Haloalkanes and Haloarenes Notes PDF

For Class 22 - INEETI CUEF Mos & T8 Y 7 A I Y W = #...

For Class 22 - INEETI CUEF Mos & T8 Y 7 A I Y W = # Y = - = = = = = x Source of & Nico Pris L plane Diffused light light Polariser) polavised light I H - U 4 no........... I n Ono Y X S no -c + Xe / - - u Transition State bharat panchal 92. Chemistry Bj ⑳ # demistry g j m  HALOALKANES AND HALOARENES The halogen derivatives of aliphatic hydrocarbons are called hal alkanes p and the halogen derivatives of aromatic hydrocarbons are called as haloarenes. Haloalkanes are commonly known as alkyl halides and haloarenes as anyl halides General Formula : Alkyl Halide Ary1 Halide R-Y where R-Cullanti , X F, C, Br I Bu - , Example : CH5 - C F Chloro ethane Bromobenzene NOTE : · chlorine containing antibiotic CHLORAMPHENICOL is very effective against the treatment of typhoid fever. · chloroquine is used for the treatment of malaria. · Thyroxine is a harmone produced by our body has iodine and the deficiency of this harmone disease called "goiter a cause a CLASSIFICATION : In Aliphatic Compounds In Aromatic compounds * monohaloarenes ↳ Monohaloalkanes - GH5 -X > - F ↳ Dihaloalkane X - - - X Dihaloarenes - > * ↳ Trinalo alkanes CH2 -X Tribaloarenes > - In - X - X ↳ MONOMALOGEN COMPOUNDS CONTAINING (SPEC-XBOND) : Primary secondary Tertiary Alkyl Halide (2% Halide (2) Alkyl Halide (39 Alkyl & " R CH2-X R" R' X c Ro - - - - CH-X ins CH3 Ri Ou CHz-CH2-C CHy-CH-Cl CMs D < - - 'CH3  Allylic Halide These are the compounds in which halogen is bonded to sp> hybridised carbon next to -(double bond (C = C). Y CH2 = CH-CH2-X and ii V Benzylic Halide These are the compounds in which halogen is bonded to sp3 hybridised carbon atom next to an aromatic ring - U I 19 CHj C C - - I 2 a Halogen bonded to sp2 hybridised carbon atom : VINYL HALIDE : Halogen atom is bonded spl hybridised carbon to an atom of a carbon-carbon double bond (( = C) i) (He CH-X CH CH-l P = or = or is ARYI HALIDE X : Halogen Cl atom directly S bonded to benzene ring. N 101 - F # -Methylchlorobenzene Chlorobenzene 'CH] DIHALOALKANES ↳ Geminal dihalide Halogen atoms are attached to same carbon atom. Cl These are also known as alkylidine dihalides eg CHz-CH-P ↳ Vicinal dihalides : Halogen atom are attached to adjacent carbon atoms are also known alkylene dihalides (H2-chThese as. eg , '' IUPAC NOMENCLATURE : CHy-CHy-Bu Bromo ethane CHy-CHCH-2-chloro-2-methylpropane a  CHy CHy-in-cu-y 2 Chloro-3-methyl butane CH3 2-Chloro-2-methyl CH3-P propane CH3 CHz-C-Cy-Br. Bromo-2, 2-dimethylpropane 1 any NOTE The prefix n, iso- , neo- are used for following alkyl groups. n- CHy-CHy-CH-CH The prefixn-is used too alleys group having - continuous chain of catoms with no branching. iso-cry-CM- - iso-is used when one methyl group is attached to the next to end catom CHy-ccn-cH neo- The prefix neo - is used when two melya groups attached to next to end atom. Remember Bu Br I I I Bu I Ortho- G Ortho T T Bu X / Br II I Chlorobenzene.2-Dibromobenzene 2. 3,5 1 Tribromo benzene - metaX-meta Ortho-Dibromobenzene or Sym-Tribromo benzene para NATURE OF C-X BOND Yalogen is more electronegative than carbon. So , the is positive carbon halogen bond a polar. The carbon bond bears a small whereas the charge halogen bears a partial negative charge. St S- - - X ↳ charge x distance As the size of halogen atom increases on moving down the group , the -X bond increases and polarity of -Xbond decreases length also.  