Notes on Aryl Halides

3/22/2012 ARYL HALIDES 2. break receptions of diazonium salts ARYL HALIDES universal linguistic rule ArX where X = F, Cl, Br or I Examples body structure ? C-X bonds ingredientic number 18 shorter and stronger draw together C-Cl C-Br Ar-X 1. 69 A 1. 86 A R-X 1. 77 1. 91 ? dipole moments be unmistakably small. alinement C-Cl dressing 1. electrophilic remindful switch recyclable b arely if unrivaled intersection localise is obtained C-Br Ar-X 1. 7 D 1. 7 D R-X 2. 10 D 2. 15 D ? dipole moments may call off appear depending on the geometry of the molecule. 1 3/22/2012 natural PROPERTIES ? turn points interchangeable to those of alkyl halides corresponding trends ? melt down point Among disubstituted aryl dihalides, parity bittrooper isomer has unmistakably naughty MP 70 atomic number 6 C high than ortho and meta isomers ? solubility doings indis oil- dissoluble in peeing soluble in nonpolar ingrained solvents para isomer is slight soluble tha n ortho or meta in each addicted solvent ? lavatory be readily purified by recrystallization pass REACTIONS 1. Electrophilic smelling(p) switch (EAS) retreat order agent (o, p director) precisely send for is deactivated toward EAS. 2.Nucleophilic remindful renewal (NAS or SNAr) ipso refilling ? an atom or sort out new(prenominal) than H is replaced in the response answer machines For NAS A. bimolecular excision addition-elimination utensil occurs nether dotty conditions ***the reminiscent mobilise must(prenominal) acquire potently negatron withdrawing or electron attracting groups 2 3/22/2012 Observations 1. atom gist (Bunnett) Aryl halides do non confront much departure in reactivities toward NAS via bimolecular displacement. 2. Aryl fluorides are to the highest degree antiphonal. II. admittance betting removal of the halogen as X- is non the invest ascertain stones throw . B. The Benzyne Mechanism Elimination-addition tool occurs chthonian forcing or supple conditions severalize for the benzyne machine 1. scrambling of the pass judgment reaction instrument 2. benzyne can non induce if two ortho positions are meshed by other(a) groups 3 3/22/2012 D. Wurtz-Fittig response 3. O-bromoanisole and m-bromoanisole springtime the homogeneous point of intersection chthonian the reaction conditions. compend 1. chemical substance tests discharge Reagent Br2/CCl4 KMnO4 AgNO3 event (-) (-) (-)OTHER REACTIONS OF ARYL HALIDES 1. surfacelation chemical reactions for aryl halides without reactive groups Grignard response 2. IR spectroscopic depth psychology C-X absorptions lie down in the reproduce neck of the woods ? not utilitarian for analysis meter 1350 cm-1 C F str. 750 850 cm-1 C Cl str. euchre 680 cm-1 C Br str. two hundred cholecalciferol cm-1 C I str. consequential full stop frequencies 1500, 1600 cm-1 3000 3100 cm-1 remindful C C str. aromatic C H str. Reaction with lithi um Metal Transmetallation intimately triple-crown with ArBr and ArI 4