Editing Imide

{{Short description|Class of chemical compounds}}
{{Distinguish|Amide|Imine}}
[[Image:Imide functional group.svg|thumb|A general linear imide functional group]]
In [[organic chemistry]], an '''imide''' is a [[functional group]] consisting of two [[acyl]] groups bound to [[nitrogen]].<ref>{{Cite book | chapter-url=http://goldbook.iupac.org/I02948.html | doi=10.1351/goldbook.I02948| chapter=Imides| title=IUPAC Compendium of Chemical Terminology| year=2009| isbn=978-0-9678550-9-7}}</ref> The compounds are structurally related to [[acid anhydride]]s, although imides are more resistant to hydrolysis. In terms of commercial applications, imides are best known as components of high-strength polymers, called [[Polyimide|polyimides]]. [[Inorganic imide]]s are also known as solid state or gaseous compounds, and the imido group (=NH) can also act as a [[ligand]].

==Examples==
Simple example is [[diacetamide]] with the formula {{chem2|HN(COCH3)2}}, formally the diacetylated derivative of ammonia. Commonly encountered imides, however, are cyclic, being derived from [[dicarboxylic acid]]s.  A common example is [[succinimide]] derived from [[succinic acid]] and ammonia.  The names of these cyclic imides reflect the parent acid.<ref>{{Cite journal|last=Martynov|first=A. V.|date=2005-12-06|title=New Approach to the Synthesis of trans-Aconitic Acid Imides | journal=ChemInform|language=en|volume=36|issue=49|pages=no|doi=10.1002/chin.200549068|issn=1522-2667}}</ref> 

Many imides are derived from primary [[amine]]s as opposed to ammonia.  These are indicated by ''N''-substituent in the prefix. For example, N-ethylsuccinimide is derived from succinic acid and [[ethylamine]]. 

:{| class="wikitable"
|+Cyclic imides.<ref>{{cite journal |doi=10.1021/cr60266a001 |title=Cyclic carboxylic monoimides |date=1970 |last1=Hargreaves |first1=Michael K. |last2=Pritchard |first2=J. G. |last3=Dave |first3=H. R. |journal=Chemical Reviews |volume=70 |issue=4 |pages=439–469 }}</ref>
|-
|+
!n!!Common name!!Systematic name!!Structure!!PubChem!!Parent acid!!Structure
|-
|2||[[Succinimide]]||Pyrrolidine-2,5-dione||[[File:Succinimide.svg|60px]]||[https://pubchem.ncbi.nlm.nih.gov/compound/11439 11439]||[[Succinic acid]]||[[Image:Succinic acid.png|120px]]
|-
|2, unsaturated, cis carbon-carbon double bonds||[[Maleimide]]||Pyrrole-2,5-dione|| [[File:Maleimide.png|120px]]||[https://pubchem.ncbi.nlm.nih.gov/compound/10935 10935]||[[Maleic acid]]||[[Image:Maleic-acid-2D-skeletal-A.svg|100px]]
|-
|3||[[Glutarimide]]||Piperidine-2,6-dione||[[File:Glutarimide.svg|90px]]||[https://pubchem.ncbi.nlm.nih.gov/compound/70726 70726]||[[Glutaric acid]]||[[Image:Glutaric acid.png|150px]]
|-
|6||[[Phthalimide]]||Isoindole-1,3-dione||[[File:Phthalimide.svg|100px]]||[https://pubchem.ncbi.nlm.nih.gov/compound/6809 6809]||[[Phthalic acid]]||[[File:Phthalic-acid-2D-skeletal.png|120px]]
|}

==Properties==
Being highly polar, imides exhibit good solubility in polar organic solvents. Unlike the structurally related acid anhydrides, they resist hydrolysis and some can even be [[Recrystallization (chemistry)|recrystallized]] from boiling water.  

