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Anionic products of the two‐electron reduction of aromatic nitriles in liquid ammonia
Author(s) -
Bilkis Isaak I.,
Vaganova Tamara A.,
Panteleeva Elena V.,
Salnikov Georgij E.,
Tananakin Andrej P.,
Mamatyuk Victor I.,
Shteingarts Vitalij D.
Publication year - 1994
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610070307
Subject(s) - chemistry , nitrile , protonation , benzonitrile , ring (chemistry) , ammonia , chemical shift , photochemistry , methanol , ion , medicinal chemistry , organic chemistry
Abstract The reduction of 9‐cyanoanthracene by two equivalents of potassium in liquid ammonia was shown to yield the 9‐cyanoanthracene dianion, whereas 1‐naptho‐ and benzonitrile gave the cyanodihydroaryl anions corresponding to the protonation of nitrile dianions at a position para to the cyano group. The 9‐cyanoanthracene dianion underwent the same transformation in the presence of a stronger protonating agent, methanol. According to 13 C NMR spectral data of the generated species, the cyano group extracts the negative charge from the π‐electronic system: ca 0·20:0·25 e in the case of the 9‐cyanoanthracene dianion and ca 0·14:0·17 e in the case of cyanodihydroaryl anions. These estimations and the general NMR pattern of π‐charge distribution in all the anionic species under investigation are in accordance with data from quantum molecular orbital calculations at the PM3 and INDO levels, being reflected by the fairly good linear relationships between the changes of ring carbon chemical shifts on going to the anionic species from the respective neutral precursors on the one hand and the calculated π‐charges on the other. The para ‐orienting effect of the cyano group in the protonation of nitrile dianions is discussed in terms of the π‐charge distribution in the starting dianion and the tendency to form a most stable cyanodihydroaryl anion isomer.