The Pinner reaction refers to the acid catalysed reaction of a nitrile with an alcohol to form an imino ester salt (

alkyl In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl is derived from a cycloa ...

imidate salt); this is sometimes referred to as a Pinner salt. The reaction is named after

Adolf Pinner Adolf Pinner (August 31, 1842 – May 21, 1909) was a German chemist. Early life and education He was educated at the Jewish Theological Seminary of Breslau, Jewish Theological Seminary at Breslau and at the University of Berlin (Phd in Chemis ...

, who first described it in 1877. Pinner salts are themselves reactive and undergo additional nucleophilic additions to give various useful products: * With an excess of alcohol to form an

orthoester In organic chemistry, an ortho ester is a functional group containing three alkoxy groups attached to one carbon atom, i.e. with the general formula . Orthoesters may be considered as products of exhaustive alkylation of unstable orthocarboxylic ...

* With

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...

or an

amine 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 Hydrogen is the chemical element wi ...

to form an

amidine Amidines are organic compounds with the functional group RC(NR)NR2, where the R groups can be the same or different. They are the imine derivatives of amides (RC(O)NR2). The simplest amidine is formamidine, HC(=NH)NH2. Examples of amidines includ ...

(di-nitriles may form

imidine In chemistry imidines are a rare functional group, being the nitrogen analogues of anhydrides and imides. They were first reported by Adolf Pinner in 1883, but did not see significant investigation until the 1950s, when Patrick Linstead and John ...

s, for instance succinimidine from succinonitrile) * With water to form an

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides a ...

* With hydrogen sulfide to form a

thionoester In organic chemistry, thioesters are organosulfur compounds with the functional group . They are analogous to carboxylate esters () with the sulfur in the thioester playing the role of the linking oxygen in the carboxylate ester, as implied by t ...

Commonly the Pinner salt itself is not isolated, with the reaction being continued to give the desired functional group (orthoester etc.) in one go. It should be appreciated that the Pinner reaction refers specifically to an acid catalyzed process, but that similar results can often be achieved using base catalysis. The two approaches can be complementary, with nitriles which are unreactive under acid conditions often giving better results in the presence of base, and vice versa. The determining factor is typically how electron-rich or poor the nitrile is. For example: an electron-poor nitrile is a good electrophile (readily susceptible to attack from alkoxides etc.) but a poor nucleophile would typically be easier to protonate than to participate in the reaction and hence would be expected to react more readily under basic rather than acidic conditions.

References

{{DEFAULTSORT:Pinner Reaction Addition reactions Name reactions

See also

References