Imide
Overview
 
In organic chemistry
Organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...

, an imide is a functional group
Functional group
In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of...

 consisting of two carbonyl
Carbonyl
In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups....

 groups bound to nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

. These compounds are structurally related to acid anhydrides. The relationship between ester
Ester
Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...

s and amide
Amide
In chemistry, an amide is an organic compound that contains the functional group consisting of a carbonyl group linked to a nitrogen atom . The term refers both to a class of compounds and a functional group within those compounds. The term amide also refers to deprotonated form of ammonia or an...

s and between imides and anhydrides is analogous, the amine-derived groups are less reactive. In terms of commercial applications, imides are best known as components of high-strength polymers.
"Imide" refers to derivatives of imide itself (NH) or its organic derivatives (RN).
Unanswered Questions
Encyclopedia
In organic chemistry
Organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...

, an imide is a functional group
Functional group
In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of...

 consisting of two carbonyl
Carbonyl
In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups....

 groups bound to nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

. These compounds are structurally related to acid anhydrides. The relationship between ester
Ester
Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...

s and amide
Amide
In chemistry, an amide is an organic compound that contains the functional group consisting of a carbonyl group linked to a nitrogen atom . The term refers both to a class of compounds and a functional group within those compounds. The term amide also refers to deprotonated form of ammonia or an...

s and between imides and anhydrides is analogous, the amine-derived groups are less reactive. In terms of commercial applications, imides are best known as components of high-strength polymers.

Nomenclature

"Imide" refers to derivatives of imide itself (NH) or its organic derivatives (RN). The organic functional group called an imide contains two acyl groups are attached to NH or NR.

Most imides are derived from dicarboxylic acid
Dicarboxylic acid
Dicarboxylic acids are organic compounds that contain two carboxylic acid functional groups. In molecular formulae for dicarboxylic acids, these groups are often written as HOOC-R-COOH, where R may be an alkyl, alkenyl, alkynyl, or aryl group...

s and their names reflect the parent acid. Examples are succinimide
Succinimide
Succinimide is a cyclic imide with the formula C4H5NO2. It is used in a variety of organic syntheses, as well as in some industrial silver plating processes.-Succinimides:...

 derived from succinic acid
Succinic acid
Succinic acid is a dicarboxylic acid. Succinate plays a biochemical role in the citric acid cycle. The name derives from Latin succinum, meaning amber, from which the acid may be obtained....

 and phthalimide derived from phthalic acid
Phthalic acid
Phthalic acid is an aromatic dicarboxylic acid, with formula C6H42. It is an isomer of isophthalic acid and terephthalic acid. Although phthalic acid is of modest commercial importance, the closely related derivative phthalic anhydride is a commodity chemical produced on a large...

. For imides derived from amine
Amine
Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are 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,...

s (vs. ammonia), the N-substituent is indicated by a prefix, e.g., N-ethylsuccinimide is derived from succinic acid and ethylamine
Ethylamine
Ethylamine is an organic compound with the formula CH3CH2NH2. This colourless gas has a strong ammonia-like odor. It is miscible with virtually all solvents and is considered to be a weak base, as is typical for amines. Ethylamine is widely used in chemical industry and organic...

.

Carbodiimide
Carbodiimide
A carbodiimide or a methanediimine is a functional group consisting of the formula RN=C=NR. Carbodiimides hydrolyze to form ureas, which makes them uncommon in nature.-Carbodiimide formation:...

s have the formula RN=C=NR, they are unrelated to imides.

The ligand
Ligand
In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...

 in coordination chemistry known as imide has the formula NH. An imide is an intermediate in nitrogen fixation
Nitrogen fixation
Nitrogen fixation is the natural process, either biological or abiotic, by which nitrogen in the atmosphere is converted into ammonia . This process is essential for life because fixed nitrogen is required to biosynthesize the basic building blocks of life, e.g., nucleotides for DNA and RNA and...

,

Properties

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 bond
Hydrogen bond
A hydrogen bond is the attractive interaction of a hydrogen atom with an electronegative atom, such as nitrogen, oxygen or fluorine, that comes from another molecule or chemical group. The hydrogen must be covalently bonded to another electronegative atom to create the bond...

ing. Unlike the structurally related acid anhydrides, they resist hydrolysis and some can even be recrystallized
Recrystallization (chemistry)
-Chemistry:In chemistry, recrystallization is a procedure for purifying compounds. The most typical situation is that a desired "compound A" is contaminated by a small amount of "impurity B". There are various methods of purification that may be attempted , which includes recrystallization...

 from boiling water.

