Alcohol, Phenol & Ether PDF

Alcohols Alcohols are hydroxy derivatives of alkanes or Concept Ladder alkyl derivatives of water with a general formula R–OH. Types of Alcohols Alcohols are of following types: Monohydric alcohols: (ii) These are alcohols with only one –OH gr...

Alcohols Alcohols are hydroxy derivatives of alkanes or Concept Ladder alkyl derivatives of water with a general formula R–OH. Types of Alcohols Alcohols are of following types: Monohydric alcohols: (ii) These are alcohols with only one –OH group. Their general formula is CnH2n + 1 OH. They are further divided in following types: Primary alcohol (1°) RCH2OH, for example, CH3OH methyl alcohol (Methanol). Secondary alcohol (2°) R2CHOH, for example, (CH3)2CHOH isopropyl alcohol (Propan-2-ol). Tertiary alcohol (3°) R3COH, for example, (CH3)3COH–tertiary butyl alcohol (2-Methyl- propan-2-ol). Rack your Brain Dihydric alcohols: Alcohols that have two –OH groups. For example, glycol, Propan 1, 2 diol Trihydric alcohols: Alcohols that having three –OH groups. For example, glycerol Previous Year’s Ǫuestions Nomenclature of Alcohols Alcohols are named as alkanol as below. CH3–CH2–CH2OH Propanol Propan-2-ol Alcohol, Phenol & Ether (CH3)3COH 2-Methyl-propan-2-ol Ethan-1, 2-diol 1.  Isomerism Shown by Alcohols Alcohol may show chain, position and functional isomerism. For example, 1. Butan-1-ol and 2-Methylpropan-1-ol are chain Rack your Brain isomers. 2. Propan-1-ol and Popan-2-ol are position isomers. 3. Benzyl alcohol and Anisole are functional isomers. General Methods of Preparation Alcohols are mainly prepared by following methods: From alkanes (R–H): (Only by tertiary alkanes) KMnO /OH− R3C − H ⎯⎯⎯⎯⎯⎯→ 4 R3C − OH KMnO /OH− (CH3 )3 C − H ⎯⎯⎯⎯⎯⎯→ 4 (CH3 )3C − OH 2−methyl Tertiary butyl alcohol Previous Year’s Ǫuestions propane (2−methylpropan−2−ol) ⚫ Here pink colour of KMnO4 disappears as the reaction proceeds forward. From haloalkanes (R–X): Alkyl halides on hydrolysis by aqueous alkali like NaOH, KOH or moist Ag2O, give alcohols by substitution reaction as follows: R − X + AgOH(aq) or KOH(aq) ⎯⎯⎯→ R − OH + AgX or KX CH3Br + AgOH(aq) or KOH(aq) ⎯⎯⎯→ CH3OH + AgBr or KBr ⚫ This method is suitable only for the production of primary alcohols as secondary alkyl halides give a mixture of alcohol and alkene. Tertiary alkyl halides give only alkenes. Alcohol, Phenol & Ether For example, (CH ) CHBr ⎯⎯KO⎯H(⎯aq)⎯→ CH 3 2 ( 3) CHOH + CH − CH = CH + KBr + H O 3 2 2 2 Iso−proylbromide Isopropylalcohol Propene (2−halide) 2. From ether (R–O–R): Ethers, on hydrolysis by dilute acids, produce Concept Ladder alcohols. S R − O − R + H.OH ⎯⎯dil⎯.H2⎯O4⎯, ⎯→2R − OH For example, S CH − O − CH + H.OH ⎯⎯dil⎯.H2⎯O4⎯, ⎯→2CH − OH 3 3 3 Dimethyl ether Methanol ⚫ If alkyl groups are different, two types of alcohols will be formed. For example, S C H − O − C H + H O ⎯⎯dil⎯.H2⎯O4⎯, ⎯→C H − OH + C H OH 2 5 3 7 2 2 5 3 7 Ethylproyl ether Ethanol Pr opyl alcohol From grignard reagent: Preparation of primary, secondary and tertiary alcohols using Grignard reagent is the ideal method Grignard reagent reacts with carbonyl compounds to form an intermediate compound, which on hydrolysis, gives alcohol. ⚫ Formaldehyde when reacted with Grignard reagent gives primary alcohol while the other aldehydes give secondary alcohols. Ketones Previous Year’s Ǫuestions give tertiary alcohols. Alcohol, Phenol & Ether tertiary alcohols 3.  Grignard reagent also reacts with oxirane (Epoxy ethane) to give alcohol as follows: Grignard reagent on reaction with Ethyl formate gives 2°-alcohols and with other esters give 3°-alcohols as follows. By the reduction of carbonyl compound (R–CHO and R–CO–R): Carbonyl compounds on reduction by reducing agents like LiAlH4, NaBH4, Zn/HCl or H2/ Ni, produce alcohols. ⚫ Aldehydes on reduction, give primary alcohols as shown: Concept Ladder R − CHO + H ⎯⎯⎯Ni⎯⎯→ R − CH OH 2 orLiAlH4 2 Pr imary alcohol For example, CH CHO + H ⎯⎯⎯⎯Ni ⎯⎯→ CH CH OH 3 2 orNa/C2H5OH 3 2 Ethanal Ethanol platinum, palladium, nickel ⚫ Ketones on reduction, give secondary alcohols. R − CO − R'+ H ⎯⎯⎯Ni⎯⎯→ R CHOH 2 orLiAlH4 2 Alcohol, Phenol & Ether For example, CH − CO − CH + H ⎯⎯⎯Ni⎯⎯→ (CH ) CHOH 3 3 2 orLiAlH4 3 2 Pr opan−2−one Pr opan−2−ol 4. By the reduction of acids and acid derivatives (R– COOH, R–COX, R–COOR): Concept Ladder These undergo reduction into alcohols with the help of reducing agents like LiAlH4 B2H6/T.H.F The reduction of aldehydes, or NaBH4 as follows: O || /T R − C− OH ⎯⎯BH⎯3 ⎯HF⎯→ R − CH OH H2O/H+ 2 O || R − C− OH + 4[H] ⎯⎯LiA⎯lH4⎯→R − CH2 OH + H2O Here, R may be H, CH3, C2H5 etc. For example CH 3COOH + 4[H] ⎯⎯LiA⎯lH4⎯→ CH 3 CH2 OH+ H3O Ethanol O Rack your Brain || R − C− Cl+ 4[H] ⎯⎯⎯LiA⎯lH4⎯⎯→R − CH OH+ HCl Cuo.CuCr2O4 2 Acidchloride Alcohol For example, LiAlH CH3COCl + 4[H] ⎯⎯⎯4⎯→ CH3CH2OH + HCl Acetyl chloride O || R − C− OR'+ 4[H] ⎯⎯⎯LiA⎯lH4⎯⎯→ R − CH OH+ R'− OH CuO.CuCr2O4 2 Ester For example, CH 3COOC H2 +54[H] ⎯⎯LiA⎯lH4⎯→ 2C2H5OH Ethyl acetate Previous Year’s Ǫuestions In case a group is also present along with –COOH or –COOR groups and we use NaBH4 Alcohol, Phenol & Ether then reduction occurs at group mainly. Aldehyde (2) Ketone (3) Alkene (4) Acid 5.  