Methods ofPreparation of Halo alkanes : 1) from Hydrocarbons : By free Radical Halogenation : ni [2 Cl2 CHA + 112 Y CD + C C -C - UCI HCI - - UCI Chloroethane dichloro methane Chlor um carbon Tetrachloride. up CDy-CHg + 12 > CHy-CH2-Cl C CHy-(M2-Chi-CHy + C nixCHy-Me-(H-C-D + Chy-Cha-Ch-chy minor major > - chloro and bromo alkanes are prepared industrially by this method > - todination of alkanes is not carried out because the reaction is highly endothermic - fluorination of alkanes takes place explosively with rupture of GC bonds in higher alkanes. FROM ALKENES Alkenes give haloalkanes by electrophilic addition of halogen acids (HX) Ca Chy-Cha (H2 = +HC > - MARKOWNIKOY'S RULE : The halogen tends to attach to the carbon alom with less number of hydrogen atoms. The addition of UX to M R unsymmetrical alkenes takes. + H1 > C1-( (2 CHy-ch- = - place acc · to Markowhikov's Rule. ANTI-MARKOWNIKON'S RULE OU PEROXIDE EFFECT OR KHARASCH EFFECT The addition of HBV to unsymmetrical alkenes in the presence of an peroxide takes place according to Anti-Markownikov's Rule in which halogen tends to attach to the carbon atom with more number of hydrogen aloms. HBr Benzoyl Peroxide (Hy-(H2-(Ha-Bu CHy-CH CH2 = + in the presence of benzoyl chloride reaction takes place by free radical mechanism.  Detection of Double Bond : Addition of bromine in CCa to an alkene in discharge reddish resulting of brown colour of bromine , hence helpful in the detection of double bond. CCI 4 Che = CH + Bug > Cnz-ina (vic-dibromide Reddish ↳ u Bu Brown colourless. FROM ALCONOL By the Action of Halogen Acids · when alcohol is treated with UX , then haloalkane and water are formed R- On + UX > R-X +H 0 , 1 ↳ and 20 alcohols when treated with in the presence of UC anhydrous Zuck gives chloroalkanes this process is called , GROOVE'S PROCESS order of reactivity of UX ; UI) HBUUCHI order of reactivity of alcohols ; % >2 % 1 3 FUNCTIONS OF ANHYDROUS Zinc Chloride : I behaves as Lewis acid and easily form a coordinate bond with oxygen atom of alcoholic group (-OH). So , to bond in alcohols becomes weak and break easily. jo alcohols are very reactive So anhydrous Inck is not. They required ·. required ull readily with concentrated. DARZEN PROCESS : When alcohol is heated with thinyl chloride in pyridine alkyl chloride is obtained with Us and so presence of along , Puridine R-OH + SOC Y R C1- SOz(g)4 + H((g)9 + GUsOn + SOCk Puridine) Cls-ll + SOzg* + HCg * This method is considered as best method tor the preparation of alkyl halide from alcohol because side products are gases and easily escapable. ↳ By the action of Phosphorous Halides R-OU + PCs > R x + 4)) + - POC]  Poly Phosphorous CH5-OH PCs CH5-D · + > + 4) + Oxy chloride 3R-OU + PC3 > 3R-11 + R3PO Phosphorous Acid. Bromoalkanes and iodoalkanes are prepared only by the action of PBry and PES but pBry and Plz are not stable compounds So , in sity (means these are prepared during the reaction) by the action of red phosphorous with Br or I , 2P + 3BU2 > 20BUs 2p + 322" 2PI3 By Halide Exchange a) Finkelstein Reaction Only iodoalkanes are prepared by this method , when chloro or bromoalkanes are heated with concentrated sodium iodide in presence of acetoue. Acetone R -X + NaI > P-1 + NaX Acetone CH5 - Br + Nat > C45-I + Nack CU5-D + Nat Acetoney CqH5-I + NaCl SWARTS REACTION : The only method for the preparation of fluoroalkanes. These prepared by treating alkyl chloride or are bromide with heavy metal fluoride like UgeFe , AgF Lofs SbEy , , etc R-X + AgF YR-f + AgX GH5-Br + AgF > (45-F + AgBr. FROM SILVER SALTS OF ACIDS ↳ Hunsdiecker Rxn In this reaction , silver salts of carboxylic acids in CC4 is treated with Brz to form bromoalkanes. CC4 R-COOAg + Bu > R-BU + 102 + AgBr CJ4 ChyCOOAg + Bug > C #Br + CO2 + AgBr - METHODS OF PREPARATION OF HALOARENES :· By ElectrophilicSubstitution Aryl chloride and bromides are prepared by electro- - philic substitution of arenes with chlorine and bromine respectively in the presence of Lewis acid catalyst like iron or felly or Ally in dark. N FeX] + ux 1) + X2 dark + dark I FBUs To + Br tubr If halogen is taken in excess , then dihalo derivatives are formed + Cl To + P Fells dark , C p-Dichlorobenzene 0 Dichloro benzene Chlorination of toluene also gives a mixture of o-and p-isomers. These can be separated by distillation because they have large point difference boiling and melting point difference. CH3 i CHI To I + D fells or 2 + Fo Fe dark 'CI p-chlorotoluene O-Chlorotoluene ↳ The reaction with fluorine