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3/22/2012 ARYL HALIDES installment payments on your displacement reactions of diazonium salts ARYL HALIDES Basic formula: Ar–X where By = Farreneheit, Cl, Bayerischer rundfunk or My spouse and i Examples Structure:? C-X bonds are short and more robust Bond C-Cl C-Br Ar-X 1 . 69 A° 1 .

86 A° R-X 1 ) 77 1 . 91? Dipole moments happen to be unusually small. Bond C-Cl Preparation: 1 ) electrophilic fragrant substitution – useful only when one system is obtained C-Br Ar-X 1 ) 7 M 1 . six D R-X 2 . 15 D installment payments on your 15 G? Dipole occasions may block out depending on the angles of the molecule. 1 3/22/2012 PHYSICAL REAL ESTATE:?

Boiling points – just like those of alkyl halides, same trends? Shedding point – Among disubstituted aryl dihalides, para isomer has abnormally high MP, ~70 – 100 °C higher than ortho and meta isomers? Solubility behavior – insoluble in water, soluble in non-polar organic solvents – para isomer is less soluble than ortho or meta in a given solvent? can be readily purified by recrystallization Consider: REACTIONS: 1 . Electrophilic aromatic substitution (EAS) – remember directing electricity (o, p director) but ring is deactivated toward EAS. installment payments on your

Nucleophilic Perfumed Substitution (NAS or SNAr) ipso substitution? an atom or group other than They would is changed in the reaction Reaction Mechanisms For EM: A. BIMOLECULAR DISPLACEMENT: addition-elimination mechanism, takes place under mild conditions ***the aromatic ring must contain strongly electron – pulling out or electron – attracting groups a couple of 3/22/2012 Findings: 1 . Element effect (Bunnett): Aryl halides do not present much difference in reactivities toward NAS via bimolecular displacement. 2 . Aryl fluorides are many reactive. II. Addition , fast associated with the tungsten-halogen as X- is not the rate deciding step. M. The Benzyne Mechanism: Elimination-addition mechanism , occurs underneath forcing or perhaps vigorous conditions Evidence to get the benzyne mechanism: 1 . scrambling of the label , reaction system: 2 . benzyne cannot type if the two ortho positions are busy by other groups several 3/22/2012 D. Wurtz-Fittig Response 3. O-bromoanisole and m-bromoanisole give the same product within the reaction circumstances. ANALYSIS: 1 ) Chemical tests: Test Reagent Br2/CCl4 KMnO4 AgNO3 Result (-) (-) (-)

VARIOUS OTHER REACTIONS OF ARYL HALIDES 1 . Metallation Reactions pertaining to aryl halides without reactive groups Grignard Reaction: 2 . IR Spectroscopy C-X absorptions lie inside the fingerprint place? not useful for analysis 1000 – 1350 cm-1 C – Farreneheit str. 750 – 850 cm-1 C – Craigslist str. five-hundred – 680 cm-1 C – Br str. 2 hundred – 500 cm-1 C – We str. Important peak frequencies 1500, 1600 cm-1 3000 – 3100 cm-1 perfumed C – C str. aromatic C – L str. Response with Li (symbol) Metal: Transmetallation – the majority of successful with ArBr and ArI some