In organic chemistry, an imide is a functional group consisting of two acyl groups bound to nitrogen. [1] The compounds are structurally related to acid anhydrides, although imides are more resistant to hydrolysis. In terms of commercial applications, imides are best known as components of high-strength polymers, called polyimides. Inorganic imides are also known as solid state or gaseous compounds, and the imido group (=NH) can also act as a ligand.
Most imides are cyclic compounds derived from dicarboxylic acids, and their names reflect the parent acid. [2] 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 PubChem links gives access to more information on the compounds, including other names, ids, toxicity and safety.
| n | Common name | Systematic name | Structure | PubChem | parent acid | structure |
|---|---|---|---|---|---|---|
| 2 | Succinimide | Pyrrolidine-2,5-dione |  | 11439 | Succinic acid |  |
| 2, unsaturated, cis carbon-carbon double bonds | Maleimide | Pyrrole-2,5-dione |  | 10935 | Maleic acid |  |
| 3 | Glutarimide | Piperidine-2,6-dione |  | 70726 | Glutaric acid |  |
| 6 | Phthalimide | Isoindole-1,3-dione |  | 6809 | Phthalic acid |  |
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.
Many high strength or electrically conductive polymers contain imide subunits, i.e., the polyimides. One example is Kapton where the repeat unit consists of two imide groups derived from aromatic tetracarboxylic acids. [3] Another example of polyimides is the polyglutarimide typically made from polymethylmethacrylate (PMMA) and ammonia or a primary amine by aminolysis and cyclization of the PMMA at high temperature and pressure, typically in an extruder. This technique is called reactive extrusion. A commercial polyglutarimide product based on the methylamine derivative of PMMA, called Kamax, was produced by the Rohm and Haas company. The toughness of these materials reflects the rigidity of the imide functional group.
Interest in the bioactivity of imide-containing compounds was sparked by the early discovery of the high bioactivity of the Cycloheximide as an inhibitor of protein biosynthesis in certain organisms. Thalidomide, famous for its adverse effects, is one result 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. [4]
In the 21st century new interest arose in thalidomide's immunomodulatory effects, leading to the class of immunomodulators known as immunomodulatory imide drugs (IMiDs).
Most common imides are prepared by heating dicarboxylic acids or their anhydrides and ammonia or primary amines. The result is a condensation reaction: [5]
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. [6]
Certain imides can also be prepared in the isoimide-to-imide Mumm rearrangement.
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.
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. [7]
In chemistry, amines are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines, trimethylamine, and aniline. Inorganic derivatives of ammonia are also called amines, such as monochloramine.
In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula R−C(=O)−NR′R″, where R, R', and R″ represent any group, typically organyl groups or hydrogen atoms. The amide group is called a peptide bond when it is part of the main chain of a protein, and an isopeptide bond when it occurs in a side chain, such as in the amino acids asparagine and glutamine. It can be viewed as a derivative of a carboxylic acid with the hydroxyl group replaced by an amine group ; or, equivalently, an acyl (alkanoyl) group joined to an amine group.
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group attached to an R-group. The general formula of a carboxylic acid is R−COOH or R−CO2H, with R referring to the alkyl, alkenyl, aryl, or other group. Carboxylic acids occur widely. Important examples include the amino acids and fatty acids. Deprotonation of a carboxylic acid gives a carboxylate anion.
In chemistry, an ester is a compound derived from an acid in which the hydrogen atom (H) of at least one acidic hydroxyl group of that acid is replaced by an organyl group. Analogues derived from oxygen replaced by other chalcogens belong to the ester category as well. According to some authors, organyl derivatives of acidic hydrogen of other acids are esters as well, but not according to the IUPAC.
Phthalic anhydride is the organic compound with the formula C6H4(CO)2O. It is the anhydride of phthalic acid. Phthalic anhydride is a principal commercial form of phthalic acid. It was the first anhydride of a dicarboxylic acid to be used commercially. This white solid is an important industrial chemical, especially for the large-scale production of plasticizers for plastics. In 2000, the worldwide production volume was estimated to be about 3 million tonnes per year.
In organic chemistry, an imine is a functional group or organic compound containing a carbon–nitrogen double bond. The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bonds. Imines are common in synthetic and naturally occurring compounds and they participate in many reactions.
In organic chemistry, an acyl chloride is an organic compound with the functional group −C(=O)Cl. Their formula is usually written R−COCl, where R is a side chain. They are reactive derivatives of carboxylic acids. A specific example of an acyl chloride is acetyl chloride, CH3COCl. Acyl chlorides are the most important subset of acyl halides.