is violent and can not be controlled during reaction & Todoarenes are also difficult to prepare. The UI formed behave as reducing agent and causes the reaction in backward direction. So reaction is carried out in presence , of an oxidising agent like NIO , which converts UI formed into 12 I 1 + 12 > HI 10) + SHI + HI03 Y 342 + 372 Iodic Acid preparation of Avalkyls : CHIC Monochlorination CH] X + 12 no fo He ↓01 , / Benzyl chloride when excess of Ch is used , then all hydrogens are substituted. CHC12 +1 CH3 CHILL 1 I - 10) + + ( Benzo Benzyl chloride Benedichloride trichloride FROM DIAZONUM SALTS : SANDMEYER REACTION : 0-50C NaNO , + HC > NaCl + UNUz NH2 NIx- I e + UNO + HC 0 5 Diazotization - > 1 + 24, 0 Diazonium Reaction Benzene Chloride N2ts- C I CuCI Vot + HC - Toy + N + nC N2tcl- Bu - Sandweyer + HBU CuBr > Y + N+ HC RXn GATTERMANN'S REACTION : In this reaction , copper powder is used instead of Cull or CuBr N2Cl a Powder N+ nC Y + HC - + NzCl Bu CyPowder To I 1 + HBV , N2 + HC 1) + Todobenzene is prepared just by diazonium heating benzene chloride - and KI I N KI Warm , T + N2 + BALZ-SCHEMANN REACTION : method is used to prepare fluoro- This - benzene when fluorobenzene is heated with fluoroboric acid. F N2C YOT Y + HBF4 Fluoroboric [NBF fluoro Acid benzene  PHYSICAL PROPERTIES OF HALOALKANES 1) your Alkyl nalides are colourless. However , bromides and when pure iodides develop colour when exposed to light. 2) Smell : many volatile halides have sweet smell- 3 ) Nature : in nature while. haloalkanes higher halo alkanes Lower are gaseous and Halo arenes are liquid or solid in nature. Point : 4) Boiling B Pt <. Molecular mass BPt < /Branching Bot < Stability BPt of alkyl halides increases with the increase in of carbon atoms · no in alkyl group. e g. CHyll < CHsCIX(yHaCY CagC · Due to the polar nature of CXbond , Haloalkanes exert dipole - dipole interactions. Hence haloalkanes have higher boiling point compared to with same molecular mass. hydrocarbons eg CHyly Cha For given alkyl group the boiling point and densities of different · a alkyl halides are R-[ > R-Br > R-C1) R-F. This is because with the increase in atomic size the , magnitude of Van dev waal forces also increases. e.g CHy( < CHyBr < (Hy-I In alkyl halides the increase in branching decreases the boiling. This point · is because increase in decreases its surface area which branching weakens intermolecular forces · Pus [H] e g CHy-C-Br. CHy-CH2CHi-CHiBrY CHy-CH-CHi-Br Y ins ↳ In case of haloarenes, mpt is directly proportional to symmetry X Fox X X i ↓ > - solubility : halides are insoluble in water. This is because Alkyl they can neither form hydrogen bond with water nor can break hydrogen of water molecules. bonding  Properties of Naloalkanes - NUCLEOPUILIC SUBSTITUTION REACTION : CX bond in Haloalkanes is polar and nalide ion can be replaced by a stronger nucleophile. ]cEy5 * Nu + x -Nu +X since incomingnucleophile replaces the halide ion. So, the reaction is known as nucleophilic substitution reaction. 2) SN2 reaction (Unimolecular Nucleophilic Substitution) 2) SN2 reaction (Bimolecular Nucleophilic substitution) some basic stereochemical terms are : Optical activity , chirality , retention , inversion , racemization. etc · OPTICAL ISOMERISM : The compounds which the plane polarised light can rotate are said to be optically active. These optical active compounds show optical isomerism. PLANE POLARISED LIGHT : diffused · when a normal light from a light source also called light) is passed through nicol prism (polarizer) the emerging light is found , to oscillate only in one direction. This is called plane polarised light. a M 17 + L + + + - - - - - - - ~ source of Y Nicol Prism POLCPlane Diffused light light C Polariser) Polarised light ( Dextro Rotatory Compounds Those Laevo rotatory compounds compound compound. Those which rotate the plane of polarised which rotate plane of polarised light light towards right or clockwise, are towards left or anticlockwise