The N–H center for imides derived from ammonia is acidic and can participate in [[hydrogen bond]]ing. The N-H group is weakly acidic as indicated in the case of maleimide, with a [[pKa]] estimated at 10.<ref>{{cite journal |doi=10.1139/v76-200 |title=The hydrolysis of maleimide in alkaline solution |date=1976 |last1=Barradas |first1=Remigio Germano |last2=Fletcher |first2=Stephen |last3=Porter |first3=John Douglas |journal=Canadian Journal of Chemistry |volume=54 |issue=9 |pages=1400–1404 }}</ref>

==Occurrence and applications==
Many high strength or electrically conductive polymers contain imide subunits, i.e., the [[polyimide]]s. One example is [[Kapton]] where the repeat unit consists of two imide groups derived from aromatic tetracarboxylic acids.<ref>Walter W. Wright and Michael Hallden-Abberton "Polyimides" in ''Ullmann's Encyclopedia of Industrial Chemistry'', 2002, Wiley-VCH, Weinheim. {{doi|10.1002/14356007.a21_253}}</ref> 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 [[fungicide]]s and herbicides contain the imide functionality. Examples include [[Captan]], which is considered carcinogenic under some conditions, and [[Procymidone]].<ref>Peter Ackermann, Paul Margot, Franz Müller "Fungicides, Agricultural" in ''Ullmann's Encyclopedia of Industrial Chemistry'', 2002, Wiley-VCH, Weinheim. {{doi|10.1002/14356007.a12_085}}</ref>
[[Image:Imide'.png|thumb|600 px|center|Illustrative imides, from left: [[N-ethylmaleimide|''N''-ethylmaleimide]], a biochemical reagent; [[phthalimide]], an industrial chemical intermediate; [[Captan]], a controversial pesticide; [[thalidomide]], a drug that once caused many birth defects; a subunit of [[Kapton]], a high strength polymer used to make [[space suits]].]]

In the 21st century new interest arose in thalidomide's immunomodulatory effects, leading to the class of immunomodulators known as [[immunomodulatory imide drug]]s (IMiDs).

==Preparation==
Most common imides are prepared by heating dicarboxylic acids or their anhydrides and [[ammonia]] or primary [[amine]]s. The result is a [[condensation reaction]]:<ref>{{OrgSynth|author=Vincent Rodeschini, Nigel S. Simpkins, and Fengzhi Zhangi|year=2009|title=Illustrative imide formation from amine and anhydride|volume=|pages=|collvol=11|collvolpages= 1028|prep=CV11P1028}}</ref>
: (RCO)<sub>2</sub>O + R′NH<sub>2</sub>  →  (RCO)<sub>2</sub>NR′ + H<sub>2</sub>O
These reactions proceed via the intermediacy of [[amide]]s. 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 [[amide]]s, particularly when starting from [[lactam]]s.<ref name=Sperry/>
: R(CO)NHCH<sub>2</sub>R'  + 2 [O] →  R(CO)N(CO)R'  +  H<sub>2</sub>O

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|''N''-chlorosuccinimide]] and ''N''-[[bromosuccinimide]], which respectively serve as sources of "Cl<sup>+</sup>" and "Br<sup>+</sup>" in [[organic synthesis]].

==Isoimides==
'''Isoimides''' are isomeric with imides and have the formula RC(O)OC(NR′)R″. They are often intermediates that convert to the more symmetrical imides.  Isoimides upon heating rearrange to imides:<ref name=Sperry>{{cite journal |doi=10.1055/s-0030-1260237 |title=The Oxidation of Amides to Imides: A Powerful Synthetic Transformation |date=2011 |last1=Sperry |first1=Jonathan |journal=Synthesis |issue=22 |pages=3569–3580 }}</ref>
:{{chem2|RC(O)OC(NR′)R -> [RC(O)]2NR′}}
==Related compounds==
Organic compounds called [[carbodiimide]]s have the formula RN=C=NR. They are unrelated to imides.

==References==
{{Reflist}}

== External links ==
* [https://web.archive.org/web/20120716211320/http://www.chem.qmul.ac.uk/iupac/class/oneN.html#52 IUPAC: imides]

{{Functional Groups}}
{{Authority control}}

== See also ==
* [[Inorganic imide]]

[[Category:Imides| ]]
[[Category:Functional groups]]