | (iv) Reaction with HI CH 2OH Acetaldehyde (iii) From propene [Modern method] CH 3 CH 2 Cl CH Cl CH 2 Cl Excess of HCl Sodium salt of higher fatty acids Yeast C6 H12 O6 C3 H 8 O3 CH 3 CHO CO 2 | - Glycerol monochloro hydrin (66%) 3RCOONa (ii) By fermentation of sugar | CH 2 OH | 110 o C Oil or fat CH Allyliodide (Unstable) (iii) Reaction with HCl or HBr CH 2 OH CH 2 Cl CH 2 OH | H 3 PO3 CH Br Glycerol | 3 POCl3 3 HCl CH 2 Br 1, 2, 3 - Tribromopr opane CH 2 OH Hydrolysis CH OH CH OOCR NaOH | | CH 2 Br Fatty acids CH 2 OOCR NaOH | | CH Cl CH 2OH The only important trihydric alcohol is glycerol (propane-1, 2, 3triol). It occurs as glycosides in almost all animal and vegetable oils and fats. (1) Preparation (i) From oils and fats CH 2 OOCR CH 2 OH | CH 2OH D YG Trihydric alcohols. 3 CH 2OH O U O Disodium glycerolate CH 2Cl Glyceryl trichloride (1, 2, 3 - Trichloropropane) ID 2 O 3 3 PCl5 (a) CH OH HC | CH 2ONa (ii) Reaction with PCl , PBr and PI CH 2OH CH 2Cl O O This part does not react due to steric hindrance CH OH Room temperature CH 2 OH Monosodium glycerol C | Na | Room temperature CH 2 OH H 2 CHO CH OH E3 2 | CH OH Na | | CH || I2 CH 2 I Allyliodide CH 3 I2 CH CH 3 HI | CH I | CH 2 I CH 2 I CH 2 CH 3 Allyliodide Unstable Propene Isopropyl iodide (v) Reaction with oxalic acid (a) At 110°C Glycerol is formed | 100 110 C CH OH HOOC COOH CH OH | H 2O Oxalic acid CH 2 OH Dynamite is prepared from T.N.G. CH 2 OOC COOH | o | CH 2 OH Glycerol mono - oxalate Dynamite : A mixture of T.N.G. and glyceryl dinitrate absorbed in kieselguhr is called dynamite. It was discovered by Alfred. Nobel in 1867. It releases large volume of gases and occupy 10,900 times the volume of nitroglycerine. O C3 H5 (ONO)3 12CO 2 10 H 2O 6 N 2 O2 || CH 2 O C H | H 2O CH OH H COOH | | CH 2 OH Formic acid CH 2 OH Glycerol mono formate Blasting gelatin : A mixture of glyceryl trinitrate and cellulose nitrate (gun cotton). Cordite : It is obtained by mixing glyceryl trinitrate with gun cotton and vaseline it is smokeless explosive. Glycerol (b) At 260°C, allyl alcohol is formed CH 2 OH CH 2 OOC | | HOOC 2 H O | 2 | CH OH CH OO C | | HOOC CH 2 OH CH 2 OH (4) Uses (a) As antifreeze in automobile radiator. (b) In the preparation of good quality of soap-hand lotions shaving creams and tooth pastes. CH 2 (c) As a lubricant in watches. || 2 CO E3 | CO 2 CH OH CH 2 OH 2 CH CH 2 OH (d) As a preservatives. Allylalcohol (vi) Dehydration CH 2OH (e) As a sweetening agent in confectionary, beverages and medicines being non toxic in nature. CH 2 || conc. H 2 SO 4 / P2 O5 / KHSO 4 CH OH CH | 2H 2O | CH 2OH (5) Analytical tests of glycerol CHO Acrolene or acraldehyde (vii) Oxidation COOH | CHOH [O] CH OH 2 | Fenton’s reagent CHOH | CHOH 2 Unsaturated alcohols (Allyl alcohol) (1) Preparation | CH OH (i) From allyl halide CH OH 2 | (ii) Dunstan’s test : A drop of phenolphthalein is added approximately 5 ml of borax solution. The pink colour appears on adding 23 drops of glycerol, pink colour disappears. The pink colour appears on heating and disappears on cooling again. C=O + | 2 Glyceraldehyde CH OH Tartronic acid D YG Glyceric acid CHO 2 COOH 2 Glyceraldehyde | | CH OH 2 CH OH CHOH [O] | CH OH 3 | [O] CHOH | dil. HNO COOH | (i) Acrolein test : When glycerol is heated with KHSO 4 a very offensive smell is produced due to formation of acrolein. Its aqueous solution restores the colour of schiff’s reagent and reduces Fehling solution and Tollen’s reagent. U CHO (f) In manufacture of explosives such as dynamite. ID | Dihydroxy acetone CH 2 CH CH 2 Br H 2 O CH 2 CH CH 2 OH HBr Allylalcohol Glycerose CH OH CH OH COOH | | | CO CO CO 2 2 [O] [O] U [O] KMnO | 4 acidified CH OH 2 | COOH ST Hydroxy Pyruvic acid (ii) By heating glycerol with oxalic acid : CH 2 OH | CH OH | | COOH Dihydroxy acetone CH 2 OH Mesoxalic acid HOOC | HOOC CH 2 OOC 2 H 2O | (3) Chemical properties CO + H O 2 2 H Pt CH CH CH OH 2 Oxalic acid 3 2 | 2 2, 3-dibromopropanol-1 + 2HIO + H O CH 2ONO 2 3 HBr 2 conc. H 2 SO 4 CH BrCH CH OH 2 2 2 3-Bromopropanol-1 | CH OH 3 HNO 3 CH ONO 2 3 H 2 O CH 2OH 2 CH Br – CHBrCH OH 2 | 2 1-propanol Br HCOOH | CH 2 OH (2) Physical properties 2 2 CO 2 | CH 2 OH (b) It is soluble in water, alcohol and ether in all proportion. [O] | 2CH O 2HIO with nitric acid (viii) Reaction + CH 2OH || CH OO C CH Heat (a) It is colourless, pungent smelling liquid. COOH 4 CH 2 | Allylalcohol COOH [O] 60 CH 2 OH HOCl | CH OHCHClCH OH CH 2ONO 2 2 2 Glycerol -monochlorohydrin Glyceryl trinitrate(T.N.G.) Alk. KMnO (O + H O) 4 CH OH – CHOH – CH OH 2 2 Glycerol 2 Na CH = CH – CH OH – 2 2 CH = CH – CH ONa 2 (Allyl alcohol) CH COOH 3 2 CH = CH – CH OOCCH 2 2 Allyl acetate HCl CH = CH – CH Cl 2 2 3 (iii) From Grignard reagent C 6 H 5 Br Bromobenze ne Ether Mg C 6 H 5 MgBr Phenyl magnesium bromide O2 H 2O C 6 H 5 OMgBr C 6 H 5 OH H Phenol (iv) From salicylic acid : OH OH COOH CaO + 2NaOH + Na CO + H O 3 2 60 2 Salicylic acid (v) Middle oil of coal tar distillationPhenol : Middle oil of coal-tar distillation has naphthalene and phenolic compounds. Phenolic compounds are isolated in following steps. E3 