Imido

In organic chemistry, an imide is a functional group consisting of two acyl groups bound to nitrogen. These compounds are structurally related to acid anhydrides, although imides are less reactive. In terms of commercial applications, imides are best known as components of high-strength polymers. These are an important part of organic chemistry.

Most imides are cyclic compounds derived from dicarboxylic acids, and their names reflect the parent acid. Examples are succinimide, derived from succinic acid, and phthalimide, derived from phthalic acid. For imides derived from amines (as opposed to ammonia), the N-substituent is indicated by a prefix. For example, N-ethylsuccinimide is derived from succinic acid and ethylamine. Isoimides are isomeric with normal imides and have the formula RC(O)OC(NR′)R″. They are often intermediates that convert to the more symmetrical imides. Organic compounds called carbodiimides have the formula RN=C=NR. They are unrelated to imides.

The ligand in coordination chemistry known as imide has the formula NR. Imido ligands form multiple bond to the metal. 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.

Being highly polar, imides exhibit good solubility in polar media. The N–H center for imides derived from ammonia is acidic and can participate in hydrogen bonding. Unlike the structurally related acid anhydrides, they resist hydrolysis and some can even be recrystallized from boiling water.

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