Title 10. HALOALKANES AND HALOARENES.pdf ✅

HALOALKANE AND HALOARENE From Hydrocarbon By Electrophilic Substitution Fe dark O-halotoluene (P-halotoluene) X X X + From amines by sandmeyer's reaction CH 3 2 + X CH 3 CH 3 273-278 k Benzene Diazonium Salt Where 2 2 NH + + NaNo HX N 2x + − N 2x + − Cu 2 2 X N 2 + 1 x = Cl Br • • Rate = k [Rx][Nu- ] • Inversion of Configuration takes place • Reactivity of Halides: 1°>2°>3° • Rate a strength of Nu-a • Non-polar nu-, strong nu- and hight Concentration of Nu- favour Sn2. SN2 REACTION SN1 REACTION CH 3 2 3 3 CH Br OH CH CH OH Br − − + → + • • Rate = k [Rx] • Follows First order Kinetics. • Reactivity order of Alkyl Halide: 3° (halide) > 2° (halide) > 1° (halide) • Low concentration and weak nucleophile favour SN reaction • Partial Racemisation • Rate of reaction depends on stability of Carbocation 3 3 3 3 ( ) ( ) CH CBr OH CH C OH Br− + → − + Preferred product is the alkene which hos greater no. of Alkyl group attached to it. SAYTZEFF RULE • β-Hydrogen is Involved β-Elimination C H β α     C +BH + X–       −HX  → ELIMINATION METHOD NUCLEOPHILIC SUBSTITUTION REACTION NUCLEOPHILIC SUBSTITUTION REACTION CHEMICAL PROPERTIES HALOALKANES HALOARENES ELECTROPHILIC SUBSTITUTION REACTION FITTIG REACTION X + 2Na +2Nax 2 Ether WURTZ FITTIG REACTION X + Na + R - X R Ether nu C X C Nu X δ δ − + − + − → − + Haloarene are o-4p-directing e.g. Halogenation Sulphonation Stablization of molecule by delacalization of electron Instability of phenyl cation Less reactive than alkyl Halide PREPARATIONS OF HALOALKANE FORM ALCOHOLS HALOGEN EXCHANGE 2 2 Zncl R − + → − + OH HCL R Cl H O R OH PC 5 3 − + → − + + l R Cl POCl HCl R OH SOC 2 2 − + → − + + l R Cl SO HCl From Alkane By free Radical Halogenation 2 4 3 2 2 3 4 Cl C Hv H → + + + CH Cl CH Cl CHCl Cl Addition of Hydrogen Halide Addition of Halogens C = C + HX     ← C = C H X       C = C H H +Br2 H H     ← CCl4 Vic-Dibramide B 2 2 r − − − CH CH Br SWARTS REACTION R − + → − + X NaI R I Nax 3 3 H C Br AgF AgBr H C F − + + − FROM HYDROCARBON METHODS OF PREPARATIONS PREPARATION OF HALOARENES FROM ALKENE REACTIVITY ORDER R-I > R-BR > R-CL > R-F POLARITY ORDER RF > RCL > RBR > R-F ORDER OF M.P. AND B.P. IS R-I > RBR > RCL > RF FOR SOME HALIDE GROUP 3°(HALIDE) > 2° (HALIDE) > 1° (HALIDE) PROPERTIES OF HALOALKANES PROPERTIES OF HALOARENES PHYSICAL PROPERTIES Soluble In organic solvent M.P. OF P-ISOMER> O-ISOMER TM-ISOMER ORDER OF B.P. AR-I>AR-BR> A-CL>AR-F B.P. a size of anyl group X X VINYLIC HALIDE ARYL HALIDE X Compounds containing Sp2 C-X bond Compounds containing Sp3 C-X bond BENZYLIC HALIDE X ALLYLIC HALIDE X HALOALKANE, R-X Where X = Cl, Br, F, I as size of Halogen a C-X Bond Length α 1 Bond Fnthalpy NATURE OF C-X BOND MONOHALALKANE EG. CH2X DIHALOALKANE EG. CHX2 TRIHALOALKANE EG. CX3 ON THE BASIS OF NUMBER OF HALOGEN ATOMS CLASSIFICATION