are called called dextro rotatory ord out laevo rotatory or 1 ou-compounds 7 1 - T · X FF ---- ---- Y 2 V The angle of rotation is measured by an instrument called polarimeter. Asymmetric Carbon : It all the four substituent attached to a carbon are different, then such a carbon is called a symmetric carbon or stereocentre. such a molecule does not have a symmetry, So it is called a asymmetric. Such carbon molecule is called chiral carbon  F H e g I c C ; CHz-I-CH5 etc -. -. Br or ↳ when a compound form non superimposable mirror image. The comp - - Ound would be chiral and it will exhibit optical is omerism Bu Bu I ↓ I - C - 4 a - k - 5 Non superimposable E ↓ mirror images. OPTICAL ISOMERS : Two compounds having same molecular or more formula , same structure but differ in the rotation of plane polarised Coon light. example COO4 · : n-k-on no - c I - 4 ins ins d - lactic acid L-lactic acid optical isomers are also called enantiomers. Racemic Mixture : equimolar mixture of dextro rotatory and laevo rota - tory substance, so that net rotation of Plane Polarised light is zero is called racemic mixture. Represented by al or I Resolution : The separation of dextro rotatory (d) and laevorotatory isomers from racemic mixture is called resolution. Retention : During a reaction if the configuration of a substance and its optical rotation remains same, then it is called retention of configuration. SN2 Mechanism : R-X + 048 > R-04 + Xe Nucleophile order = 2 Molecularity = 2 It is so because the rate of reaction depends upon the concentration of both reactants i e alkyl halide. and nucleophile. H - U 4 no........... not a Ono - X > X > a I - / - 4 Transition State  - The order of reactivity in case of different halogen is (DJ-1) (HyBr > Chy() 12 > 3e - Inversion of configuration takes place, also called Walden inversion. Su-Mechanism : R - X + 048 > R-OU + XG Rate = K [R-X] molecularity = C order = 1 CH3 CH3 CHy-- Bu + one < Chs-c-on + NaB ins Enz. 1 formation of Carbocation : CH3 CH] I Slow CHy-C-Bu Ens RDs Y CBC Bo. 2 Attack of Nucleophile : CHI Chy CHI fast -on 40 k ↳ + - + 1 + one 7 X insens · Cy Chy Retention Inversion 50 % 50 % · In SN1 the order of reactivity is , 372729 · more is the stability of carbocation faster is substitution reaction , The order of reactivity for different halogen is R T)R-BUJR- C > R-F · - · Benzyl carbocation is more stabe then allyl and then allane +Y x+ Y1 Haloarenes very much less reactive towards nucleophilic substitution ↳ are Due to resonance reaction. carbon-halogen bond have partial double bond character and it becomes more difficult to break carbon halogen bond in haloarenes than in Galvalkanes. #X : pe : : : Y of  - · Action on Aqueous Naon or Kon R-X + Kon > - R-on + kX · Action onwater R-X + yon- > R-on + ux Since the nucleophile is weak only , jo alkul halide undergo this reaction. > - Action of Sodium Alcokoxide [Williamson Synthesis] R-X + RONa < R-O R- + NaX This reaction follow SE mechanism , so 1' alkyl halide is used it 20 and 30 alkyl halide is used they prefer to undergoelimination reaction and alkene is formed. CUs-ONa +CgH5-2 > C45-0-GH5 - Action of KIN : > - Action of AgCN : R-X + K(N-R- CN R-X + AgCN > R-NC > - Action of KNOC : - Action of AgNOz : R-X + KNO2 R-ONO R-X NO > - + AgNOc iR -  ELIMINATION REACTION OR DEHYDROGALOGENATION OR BELIMINATION when alkyl halide is treated with alcoholic potassium hydroxide , then hydrogen p-carbon is eliminated along with halogen. A saturated compound is changed of into unsaturated compound and alkene are formed nen + Koncal ↑ CH2 = CU + KBu +HO : NOTE & carbon : The carbon to which a functional group is directly bonded B-carbon : The carbon next to c-carbon on either side is called B-carbon if there SAYTIEFF RULE : During dehydrohalogenation reaction , are more than one B-carbon , then Hydrogen should be removed from those B-carbon which contain least number of hydrogen atom. or more substituted alkene will be the major product Ch But-2-ene 7 