In organic chemistry, an acyl halide is a chemical compound derived from an oxoacid by replacing a hydroxyl group with a halide group.
The Hofmann rearrangement is the organic reaction of a primary amide to a primary amine with one fewer carbon atom. The reaction involves oxidation of the nitrogen followed by rearrangement of the carbonyl and nitrogen to give an isocyanate intermediate. The reaction can form a wide range of products, including alkyl and aryl amines.
An organic acid anhydride is an acid anhydride that is an organic compound. An acid anhydride is a compound that has two acyl groups bonded to the same oxygen atom. A common type of organic acid anhydride is a carboxylic anhydride, where the parent acid is a carboxylic acid, the formula of the anhydride being (RC(O))2O. Symmetrical acid anhydrides of this type are named by replacing the word acid in the name of the parent carboxylic acid by the word anhydride. Thus, (CH3CO)2O is called acetic anhydride.Mixed (or unsymmetrical) acid anhydrides, such as acetic formic anhydride (see below), are known, whereby reaction occurs between two different carboxylic acids. Nomenclature of unsymmetrical acid anhydrides list the names of both of the reacted carboxylic acids before the word "anhydride" (for example, the dehydration reaction between benzoic acid and propanoic acid would yield "benzoic propanoic anhydride").
The Gabriel synthesis is a chemical reaction that transforms primary alkyl halides into primary amines. Traditionally, the reaction uses potassium phthalimide. The reaction is named after the German chemist Siegmund Gabriel.
A peroxy acid is an acid which contains an acidic –OOH group. The two main classes are those derived from conventional mineral acids, especially sulfuric acid, and the peroxy derivatives of organic carboxylic acids. They are generally strong oxidizers.
In chemistry, aminolysis (/am·i·nol·y·sis/) is any chemical reaction in which a molecule is lysed by reacting with ammonia or an amine. The case where the reaction involves ammonia may be more specifically referred to as ammonolysis.
The chemical element nitrogen is one of the most abundant elements in the universe and can form many compounds. It can take several oxidation states; but the most oxidation states are -3 and +3. Nitrogen can form nitride and nitrate ions. It also forms a part of nitric acid and nitrate salts. Nitrogen compounds also have an important role in organic chemistry, as nitrogen is part of proteins, amino acids and adenosine triphosphate.
Phthalimide is the organic compound with the formula C6H4(CO)2NH. It is the imide derivative of phthalic anhydride. It is a sublimable white solid that is slightly soluble in water but more so upon addition of base. It is used as a precursor to other organic compounds as a masked source of ammonia.
N-Hydroxysuccinimide (NHS) is an organic compound with the formula (CH2CO)2NOH. It is a white solid that is used as a reagent for preparing active esters in peptide synthesis. It can be synthesized by heating succinic anhydride with hydroxylamine or hydroxylamine hydrochloride.
Metal amides (systematic name metal azanides) are a class of coordination compounds composed of a metal center with amide ligands of the form NR2−. Amide ligands have two electron pairs available for bonding. In principle, they can be terminal or bridging. In these two examples, the dimethylamido ligands are both bridging and terminal:
In coordination chemistry and organometallic chemistry, transition metal imido complexes is a coordination compound containing an imido ligand. Imido ligands can be terminal or bridging ligands. The parent imido ligand has the formula NH, but most imido ligands have alkyl or aryl groups in place of H. The imido ligand is generally viewed as a dianion, akin to oxide.
The inorganic imides are compounds containing an ion composed of nitrogen bonded to hydrogen with formula HN2−. Organic imides have the NH group, and two single or one double covalent bond to other atoms. The imides are related to the inorganic amides (H2N−), the nitrides (N3−) and the nitridohydrides (N3−•H−).
α,β-Unsaturated carbonyl compounds are organic compounds with the general structure (O=CR)−Cα=Cβ-R. Such compounds include enones and enals. In these compounds the carbonyl group is conjugated with an alkene. Unlike the case for carbonyls without a flanking alkene group, α,β-unsaturated carbonyl compounds are susceptible to attack by nucleophiles at the β-carbon. This pattern of reactivity is called vinylogous. Examples of unsaturated carbonyls are acrolein (propenal), mesityl oxide, acrylic acid, and maleic acid. Unsaturated carbonyls can be prepared in the laboratory in an aldol reaction and in the Perkin reaction.
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