From primary amines: Primary amines react with nitrous acid Concept Ladder (NaNO2 + HCl) to give alcohols R–CH2NH2 + HNO2 ⎯⎯⎯→ R–CH2OH + N2 + H2O Example, (I) CH3NH2 + HNO2 ⎯⎯⎯→ CH3OH + N2 + H2O (II) (CH3)2 CHNH2+ HNO2 ⎯⎯⎯→ (CH3)2CHOH+N2+H2O It is not a good method for 1°-alcohols as alkenes and R–X are also formed here with R–OH. By hydrolysis of esters: Esters on hydrolysis by dilute acid or alkali, gives alcohol as follows: O O || || R − C− R'+ NaOH(aq) ⎯⎯⎯→ R − C− ONa + R'− OH Rack your Brain Example, O O || || CH3 − C− OC2H5 + NaOH ⎯⎯⎯→ CH3 − C− ONa+ C2H5OH Ethyl acetate Sodiumacetate O O || || R − C− OR'+ HOH ⎯⎯d⎯ ⎯⎯ →R − C− OH + R'− OH il ute aci d Example, Previous Year’s Ǫuestions O O || || KC H O+ LiAlH4 CH3 − C− OC2H5 + H2O ⎯⎯⎯→ CH3 − C− OH + C2H5 − OH 3 ether Alcohol, Phenol & Ether Ethyl acetate Acetic acid Industrial preparation: Alkenes undergo hydrolysis to form alcohols acetone by following Markovnikov’s addition. 6. Indirect hydrolysis: Here alkenes are hydrolyzed by dilute acid like H2SO4 into alcohols as follows: CH − CH = CH + H SO ⎯⎯⎯→ CH − CH − CH H.SO ⎯⎯H.O⎯H⎯→CH − CH − CH OH + H SO 3 2 2 4 3 2 2 4 3 2 2 2 4 Pr opene Pr opanol Direct hydrolysis: It occurs according to Markovnikov’s rule and here rearrangement occurs in case of less stable carbocation. Rack your Brain Example, S R − CH = CH + H.OH ⎯⎯dil⎯.H2 ⎯O4⎯→R − CHOH − CH What is the final product when 2 3 carboxylic acid and esters are reduced by BH3? Oximercuration and demercuration of alkenes: Alkenes undergo oximercuration by mercuric acetate in presence of tetrahydrofuran (THF) and water followed by reduction by NaBH4 (demercuration) to give alcohols according to Markovnikov’s rule. Here no rearrangement is made if C+ is less stable. Alcohol, Phenol & Ether R may be H, CH3, C2H5 etc. 7.  Oxo process: Here aldehyde is formed when an alkene in presence of cobalt carbonyl, is treated with CO and H, which on reduction with Ni or Zn- Cu gives alcohol. It is called carbonylation hydroformylation. Example, Some specifc preparations Methyl Alcohol (CH3OH) CH + O ⎯⎯⎯Cu⎯−tu⎯be⎯⎯→CH OH 4 2 ,200atm300C 3 CO + H + H ⎯⎯ox⎯ides⎯of⎯Cu,Zn⎯⎯→CH OH ––2 2  3 Previous Year’s Ǫuestions Water gas ⚫ The fractional distillation of pyroligneous acid (obtained by distillation of wood) gives CH3OH. ⚫ Pyroligneous acid has 0.1%–0.5% CH COCH 3 3 (56°C), 1%–3% CH3OH (64°C), 6%–10% CH3COOH. ⚫ Acetic acid can be removed in the form of calcium acetate precipitate when pyroligneous acid is treated with calcium hydroxide. The liquor having acetone and methyl alcohol on Alcohol, Phenol & Ether fractional distillation gives methyl alcohol as acetone is removed first as it is more volatile than methylalcohol. 8. Synthesis using sugar: The formation of ethanol is processed by fermentation of sugars present in molasses. The molasses with an initial sugar content of around 20 % is diluted to nearly 10 to 20 % of its original volume by adding H2O. Small amount of conc. Concept Ladder H2SO4 and yeast is then added. The solution is fermented for 2 to 3 days and 298 K to produce ethanol as shown below: C H O + H O ⎯⎯Inv⎯ert⎯ase⎯→C H O + C H O 12 22 11 2 in yeast 6 12 6 6 12 6 barley, Sugar Glucose Fructose C H O ⎯⎯Zy⎯ma⎯ s e ⎯→2C H OH + 2CO  6 12 6 in yeast 2 5 2 Glucose Synthiesis using starch: Starchy substances are treated with steam and malt (a source of diastase) to prepare ethyl alcohol as shown below: O 2(C H O ) + nH O ⎯⎯dia⎯sta⎯se⎯→nC H O ⎯⎯H2 ⎯ye⎯ast⎯→ 2C H O 6 10 5 n 2 12 22 11 Maltase 6 12 6 Starch Maltose Glucose C H O ⎯⎯⎯ ⎯ ⎯→2C H OH + 2CO  Zy mas e 6 12 6 in yeast 2 5 2 Glucose Physical Properties of Alcohol ⚫ Lower alcohols (ethanol, methanol) are sweet smelling liquids and colourless. Previous Year’s Ǫuestions ⚫ Higher alcohols are odourless, colourless, waxy solids. ⚫ Due to formation of intermolecular H- bonding with H2O molecules, alcohols are highly soluble in water when present in any proportion,. ⚫ Boiling points of alcohols are greater than alkyl halides or corresponding ethers due to presence of intermolecular H-bonding in Alcohol, Phenol & Ether alcohols. For example, C2H5OH > CH3OCH3 or C2H5X 9.  Chemical Properties of Alcohols Alcohols give the following type of reactions: Reactions with cleavage of O–H bond: Concept Ladder The acidic nature of alcohols is exhibited by these reactions. They do not give H+ in aq. solution as they are less acidic than water. Reaction with metals: Alcohols reacts with alkali metals like Na and K for the formation of metal alkoxides which further react with haloalkanes to form ethers. Example, 2CH3 − OH + 2Na ⎯⎯⎯→ 2CH3 − ONa + H2  Sodiummethoxide CH3ONa + C2H5Cl ⎯⎯⎯→ CH3 − O − C2H5 + NaCl Methyl ethyl ether Rack your Brain Ester formation: Esters are formed when alcohols reacts with acids and acid derivatives as follows: of tertiary alcohols. Why? R'− OH + R − COOH ⎯⎯dil⎯.ac⎯id ⎯→R − COOR'+ H 2O Example, O O || || CH3 − C− OH + HO − C2H5 ⎯⎯⎯→ CH3 − C− OC2H5 + H2O Ethylacetate Mechanism: Alcohol, Phenol & Ether 10. 11.  Here –OH is removed from R–COOH and ‘H’ is removed from R–OH. In it R–OH acts as a Concept Ladder nucleophile. Reactivity order: (1) HCOOH > CH3COOH > C2H5COOH (2) CH OH > C H OH > C H OH > 3 2 5 3 7 Reaction with Grignard reagent: Alkanes are formed on reacting alcohols with Grignard reagent. R − OH + R'MgX ⎯⎯⎯→ R'H + R − OMgX For example, C2H5 − OH + CH3MgBr ⎯⎯⎯→ CH4 + C2H5 − OMgBr Reaction with Carbonyl Compounds: An alcohol reacts with a carbonyl compound Rack your Brain for formation of Ketal or acetal as follows: Tert. Reaction Due to–OH Group (Cleavage of C–OH type) Previous Year’s Ǫuestions Reaction With HX: Here, alkyl halide is formed when alcohol reacts with HX. (SN1 Reaction Mainly) Alcohol, Phenol & Ether R − OH + HX ⎯⎯An⎯hy.⎯ZnC⎯l2⎯→R − X + H 2O C 2H5OH + HBr ⎯⎯An⎯hy.