Background for Aldehydes and Ketones
An aldehyde contains at least one hydrogen attached to the C of a C=O (carbonyl group). A ketone contains two alkyl groups attached to the C of the carbonyl group. The carbon in the carbonyl is sp2 hybridized, has a bond angle of 120o, and is trigonal planar. Aldehydes and ketones have dipole-dipole attractions between molecules, and no hydrogen bonding between molecules. These compounds can hydrogen bond with compounds have O-H or N-H bonds. The melting points and boiling points of aldehydes and ketones are between alkanes and alcohols. Small aldehydes and ketones are soluble in water. Some compounds are very flammable.
Uses of Aldehydes and Ketones
Formaldehyde can be used to preserve dead animals. Acetone is a common fingernail polish remover and is a solvent. Acetone is very flammable. 2-Butanone (MEK, methyl ethyl ketone) is used as a solvent and paint stripper. 2-Butanone is very flammable. Benzaldehyde is an almond extract. (-)-Carvone is used as spearmint flavoring. (+)-Carvone is used as caraway seed flavoring. Vanillin is the vanilla flavoring.
IUPAC Nomenclature for Aldehydes and Ketones
For the IUPAC nomenclature, the longest continuous carbon chain is the parent compound. Number the chain so that the C-O or bond has the lowest possible number. Give the location of the C-O bond with a number for ketones. From the alkyl prefixes, use Aanal@ for aldehydes, and Aanone@ for ketones. Name and number substituents.
Common Nomenclature for Aldehydes and Ketones
A ketone is named as an alkyl alkyl ketone. Use the common prefixes (n, iso, sec, tert, neo). Alphabetize the groups.
Synthesis of Aldehydes and Ketones
Zero degree and primary alcohols are oxidized with pyridinium chlorochromate to form aldehydes. Secondary alcohols are oxidized with sodium dichromate, potassium dichromate, potassium permanganate, sodium hypochlorite, nitric acid, chromium trioxide, or pyridinium chlorochromate to ketones. Benzene reacts with aluminum chloride and an acid halide to form a ketone. Alkenes are oxidized to aldehydes and / or ketones with ozone. Acid chlorides are reduced to aldehydes with lithium aluminum tri(t-butoxy) hydride. Acid chlorides react with dialkyl lithium cuprates to yield ketones.
Reactions of Aldehydes and Ketones
Organolithium or Grignard reagents react with aldehydes or ketones, followed by acidification, produce alcohols. Aldehydes and ketones are reduced to alcohols with hydrogen and Raney nickel, lithium aluminum hydride, or sodium borohydride. Aldehydes and ketones are reduced to alkanes with amalgamated zinc (zinc treated with mercury) and hydrochloric acid in the Clemmenson reduction. Aldehydes and ketones are reduced to alkanes with hydrazine and potassium hydroxide in the Wolff-Kishner reduction. Aldehydes and ketones react with ammonia derivatives, in the presence of acid, to form imine derivatives. Aldehydes are oxidized with sodium dichromate, potassium dichromate, potassium permanganate, sodium hypochlorite, nitric acid, or chromium trioxide to form carboxylic acids.