Step I : Middle oil is washed with H 2 SO 4. It dissolves basic impurities like pyridine (base). Step II : Ecessive cooling separates naphthalene (a low melting solid) Step III : Filtrate of step II is treated with aqueous NaOH when phenols dissolve as phenoxides. Carbon dioxide is then blown through the solution to liberate phenols. C6 H5 OH NaOH C6 H5 ONa H 2O CO 2 , H 2 O C6 H 5 OH Na 2CO 3 ID Phenol (Carbolic acid), C6H5OH or Hydroxy benzene C6 H 5 SO 3 Na Sodium benzene sulphonate C6 H 5 SO 3 H H 2 SO 4 (f uming ) NaOH D YG C6 H 6 Benzene Benzene sulphonic acid H / H 2O NaOH C6 H 5 ONa C6 H 5 OH Fuse or CO 2 / H 2 O Sodium phenoxide Phenol This is one of the laboratory methods for the preparation of phenol. Similarly methyl phenols (cresols) can be prepared. SO H OK 3 OH Solid KOH Fuse 3 H /H O 2 CH CH 3 p-Toluene p-Cresol ST HNO 3 C6 H 6 C6 H 5 NO 2 o Benzene H 2 SO 4 , 45 C Nitrobenzene 2 NaNO HCl , 0 5 o C C 6 H 6 HCl Benzene xylols (hydroxy xylenes) 1 CuCl 2 / FeCl3 O 2 C 6 H 5 Cl H 2 O 2 250 o C Chlorobenz ene o 425 C C 6 H 5 Cl H 2 O C 6 H 5 OH HCl Chlorobenz ene Phenol steam (vii) Dow process o 300 C C 6 H 5 Cl 2 NaOH C 6 H 5 ONa NaCl H 2 O High pressure Chlorobenz ene sodium phenoxide on treatment with mineral acid yields phenol. 2C6 H 5 ONa H 2 SO 4 2C6 H 5 OH Na 2 SO 4 (viii) Oxidation of benzene 315 C HC H O Benzene diazonium chloride Warm + CH CH CH Cl AlCl 3 + CH CH = CH AlCl 3 3 2 C6 H 5 OH C6 H 5 N 2Cl CH 3 Aniline N Cl 2 3 CH 2 Phenol OH 2 HO 2 CH 211°-235°C (vi) Raschig’s process Sn / HCl C6 H 5 NH 2 HNO HCl m-Toluidine fractional distillation Crude phenols (ix) Oxidation of isopropyl benzene [Cumene] (ii) From benzene diazonium chloride 2 o, m, p-cresols V2 O5 2C 6 H 6 O 2 2C 6 H 5 OH o 3 sulphonic acid NH 180°C + U CH Step IV : Crude phenol (of step III) is subjected to fractional distillation. U It was discovered by Runge in the middle oil fraction of coal-tar distillation and named it ‘carbolic acid’ (carbo = coal, oleum = oil) or phenol containing 5% water is liquid at room temperature and is termed as carbolic acid. It is also present in traces in human urine. (1) Preparation (i) From benzene sulphonic acid 3 Cumene 2 2 CH 3 m-Toluene CH 3 O – OH | 3 C(CH ) m-Cresol 3 OH 2 diazonium chloride Diazonium salts are obtained from aniline and its derivatives by a process called diazotisation. H O/H O + (CH ) CO + 2 2 Catalyst 3 2 Acetone Cumene hydroperoxide Phenol + – + – H – O-------H – O-------H – O-------H – O------ + – + – (intermolecular H-bonding H among phenol molecules) H | | H – O-------H – O-------H – O------H –O------+ + – + + – – of electron releasing group, CH 3 , (e.g., C 2 H 5 , OCH 3 , NR 2 ) on the benzene ring decreases the acidity of phenol as it strengthens the negative charge on phenoxy oxygen and thus proton release becomes difficult. Thus, cresols are less acidic than phenol. However, m-methoxy and m-aminophenols are stronger acids than phenol because of –I effect and absence of +R effect. m-methoxy phenol > m-amino phenol > phenol > o-methoxy phenol > p-methoxy phenol Chloro phenols : o- > m- > pCresols : m- > p- > oDihydric phenol : m- > p- > oThe acidic nature of phenol is observed in the following : (a) Phenol changes blue litmus to red. (b) Highly electropositive metals react with phenol. 2C6 H 5 OH 2 Na 2C6 H 5 ONa H 2 E3 Presence 60 (2) Physical properties (i) Phenol is a colourless crystalline, deliquescent solid. It attains pink colour on exposure to air and light. (ii) They are capable of forming intermolecular H-bonding among themselves and with water. Thus, they have high boiling points and they are soluble in water. ring to draw more electrons from the phenoxy oxygen and thus releasing easily the proton. Further, the particular effect is more when the substituent is present on o- or p-position than in m-position to the phenolic group. The relative strengths of some phenols (as acids) are as follows : p-Nitrophenol > o-Nitrophenol > m- Nitrophenol > Phenol – ID (c) Phenol reacts with strong alkalies to form phenoxides. C6 H 5 OH NaOH C6 H 5 ONa H 2 O However, phenol does not decompose sodium carbonate or sodium bicarbonate, i.e., CO 2 is not evolved because phenol is weaker than carbonic acid. (ii) Reactions of –OH group (a) Reaction with FeCl : Phenol gives violet colouration with ferric chloride solution (neutral) due to the formation of a coloured iron complex, which is a characteristic to the existence of keto-enol tautomerism in phenols (predominantly enolic form). D YG U (crossed intermolecular H-bonding between water and phenol Due molecules) to intermolecular H- bonding and high dipole moment, melting points and boiling points of phenol are much higher than that of hydrocarbon of comparable molecular weights. (iii) It has a peculiar characteristic smell and a strong corrosive action on skin. (iv) It is sparingly soluble in water but readily soluble in organic solvents such as alcohol, benzene and ether. (v) It is poisonous in nature but acts as antiseptic and disinfectant. (3) Chemical properties (i) Acidic nature : Phenol is a weak acid. The acidic nature of phenol is due to the formation of stable phenoxide ion in solution. 