⎯ZnC⎯l2⎯→C 2H5Br + H 2O 12. ⚫ For this case the reactivity order of alcohols is tertiary > secondary > primary. Concept Ladder ⚫ For this case the reactivity order of HX is HI > HBr > HCl > HF the Reaction with PX , PX , SOCl : 5 3 2 R − OH + PX ⎯⎯ ⎯→R − X + POX + HX  5 3 Major For example, C H − OH + PCl ⎯⎯ ⎯→C H Cl + POCl + HCl 2 5 5 2 5 3 3R − OH + PX ⎯⎯ ⎯→3R − X + H PO 3 3 3 For example, 3C2H5 − OH + PCl 3 ⎯⎯⎯ → 3C2H5Cl + H3PO 3 Rack your Brain R − OH + SOCl 2 ⎯⎯Pyr⎯idin⎯e ⎯→R − Cl + SO 2 + HCl C H − OH + SOCl ⎯⎯Pyr⎯idin⎯e ⎯→C H Cl + SO + HCl rapidly with HX? 2 5 2 2 5 2 ⚫ Here pyridine refluxes the gaseous byproducts HCl and SO2. This method is known as Dorzen’s method. ⚫ An alcohol cannot give such reactions with Cl2 or S2Cl2. Reaction with NH3: Previous Year’s Ǫuestions When an alcohol reacts with NH4 over heated alumina, a primary amine is obtained along with 2° and 3° amines. R − OH + NH ⎯⎯A⎯Ol2⎯3 →R − NH + H O 3 350C 2 2 ⎯⎯R−⎯OH⎯→R NH ⎯⎯R−⎯OH⎯→R N R − NH 2 −H2O 2 −H2O 3 2 3 Alcohol, Phenol & Ether Example, C H OH + NH ⎯⎯A⎯Ol2⎯3 → C H NH + H O 2 5 3 350C 2 5 2 2 13.  Reaction of R–OH: Complete alcohol molecule is involved in these reaction. Dehydration: Concept Ladder Alcohols can be dehydrated into ethers or alkenes depending upon the temperature, amount of alcohol and nature of the dehydrating agent used. Some common dehydrating agents are conc. H3PO4, conc. H2SO4, Al2O3 etc. (1) Ether is formed for excess of alcohols, H2SO4 is the dehydrating agent and the temperature is 140°C. R − OH + H SO ⎯⎯100⎯−⎯110⎯C⎯→RHSO + H O 2 4 4 2 RSHO + R − OH ⎯⎯140⎯C⎯→ R − O − R + H SO 4 2 4 For example, C H − OH + H SO ⎯⎯100⎯−⎯110⎯C⎯→C H HSO + H O 2 5 2 4 2 5 4 2 Ethylhydrogensulphate C H HSO + C H − OH ⎯⎯140⎯C⎯→ C H − O − C H + H SO 2 5 4 2 5 2 5 2 5 2 4 Diethyether (2) An alkene is formed for excessive H2SO4 at 170°C. C H − OH + H SO ⎯⎯100⎯−⎯110⎯C⎯→C H HSO + H O 2 5 2 4 2 5 4 2 Ethyl hydrogensulphate C H HSO ⎯⎯170⎯C⎯→C H + H SO 2 5 4 2 4 2 4 Ethene Rack your Brain CH − OH + H SO ⎯⎯100⎯−⎯110⎯C⎯→ CH HSO + H O 3 2 4 3 4 2 Methyl hydrogensulphate 3° alcohols? ⚫ Here -carbon atom having less no. of H atom removes -hydrogen atom, to give a Alcohol, Phenol & Ether more stable alkene as a major product, in accordance with Saytzeff rule. 14. Example, (3) When on heated alumina (Al2O3), vapours of alcohol are passed over, following changes occur: At 250°C ether is formed R − OH + R − OH ⎯⎯Al2⎯O3⎯→R − O − R + H O Rack your Brain 250C 2 Example, 2C H OH ⎯⎯Al2⎯O3⎯→ C H − O − C H + H O 2 5 250C 2 5 2 5 2 ⚫ Three different types of ethers are formed When both the alcohols are different. Example, CH OH + C H OH ⎯⎯Al2⎯O3⎯→ CH − O − CH + C H − O − C H + CH − O − C H + H O 3 2 5 250C 3 3 2 5 2 5 3 2 5 2 At 350°C alkene is formed C H OH ⎯⎯Al2⎯O3⎯→ C H + H O 2 5 250C 2 4 2 Dehydrogenation (Cu/300°C): It is a test for the detection of all three Previous Year’s Ǫuestions alcohols i.e. primary, secondary and tertiary as they give different products at 300°C on reaction with copper. Alcohol, Phenol & Ether 15.  Oxidation: It is a test which gives different products Concept Ladder on oxidation of different alcohols as primary secondary & tertiary alcohols. (a) Primary alcohols on oxidation with K2Cr2O7 or KMnO4 give acids which have the same number of carbon atoms, as the parent alcohol. [O]acidicKMnO R − CH2OH ⎯⎯⎯⎯− ⎯⎯4⎯→ R − CHO H2O RCHO ⎯⎯[O]⎯aci⎯dic⎯KM⎯nO4⎯→R − COOH Acid CH CH OH ⎯⎯[O]⎯aci⎯dic⎯KM⎯nO4⎯→CH − CHO ⎯⎯[O]⎯ac⎯ ⎯ ⎯ ⎯→CH COOH i dic KM nO4 3 2 −H2O 3 3 Acetic acid The colour of the solution disappears on proceeding oxidation reaction which is imparted by the oxidizing agent. Rack your Brain (b) Ketones are formed when secondary alcohols are oxidized, which on further oxidation give acids with one carbon atom less than the parent alcohol, under drastic conditions by strong oxidizing agents like HNO3. (c) Like in previous point, tertiary alcohols cannot undergo oxidation by mild oxidizing agents. However, they forms an acid with two carbon atom less than the parent alcohol by oxidizing Alcohol, Phenol & Ether under drastic conditions by strong oxidizing agents. 16. Test For Primary, Secondary and Tertiary Alcohols Lucas Method: Rack your Brain A mixture of conc. hydrochloric acid and anhydrous zinc chloride is called as Lucas reagent. ⚫ The reactivity of alcohols towards Lucas reagent follows the order: tertiary > secondary > primary. ⚫ R − CH OH ⎯⎯Lu⎯cas⎯era⎯gen⎯t ⎯→ No reaction in cold conditions 2 Pr imary alcohol ⚫ R 2CH2OH ⎯⎯Lu⎯cas⎯rea⎯gen⎯t⎯→ Formation of ppt. after 5–10 minutes. Secondary alcohol ⚫ R 3C.OH ⎯⎯Lu⎯cas⎯rea⎯gen⎯t⎯→ An oily layer (turbidity) is formed at once in cold Tertiary alcohol e.g., (CH )COH ⎯⎯Lu⎯cas⎯rea⎯gen⎯t⎯→ (CH ) C.Cl 3 3 3 3−butylchloride(whiteppt.) Victor Mayer method: Here, all three primary, secondary & tertiary alcohols give different colours on undergoing a set of reactions. Alcohol, Phenol & Ether 17. 18. Some Facts about Alcohols ⚫ Alcohols show position, chain and functional Concept Ladder isomerism, For ex. CH3OCH3 and C2H5OH are functional isomers. ⚫ R–OH + ceric ammonium nitrate Red colour ⚫ CH3OH is called wood sprit or carbinol. (60% CH3OH). ⚫ Ethanol is also known as grain alcohol. ⚫ 100% ethanol is absolute alcohol. ⚫ Power alcohol is 20% ethanol + 80% gasoline. It is used as fuel in motor vehicles. ⚫ Rectified spirit is 95.47% ethanol + 4.53% ⚫ water. ⚫ Isopropyl alcohol is also known as rubbing alcohol. ⚫ Commercial ethanol is deleberately made unfit for human consumption as liquor by Rack your Brain mixing it with methanol or petrol. (Denatured or methylated sprit.) ⚫ Tendency of alcohols to form H-bonds: primary > secondary > tertiary. ⚫ Order of R–OH to form ester with inorganic acids follows the order: tertiary > secondary > primary. ⚫ A mixture of 95.57% C2H5OH and 4.43% water boils at constant temp., i.e., an azeotropic mixture. ⚫ Wine ⎯⎯ox⎯idat⎯ion⎯→ Sour C2H5OH open CH3COOH ⚫ Both the hydrates shown below are stable Previous Year’s Ǫuestions due to intramolecular H-bonding and electron withdrawing groups. Alcohol, Phenol & Ether 19.  