Question

2, 2- Dimethyloxirane can be cleaved by:
(A) Acid
(B) Water
(C) Bromine
(D) None of these

Answer 1

Hint: The structure of 2, 2-dimethyloxirane contains a cyclopropane ring. 2, 2-Dimethyloxirane contains a heterocyclic ring in its structure. 2, 2-Dimethyloxirane also called as 1, 2-isobutylene oxide. The structure of 2, 2- Dimethyloxirane is as follows.

Complete step by step solution:-
-The ring strain is too high in cyclopropane rings when compared to cyclobutane, cyclopentane and cyclohexane.
-Because of ring strain in the structure of 2, 2-dimethyloxirane, it will undergo cleavage very easily.
-The cleavage of the 2, 2-dimethyloxirane is as follows.


-The mechanism of the cleavage of the 2, 2-dimethyloxirane is as follows.


-In the above mechanism we can see clearly that the ring cleavage is going to be initiated by an acid.
-In the first step the acid is going to form a bond with oxygen which is present in the ring and oxygen gets a positive charge because oxygen forms three bonds with the acid.
-Later the lone pair of electrons in the water molecule reacts with tertiary carbon atoms in the ring.
-Then the ring slowly destabilizes and the ring is going to cleave and forms an acyclic compound.
-Therefore the oxirane ring in 2, 2- dimethyloxirane is cleaved by the presence of an acid.

So, the correct option is A.

Note: Because of the presence of ring strain in the given molecule 2,2- dimethyloxirane, it undergoes ring cleavage easily with very small amounts of the acid. Cyclopropane has the highest strain in the ring of 114kJ/mol.