Question

Grignard reagents and organolithium compounds on addition to dry ice separately, followed by hydrolysis gives:
A. ketones and carboxylic acids, respectively
B. carboxylic acids and ketones, respectively
C. only carboxylic acids
D. only ketones

Answer 1

Hint: Electronegativity of the compound is the main focus of this question. Finding the same would help us determine which one of them, i.e., Grignard reagents or organolithium compound, gives us the required compound. The question is from chapter Aldehydes, Ketones, and Carboxylic acids.

Complete step by step answer:
Grignard Reagent reacts with dry ice (solid $C{O_2}$) to give carboxylic acids, followed by aqueous acid work-up.
RMgX and RLi show the same type of reaction with dry ice. Now let's consider the following to determine the electronegativity to determine which of the above options fits us the best.
Lithium (EN=1.0) is less electronegative than Mg(EN=1.2), resulting in more nucleophilic compounds with organolithium than Grignard reagents.
As a result, organolithium compounds add more reactive $C{O_2}$ and less reactive resonance stabilized lithium salt of carboxylic acid; thus, formed to produce ketones. It is possible to think of $C{O_2}$as a dicarbonyl compound: $O = C = O$

Hence the correct option after the analysis is B. carboxylic acids and ketones, respectively

Note:
Students should keep in mind that, when compared with the original halide from which the Grignard reagent was prepared, the carboxylic acid contains one additional C atom.
The topic from which this question is, i.e., methods of preparation of carboxylic acid, is the one to be learned properly.


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