3 OH C6 H 5 OH H 2 O ⇌ C 6 H 5 O H 3 O O Enol Phenoxide ion Keto OH The phenoxide ion is stable due to resonance. – O O U O O..–..– ST (10 5 ) (10 7 ) (10 10 ) (10 14 ) (10 18 ) RCOOH H 2 CO 3 C6 H 5 OH HOH ROH Carbonic acid + FeCl 3H + Fe + 3HCl O + 3 6 This is the test of phenol. (b) Ether formation : Phenol reacts with alkyl halides in alkali solution to form phenyl ethers (Williamson’s synthesis). The phenoxide ion is a nucleophile and will replace halogenation of alkyl halide. – carboxylic acids or even carbonic acid. This is indicated by the values of ionisation constants. The relative acidity follows the following order Carboxylic acid 6..– The negative charge is spread throughout the benzene ring. This charge delocalisation is a stabilising factor in the phenoxide ion and increase acidity of phenol. [No resonance is possible in alkoxide ions ( RO ) derived from alcohols. The negative charge is localised on oxygen atom. Thus alcohols are not acidic]. Phenols are much more acidic than alcohols but less so than Ka (approx. ) 3– Phenol Water Alcohols Effects of substituents on the acidity of phenols : Presence of electron attracting group, (e.g., NO 2 , –X, NR 3 , –CN, –CHO, – COOH) on the benzene ring increases the acidity of phenol as it enables the C 6 H 5 OH NaOH C 6 H 5 ONa H 2 O Sod. phenoxide C 6 H 5 ONa ClCH 3 C 6 H 5 OCH 3 Methyl phenyl ether (Anisole) NaCl C 6 H 5 OK IC2 H 5 C 6 H 5 O C 2 H 5 KI Ethoxy benzene (Phenetol) C6 H 5 ONa Cl HC(CH 3 )2 C 6 H 5 O HC(CH 3 )2 Isopropyl chloride Isopropyl phenyl ether Ethers are also formed when vapours of phenol and an alcohol are heated over thoria (ThO 2 ) or Al2 O 3. , ThO 2 C 6 H 5 OH HOCH 3 C 6 H 5 O CH 3 Methoxy benzene (c) Ester formation : Phenol reacts with acid chlorides (or acid anhydrides) in alkali solution to form phenylesters (Acylation). This reaction (Benzoylation) is called Schotten-Baumann reaction. C6 H 5 OH NaOH C6 H 5 ONa H 2 O OH O || C 6 H 5 ONa Cl C CH 3 Sodium phenoxide Acetyl chloride OH C 6 H 5 OOCCH 3 NaCl Br Phenyl acetate + 3Br NaOH C 6 H 5 OH (CH 3 CO ) 2 O Br + 3HBr 2 Aceticanhydride C 6 H 5 OOCCH 3 CH 3 COOH Br Phenyl acetate (ester) Phenol forms a white precipitate with excess of bromine water yielding 2, 4, 6-tribromophenol. O || NaOH C 6 H 5 OH Cl C C 6 H 5 (b) Sulphonation : Phenol reacts with conc. H 2 SO 4 readily to form mixture of ortho and para hydroxy benzene sulphonic acids. O || C 6 H 5 O C C 6 H 5 NaCl H 2 O Phenyl ben zoate The phenyl esters on treatment with anhydrous AlCl3 undergoes Fries rearrangement to give o- and p- hydroxy ketones. OH OH heat 3 2 4 Phenyl acetate COCH p- 3 hydroxy acetophenone (d) Reaction with PCl : Phenol reacts with PCl5 to form chlorobenzene. The yield of chlorobenzene is poor and mainly triphenyl phosphate is formed. D YG 5 OH (e) Reaction with zinc dust : When phenol is distilled with zinc dust, benzene is obtained. C 6 H 5 OH Zn C 6 H 6 ZnO NO 2 HNO (dil.) (5-10°C) + 3 o-Nitrophenol NO 2 p-Nitrophenol It is believed that the mechanism of the above reaction involves the formation of o- and p- nitroso phenol with nitrous acid, HNO 2 (NaNO 2 HCl) at 0-5°C, which gets oxidised to o- and pnitrophenol with dilute nitric acid. OH NO HONO (0-5°C) + C 6 H 5 OH NH 3 C 6 H 5 NH 2 H 2 O ST ZnCl 2 o-Nitrosophenol Aniline NO (g) Action of P S : By heating phenol with phosphorus penta sulphide, thiophenols are formed. 2 Thiophenol (iii) Reactions of benzene nucleus : The –OH group is ortho and para directing. It activates the benzene nucleus. (a) Halogenation : Phenol reacts with bromine in carbon disulphide (or CHCl 3 ) at low temperature to form mixture of ortho and para bromophenol. OH Br + Br [O] HNO (Dil.) + 3 2 NO o- presence of concentrated H 2 SO 4 , 2,4,6-trinitrophenol (Picric acid) is formed. OH OH ON NO 2 o-Bromophenol 2 HNO (conc.) H SO (conc.) 3 Br 2 p- However, when phenol is treated withNitrophenol concentrated HNO 3 in + 2 OH NO 5 C 6 H 5 OH P2 S 5 5 C 6 H 5 SH P2 O 5 OH p-Nitrosophenol OH 5 (CS ) OH OH U (f) Reaction with ammonia : Phenol reacts with ammonia in presence of anhydrous zinc chloride at 300°C or (NH 4 ) 2 SO 3 / NH 3 at 150°C to form aniline. This conversion of phenol into aniline is called Bucherer reaction. OH OH 3C 6 H 5 OH POCl3 (C 6 H 5 )3 PO4 3 HCl OH 3 At low temperature (25°C), the ortho-isomer is thesulphonic major acid product, whereas at 100°C, it gives mainly the para-isomer. (c) Nitration : Phenol reacts with dilute nitric acid at 5-10°C to form ortho and para nitro phenols, but the yield is poor due to oxidation of phenolic group. The –OH group is activating group, hence nitration is possible with dilute nitric acid. C 6 H 5 OH PCl5 C 6 H 5 Cl POCl3 HCl 2 SO H p-Hydroxybenzene U o- 300 o C + sulphonic acid 3 + 3 SO H (H SO ) ID AlCl (anhydrous) OH OH o-Hydroxybenzene 3 COCH OH E3 Benzoyl chloride OOCCH 60 2, 4, 6-Tribromophenol 2 4 p-Bromophenol NO 2 2, 4, 6-Trinitrophenol (picric acid) (o-hydroxy benzaldehyde) and a very small amount of p-hydroxy benzaldehyde. However, when