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Ionization constants of 5‐pyridylmethylenehydantoins in 80% (w/w) dimethyl sulphoxide–water at 25 °C
Author(s) -
Tan SauFun,
Ang KokPeng,
How GeeFung,
Yeo YamKhoon
Publication year - 1990
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.610031103
Subject(s) - chemistry , intramolecular force , hydantoin , hydrogen bond , ionization , medicinal chemistry , stereochemistry , molecule , organic chemistry , ion
The ionization constants of nine amphoteric 5‐pyridylmethylenehydantoins were measured in 80% (w/w) dimethyl sulphoxide–water at 25 °C. The effects of structure and Z / E configuration on both p K a Iand p K a IIvalues are discussed. The especially low basicity and acidity of the Z ‐isomers of the N ‐unsubstituted and 3‐methyl‐substituted 5‐(2‐pyridylmethylene)hydantoin are attributed to the formation of intramolecular N(1)H…N hydrogen bond in the s ‐ cis conformation of these compounds. The existence of N(1)CH 3 …N attraction is also postulated for the Z ‐isomer of 1‐methyl‐5‐(2‐pyridylmethylene)hydantoin.