Hydrogen bonding abilities and self‐association of thiazolidin‐and imidazolidin‐2‐ones and 2‐selenones

The hydrogen bonding abilities of iV‐methylimidazolidin‐2‐one and ‐2‐selone and thiazolidin‐2‐one and ‐2‐selenone have been studied by ir spectroscopy at 25° in carbon tetrachloride solutions, using dimethyl sulphoxide and 4‐chlorophenol as proton acceptor (K A ) and proton donor (K B ), respectively. The results are compared with those previously reported for N ‐methylimidazolidine‐2‐thione and thiazolidine‐2‐thione. The K A values increase in each series in the order O < S < Se and Kg in the reverse order. The and K B values are discussed in terms of the substituent in ring. The self‐association constants (K D ) are dependent on both K A and K B , although K A seems to be much more important.