carbon tetrachloride is used, salicylic acid (predominating product) is formed. OH ONa H HO + To get better yield of picric acid, first sulphonation of phenol is made and then nitrated. Presence of SO 3 H group prevents oxidation of phenol. (d) Friedel-Craft’s reaction : Phenol when treated with methyl chloride in presence of anhydrous aluminium chloride, p-cresol is the main product. A very small amount of o-cresol is also formed. + CH Cl OH CHCl NaOH(aq.) 60°C OH 3 3 OH + 3 3 CHCl 2 CH AlCl NaOH OH OH CHO Salicylaldehyde 60 OH 2 CHO CCl NaOH(aq.) 60°C 4 o-cresol (minor) CCl 3 NaOH 3 p-Cresol (major product) RX and AlCl3 give poor yields because AlCl3 coordinates with O. So Ring alkylation takes place as follows, E3 CH OH ONa H HO + 2 C6 H 5 OH AlCl3 C6 H 5 OAlCl2 HCl OH OH 3 OH + 3 3 OH AlCl HCl + ClCH = NH HO 3 2 –NH 3 CH = NH Acetyl chloride COCH ortho 3 (h) Mercuration benzaldehyde OH OH + (CH COO) Hg 3 Rearrangement 130-140°C 6 atm U 2 ST Sodium phenyl carbonate o-Hydroxy phenyl mercuric acetate 6 OH 5 Ni 2 150-200°C Cyclohexanol (C H OH) (used as a good solvent) Phenol (C H OH) Salol 6 6 5 11, (iv) Miscellaneous reactions (a) Coupling reactions : Phenol couples with benzene diazonium chloride in presence of an alkaline solution to form a red dye (p-hydroxy azobenzene). 3 COOH H HO OH + 3H OCOCH COOH + CH COCl 3 2 Salicylic acid Aspirin N = NCl + OH COOCH 3 mercuric acetate (i) Hydrogenation OH HgOCOCH p-Hydroxy phenyl OH Sodium salicylate COOC H 3 + 2 COONa + CO OH HgOCOCH OH OCOONa CHO p-Hydroxy Para (e) Kolbe-Schmidt reaction (Carbonation) : hydroxy acetophenone ONa OH CH (CH 3 )2 D YG + CH COCl AlCl3 HCl HC N ClCH NH OH COCH anhydrous AlCl / \ OH U CH 3 CH CH 2 H SO 4 C6 H 5 OH 2 o - and p - C6 H 4 or HF (CH 3 )2 CH OH hydrogen cyanide and hydrochloric acid gas in presence of anhydrous aluminium chloride yields mainly p-hydroxy benzaldehyde (Formylation). ID Thus to carry out successful Friedel-Craft’s reaction with phenol it is necessary to use a large amount of AlCl3. The Ring alkylation takes place as follows : COOH COONa Salicylic acid (g) Gattermann’s reaction : Phenol, when treated with liquid 3 Benzene diazonium chloride OH NaOH –HCl Phenol CH OH (f) Reimer-Tiemann reaction : Phenol, on refluxing with chloroform and sodium hydroxide (aq.) followed by acid hydrolysis yields salicylaldehyde 3 N=N Oil of winter green p-Hydroxyazobenzene OH Phenol couples with phthalic anhydride in presence of concentrated H 2 SO 4 to form a dye, (phenolphthalein) used as an indicator. O O | | C – OH C (d) Oxidation : Phenol turns pink or red or brown on exposure to air and light due to slow oxidation. The colour is probably due to the formation of quinone and phenoquinone. O C H OH or 6 C – OH C | | Phthalic anhydride O by air or CrO O 2 H OH - - - O H O | 2 2 + HO 2 2 Phenol O O 4 O - - - HO O [O] CrO Cl OH C Phenol (2 molecules) 2 But on oxidation pwith potassium persulphate in alkaline solution, -benzoquinone phenol forms 1, 4-dihydroxy benzene (Quinol). This is known as Elbs persulphate oxidation. ID C U OH OH OH : Phenol condenses with (b) Condensation with formaldehyde Phenolphthalein D YG formaldehyde (excess) in presence of sodium hydroxide or acid (H ) for about a week to form a polymer known as bakelite (a resin). OH OH OH CH OH 2 NaOH + CH O 2 + o-hydroxy benzyl alcohol CH OH 2 p-hydroxy benzyl alcohol OH U OH Condensation with CH HCHO CH 2 CH 2 2 ST continues give CH CH 2 2 When(a phenol is reacted with (c) Liebermann’s nitroso reaction Polymer: Bakelite resin) NaNO 2 and concentrated H 2 SO 4 , it gives a deep green or blue colour which changes to red on dilution with water. When made alkaline with NaOH original green or blue colour is restored. This reaction is known as Liebermann’s nitroso reaction and is used as a test of phenol. OH HONO NO O OH p-Nitrosophenol O NOH Quinoxim N OH + H OH H SO HO 2 4 2 O N OH NaOH –H O 2 Indo phenol (Red) 5 E3 Conc. H SO (–H O) 6 Phenoquinone (pink) OH OH C H OH p-benzoquinone O Phthalic acid O 3 60 O OH 5 Sod. Salt of indophenol (blue) OH K S O in alkaline solution 2 2 8 Phenol OH Quinol (4) Uses : Phenol is extensively used in industry. The important applications of phenol are (i) As an antiseptic in soaps, lotions and ointments. A powerful antiseptic is “Dettol” which is a phenol derivative (2, 4-dichloro-3, 5dimethyl phenol). (ii) In the manufacture of azo dyes, phenolphthalein, etc. (iii) In the preparation of picric acid used as an explosive and for dyeing silk and wool. (iv) In the manufacture of cyclohexanol required for the production of nylon and used as a solvent for rubber and lacquers. (v) As a preservative for ink. (vi) In the manufacture of phenol-formaldehyde plastics such as bakelite. (vii) In the manufacture of drugs like aspirin, salol, phenacetin, etc. (viii) For causterising wounds caused by the bite of mad dogs. (ix) As a starting material for the manufacture of nylon and artificial tannins. (x) In the preparation of disinfectants, fungicides and bactericides. (5) Tests of phenol (i) Aqueous solution of phenol gives a violet colouration with a