thumb|right|150px|The general structures of nitrilium ions
A '''nitrilium''' ion is a nitrile that has been protonated, [RCNH]<sup>+</sup>, or alkylated, [RCNR′]<sup>+</sup>.<ref>IUPAC Gold Book: [http://goldbook.iupac.org/N04156.html nitrilium ions]</ref>
==Synthesis== Nitriles are only weakly basic<ref name="Clayden">{{Clayden|page=200}}</ref> and are poor nucleophiles, but they will attack very reactive electrophiles such as carbocations.<ref>{{Clayden|page=436}}</ref>
Nitrilium salts can be prepared by reacting nitriles with trialkyloxonium salts. The nitrilium ions thus formed can then be reduced to secondary amines with sodium borohydride in diglyme. This is a convenient route to secondary amines of the form RCH<sub>2</sub>—NH—R′.<ref>{{cite book |title= Advanced Organic Chemistry |url= https://archive.org/details/marchsadvancedor00smit_543 |url-access= limited |last= March |first= J. |author2=Smith, M. |authorlink= Jerry March |year= 2007 |publisher= John Wiley & Sons |location= New York |isbn= 978-0-471-72091-1 |edition= 6th |page= [https://archive.org/details/marchsadvancedor00smit_543/page/n1833 1814]}}</ref>
==As intermediates== Nitrilium ions are believed to be intermediates in the hydrolysis of nitriles,<ref>{{Clayden|page=294}}</ref> the Beckmann rearrangement, the Friedel-Crafts cyclization of amines to isoquinolines,<ref>{{cite book |title= Advanced Organic Chemistry |url= https://archive.org/details/marchsadvancedor00smit_543 |url-access= limited |last= March |first= J. |author2=Smith, M. |authorlink= Jerry March |year= 2007 |publisher= John Wiley & Sons |location= New York |isbn= 978-0-471-72091-1 |edition= 6th |page= [https://archive.org/details/marchsadvancedor00smit_543/page/n735 716]}}</ref> the Schmidt reaction with ketones,<ref>{{cite book |title= Advanced Organic Chemistry |url= https://archive.org/details/marchsadvancedor00smit_543 |url-access= limited |last= March |first= J. |author2=Smith, M. |authorlink= Jerry March |year= 2007 |publisher= John Wiley & Sons |location= New York |isbn= 978-0-471-72091-1 |edition= 6th |page= [https://archive.org/details/marchsadvancedor00smit_543/page/n1632 1613]}}</ref> and the Ugi, Ritter, Pinner and Passerini reactions.
==References== {{reflist}} {{organic-compound-stub}} Category:Nitriles