Reduction of Carboxylic Acids

The carbon atom of a carboxyl group is in a relatively high oxidation state. Reduction to a 1º-alcohol takes place rapidly on treatment with the powerful metal hydride reagent, lithium aluminum hydride, as shown by the following equation. One third of the hydride is lost as hydrogen gas, and the initial product consists of metal salts which must be hydrolyzed to generate the alcohol. These reductions take place by the addition of hydride to the carbonyl carbon, in the same manner noted earlier for aldehydes and ketones. The resulting salt of a carbonyl hydrate then breaks down to an aldehyde that undergoes further reduction.

Diborane, B₂H₆, reduces the carboxyl group in a similar fashion. Sodium borohydride, NaBH₄, does not reduce carboxylic acids; however, hydrogen gas is liberated and salts of the acid are formed. Partial reduction of carboxylic acids directly to aldehydes is not possible, but such conversions have been achieved in two steps by way of certain carboxyl derivatives. These will be described later.

مواضيع ذات صلة

Organic compounds are more soluble in water as ions

Heterocyclic aromatic compounds

Hückel’s rule tells us if compounds are aromatic

Molecular orbitals and aromaticity

The π molecular orbitals of other conjugated cyclic hydrocarbons

Benzene has six π molecular orbitals

Varying the number of electrons

Heats of hydrogenation of benzene and cyclooctatetraene

? What makes benzene special

Aromaticity

Conjugation and reactivity: looking forward to Chapter 10

The amide group