drop of ferric chloride. (ii) Aqueous solution of phenol gives a white precipitate of 2, 4, 6tribromophenol with bromine water. (iii) Phenol gives Liebermann’s nitroso reaction. Phenol in conc. sulphuric acid NaNO2 Red colour Excess of water Blue colour NaOH (Excess) (iv) Phenol combines with phthalic anhydride in presence of conc. H 2 SO 4 to form phenolphthalein which gives pink colour with alkali, (v) With ammonia and sodium hypochlorite, phenol gives blue colour. and used as an indicator. Table : 26.2 Difference between phenol and alcohol Phenol (C H OH) Typical phenolic odour Acidic, dissolves in sodium hydroxide forming sodium phenoxide. Gives violet colouration due to formation of complex compound. No reaction with halogen acids. Pink or brown colour due to formation of quinone and phenoquinone. Forms polymer (bakelite). Positive. Forms azo dye. Mainly forms triphenyl phosphate. Does not show. Reaction with neutral FeCl 3 Reaction with halogen acids Oxidation Reaction with HCHO Liebermann’s nitroso reaction Coupling with benzene diazonium chloride Reaction with PCl Iodoform test 5 Alcohol (C H OH) Pleasant alcoholic odour Neutral, no reaction with alkalies. 5 2 No reaction. Forms ethyl halides. Undergoes oxidation to give acetaldehyde and acetic acid. No reaction. Does not show. Does not form any dye. Forms ethyl chloride Positive. The lowest melting point of o-isomer is due to intramolecular hydrogen bonding whereas meta and para isomers possess intermolecular hydrogen bonding and thus, they have higher melting points. Derivatives of phenol ID NITROPHENOLS (1) Preparation They are stronger acids than phenol. The order is : OH OH OH p-isomer > o-isomer > m-isomer > phenol NO When reduced, they form corresponding aminophenols. o- and pNitrophenols react with bromine water to form 2, 4, 6-tribromophenol by replacement of nitro group. Dil. HNO U 2 + 3 o-isomer (steam volatile) OH D YG NO Br 2 p-isomer (non-volatile) Cl (ii) 120 C C6 H 4 o - and p - nitropheno l OH Solid KOH C6 H 4 (iii) C6 H 5 NO 2 NO 2 o - and p - nitropheno l NH U NO heat 2 Br 2,4,6 Tribromophenol 6-trinitrophenol) Picric acid (2, 4, (1) Preparation : It is obtained when phenol is treated with conc. HNO 3. However, the yield is very poor. It is prepared on an industrial scale : (i) From chlorobenzene Cl NO NaNO /HCl 0-5°C 2 2 NO ST NO 2 Cl 4 m-Dinitrobenzene Br Br2 2 NH HS or Na S 2 OH o - or p - isomer NO 2 o - and p - chloro nitrobenzene Nitrobenzene / C6 H 4 \ OH NaOH C6 H 4 NO 2 (iv) 5 E3 6 60 Property Odour Nature, reaction with alkali 2 HNO H SO NO m-Nitroaniline N Cl 2 2 2 NO 2 2, 4-Dinitrochlorobenzene OH HO OH 2 NO 2 m-Nitrobenzene NO NO m-Nitrophenol ON 2 NO 2 HNO H SO 2 diazonium chloride 2 (2) Properties : o-Nitrophenol is a yellow coloured crystalline compound, while m- and p-isomers are colourless crystalline compounds. 2 3 4 NO NO 2 Isomer ortho meta m.pt. (C) 45 97 3 4 Chlorobenzene OH 2 Aq. Na CO 3 para 114 2 Picric acid (2, 4, 6-Trinitrophenol) (ii) From phenol through disulphonic acid OH OH OH ON SO H 2 NO 2 3 2 HNO H SO 3 4 Phenol SO H 3 Phenol disulphonic acid NO 2 Picric acid (iii) CHO OH + H O + NaOH 2 + HCOONa + H O 2 2 OH OH Salicylaldehyde (2) Properties (iii) : It is a colourless Catechol crystalline solid, melting points 105°C. it is soluble in water. It is affected on exposure to air and light. It acts as a reducing agent as it reduces Tollen’s reagent in cold and Fehling’s solution on heating. With silver oxide it is oxidised to o-benzoquinone. OH NO 2 ON 2 NO 2 Ke Fe(CN) + [O] 3 2 OH O 6 OH 60 ON O + Ag O 2 NO 2 o-Benzoquinone Picric acid OH NH NO ON 2 2 3 2 NO NO 2 2 D YG heated. These are prepared carefully. U (3) Uses : It is used as a yellow dye for silk and wool, as an explosive and as an antiseptic in treatment of burns. Catechol (1, 2-Dihydroxy benzene) (1) Preparation (i) OH OH OH ST ; O+ 2 2 | O Alizarin SO H NaOH HCl Fuse SO H ONa 3 OH Br OH + 3HBr 2 OH Br H /H O On nitration, it forms 2, 4, 6-trinitro-1, 3-dihydroxybenzene. + 2 2+ OH OH OK SO K 3 OH ON OH OK OH 2HCl NO 2 2 HNO H SO 3 2 + 3KOH 4 OH Resorcinol acid Br OH OH ONa OH (2) Properties : It is a colourless crystalline solid, melting points 110°C. it is affected on exposure by air and light. It is soluble in water, alcohol and ether. It shows tautomerism. Its aqueous solution gives violet colour with FeCl3. It reduces Fehling’s solution and Tollen’s reagent on warming. With bromine water, it gives a crystalline precipitate, 2, 4, 6tribromoresorcinol. + 3Br ONa OH ONa 3 2 (ii) o-phenol sulphonic C OH + CO + NaCl NaOH 200°C, Cu 4 (3) Uses : It finds use as photographic developer, in the manufacture of alizarin and adrenaline hormone and as an antioxidant (inhibitor in auto oxidation) for preserving gasoline. Resorcinol (1, 3-Dihydroxy benzene) (1) Preparation : It is prepared by alkali fusion of 1,3, benzene disulphonic acid (Industrial method). Catechol ClCOOH Cl OH Con H SO (–H O) Phthalic anhydride NO 2 NaOH C OH O Picryl chloride When distilled with a paste of bleaching powder, Picramide it gets decomposed and yields chloropicrin, CCl 3 NO 