Lactam

From left to right, general structures of a β-lactam, a γ-lactam and a δ-lactam.

A lactam (the noun is a portmanteau of the words lactone + amide) is a cyclic amide. Prefixes may indicate the ring size: β-lactam (4-membered), γ-lactam (5-membered), δ-lactam (6-membered ring). That order in the nomenclature is because beta β, gamma γ and delta δ are the second, third and fourth letters in the alphabetical order of the Greek alphabet, respectively.

Synthesis

General synthetic methods exist for the organic synthesis of lactams.

• Lactams form by the acid-catalyzed rearrangement of oximes in the Beckmann rearrangement.
• Lactams form from cyclic ketones and hydrazoic aicd in the Schmidt reaction.
• lactams form from cyclisation of amino acids.
• In iodolactamization an iminium ion reacts with an halonium ion formed in situ by reaction of an alkene with iodine.

• Lactams form by copper catalyzed 1,3-dipolar cycloaddition of alkynes and nitrones in the Kinugasa reaction

Reactions

• Lactams can polymerize to polyamides.

See also

• β-lactam with a four-membered ring found in beta-lactam antibiotics. Penicillin, considered the most famous antibiotic, is a β-lactam antibiotic.
• Lactone, a cyclic ester.
• Caprolactam