Abstract
The application of the electronic theory of valency to chemical problems has shea a new light on many hitherto obscure problems and has provided the inspiration for several epoch-making researches. In particular, Lowry, in 1923, from theoretical considerations based on the above theory, introduced the conception of "mixed" or "semipolar" double bonds. The possible existence of semipolar double bonds, revealed by the application of the electronic theory of valency, has been confirmed experimentally by two unique methods. On the one hand, Sugden, in 1925, after determining the parachors of a number of compounds containing a double bond, showed that substances, which could be represented on theoretical grounds as possessing a semipolar double bond, gave values lower than those calculated for an ordinary double covalency. On the other hand, Phillips, in the same year, detected a new kind of optical activity in a series of sulphinates of the type CH[3].C[6]H[4].SO.OR. The present thesis is concerned with further research on this new type of optical activity. For instance, it is now shown that mixed sulphoxides, which, according to the older formulation R > S = 0 , could not be suspected of existing in enantiomorphously related forms, are capable of being resolved into their optically active forms. Furthermore, a mixed sulphilimine, C[6]H[4].CH[3].SO[2].N = S.C[2]H[5].C[6]H[4].COOH, an example of the new type of quadrivalent sulphur compound discovered by Raper, has been shown to exist in enantiomorphously related forms. It is pointed out that the successful resolution of this compound throws considerable light on its constitution and also on the constitution of chloramine.T. from which it is prepared. The most recent development of the theories discussed in the thesis is the question as to the mode of attachment of two univalent atoms or groups when they replace the divalent element or group attached to a quadrivalent sulphur atom by a semipolar double bond. Experimental evidence is not yet sufficiently great to determine whether the component covalency and electrovalency of the semipolar double bond are utilised Separately or whether the univalent atoms or groups become attached to the sulphur atom by identical valencies each equal in value to half a semipolar double bond, in other words, by a semipolar single bond. Enough data, are, however, available to give verisimilitude to the idea of the semipolar single bond and to stimulate further research along these lines.