2 , as one of the products and is thus employed for the manufacture of tear gas. It forms yellow, orange or red coloured molecular compounds called picrates with aromatic hydrocarbons, amines and phenols which are used for characterisation of these compounds. Picrates are explosive in nature and explode violently when Cl C OH | U 5 NO 2 NH PCl HO O OH | | 2 ON 2 2 O C Cl NO 2 on adding Na 2 CO 3 solution. It forms alizarin dye stuff when condensed with phthalic anhydride in the presence of sulphuric acid. ID which on shaking with NH 3 yields picramide. It forms insoluble lead salt (white ppt.) when treated with lead acetate solution and gives green colour with FeCl 3 which changes to red E3 TNB (2) Properties : It is a yellow crystalline solid, melting points 122°C. it is insoluble in cold water but soluble in hot water and in ether. It is bitter in taste. Due to the presence of three electronegative nitro groups, it is a stronger acid than phenol and its properties are comparable to the carboxylic acid. It neutralises alkalies and decomposes carbonates with evolution of carbon dioxide. Dry picric acid as well as its potassium or ammonium salts explode violently when detonated. It reacts with PCl5 to form picryl chloride ON 2 NO 2 + 2Ag + H O Catechol OH NO 2 It condenses with phthalic anhydride andStyphnic forms acid fluorescein. OH H C= O+ O=C OH O Conc. H SO –2H O 2 H OH Phloroglucinol is obtained from trinitrotoluene (TNT) by following sequence of reactions. O C O=C 4 2 CH Phthalic Withanhydride nitrous OH acid, it Resorcinol forms 2, (2 moles) OH COOH 3 OH O N NO 2 Fluorescein 4-dinitrosoresorcinol OH ON 2 O NO NO NOH OH OH O HN NH 2 OH + +CO2+3NH4Cl 2 Resorcinol behaves as a tautomeric compound. This is shown by the fact that it forms a dioxime and a bisulphite derivative. OH HO 2 H O/H 100°C NOH E3 NO Fe/HCl [H] 2 COOH 2 2 4 NO 2 2, 4, 6-trinitro toluene HNO NO 2 KMnO [O] 60 O OH NH O OH 2 Hydroxyquinol is prepared by the Phloroglucinol alkaline fusion of hydroquinone in air. ID OH D YG O O+SO +2H O 2 HO 2 OH+H SO 2 4 H SO +H O Quinol (p-Benzoquinone is obtained by oxidation of aniline) 2 NH 3 [O] MnO /H SO 2 OH Fe/H O [H] 2 4 U Aniline 2 O OH ST (2) Properties : It is a colourless crystalline solid, melting Quinol points 170°C. it is soluble in water. It also shows tautomerism. It gives blue colour with FeCl3 solution. It acts as a powerful reducing agent as it is easily oxidised to pbenzoquinone. It reduces Tollen’s reagent and Fehling’s solution. HO OH [O] FeCl O Quinol O p-Benzoquinone OH OH OH OH heat 220°C Gallic acid Fuse 2 OH OH Hydroxycompounds. Quinol The three Quinol isomers are colourless crystalline All are soluble in water and their aqueous solutions give characteristic colour with FeCl3 (Red, brown or bluish violet). Alkaline solutions absorb oxygen rapidly from air. OH Uses of pyrogallol (i) As a developer in photography. (ii) As a hair dye. (iii) In treatment of skin diseases like eczema. (iv) For absorbing unreacted oxygen in gas analysis. Ether Ethers are anhydride of alcohols, they may be obtained by elimination of a water molecule from two alcohol molecules. R OH HO R R O R H 2 O Ether General formula is Cn H 2n 2 O General methods of preparation of ethers (1) From alkyl halides (i) Williamson’s synthesis 3 Due to this property, it is used as photographic developer. (3) Uses : It is used as an antiseptic, developer in photography, in the preparation of quinhydrone electrode and as an antioxidant. Trihydric Phenols : Three trihydroxy isomeric derivatives of benzene are Pyrogallol (1, 2, 3), hydroxy quinol (1, 2, 4) and phloroglucinol (1, 3, 5). Pyrogallol is obtained by heating aqueous solution of gallic acid at 220°C. HOOC OH 2 O 2 OH NaOH +½O U (3) Uses OH O form Diketo form (i) It is usedDienol as antiseptic and for making dyes. (ii) It is also used in the treatment of eczema. 2, 4, 6trinitroresorcinol is used as an explosive. Hydroquinone or quinol (1, 4-Dihydroxy benzene) (1) Preparation : It is formed by reduction of p-benzoquinone with sulphurous acid (H 2 SO 3 H 2 O SO 2 ). + CO 2 Pyrogallol OH It is a nucleophilic substitution reaction and proceed through S N 2 mechanism. RONa RX ROR NaX C2 H 5 ONa Sodium ethoxide CH 3 I CH 3 OC2 H 5 NaI C 2 H 5 ONa C 2 H 5 Br Sodium ethoxide Ethyl bromide Ethyl methyl ether C 2 H 5 OC2 H 5 NaBr Ethoxyetha ne (b) Order of reactivity of primary CH 3 X CH 3 CH 2 X CH 3 CH 2 CH 2 X. Tendency of alkyl halide to undergo halide is elimination is 3 o 2o 1o. (c) For better yield alkyl halide should be primary and alkoxide should be secondary or tertiary. CH 3 CH 3 | | | | CH 3 Sodium salt of tert. butyl alcohol CH 3 Ethyl tert. butyl ether (d) Secondary and tertiary alkyl halides readily undergo E 2 elimination in the presence of a strong base to form alkenes. CH 3 CH 3 | | CH 3 C Cl CH 3 C Cl , | | CH 3 C C 2 H 5 O CH 3 C C 2 H 5 OH | || CH 2 H (4) Solubility : Solubilities of ethers in water are comparable with those of alcohols. Example : Di ethyl ether and n-butyl alcohol have approximately the same solubility in water. This is because, ether form