SolutionsSubstitution of Substituted Benzenes
1. Reading the table
Using the data in the nitration table (relative rate and isomer ratio), rank in order of decreasing reactivity towards nitration: chlorobenzene, phenol, nitrobenzene, toluene and benzene.
Phenol (krel = 1000) > toluene (25) > benzene (1) > chlorobenzene (0.03) > nitrobenzene (6·10−8).
2. Major products
Give the major product of the nitration of: a) toluene; b) bromobenzene; c) benzoic acid; d) trifluoromethylbenzene.
- o-Nitrotoluene (58%), with 38% of the para isomer.
- p-Bromonitrobenzene (60%), with 40% of the ortho.
- m-Nitrobenzoic acid (80%).
- m-Nitro(trifluoromethyl)benzene (91%).
3. Statistical factor
Toluene gives 58% of the ortho product and 38% of the para. Which position is more reactive?
There are two ortho positions and one para. Per position, the ortho:para rate ratio is 29:38, i.e. each para position reacts about 1.3 times faster than each ortho one.