benzene Flashcards
Proof for structure
Does not form isomers when halogen subbed in (no double bonds).
X-ray diffraction says all bond lengths same.
Stability of benzene
Less exothermic when hydrogenated compared to Kelcule structure
Typical reaction with benzene
Electrophilic sub as it will not lose ring (delocalisation energy not lost)
Nitration of benzene
Conc HNO3 (base) and conc H2SO4 (acid) mix and break apart to form NO2
Amination of benzene
Sn and c. HCl reduces it, can also be hydrogenated with Ni and H2 at 170C
Bromination of benzene
Liquid Br and FeBr3 make FeBr4- and Br+. Br+ then undergoes electro sub. H+ accepted by FeBr4- to regen cat
Friedel Crafts Alkylation
Anhydrous conditions AlCl3 accepts Cl from R-Cl to form AlCl4- and R+. R+ electro sub, H+ regens catalyst
Problems with Friedal Crafts Alkylation
R donates into electron ring, meaning more R+ can attack so multiple subs (Excess benzene needed).
Friedel Crafts Acylation
ROCl used with AlCl3 cat. Cl accepted to form RC+O then electro sub, catalyst regen. The end group is electron withdrawing so ring less susceptible to attack.
Oxidation of side chain to COOH
Hot KMnO4 in alkaline conditions, all side chains to COOH
Properties of phenol
Acidic because C6H5O is stable (lone pairs delocalise into ring)
Only soluble in alkaline as O- dipole stronger dipole.
Phenol reacts with bromine
Substitutes 3 times on 2, 6, 4, because ring has e- from O donated.
Phenol reaction to form ester
Reacts with acyl chloride in alkanline solution (less likely to react when electrons are associated in ring.
Nitration of phenol
Dilute HNO3
Examples of EWG
CHO, NO2
