Abstract
Molecular species of N-(2-thiazolyl) thioureas and their Cu (II) chelates present in solution were estimated by analysis of the absorption spectra in the ultraviolet region obtained under various conditions. The N-(2-thiazolyl) thioureas studied were 1, 1-dimethyl-3-(4-methyl-2-thiazolyl) thiourea (1a), 1, 1-dimethyl-3-[3, 4-dimethyl-2 (3H)-thiazolylidene] thiourea (2a), 1, 1-dimethyl-3-(4-methyl-2-thiazolyl)-S-methylisothiourea (3a). 1, 1, 3-trimethyl-3-(4-methyl-2-thiazolyl) thiourea (4a), 1-monomethyl analogs of 1a, 2a, 3a, and 4a (1b, 2b, 3b, and 4b, respectively), 1-unsubstituted analogs of 1a and 2a (1c and 2c, respectively), 1, 3-dimethyl-3-(4-methyl-2-thiazolyl)-S-methylisothiourea (5b), 1-methyl-3-[3, 4-dimethyl-2 (3H)-thiazolylidene]-S-methylisothiourea (6b), and their derivatives, in which some of the methyl groups were replaced by ethyl groups or the 4-position and/or 5-position of the thiazole moiety were substituted. The thiazole nitrogen atom was more basic than the thiourea nitrogen and sulfur atoms in 1a, and the predominant species in neutral solvents was the thiazolinylidenethiourea form (II). The predominant species of 1b and 1c in neutral media were the thiazolylthiourea (I) form, probably stabilized by an intramolecular hydrogen bond. There was also a difference in the predominant species between 3a and 3b. In methanol, 1a, 1b, and 1c formed Cu (II) chelates, which were extracted with chloroform. Cu (II) chelates were also formed from 2a, 2c, 3a, and 3b, but they were not soluble in chloroform.