Ethylene Glycol Ethane 1, 2 diol or ethylene glycol is a dihydric alcohol. Previous Year’s Ǫuestions Methods of preparation: Ethane-1, 2-diol is prepared by the following methods: From ethylene oxide or oxirane On reduction, any aldehyde gives From ethylene ⚫ Ethylene glycol is formed on hydroxylation of ethylene by Baeyer’s reagent. Prileschaiev Reaction Alcohol, Phenol & Ether 20. From ethylene diammine: Glycol is formed when ethylene diammine re- acts with nitrous acid. By hydrolysis of vicinal dihalides From glyoxal Concept Ladder From ketones Ketones can be converted into diols as follows: Example : Physical properties of ethylene glycol ⚫ Ethylene glycol is a clear, sweet, slightly viscous liquid. Rack your Brain ⚫ It is soluble in ethanol and water. Alcohol, Phenol & Ether ⚫ The B.P. of glycol is 470 K. ⚫ Ethylene glycol is highly poisonous; animals or humans that drink the solution become very ill and may die. 21.  Chemical properties of ethylene glycol Reaction with sodium Concept Ladder glycol Reaction with PCl5 or SOCl2 Reaction with HNO3 (Nitration) Rack your Brain Reaction with HCl Oxidation: Previous Year’s Ǫuestions Glycol on oxidation by different reagents gives different products. For example, ⚫ Glycol gives oxalic acid on reacting with HNO3. Alcohol, Phenol & Ether 22. ⚫ Glycol is formed when glycol reacts with copper. Concept Ladder ⚫ Formic acid is formed when glycol reacts with acidic KMnO4. Oxidation By Periodic Acid (HIO4): When 1,2 di-ols are oxidised by (CH3OCO)4Pb or HIO4 1, 2 glycol splitting occurs to give alde- hydes or ketones or both. Rack your Brain e.g., Alcohol, Phenol & Ether 23.  Dehydration: Different producta can be formed by dehy- dration of glycol as given below: ⚫ At 500°C Rack your Brain ⚫ Glycol reacts with concentrated sulphuric acid to yield 1,4-dioxane. ⚫ Glycol reacts with boric acid to yield diethylene glycol. PO HO − CH − CH − OH + HO − CH − CH − OH ⎯⎯Co⎯nc.H⎯3 4⎯⎯→ 2 2 2 2 ⚫ Glycol reacts with ZnCl2 to yield ethanal. Acetylation: Glycol on acetylation by acetic anhydride or acetic acid or acetyl chloride gives glycol di ace- tate. Previous Year’s Ǫuestions Uses of ethylene glycol Alcohol, Phenol & Ether 1. In manufacturing dioxane and Dacron. 2. As a solvent and as a preservative. 3. As an anti-freeze in automobile radiators. 4. As an explosive in the form of dinitrate. 5. As a cooling agent in aeroplanes. 24. Glycerol or Glycerine Glycerol is an example of trihydric alcohol. Concept Ladder Glycerol may be considered obtained by replacement of Method of preparation of glycerol: Glycerol is prepared as follows: By saponifcation: The process by which oils and fats are hy- drolyzed to give glycerol and salt of higher fatty acids, is known as saponifcation. Here, R may be: C H (Olein), C H (Steric), C H Rack your Brain 17 33 17 35 15 31 (Palmitis) From propene: By propene, glycerol can also formed as follows: Synthesis of glycerol: Glycerol is synthesized by the following method: Previous Year’s Ǫuestions Alcohol, Phenol & Ether 25.  Physical properties of Glycerol ⚫ Due to presence of greater extent of H-bonding Concept Ladder in glycerol, it becomes more viscous than other alcohols. ⚫ Similarly due to greater extent of hydrogen ⚫ Bonding, glycerol has highest boiling point ⚫ Among alcohols (290°C). ⚫ Glycerol is soluble in water and is a colourless ⚫ oily liquid. ⚫ Glycerol is hygroscopic in nature. Chemical properties of Glycerol Reaction with sodium Rack your Brain ⚫ Due to non acidic nature of hydrogen, reaction at -carbon atom does not take place. Reaction with PCl5 Acetylation by CH3COCl or (CH3CO)2O ⚫ Here the formation of glycerol triacetate confirms that glycerol has 3 –OH groups present on different carbon atoms. Previous Year’s Ǫuestions ⚫ Alcohol, Phenol & Ether If (CH3CO)2O is used in place of HCl, acetic acid is formed. 26. Reaction with HNO3: On adding glycerol, concentrated nitric acid Concept Ladder and concentrated sulphuric acid in the propor- tion of 1 : 3 : 5 respectively and also on heating, glycerol trinitrate is formed. ⚫ Glycerol trinitrate is a poisonous, yellow in colour, oily liquid and causes headache. ⚫ It releases large volume of gases on explosion. Glycerol trinitrate ⎯⎯⎯→ 12CO2 + 10H2O + 6N2 + O2 ⚫ When absorbed on kieselguhr, it becomes a safer explosive. In this form, it is called Rack your Brain dynamite. ⚫ Cordite-like explosives and blasting-gelatin can also be prepared from glycerol trinitrate. Dehydration: Glycerol on heated with dehydrating agents like P2O5 or KHSO4, acrolein is obtained which has a characteristic of bad pungent odour. Previous Year’s Ǫuestions Reaction with Oxalic acid: Different products are formed under different KC H O+ LiAlH conditions. 3 ether ⚫ Formic acid is formed at 110°C with excess of Alcohol, Phenol & Ether oxalic acid. acetone 27.  ⚫ It is a lab method to prepare formic acid and it can be formed in a good amount. ⚫ Allyl alcohol is formed, at 220°C. Reaction with benzaldehyde: Acetals are fromed on reacting glycerol with benzaldehyde. Concept Ladder Reaction with HI : ⚫ Allyl iodide is formed by warming glycerol with a small amount of HI. Previous Year’s Ǫuestions ⚫ 2-iodopropane is formed, when HI is in excess Alcohol, Phenol & Ether reaction proceeds further. 28.  