Acid Chloride Reactions: Alcohol formation using Grignard Reagents

Acid chlorides react with Grignard reagents (RMgX) in acidic conditions (H3O+) to form tertiary alcohols:

The reaction mechanism is depicted below:

In the first step, the Grignard reagent attacks the carbonyl chloride, adding the R group to the molecule and sending the pi electrons from the double bond to the oxygen atom.

In the second step, the molecule rearranges by having the electrons from the negatively charged oxygen atom reform the double bond with the carbon atom, thereby kicking off the chloride atom.

In the third step, another Grignard reagent attacks the carbonyl chloride, adding the R group to the molecule and sending the pi electrons from the double bond to the oxygen atom (again).

In the fourth and final step, the acid work-up (H3O+) protonates the negatively charged oxygen atom.

In these examples, the "R" group represents carbon chains as small as methane (-CH3) and even as large as cyclohexanes. The "X" group refers to halogens, such as Br or Cl, with Br being the more common halogen component of Grignard reagents.

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