Question

Orgo II: Aromatic Side Chain Rxns

Answer 1

\({\bf{Benzylic~Halogenation:}}\) makes use of radical rxns (think back to orgo I) to add a halogen (like chlorine or bromine) at the benzylic position

Answer 2

if we desire monohalogenation we can use NBS along w/ peroxides (ROOR) or light which will only add one halogen at the same position

this can be especially useful if we want to conduct a substitution with something like NaOEt + EtOH to substitute an O-Et for the halogen

Answer 3

Eliminations: (mostly borrowed from Orgo I)

- NaOEt can also be used for eliminations (major product will be the more substituted double bond)
- adding an acid + heat will make -OH a good leaving group by protonating it

Answer 4

Additions: (again, borrowed from Orgo I)
- adding HBr with peroxides will use a radical mechanism and add Br to the anti-markovnikov position (radical stability)
- adding HBr without peroxides will use a carbocation mechanism and add Br to the markovnikov position (carbocation stability)

Answer 5

Oxidation:

using potassium permanganate + OH- + heat + H3O+ will oxidize an alkane into a carboxylic acid group (so it's sort of like the opposite of clemmenson)

will work for double bonds, triple bonds, and existing carbonyl groups

using ozonolysis (O3, CH3CO2H) and peroxide will turn a benzene ring into a carboxyl group (the mechanism is beyond this class) while preserving the attached group.

Answer 6

Anyway, that's the end of my tutorial, I hope it was a helpful resource. Source material is Organic Chemistry 12th edition by Solomons, et. al.