Occurrence and applications

Many high strength or electrically conductive polymers contain imide subunits, i.e., the polyimide
Polyimide
Polyimide is a polymer of imide monomers. The structure of imide is as shown. Polyimides have been in mass production since 1955...

s. One example is Kapton
Kapton
Kapton is a polyimide film developed by DuPont which can remain stable in a wide range of temperatures, from -273 to +400 °C...

 where the repeat unit consists of two imide groups derived from aromatic tetracarboxylic acids. 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 (TM), 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
Cycloheximide
Cycloheximide is an inhibitor of protein biosynthesis in eukaryotic organisms, produced by the bacterium Streptomyces griseus. Cycloheximide exerts its effect by interfering with the translocation step in protein synthesis thus blocking translational elongation...

 as an inhibitor of protein biosynthesis in certain organisms. Thalidomide
Thalidomide
Thalidomide was introduced as a sedative drug in the late 1950s that was typically used to cure morning sickness. In 1961, it was withdrawn due to teratogenicity and neuropathy. There is now a growing clinical interest in thalidomide, and it is introduced as an immunomodulatory agent used...

, famous for its adverse effects, is one result of this research. A number of fungicide
Fungicide
Fungicides are chemical compounds or biological organisms used to kill or inhibit fungi or fungal spores. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality and profit. Fungicides are used both in agriculture and to fight fungal infections in animals...

s and herbicides contain the imide functionality. Examples include Captan
Captan
Captan is the name of a general use pesticide that belongs to the phthalimide class of fungicides. Though it can be applied on its own, Captan is often added as a component of other pesticide mixtures. It is used to control diseases on a number of fruits and vegetables as well as ornamental plants...

, which has been phased out because of its carcinogenic properties, and Procymidone
Procymidone
Procymidone is a pesticide. It is often used for killing unwanted ferns and nettles, and as a dicarboximide fungicide for killing fungi. It is a known endocrine disruptor ....

.

Preparation

Most common imides are prepared by heating dicarboxylic acids or their anhydrides and ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

 or primary amine
Amine
Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are 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,...

s. The result is a condensation reaction
Condensation reaction
A condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule. When this small molecule is water, it is known as a dehydration reaction; other possible small molecules lost are hydrogen chloride,...

:
(RCO)2O + R'NH2 → (RCO)2NR' + H2O

These reactions proceed via the intermediacy of amide
Amide
In chemistry, an amide is an organic compound that contains the functional group consisting of a carbonyl group linked to a nitrogen atom . The term refers both to a class of compounds and a functional group within those compounds. The term amide also refers to deprotonated form of ammonia or an...

s. The intramolecular reaction of a carboxylic acid with an amides is far faster than the intermolecular reaction, which is rarely observed.

Certain imides can also be prepared in the isoimide-to-imide Mumm rearrangement
Mumm rearrangement
The Mumm rearrangement is an organic reaction and a rearrangement reaction. It describes a 1,3 acyl transfer of an acyl imidate or isoimide group to an imide.The reaction is of relevance as part of the Ugi reaction....

.

Reactions

For imides derived from ammonia, the N-H center is acidic. Thus, alkali metal salts of imides are well known, a well known example being potassium phthalimide
Potassium phthalimide
Potassium phthalimide is a chemical compound of formula C8H4KNO2. It is commercially available, and usually presents as fluffy, very pale yellow crystals. It is the potassium salt of phthalimide...

. These salts 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
Hydrazine
Hydrazine is an inorganic compound with the formula N2H4. It is a colourless flammable liquid with an ammonia-like odor. Hydrazine is highly toxic and dangerously unstable unless handled in solution. Approximately 260,000 tons are manufactured annually...

 are used in the release step.

The nitrogen in imides is not very basic, which allows it to form stable compounds with halogens. Treatment of imides with halogens and base gives the N-halo derivatives. Examples that are useful in organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...

 are N-chlorosuccinimide
N-Chlorosuccinimide
N-Chlorosuccinimide is used for chlorinations and as a mild oxidant.N-Iodosuccinimide , the iodine analog of N-chlorosuccinimide, and N-bromosuccinimide , the bromine analog, are used for similar applications.-External links:...

 and N-bromosuccinimide, which respectively serve as sources of "Cl+" and "Br+" in organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...

.
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