Question

Dehydrohalogenation of 1-chloro-1-methyl cyclopropane affords two alkenes (A and B) as products. Explain why A is the major product despite the fact that it contains the less substituted double bond.

Short answer

Alkene A is considered the major product since the double bond is present outside the 3-membered ring and, as a result, it does not suffer from angle strain.

Step-by-step solution

Identification of the double-bonded carbons

Representation of the double bond

Classification based on substitution

A is disubstituted, whereas B is trisubstituted.

Representation of the substitutions present

Stability based on angle strain

A double bond inside a cyclic ring suffers from more angle strain than a double bond present outside the ring.

Formation of the products

Here, two different elimination products are formed due to the presence of two different types of $\text{β}$hydrogens.

Representation of the reaction schemes

Though two different products are formed, alkene A is considered the major product since the double bond is present outside the 3-membered ring. As a result, it does not suffer from angle strain.