Which of the following would be the best synthesis of the acid shown below?

Chemical Reaction Explanation

The image shows a series of chemical reactions. Below is the explanation of each step:

Step 1: Grignard Reaction

The first compound is an aldehyde (CH₃COCH₃), which undergoes a Grignard reaction with methylmagnesium bromide (CH₃MgBr) in an anhydrous solvent (probably ether). The Grignard reagent adds a methyl group (CH₃) to the carbonyl carbon, resulting in the formation of a tertiary alcohol (CH₃C(OH)(CH₃)CH₃).

Step 2: Substitution Reaction

The alcohol undergoes a substitution reaction with SOBr (likely sulfuryl bromide), replacing the hydroxyl group (OH) with a bromine atom (Br), yielding an alkyl bromide (CH₃CH(Br)CH₃).

Step 3: Magnesium Insertion

In this step, the alkyl bromide (CH₃CH(Br)CH₃) reacts with magnesium in dry ether, forming a new Grignard reagent, CH₃C(MgBr)CH₃. This intermediate contains a magnesium bromide group attached to the carbon atom.

Step 4: Carboxylation

The Grignard reagent undergoes carboxylation, reacting with carbon dioxide (CO₂) in the presence of water, leading to the formation of a carboxylic acid (CH₃COOH), a product of this reaction.

In summary, the series of reactions involves the creation of an alcohol, substitution to form an alkyl bromide, formation of a Grignard reagent, and finally carboxylation to yield a carboxylic acid.