42 E - Organic Chemistry (Mcmurry)

Question

Question: Why do you suppose it’s not possible to prepare a Grignard reagent from a bromo alcohol such as $\mathbf{4}-\mathbf{bromo}-\mathbf{1}-\mathbf{pentanol}$? Give another example of a molecule that is unlikely to form a Grignard reagent.

Step-by-Step Solution

Answer

Grignard reagent can’t be synthesized because the alcoholic group present on this alkyl halide is slightly acidic. Other molecules with no Grignard reagent can be $BrC{H}_{2}C{H}_{2}C{H}_{2}COOH$:

Step-by-Step Solution Step 1: Grignard reagents and hydronium ion reaction

Grignard reagents and hydronium ion reaction gives alkane. If a acidic group is present on alkyl halide then Grignard reagent will not form.

Step 2: Reason for no Grignard reagents synthesis

Grignard reagent can’t be synthesized because the alcoholic group present on this alkyl halide is slightly acidic and the hydrogen atom of this alcohol group reacts with Grignard's reagent. 

Step 3: Another compound with no Grignard reagents synthesis

Carboxylic acid group, alcohol, and many other groups are acidic groups. In their presence Grignard reagent can’t be synthesized so other compounds with no Grignard reagent can be $BrC{H}_{2}C{H}_{2}C{H}_{2}COOH$: