In which of the reactions, there is a migration of alkyl group to carbene `(ddot C H_2)`, i.e., rearrangement occurs ?

Options

A.
B.
C.
D.

Answer

A, B, C

Explanation

The reaction (a) is Arndt-Eistert reaction.
The reactions (b) and (c) are Wolff rearrangement reactions.
The reaction (d) is Hofmann bromamide rearrangement reaction.
It involves acylnitrene intermediate and migration if alkyl group to `N` atom occurs to form `(R - N = C = O)`
(a,b,c) involves the formation of
intermediate in which `R` migrates to carbene to form `R-CH=C=O`.