Rack your Brain Reaction with HCl or HBr : When HCl is passed through glycerol at 110oC, both  and  glycerol monochlorohydrins are formed. If the HCl gas is passed for sufcient time, glycerol-, ’-dichlorohydrin and glycerol , -di- chlorohydrin are formed. Oxidation : Depending on the nature of oxidizing agent, glycerol gives different products. Different Oxidizing Agents ⚫ Dilute nitric acid oxidizes glyceric acid from glycerol. Previous Year’s Ǫuestions ⚫ Concentrated nitric acid oxidizes glycerol to tartonic acid and glyceric acid. ⚫ Bi(NO3)3 reacts with glycerol to give meso oxalic acid. ⚫ Fenton’s reagent (H2O2 + FeSO4) or Br2/H2O Alcohol, Phenol & Ether in the presence of Na2CO3 oxidises a mixture of dihydroxy acetone (or glyerose) and glyceraldehyde from glycerol. ⚫ Solid KMnO4 oxidizes glycerol into oxalic acid and carbon oxide. This reaction is explosive. 29.  Reaction with HiO4 : Formaldehyde and formic acid are formed by glycerol which undergoes oxidative cleavage by HIO4 (periodic acid). Tests of glycerol Acrolein test Glycerol ⎯⎯KH⎯OS⎯4 → Acrolein ⎯⎯To⎯llen⎯'sr⎯eag⎯ent⎯→ Silver mirror (Blackprecipitate) Dunstan test A drop of HPH + 5ml borax ⎯⎯⎯→Pink colour ⎯⎯Gly⎯Drops ⎯ ⎯→NoPink colour cer ol Phenol + Glycerol + conc.H SO ⎯⎯⎯⎯→ Redcolour 2 4 130C Rack your Brain Uses of glycerol Glycerol finds its application in various field as listed below: ⚫ It is used as sweetening agent in beverages, confectionary & medicines being non-toxic in nature. ⚫ It is used as lubricant in watches. ⚫ It is used as a preservative ⚫ In the preparation of printing inks, non-drying inks and stamp pad inks. ⚫ In the manufacture of synthetic fibres and Previous Year’s Ǫuestions plastics. ⚫ In the preparation of good quality soap, vanishing creams, hand lotions, tooth pastes and shaving creams. ⚫ Dynamite is a mixture of Kieselguhr and Alcohol, Phenol & Ether glycerol. 30. Phenols Dihydroxy derivatives of benzene Phenol or Carbolic Acid ⚫ Phenol is a hydroxy derivative of benzene and, Rack your Brain hence, is known as hydroxybenzene. ⚫ Runge discovered Phenol during coal tar distillation in the middle oil fraction. ⚫ Phenol is antiseptic, acidic, and can also be used as a disinfectant. ⚫ It is insoluble in aqueous NaHCO3 but soluble in aq. NaOH and KOH, while benzoic acid, are ⚫ soluble in KOH, NaOH and aq. NaHCO3. ⚫ On reacting with aq. FeCl3, it forms a violet coloured product (C6H5O)3Fe. Methods of Preparation Previous Year’s Ǫuestions From middle oil fraction of coal tar distillation: The middle oil fraction mostly contains naphthalene (neutral) and phenol (acidic). The mixture is dissolved in sodium hydroxide, in which Naphthalene is insoluble and phenol is soluble. The aqueous solution on acidifcation gives phe- nol. Lab method (1) —COOH C H SO H ⎯⎯Na⎯OH⎯→C H SO Na ⎯⎯Na⎯OH⎯→C H OH + Na CO 6 5 3 Fuse 6 5 3  6 5 2 3 Alcohol, Phenol & Ether Commercial process or Dow’s method 31.  From benzene diazonium chloride Rack your Brain carbonyl group in Dakin reaction? From grignard reagent From salicylic acid Industrial method (From cumene) Physical Properties of Phenol 1. It is a deliquescent, crystalline solid with melting point and boiling point of 42°C and 182°C Previous Year’s Ǫuestions respectively. 2. Due to presence of H-bonding it is soluble in water. 3. Phenol attains a pink colour on exposure to light and air. Alcohol, Phenol & Ether Chemical Properties of Phenol Electrophilic subsitution: It is easier and takes place at a higher rate than in benzene the –OH group in phenol is highly ring activating. 32. Halogenation Concept Ladder developed in 1877, to attach ring. These are of two types Nitration Rack your Brain ⚫ A mixture of para and ortho nitrophenol, can be separated by steam distillation because of chelation, o-nitrophenol is volatile in steam. Sulphonation Previous Year’s Ǫuestions Freidal–Craft reaction Alcohol, Phenol & Ether 33.  Reduction Concept Ladder Reaction due to OH group 1. Salt formation 2. Acidic nature: Due to the formation of phenoxide ion (resonance stablised) phenol is weakly acidic in nature. Rack your Brain 3. Ether formation C6H5OH + CH2N2 ⎯⎯⎯→ C6H5OCH3 + N2 Anisole C H ONa + ClCH ⎯⎯⎯→ C H OCH + NaCl 6 5 3 6 5 3 C H OH + (CH ) SO ⎯⎯KO⎯H⎯→C H OCH + CH HSO 6 5 3 2 4 6 5 3 3 6 C H OH + (C H )SO ⎯⎯KO⎯H⎯→C H OC H + C H HSO 6 5 2 5 4 6 5 2 5 2 5 4 (phenatol) 4. Acetylation 5. Benzoylation (Schotten – Baumann reaction) Alcohol, Phenol & Ether 34. 6. Fries migration 7. With Ammonia Previous Year’s Ǫuestions 8. Reduction 9. With P S 2 5 5C6H5OH + P2S5 ⎯⎯⎯→ 5C6H5SH + P2O5 Other reactions 1. With B.D.A.C. (Benzene diazonium chloride) 2. Kolbe’s reaction 3. Reimer Tiemann Reaction 4. Condensation with formaldehyde: Phenol on condensation with HCHO gives Ba- kelite (Resin) Alcohol, Phenol & Ether 35.  5. Condensation with Phthalic anhydride: Phenol on condensation with phthalic anhy- Concept Ladder dride gives Phenolphthalein (Dye and indicator) 6. Oxidation: Phenol on oxidation by different oxidants gives different products as follows: Rack your Brain Name the reaction used in the treatment of phenol with chloroform in the presence of ⚫ Both are antioxidants free radicals inhibitors aqueous base? usde in photography as developes because of strong reducing agent. Test of Phenol 1. C 6H 5OH ⎯⎯Fe⎯Cl3 ⎯→Violet colour product(C6 H5O) 3Fe Alcohol, Phenol & Ether 2. Liebermann’s Nitroso Reaction C H OH ⎯⎯⎯N⎯aNO⎯2 ⎯⎯→ Red ⎯⎯⎯NaO⎯H⎯⎯→ Bluecolouration 6 5 inexcessofH2O2 Excess colouration 3. Phenol gives a blue coloured product on treacting with ammonia and sodium hypochlorite. 