nitrenium ion

{{Short description|Class of reactive intermediate species based on nitrogen and isoeletronic with carbene}}

{{About|the positive ions|other compounds with the formula NH₂ but different charges|amino radical|and|azanide}}

{{Chembox

| ImageFile = Nitrenium-general.svg

| Section1 = {{Chembox Identifiers

| ChEBI = 29338

| ChemSpiderID = 4574106

| StdInChI=1S/H2N/h1H2/q+1

| StdInChIKey = QTLMMXDMXKCANI-UHFFFAOYSA-N

| SMILES = [NH2+]

}}

| Section2 = {{Chembox Properties

| N=1| H=2

| Formula_Charge = +

}}

| Section8 = {{Chembox Related

| OtherCompounds = NH₄⁺; NH₂⁻; N^•H₂

}}

}}

A nitrenium ion (also called: aminylium ion or imidonium ion (obsolete)) in organic chemistry is a reactive intermediate based on nitrogen with both an electron lone pair and a positive charge and with two substituents ({{chem2|R2N+}}).{{cite book|title=Reactive Intermediate Chemistry|editor1-last=Moss|editor1-first=Robert A.|editor2-last=Platz|editor2-first=Matthew S.|editor3-last=Jones|editor3-first=Maitland Jr|publisher=Wiley|date=2004|isbn=9780471233244}}{{page needed|date=September 2020}}{{GoldBookRef|file=N04146|title=nitrenium ions}} Nitrenium ions are isoelectronic with carbenes, and can exist in either a singlet or a triplet state. The parent nitrenium ion, {{chem2|NH2+}}, is a ground state triplet species with a gap of {{cvt|30|kcal/mol|kJ/mol}} to the lowest energy singlet state. Conversely, most arylnitrenium ions are ground state singlets. Certain substituted arylnitrenium ions can be ground state triplets, however. Nitrenium ions can have microsecond or longer lifetimes in water.{{cite journal|last1=de Carvalho|first1=Marcia|last2=Sorrilha|first2=Ana E. P. M.|last3=Rodrigues|first3=J. Augusto R.|date=1999|title=Reaction of aromatic azides with strong acids: Formation of fused nitrogen heterocycles and arylamines|url=http://www.scielo.br/pdf/jbchs/v10n5/a12v10n5.pdf|journal=Journal of the Brazilian Chemical Society|volume=10|issue=5|pages=415–420|doi=10.1590/S0103-50531999000500012|doi-access=free}}

Aryl nitrenium ions are of biological interest because of their involvement in certain DNA damaging processes. They are generated upon in vivo oxidation of arylamines. The regiochemistry and energetics of the reaction of phenylnitrenium ion with guanine has been investigated using density functional theory computations.{{cite journal|last1=Parks|first1=J. M.|last2=Ford|first2=G. P.|last3=Cramer|first3=C. J.|date=2001|title=Quantum chemical characterization of the reactions of guanine with the phenylnitrenium ion|journal=Journal of Organic Chemistry|volume=66|issue=26|pages=8997–9004|doi=10.1021/jo016066+|pmid=11749633}}

Nitrenium species have been exploited as intermediates in organic reactions.{{Cite journal|last1=Borodkin|first1=G I|last2=Shubin|first2=V G|date=2008-05-31|title=Nitrenium ions: structure and reactivity|url=http://stacks.iop.org/0036-021X/77/i=5/a=R01?key=crossref.7d80faaba7f35a8bbfae3e1d87e635aa|journal=Russian Chemical Reviews|volume=77|issue=5|pages=395–419|doi=10.1070/RC2008v077n05ABEH003760|bibcode=2008RuCRv..77..395B|s2cid=250845065 |issn=0036-021X|url-access=subscription}} They are typically generated via heterolysis of N–X (X = N, O, Halogen) bonds. For instance, they are formed upon treatment of chloramine derivatives with silver salts or by activation of aryl hydroxylamine derivatives or aryl azides with Brønsted or Lewis acids.{{Cite journal|last=Kikugawa|first=Yasuo|date=2009|title=Application of Stable Nitrenium Ions to Preparative Organic Chemistry|url=http://www.heterocycles.jp/newlibrary/libraries/abst/20309|journal=Heterocycles|language=en|volume=78|issue=3|pages=571|doi=10.3987/REV-08-644|issn=0385-5414|doi-access=free}} The Bamberger rearrangement is an early example of a reaction that is now thought to proceed via an aryl nitrenium intermediate. They can also act as electrophiles in electrophilic aromatic substitution.{{cite journal|title=Microwave-assisted generation of carbazolyl nitrenium cation|first=Dariusz|last=Bogdał|journal=Arkivoc|volume=2001|date=2001|issue=6|pages=109–115|doi=10.3998/ark.5550190.0002.611|doi-access=free|hdl=2027/spo.5550190.0002.611|hdl-access=free}}