Question

Alkyl cyanides when react with grignard reagent, the product on hydrolysis found, is

Answer 1

Nitriles reacts with Grignard reagents/organolithium reagents to produce ketones.

Strongly nucleophilic organometallic reagents add to the C≡Nbond in the same way to  aldehydes and ketones.

Reaction proceeds via an imine salt intermediate that is then hydrolysed to give the ketone product and  

addition of a Grignard to a nitrile giving the ketone.

Since the ketone is not formed until after the addition of water the organometallic reagent does not get the chance to react with the ketone product.

Nitriles are less reactive than aldehydes and ketones.

That mechanism is an example of the reactive system type.