Isothiazoles physical properties

Physical Properties of Isothiazoles and Isothiazolines. - HUckel molecular orbital calculations have been performed for a large number of 5-membered rings with 1 or 2 heteroatoms, including isothiazoles. The calculated relative order of stabilities... 

Synthesis of Isothiazoles, Isothiazolines, and Isothiazolidines 151 From amidoketones and hydrogen sulphide (Type A C-C-C-N + S) 151 From iminonitriles and mercaptoacetic acid derivatives (Type B C-C-N + S-C) 151 From cyclisation of enaminothiones (Type C N-C-C-C-S) 152 From sulphonamidoacetates and diethyl oxalate (N-S-C + C-C) 152 From ketenes and sulphur di-imides (N-S-C + C-C) 152 Physical Properties of Isothiazoles and Isothiazolines 152 Chemical Properties of Isothiazoles, Isothiazolines, and Isothiazolidines 153... 

Physical Properties.— I.r. and Raman spectra of 5-monosubstituted isothiazoles (5-CH3, -CDs, -Cl, -Br, or -I) in their liquid and solid states have been correlated with the fundamental modes of vibration of the ring system. Detailed experimental and theoretical studies of the C and n.m.r. spectra of isothiazoles, including long-range couplings, have been reported. A comparison with theoretical results based on a CNDO model revealed some deficiencies. 

The intensified activity in the study of the chemistry of isothiazole, noted in the previous Report, has been sustained, possibly with an emphasized interest in condensed ring-systems. Now that numerous syntheses of isothiazoles are available, the careful and detailed investigation of both the physical and chemical properties of this ring-system, and its correlation with related structures, are particularly timely. The possible involvement of isothiazole derivatives in the biosynthetic pathway to penicillins and cephalosporins is a suggestion of exceptional interest (see ref. 43, below) that will no doubt stimulate further significant work. 

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