Question

In $ C{H_3}C{H_2}CON{H_2}\xrightarrow{{{P_2}{O_5}}}A\xrightarrow[{2){H^ + }/{H_2}O}]{{1)C{H_3}MgBr}}B $
Identify A and B in the reaction.

Answer 1

Hint: We need the products of the following chain reactions. Also, Grignard reagent is there. The Grignard acts as a reducing agent which is a hydride donor rather than as a carbon nucleophile. Here it is formed by the reaction of magnesium metal with alkyl or alkenyl halides. They're extremely good nucleophiles, reacting with electrophiles such as carbonyl compounds (aldehydes, ketones, esters, carbon dioxide, etc). The product A shall be a cyanide and B shall be a ketone.

Complete step by step answer
We already know that,
A Grignard reagent of Grignard compound is a chemical compound with the generic formula R−Mg−X, where X is a halogen and R is an organic group, normally an alkyl or aryl.
Here we have, $ C{H_3}MgBr,{H^ + }/{H_2}O $ as Grignard reagent.
Amides in reaction with $ {P_2}{O_5} $ ​ gives Nitriles and $ {P_2}{O_5} $ ​ is a strong reducing agent. Nitriles on reaction with Grignard reagent gives Ketones.
Thus, the reaction is as follows:
 $ C{H_3}C{H_2}CON{H_2}\xrightarrow{{{P_2}{O_5}}}C{H_3}C{H_2}C \equiv N\xrightarrow[{2){H^ + }/{H_2}O}]{{1)C{H_3}MgBr}}C{H_3}C{H_2}C(C{H_3}) = NMgBr\xrightarrow{{{H_3}{O^ + }}}C{H_3}C{H_2}COC{H_3} $
So, A and B are $ C{H_3}C{H_2}C \equiv N $ and $ C{H_3}C{H_2}COC{H_3} $ .

Note
The Grignard reaction is an organometallic chemical reaction in which alkyl, allyl, vinyl, or aryl-magnesium halides (Grignard reagent) is added to a carbonyl group in an aldehyde or ketone. Grignard reagents are formed by the reaction of magnesium metal with alkyl or alkenyl halides. They are extremely good nucleophiles, reacting with electrophiles such as carbonyl compounds (aldehydes, ketones, esters, carbon dioxide, etc) and epoxides This reaction is important for the formation of carbon–carbon bonds. THF and Diethyl Ether are both used for Grignard reactions because the Grignard reagent readily forms in them, is soluble in them and does not react with the Grignard reagent. The interesting thing about THF as it is more polar and will stabilize metal cations better. The magnesium metal used in the synthesis contains a layer of oxide on the surface that prevents it from reacting with the alkyl bromide. The pieces of metal must be gently scratched while in the ether solution to expose fresh surface area so that the reaction can commence.