hydrogen bond with water much in the same way as alcohol do with water. R R U heat 2 RX Ag2O R O R 2 AgX , Ag2 O C2 H 5 OC2 H 5 2 AgBr D YG heat O.......... H Ether O H........... O Water 2 4 ROH HOR 24 ROR H 2 O. H SO (conc.) 140 o C 2 moleculesof alcohol Ether U In this reaction alcohol must be present in excess. This reaction is mainly applicable for the dehydration of primary alcohols. Secondary and tertiary alcohols form alkenes mainly. When this reaction is carried out between different alcohols then there is a mixture of different ethers is obtained. (b) With Al O at 250° C : 3 3 2 ROH 2 R O R H 2O Al O ST 250 o C (ii) By the action of diazomethane on alcohols : This reaction is in presence of catalyst, boron trifluoride or HBF4. BF (a) This method is very useful for preparing mixed ethers. (b) In higher cases, there can be 1, 2-hydride or 1, 2-methyl shift to form more stable carbonium ion. (3) Alkoxy mercuration-demercuration C C R OH Hg[OOCCF3 ]2 alkene Mercuric trifluoro acetate | | | | C C OR HgOOCCF3 | | | | C C NaBH 4 Solubility of ether in water decreases with the size of alkyl groups. (5) Hydrogen bonding : There is no hydrogen directly attach (bonded) to oxygen in ethers, so ethers do not show any intermolecular hydrogen bonding. R R R | | | H O- - - H O- - - H O- - hydrogenbo nding in alcohols OR H Ether R O R No hydrogen bond in ether (6) Density : Ethers are lighter than water. Chemical properties : Ethers are quite stable compounds. These are not easily attacked by alkalies, dilute mineral acids, active metals, reducing agents or oxidising agents under ordinary conditions. (1) Reaction due to alkyl group (i) Halogenation : Cl 2 CH 3 CH 2 OCH 2 CH 3 CH 3 CHClOCH 2 CH 3 Diethyl ether 3 ROH CH 2 N 2 R O CH 3 N 2 R R Ether Diethyl ether (2) From alcohols (i) By dehydration of alcohols (a) With conc. H SO at 140° C 2 (2) Dipole moment (D.M.) : Bond angle of ether is due to sp 3 hybridisation of oxygen atom. Since C – O bond is a polar bond, hence ether possess a net dipole moment, even if they are symmetrical. dipole moment of dimethyl ether is 1.3 D and dipole moment of di ethyl ether is 1.18 D. The larger bond angle may be because of greater repulsive ID CH 2 Aryl halide and sodium alkoxide cannot be used for preparing phenolic ethers because aryl halide are less reactive toward nucleophilic substitution reaction than alkyl halides. (ii) By heating alkyl halide with dry silver oxide 2C2 H 5 Br Ethyl bromide (i) Higher members can be prepared by the action of grignard reagent on lower halogenated ethers. (ii) Ether form soluble coordinated complexes with grignard reagent. (3) Boiling points : Boiling points of ethers are much lower than those of isomeric alcohols, but closer to alkanes having comparable mass. This is due to the absence of hydrogen bonding in ethers. CH 3 | Higher ether interaction between bulkier alkyl groups as compared to smaller H-atoms in water. | CH 3 CH 3 Grignard reagant E3 C 2 H 5 ONa CH 3 Halogenate d ether Physical properties (1) Physical state : Methoxy methane and methoxy ethane are gases while other members are volatile liquid with pleasant smell. C 2 H 5 Br NaO C CH 3 C 2 H 5 O C CH 3 Ethyl bromide This is the best method for the preparation of t-ethers. (4) Reaction of lower halogenated ether with grignard reagent ROCH 2 X XMgR ROCH 2 R MgX2 60 (a) dark ( -Monochloro diethyl ether ) Cl 2 CH 3 CH 2 OCH 2 CH 3 CH 3 CHClOCHClCH 3 Diethyl ether dark ( , -Dichlorodiethyl ether ) Cl 2 C 2 H 5 OC 2 H 5 10 Cl 2 C 2 Cl 5 OC 2 Cl 5 10 HCl light (Perchlorod iethyl ether ) (ii) Burning : Ethers are highly inflammable. They burn like alkanes. C 2 H 5 O C 2 H 5 6O 2 4 CO 2 5 H 2 O (2) Reaction due to ethernal oxygen (i) Peroxide formation : Ether is removed from alkyl halides by shaking with conc. H 2 SO 4..... (a) The boiling point of peroxide is higher than that of ether. It is left as residue in the distillation of ether and may cause explosion. Therefore ether may never be evaporated to dryness. (b) Absolute ether can be prepared by distillation of ordinary ether from conc. H 2 SO 4 and subsequent storing over metallic sodium. Formation of peroxide can be prevented by adding small amount of Cu 2 O to ether. With strong oxidising agent like acid, dichromate ethers are oxidised to aldehydes. 2[O ] CH 3 CH 2 OCH 2 CH 3 2CH 3 CHO H 2 O Ethers can be distinguished from alkanes with the help of this reaction. (iv) Reaction with Lewis acids : Being Lewis bases, ethers form complexes with Lewis acids such as BF3 , AlCl3 , FeCl3 , etc. These complexes are called etherates... CH 3 CH 2 CH 3 CH 2 Boron trifluoride etherate (complex) 2(CH 3 CH 2 )2 O RMgX blood red colour complex in the following reaction. Fe 3 [Fe(SCN )n ] 3 n (ii) Oxidation with K Cr O / H 2 2 7 R R (a) Oxidation of ether can only be possible if any one of the alkyl groups of ether has hydrogen on -carbon. CH 3 CH 2 O CH 2 CH 2 CH 3 CH 3 COOH CH 3 CH 2 COOH K 2 Cr2O7 D YG / CH 3 CH 2 O CH CH 3 CH 3 O || CH 3 COOH CH 3 C CH 3 K 2 Cr2 O7 H / U (iii) Salt formation : Due to lone pair of electrons on oxygen atom. Ether