Question

why do (R)-3-chloro-1-methylcycloprop-1-ene and 5-Bromo-1,3-Cyclohexadiene react differently with cyanide (why doesn't cyanide pass through its usual mechanism for these two products and what did you obtain these specific products)

Br CN 1. + HCN + Br" OCN NC II. it + CI CI

Answer 1

The two starting materials reacts differently with the cyanide ion. In the reaction of the cyanide ion with 5 - bromo - 1,3 - cyclohexadiene cyanide ion act as a base and lead to the elimination of hydrogen cyanide by the abstraction of the proton. However the cyanide ion act as a nucleophile in the reaction with (R) - 3 - chloro -1 methyl cycloprop -1- ene. The cyanide ion reacts differently with the two substrate because the two substrate are quite different from one another. The 5 - bromo -1,3- cyclohexadiene is an non aromatic compounds which upon elimination reaction lead to the formation of the much more stable aromatic compounds benzene. However the (R) -3-chloro -1-methylcycloprop -1-ene is an non aromatic compounds which undergo nucleophilic substitution with cyanide ion in SN​​​​​2' manner to give non aromatic substitution compound