91Ó°ÊÓ

Weak bases favor E1 reactions, while strong and bulky bases favor E2 reactions only.

For reaction (c), DBU is used, which is a strong and bulky base. Hence the product formed is an E2 product.

Weak nucleophiles such as water and methanol promote a mixture of both${\text{S}}_{\text{N}}\text{1}$ and E1 reactions. Strong nucleophiles such as hydroxides and ethoxides and promote a mixture of both ${\text{S}}_{\text{N}}\text{2}$and E2 reactions.

Both ethoxides and potassium cyanides are powerful nucleophiles. Hence they promote ${\text{S}}_{\text{N}}\text{2}$ reactions. Hence, ${\text{S}}_{\text{N}}\text{2}$ products are formed from reactions (a) and (b).

Keeping into account all the key points, the products with their mode of reaction are shown below:

Representation of all possible substituted products from reagent a

Representation of all possible substituted products from reagent b

Representation of all possible eliminated products from reagent c