of this research. A number of fungicides and herbicides contain the imide functionality. Examples include Captan, which is considered carcinogenic under some conditions, and Procymidone. In the 21st century new interest arose in thalidomide's immunomodulatory effects, leading to the class of immunomodulators known as immunomodulatory imide drugs (IMiDs). Preparation Most common imides are prepared by heating dicarboxylic acids or their anhydrides and ammonia or primary amines. The result is a condensation reaction: (RCO)2O + R′NH2 → (RCO)2NR′ + H2O These reactions proceed via the intermediacy of amides. The intramolecular reaction of a carboxylic acid with an amide is far faster than the intermolecular reaction, which is rarely observed. They may also be produced via the oxidation of amides, particularly when starting from lactams. R(CO)NHCH2R' + 2 [O] → R(CO)N(CO)R' + H2O Certain imides can also be prepared in the isoimide-to-imide Mumm rearrangement. Reactions For imides derived from ammonia, the N–H center is weakly acidic. Thus, alkali metal salts of imides can be prepared by conventional bases such as potassium hydroxide. The conjugate base of phthalimide is potassium phthalimide. These anion can be alkylated to give N-alkylimides, which in turn can be degraded to release the primary amine. Strong nucleophiles, such as potassium hydroxide or hydrazine are used in the release step. Treatment of imides with halogens and base gives the N-halo derivatives. Examples that are useful in organic synthesis are N-chlorosuccinimide and N-bromosuccinimide, which respectively serve as sources of "Cl+" and "Br+" in organic synthesis. Imides in coordination chemistry In coordination chemistry transition metal imido complexes feature the NR2- ligand. They are similar to oxo ligands in some respects. In some the M-N-C angle is 180º but often the angle is decidedly bent. The parent imide (NH2-) is an intermediate in nitrogen fixation by synthetic catalysts. References External links IUPAC: imides Functional groups