36. Ethers (R–O–R ) ⚫ These are aryl or dialkyl derivatives of water, having a general formula C H O. which contain one divalent oxygen n 2n+2 ⚫ In simple ethers, both the aryl or alkyl groups ⚫ are same. ⚫ For ex. C6H5–O–C6H5, C2H5–O–C2H5, ⚫ In mixed ethers, the two aryl or alkyl groups ⚫ are different. For example, Methyl-ethyl ether, CH3–O–C6H5 Nomenclature of Ethers Ethers are named as alkoxy alkane. For exam- ple C2H5–O–C2H5, CH3–O–CH2–CH2–CH3 Ethoxy ethane Methoxy propane Rack your Brain CH3–CH2–O–CH2CH(CH3)2 Ethoxy 2-methyl propane Isomerism Shown by Ethers ⚫ Ethers are functional isomers of ethers and alcohols themselves show metamerism. For example, C2H5–O–C2H5 and CH3–O–CH2–CH2–CH3 are metamers. C6H5–CH2–OH and C6H5–O–CH3 are functional isomers. Previous Year’s Ǫuestions Methods of Preparation Williumson synthesis: Alcohol, Phenol & Ether It is the best method for preparation of all type of ethers, i.e. simple, aromatic or mixed. ⚫ Here for ether formation, alkyl halides in presence of magnesium, are treated with sodium alkoxide. 37.  ⚫ The attack on R–X by R–O–, occurs from the Concept Ladder rear side, i.e. it involves SN2 mechanism. Mechanism R − X + R'− ONa ⎯⎯,M⎯g ⎯→R'− O − R + NaX R − OH + Na ⎯⎯⎯→ R − ONa + H+ R − ONa ⎯⎯⎯→ R − O− + Na+ R − O− + R '− X ⎯⎯ ⎯ → (R − O R '− X) ⎯⎯X⎯ → R '− O − R + Br− Unstabletransitionstate Example, C 2H 5− ONa+ C H2 Br5 ⎯⎯,M⎯g ⎯→2C H 5 − O − C2 H5 + NaBr Sodiumethoxide Diethyl ether ⚫ In case of tertiary halides, there is formation of an alkene takes place. Rack your Brain Ex., From R–X: When an aryl or alkyl halide is treated with dry silver oxide, ether is formed as follows: 2 R − X + Ag2O ⎯⎯⎯→R − O − R + 2 AgX Examples, 2C H Br + dry Ag O ⎯⎯ ⎯→C H − O − C H + 2AgBr 2 5 2 2 5 2 5 CH Br + C H Br + Ag O ⎯⎯ ⎯→CH − O − CH + C H − O − C H + CH − O − C H 3 2 5 2 3 3 2 5 2 5 3 2 5 From alcohols: Alcohols on dehydration, give ethers, depend- Previous Year’s Ǫuestions ing upon the amount of alcohol used and the temperature condition employed. Alcohol, Phenol & Ether (a) By dehydration of alcohols using concentrat- ed sulphuric acid at 140°C, ethers are formed as follows: 38.  R − OH + H SO ⎯⎯ ⎯→R − HSO + H O 2 4 4 2 R − HSO + R − OH ⎯⎯⎯⎯→ R − O − R + H SO (1) 4 140C 2 4 C H − OH + H SO ⎯⎯ ⎯→C H − HSO + H O 2 5 2 4 2 5 4 2 C H − HSO + C H − OH ⎯⎯⎯⎯→ C H − O − C H + H SO 2 5 4 2 5 140C 2 5 2 5 2 4 (b) At 250°C when vapours of an alcohol are passed over alumina or thoria, an ether is formed. Concept Ladder R − OH + R − OH ⎯⎯Al2⎯O3⎯→R − O − R + H O 250C 2 Example, C H − OH + C H − OH ⎯⎯Al2⎯O3⎯→ C H − O − C H + H O 2 5 2 5 250C 2 5 2 5 2 Diethyl ether ⚫ Three different types of ether are formed, by using two different alcohols R − OH + R '− OH ⎯⎯Al2⎯O3⎯→ R − O − R + R '− O − R '+ R − O − R '+ H O 250C 2 By alkoxy mercuration-demercuration: Previous Year’s Ǫuestions By the help of trifluoro mercuricacetate (mer- curation) followed by reduction with NaBH4 (de- mercuration), alkenes undergo alkoxylation with alcohols. nucleophilic According to Markovnikov’s rule, addition can takes place here as follows: Example, (3) Acetamide (4) Methyl acetate CH − CH − CH = CH ⎯⎯Hg⎯(OC⎯H3C⎯O2)⎯→CH − CH − CH = CH ⎯⎯NaB⎯H4⎯→CH − CH − CH = CH 3 2 2 CH OH 3 2 3 2 3 2 3 | | | OCH3 HgOAc OCH3 From grignard reagent Alcohol, Phenol & Ether R − O − CH2X + X'Mg − R' ⎯⎯⎯→ R − O − CH2 − R'+ X − Mg − X' C2H5 − O − CH2Cl + Br = Mg − C2H5 ⎯⎯⎯→ C2H5 − O − CH2 − CH2 − CH3 + MgBrCl Methoxy propane 39.  Synthesis of methoxy ethers: For formation of methoxy ethers, alcohol is Concept Ladder treated with diazomethane. R − OH + CH N ⎯⎯HB⎯F4⎯→R − OCH + N 2 2 3 2 Diazomethane Physical Properties of Ethers ⚫ First 2 members of the ether family, i.e. diethyl ether and dimethyl ether are solids rest are liquids. Some aromatic ethers are solid. ⚫ Ethers have a lower B.P.s than their corresponding isomeric alcohols, as they do not from H-bond like alcohols. For example, C2H5OH > CH3–O–CH3. ⚫ Ethers are partially soluble in water beacause of formation of H-bonds with water as shown below: Rack your Brain ⚫ Ethers are weak Bronsted bases or Lewis bases, as the central atom O, has 2 lone pair of electrons to donate and it can accept H+ ion also. ⚫ Because of presence of lone pair of electrons on O atom, ethers have some value of dipole moment. Previous Year’s Ǫuestions Alcohol, Phenol & Ether 40. 41.  Chemical Properties of Ethers Concept Ladder Ethers have inertness like alkanes. In nor- mal conditions they are stable towards bases, hydrogenation, dil.acids etc. This is because of the fact that (—O—) does not have any a five site like –OH group. Peroxide formation: In the presence of light and ether can form peroxides. On heating these peroxides hydro per- oxides, they will explode. C H − O − C H ⎯⎯O2⎯→ CH − CH − O − CH − CH 2 5 2 5 hr 3 2 3 | O− O − H ethoxy ethyl hydroperoxide It is a free radical reaction occuring at adjacent C-atom to O-atom. Previous Year’s Ǫuestions ⚫ When a small volume of ether is shaked with aq. KI solution, if peroxide is present the colour of the solution disappears. ⚫ By washing ether with FeSO4 solution followed by addition of KCNS it can be made free from peroxide ion. − Fe+2 ⎯⎯oxide ⎯ ⎯→Fe3+ ⎯⎯3C⎯NS⎯→ Fe(CNS)3 Pe r BloodRedcolour Reaction with lewis acids: (2) Ether are bases hence they can react with Lewis acids to form an adduct as follows: (3) Alcohol, Phenol & Ether 42. Formation of oxonium salts: Ethers being lewis bases (due to 2 lp elec- Rack your Brain trons) Can easily react with cold concentrated inarganic acids to form stable oxonium salts. Reaction with sulphuric acid With dilute sulphuric acid: Concept Ladder When ethers are heated with dil. H2SO4, give alcohols. For two type of alcohols are to be formed, mixed ethers are used. S R − O − R + H − OH ⎯⎯dil⎯.H2 ⎯O4⎯→ 2R − OH Examples, S C 2H 5− O − C H2 +5H − OH ⎯⎯dil⎯.H2 ⎯O4⎯→ 2C2 H5 − OH S R − O − R'+ H − OH ⎯⎯dil⎯.H2 ⎯O4⎯→R − OH + R'− OH Examples, S CH − O − C H + H − OH ⎯⎯dil⎯.H2 ⎯O4⎯→ CH − OH + C H − OH 3 2 5 3 2 5 If temp. is kept low, oxonium salt is formed. C H OC H + H SO ⎯⎯⎯→[(C H ) OH]+HSO− 2 5 2 5 2 4 2 5 2 4 With hot and conc. H2SO4: The products alkene and alcohols are formed as ethers undergo elimination and is mainly given by secondary and tertiary ethers. Example, Alcohol, Phenol & Ether Rack your Brain Explain how formation of peroxide 43.  