Preparation of Carboxylic Acids

By now you should have seen a few reactions that produce carboxylic acids.  Let us review some of them here.  There is one new reaction at the end (Carboxylation of Grignard reagents).

Oxidation of Primary Alcohols (Review)

The treatment of primary alcohols or aldehydes with strong oxidizing reagents (Na₂Cr₂O₇ or CrO₃/H⁺) results in the formation of carboxylic acids.

Oxidative Cleavage of Alkenes

Treating alkenes with KMnO₄, results in oxidative cleavage.

Hydrolysis of Nitriles

When we discussed the chemistry of cyanohydrins, we looked at the hydrolysis of the nitrile group.

Carboxylation of Grignard Reagents

Treating a Grignard reagent or organ lithium/sodium with CO₂, followed by an acidic work up yields carboxylic acids.  The addition of nucelophiles to CO2 is similar in nature to the addition of Grignard reagents to aldehydes/ketones.

Normally dry ide (CO₂) is used since it is easier to manipulate in comparison to gaseous CO₂, and provides some cooling for the rather exothermic reaction.  Dry ice is very cold!

The mechanism is very similar to that for the addition of Grignards to aldehydes and ketones.