CHy-CH = - CH3 Ba B (Major Product) al KOU CHS-CH-CH- I Cng = C- Cha-Chy But-1-the (Minor Product III) REACTION WITH METALS : · WURTZ REACTION R-X + 2Na + X- R dryether R-R + 2NaX > + 2Na + dry C2U5-Bu Bu-C245 emers C4420 + &NaBr · FITTIG REACTION EyX + 2Na + X-E dryether Ex + 2Nax dry [- a + 2Na + u - Y emer" [OFEX + 2NaC · WURTZ-FITTIG REACTION : yether R-XX + [Nax R-Y + 2Na + X - Ey - + &Na + -Ex dryether CHy-C , Chy-Y + Call reaction with alkyl halide is magnesium metal When treated · : with magnesium metal in presence of dry ether , then an organe metallic compound (Griguard Reagent is formed. R-X + Mg > R-MgXaGriguard Reagent C245-Bu + Mg > 45 MgBr Ethyl magnesium bromide.  reactive and react with any proton donor Grighard reagents are highly to give hydrocarbons RMgX + YOU > RX + Mg on CH5MgBu + CHsOn > Clo + Mg=By CaMs- CHEMICAL PROPERTIES OF HALOARENES : - Nucleophilic Substitution Reaction a) Dow's process chlorobenzene with aqueous Noon up to 623K : on heating and 300 atm pressure , sodium phenoxide which on hydrolysis with dilute acids give phenol diu, C ONG + ot 623K Na NaOH 300 ah - The presence of electron withdrawing group like (NO) at outho and para positions increases the reactivity of haloarenes. larger the number of NO, group is faster is the reaction. - Gl OH X i) No Nao 45 , , p-nitrophenol ↳1 int No Non Cl NO i) Non , 360k NO 2, -Dinitropheas ii) u + No NO g ONY NO Warm , no , IN NO 2. 4, 6- Trinitropheno or picric Acid No No. ELECTROPUILIC SUBSTITUTION REACTION : Naloarenes undergo electrophilic substitution reactions due to benzene group is outho and para directing So the ring. Halo. , substitution takes place at or tho and para positions. Although halogroup is 'o'p' directing but it also has deacti- rating -  effect due to -I effect (-ye inductive effect). So , drastic conditions are required for electrophilic substitution reaction and these reactions are slow reactions. 1) Halogenation : D + Fees , 'C p-Dichlorobenzene o-Dichlorobenzene 2) Nitration : G %6-Nith S No conc Maso T - Chlorobenzene + UNOs cond -Nikochloro 'N82 benzene 3. Sulphonation : C Cl C p-chloro sin+ T · t 12 Sop(onc benzene sulphonic acid oochlorobenzene sulphonic acid. 4) Friedal Craft Alkylation : > St Anhydrous + - DDT) p p -Dichloro , : dipheny trichlor ethane  1) Dichloro methane : (Methylene chloride) (Hys + Ca > CH2C2 + HC Ves: 1) used as a solvent to remove paints 2) used as a solvent in pharmaceutical companies 2) Trichloromethane (Chloroform) Chicke +Ce > CHCly + UC Uses - 1) It is used in production of the freon. 2) It is used as anesthetic in cough. syrup 3) It is used as a preservative for anatomical specimens * Chloroform should be kept in air right. Because, it undergoes dark bottles atmospheric oxidation in the presence of sunlight and form a poisonous gas called as phosgene. hu CHCly + 02 > COCk + UC ohosgene 3. Triiodomethane Ciodoform) It was earlier used as an antiseptic but the antiseptic properties are due to the liberation of tree iodine and not due to iodoform itself. CHICHON + fIgtGNaOH 1 CHIstHCOONa + SNal + SH O , res: 1 : It is used to manufacture pharmaceutical products. 2) It is used as antiseptic when it , comes in contact with skin it liberates free iodine which acts as an antiseptic.. Tetrachloromethane (Carbon 4 tetrachloride) > ((p + HC CHClz + Ca Uses : 1) It is used as fire extinguisher. 2) It is used in manufacture of chloroform. 3) It is used in dry cleaning. · freons ((* + 24F > ClaFe + 2HCl Ases : used as refrigerants in refrigerator and air conditioner  Harm : These freons are responsible for the depletion of ozone layer. p , pl-Dichloro Diphenyl Trichloroethane (DDT) DDT is a colourless , tasteless and almost odourless crystalline chemical compound. · It is very effective against the mosquitos that spread malaria and live that carry typhus. is. It is not metabolised by animals : It very toxic for fishes instead it is stored in fatty tissues. - 44 a ut u - Y - 4 - x jec-e - H20 ce Is - -1 - 1 ↑