Reaction with halogen acids: Ethers can be cleaved when treated with HBr Concept Ladder or HI as follows: R − O − R + H − X ⎯⎯dil⎯.&c⎯old⎯→R − X + R − OH R − OR + 2H − X ⎯⎯⎯⎯ ⎯⎯→ 2R − X + H O treated with ether, alcohols Hot & amount 2 ⚫ The order of reactivity for halogen acids are as follows: HI > HBr > HCl. C H − OC H + HI ⎯⎯ ⎯ → C H OH + C H I 2 5 2 5 cold 2 5 2 5 C H − OC H + 2HI ⎯⎯ ⎯ → 2C H I + H O 2 5 2 5 2 5 2 Hot ⚫ When a mixed ether is used in above reaction, X– is taken with smaller alkyl group. Example, C H − OCH + HI ⎯⎯ ⎯→C H − OH + CH I Rack your Brain 6 5 3 6 5 3 Anisole CH 3I ⎯⎯Ag⎯NO3⎯→ AgI Yellowppt ⚫ The above method is known as Zeisel method. It is used to find the no. of alkoxy groups in an ether. ⚫ Cyclic ethers can be cleaved by increasing the temperature to 100°C by heating. Example, Previous Year’s Ǫuestions Alcohol, Phenol & Ether Here, because of formation of a stable ter- tiary carbocation, I– is reacted with a large alkyl group. 44.  When this reaction is carried out with anhyd. HI in ether, the reaction forms are as Concept Ladder follows: HI (CH3 )3 C − OCH3 ⎯⎯ether ⎯ ⎯→CH3I + (CH3 )3COH get mixture of three ethers. + As protonation of C6H5OR gives. Here, C6H5 − O− R | H bond is weaker than C6H5–O bond because of presence of resonance and double bond character in O–C6H5. It means X– attacks on weak O–R bond to give R–X. Previous Year’s Ǫuestions Acylation by R–COCl or (R–CO)2O: Esters are formed when ethers are treated with acid anhydrides or acid chlorides in presence of anhyd. ZnCl2. A mixture of esters is formed by using a mixed ether as a reactant. O || O || anhy. ZnCl − R C− Cl + R − O − R ⎯⎯⎯⎯⎯2 ⎯→R − C− OR + R − Cl Example, O || O || anhy. ZnCl CH3 − C− Cl+ C2H5 − O − C2H5 ⎯⎯⎯⎯⎯2 ⎯→CH3 − C− OC2H5 + C2H5 − Cl Acetyl chloride Ethyl acetate O || Alcohol, Phenol & Ether anhy. ZnCl (R − CO)2 O + R '− O − R' ⎯⎯⎯⎯⎯ ⎯→2R − C− O − R' 2 Example, O || Anhy. ZnCl (CH3 − CO)2 O+ C2H5 − O − C2H5 ⎯⎯⎯⎯⎯2 ⎯→2CH3 − C− O − C2H5 Acetic anhydride Ethyl acetate 45.  Reaction with carbon monoxide: Ethers reacts with CO to form esters as Concept Ladder follows: O || R − R − R '+ CO ⎯⎯⎯B⎯F ⎯⎯⎯→R O − R' 3 150Cunder 'P' − C− Example, O BF || C2H5 − O − C2H5 + CO ⎯⎯⎯⎯ 3 ⎯⎯⎯→ 150Cunder 'P' C H 2 5 − C− O − C2H5 Ethyl propanoate Reaction with PCl5 → 2R − Cl + 2POCl3 R − O − R + PCl 5⎯⎯ ⎯ C H − O − C H + PCl ⎯⎯ ⎯→2C H − Cl + 2POCl 2 5 2 5 5 2 5 3 R − O − R'+ PCl 5⎯⎯ ⎯→R − Cl + R'− Cl + 2POCl 3 Example, CH − O − C H + PCl ⎯⎯ ⎯→CH − Cl + C H − Cl + 2POCl 3 2 5 5 3 2 5 3 Halogenation: The reaction of ethers with chlorine are as follows: In dark Previous Year’s Ǫuestions Alcohol, Phenol & Ether 46. Electrophilic substitution reaction of aromatic ether Aromatic ethers like anisole give reactions Concept Ladder like halogenation, nitration. Bromination Nitration Alkylation Rack your Brain Acetylation Uses of Ethers ⚫ Ethers are used as anesthetic agents and solvents. ⚫ Dr William Mortan discovers the anesthetic nature of ethers. ⚫ It is used as a reaction medium in the reduction reactions of LiAlH4. Alcohol, Phenol & Ether ⚫ It is used in the prepration organo metallic compounds like R–MgX. ⚫ Polyethers (carbo–waxes) are highly solube in water beacause of multiple H-bond formation with it. ⚫ R–X can be replaced by R–OSO2R’ in Williamson synthesis. 47.  For the solubility of alcohols in water the responsible factors are : 6.1 (I) Hydrogen bonds (II) Size of the alkyl or aryl groups (III) The molecular mass of the Alcohols. Ǫ.2 By mixing alcohol with some copper sulfate and pyridine, that are used for 6.2 drinking are made unfit for human consumption, which gives the colour and a foul smell to the liquid respectively. This is called denatured alcohol. Ǫ.3 Due to the presence of chlorine (an electron-withdrawing group), 2-chloroeth- 6.3 anol becomes more acidic. This results in a negative inductive effect and thus, the electron density in the –O-H bond decreases. It stabilizes the alkoxide ion and therefore, 2-chloroethanol can easily release a proton. Pyridinium chlorochromate (PCC) can be used as reagents. The above conver- 6.4 sion shows the oxidation of primary alcohol to an aldehyde. Ǫ.5 Alcohol, Phenol & Ether For the above conversion acidified KMnO4 can be used as a reagent. The above 6.5 conversion shows the oxidation of primary alcohol to a carboxylic acid. 48. Ǫ.6 The o-nitrophenol is more volatile because of the presence of intramolecular 6.6 hydrogen bonding between NO2 and OH group. In orth-nitrophenol due to the presence of an electron-withdrawing group NO2 6.7 at ortho position, the acidic strength is enhanced and becomes more acidic. There is decrease in acidic strength due to the presence of an electron releas- ing group in o-cresol. Ǫ.8 suitable explanation. Phenol, o-nitrophenol, o-cresol o-cresol < Phenol < o-nitrophenol is the increasing order of the acidity of the 6.8 given compounds. Due to the presence of the electron-withdrawing group, NO2 o-nitrophenol becomes more acidic. Remaining has an electron releasing group which de- creases the acidic strength. Ǫ.9 primary, secondary and tertiary alcohols Alcohol, Phenol & Ether Due to the steric hindrance property of the alkyl groups and for the 6.9 hydroxyl bond there is increase in the electron density on an oxygen atom, the reactivity of sodium metal towards tertiary alcohols is lowest. Primary alcohols > secondary alcohols > tertiary alcohols is the decreasing order of reactivity of sodium metal towards alcohols. 