behaves as Lewis base and form stable oxonium salt with strong inorganic acids at low temperature. H | C 2 H 5 OC 2 H 5 HCl (C 2 H 5 )2 O Cl or ST [(C 2 H 5 )2 O H ] Cl .. (C 2 H 5 )2 O HSO 4 or | H Diethyl oxonium hydrogen sulphate [(C 2 H 5 )2 O H ] HSO 4 The oxonium salts are soluble in acid solution and ethers can be recovered from the oxonium salts by treatment with water. (C 2 H 5 )2 O Cl 2 (C2 H 5 )2 O HCl H O | H Diethyl ether Oxonium salt The formation of oxonium salt is similar to the formation of ammonium salts from ammonia and acids. H SO 4 C2 H 5 OC2 H 5 H 2 O 2 2C2 H 5 OH H SO Diethyl ether Ethanol (b) With conc. H 2 SO 4 : C 2 H 5 OC2 H 5 H 2 SO 4 C2 H 5 OH C2 H 5 HSO 4 C2 H 5 OH H 2 SO 4 C2 H 5 HSO 4 H 2 O C2 H 5 OC2 H 5 2 H 2 SO 4 2C2 H 5 HSO 4 H 2 O Diethyl ether Ethyl hydrogen sulphate (ii) Action of hydroiodic acid (a) With cold HI Cold C2 H 5 OC2 H 5 HI C2 H 5 I C2 H 5 OH Diethyl ether OC H 2 Ethyl iodide Ethyl alcohol OH 5 + HBr Phenyl ethyl ether + C H Br 2 Phenol 5 Ethyl bromide (b) With hot HI.. Diethyl oxonium chloride C 2 H 5 OC 2 H 5 H 2 SO 4 4 (a) With dil. H 2 SO 4 : ROR H 2 O 2 2 ROH U (b) -carbon having two hydrogens converts in carboxylic group and -carbon having only one hydrogen converts into keto group. H Due to the formation of the etherate, Grignard reagents dissolve in ether. That is why Grignard reagents are usually prepared in ethers. However, they cannot be prepared in benzene, because benzene has no lone pair of electrons and therefore, cannot form complexes with them. (3) Reaction involving cleavage of carbon-oxygen bond (i) Hydrolysis ID R CH 2 O CH O(CH 2 CH 3 )2 X Mg Grignard reagent etherate SCN Blood red colour (n 1 to 6 ) R (CH 3 CH 2 )2 O E3 Peroxide Fe 2 O BF3 Similarly, diethyl ether reacts with Grignard reagent forming Grignard reagent etherate. Acetaldehyde The presence of peroxide can be indicated by the formation of.. CH 3 CH 2 CH 3 CH 2 O : BF3 60.... C 2 H 5 O C 2 H 5 O : (C 2 H 5 )2 O O. heat R O R 2 HI RI R I H 2 O (iii) Zeisel method : RI AgNO 3 (alc.) AgI RNO 3 The silver iodide thus form can be detected and estimated. This is the basis of Zeisel method for the detection and estimation of alkoxy group in a compound. (iv) Action of PCl 5 heat R O R PCl5 2 RCl POCl3. reaction in cold. (v) Reaction with acetyl chloride There is no ZnCl 2 CH 3 COCl C 2 H 5 O C 2 H 5 CH 3 COOC 2 H 5 Acetyl chloride Diethyl ether (vi) Reaction with acid anhydride heat Ethyl acetate Ethers are relatively less reactive than phenol towards electrophilic substitution reaction. CH 3 CO O OCCH 3 C2 H 5 O C2 H 5 Aceticanhydride Diethyl ether 2 2CH 3 COOC 2 H 5 ZnCl heat Ethyl acetate (vii) Dehydration Al2 O3 C 2 H 5 OC 2 H 5 2CH 2 CH 2 H 2 O 300 o C (viii) Reaction with carbon mono oxide Methyl alcohol (CH OH) is called wood spirit. It is obtained by 3 BF3 / 150 o C destructive distillation of wood. Drinking of methanol causes blindness. Ethyl alcohol (C H OH) is called grain alcohol. It is used in preparation of various beverages by using different percentages. C 2 H 5 OC 2 H 5 CO C 2 H 5 COOC 2 H 5 500 atm. Diethyl ether Ethyl propionate An alcohol-water mixture containing 57.1% alcohol by volume or 49.3% L i C H 3 H CH 2 CH 2 O CH 2 CH 3 CH 4 CH 2 CH 2 L i O C 2 H 5 (4) Ring substitution in aromatic ethers : Alkoxy group is ortho and para directing and it directs the incoming groups to ortho and para position. It activates the aromatic ring towards electrophilic substitution reaction........... :OR :O – R OR OR OR + + + .... III, IV and VIIshow high electron III density at ortho IV and para position. V (i) Halogenation : Phenyl alkyl ethers undergo usual halogenation in benzene ring. For example, Bromination of anisole gives ortho and para bromo derivative even in the absence of iron (III) bromide catalyst. OCH OCH 3 Br Br2 + CS 2 o-Bromoanisole Anisole Para isomer is obtained in 90% yield. (ii) Friedel craft reaction OCH OCH 3 Br p-Bromoanisole OCH 3 CH 3 3 + CH 3 Cl AlCl3 + Ortho 3 OCH ST OCH U Methyl chloride Anisole CH OCH Para 3 3 COCH AlCl3 + CH 3 COCl Anisole 3 3 + o-Methoxy acetophenone COCH 3 p Methoxy OCH 3 acetophenone OCH 3 3 NO 3 HNO 3 / H 2 SO 4 Methyl phenyl ether (Anisole) Methyl-2 nitrophenyl ether (o-Nitroanisole) 3 2 5 3 2 3 3 3 2 3 dehydration of diols through the formation of carbocation intermediate which rearranges to more stable compound. OH OH O CH 3 | | | | || | H CH 3 C C CH 3 CH 3 C C CH 3 CH 3 CH 3 Pinacol H 2O | CH 3 Pinacolone In general, acid strength increases as Cresols (CH )CH – COOH > (CH )C – COOH. U I OCH 4 Pyroligneous acid contains acetic acid (10%), methyl alcohol (2.5%) ID : by weight is called proof spirit. Ethyl alcohol containing 5 to 10% methyl alcohol is called methylated spirit. It is unfit for drinking purpose. Widespread deaths due to liquor poisoning occur mainly due to the presence of methyl alcohol. It is also called denatured spirit. Denaturing can also be done by adding 0.5% pyridine, petroleum naphtha, rubber distillate (caoutchoucine) or CuSO. E3 5 60 2 (ix) Action of bases + NO 2 Methyl-4 nitrophenyl ether (p-Nitroanisole)
