Grignard carboxylation

The following carboxylic acid can t be prepared from an alkyl halide by either the nitrile hydrolysis route or the Grignard carboxylation route. Explain. 

Which method—Grignard carboxylation or nitrile hydrolysis—would you use for each of the following reactions Explain. 

Scheme 2.2. Rugged processing for a Grignard-carboxylation-acetylation sequence.

The preparation of a carboxylic ester by a variant of the Grignard carboxylation route has been described.61 The arylmagnesium bromide is first prepared and added to an excess of diethyl carbonate, conditions which... 

In part (a), Grignard carboxylation must be used because the starting materials can t undergo Sn2 reactions. In (b), either method can be used. 

The alcohol product can be formed by reduction of a carboxylic acid with UAIH4. The carboxylic acid can be synthesized either by Grignard carboxylation or by nitrile hydrolysis. The product can also be formed by a Grignard reaction between benzyl bromide and formaldehyde. 

Grignard carboxylation can also be used to form the carboxylic acid. 

Only Grignard carboxylation can be used because CN brings about elimination of the tertiary bromide to form a double bond. 

Grignard carboxylation yields m-methylbenzoic acid, which can be converted to an acid chloride and treated with diethylamine. 

Which of the following carboxylic acids can be formed by both Grignard carboxylation and by nitrile hydrolysis ... 

The mechanism of Grignard carboxylation is similar to that of other Grignard reactions (Section 19.8). The organomagnesium halide adds to a C=0 bond of carbon dioxide in a typical nucleophilic addition reaction. Protonation of the carboxylate by addition of aqueous HCl in a separate step then gives the free carboxylic acid product. 

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