49.  When benzene diazonium chloride is heated with H2O, Phenol is formed along 6.10 with the hydrochloric acid, nitrogen gas and by-products. The oxidation of secondary alcohol in a ketone is shown by above chemical 6.11 reaction. It can be easily achieved by using oxidizing agents like Pyridinium chlorochromate (PCC), chromic anhydride (CrO3), etc. Ǫ.12 Invertase and zymase are the names of the enzymes involved in the prepara- 6.12 tion of ethanol from sucrose by fermentation. Invertase converts sucrose into glucose and fructose. Then, glucose and fructose undergo fermentation in the presence of zymase and ethanol is produced. C12H22O11 + H2O ⎯⎯Inv⎯erta⎯se ⎯→C6H12O6+ C6H12O6 Glucose Fructose C6H12O6 ⎯⎯Zym⎯a⎯ s e → 2 C2H5OH + 2 CO2 Ǫ.13 Alcohol, Phenol & Ether In the presence of Grignard reagent, propane-2-one is treated with CH3MgBr, 6.13 followed by the hydrolysis to yield tert- butyl alcohol. 50.  In phenol the –OH group is directly attached to the sp2-hybridized carbon 6.14 atom of the benzene ring. The carbon-oxygen bond length in alkyl alcohol is greater as compared to the carbon-oxygen bond length in phenol and this is due to the partial double bond character or due to the resonance and charge distribution in phenol. Ǫ.15 The o- and p-positions in the benzene ring becomes electron-rich due to the 6.15 presence of resonance and therefore, activates it towards electrophilic sub- stitution reaction. Therefore, nucleophilic substitution reactions are not very common in phenols. O=C=O is nonpolar because in C=O bonds the dipole moment of the two is 6.16 exactly equal and opposite of each other. Hence, they cancel each other and so, the net dipole moment of O=C=O is zero. Due to steric hindrance of the alkyl group and the stability of carbocation, 6.17 the reactivity of all three classes of alcohols with conc. HCl and ZnCl 2 (Lucas reagent) differed. Alcohol, Phenol & Ether Due to least stability of 1° carbocation the primary alcohol does not show any reaction at room temperature. On heating, turbidity appears in secondary alcohol which is not shown at room temperature. Higher stability of the carbocation causes tertiary alcohol to show turbidity after addition of Lucas reagent. 51.  Phenoxide ion is prodused when phenol is treated with NaOH. It is then 6.18 undergoes electrophilic substitution with CO2 to yield salicylic acid as the ma- jor product. This is called Kolbe’s reaction. dioxide. Why? Due to high reactivity of electrophilic aromatic substitution towards phenoxide 6.19 ion, phenoxide ion is treated with carbon dioxide, instead of phenol, in Kolbe’s reaction. 6.20 Due to the electron-withdrawing effect of the phenyl ring, so by resonance, the polarity of the C—O bond in phenol decreases, the dipole moment of phe- nol is smaller than that of methanol. Di-tert-butyl ether can’t be prepared by the above given method because in 6.21 this case, elimination is more favoured over substitution. Alcohol, Phenol & Ether 6.22 Due to the repulsion between the unshared pair of electrons or the lone pair of electrons on the oxygen atom, the C—O—H bond angle in alcohols is slightly less than the tetrahedral angle. 52. Summary ⚫ LiAlH4 and NaBH4 are highly specific reducing agents which reduce different organic compounds (e.g.-acid, aldehyde, ketone, ester) to correspondign alcohol without attacking double bond. But if double bond is present in conjugation with benzene ring aldehyde group is also reduced along with —C=C— group. ⚫ C2H5OH (or grain alcohol) is present in beverages. 100% ethyl alcohol is called absolute alcohol. It is drinking alcohol. ⚫ Rectified spirit is C2H5OH (95.87%) + H2O (4.13%). ⚫ Denatured spirit is C2H5OH + 5-10% CH3OH (it is not fit for drinking). In place of CH3OH pyridinie or CuSO4 is also used to denature C2H5OH. ⚫ Power alcohol is mixture of absolute alcohol and petrol in 1 : 4 ratio with cosolvent benzene. It is used for running automobiles. ⚫ Test for alcohols : Alcohol + ceric ammonium nitrate → Pink/red colouration. ⚫ 3° alcohols are resistant to oxidation. ⚫ Alcohols can't be dried over CaCl2 because they form addition compound, CaCl2.4CH3OH with it. ⚫ Order of acidity H2O > 1° alcohol > 2° alcohol > 3° alcohol > RCH  CH > RCH3. ⚫ CH3OH is obtained by destructive distillation of wood. It is poisonous and causes permanent blindness. ⚫ Pyroligneous acid has 10% CH3COOH + CH3OH 2.5%, and CH3COCH3 0.5%. ⚫ Fusel oil is last fraction obtained during distillation of fermented alcohol. It mainly contains n-propyl alcohol, isobutyl aocohol and isoamyl alcohol. ⚫ Aqueous solution of phenol is called carbolic acid. ⚫ Phenol is obtained from middle oil fraction of coal-tar distillation. ⚫ Acidic strengths of isomeric phenols : (i) Phenols having electron withdrawing groups p > o > m. (ii) Phenols having electron donating group m > p > o. ⚫ :CCl2 is reaction intermediate o Reimer Tiemann reaction. ⚫ Crown ethers are condensation polymers of eethylene glycol. They are in fact heterocyclic ethers having at least 4 oxygen atoms. ⚫ Dynamite is glyceryl trinitrate absorbed on keiselguhr. Alcohol, Phenol & Ether ⚫ Glycerol trinitrate also known as Nobel’s oil, is a colourless, oily liquid and an inorganic ester. It is used in the treatment of asthma and pectoris. 53.