Question

How is an alkyl halide extended by ONE carbon?

Answer 1

We could (i) pour the Grignard reagent onto dry ice, or (ii) treat iodomethane with cyanide and hydrolyze. In each case we extend the carbon chain by 1.

Explanation:

There are many alternatives:

`H_3C-I + Mg rarr H_3C-MgI + CO_2 rarr H_3C-CO_2^(-)(MgI)^+`

`H_3C-I + N-=C^(-) rarr H_3C-C-=N + I^(-) rarr "acid hydrolysis" rarr H_3C-CO_2H`