Steric Effects in Conjugated Systems [antikvár]

1 CONFIGURATION AND STERIC EFFECTS IN CONJUGATED SYSTEMS E. E. TuilNER Bedford College, University of London In view of the manifold and diverse interests represented by the present symposium and of the existence of excellent modern treatises^ on many of the subjects, it seemed to be useful in a complementary sense to make a brief historical introduction to those parts of the general problem with which the writer has been connected during the last forty odd years. These centre especially round diphenyl and related compounds. In 1907 Kaufler proposed his famous formula for benzidine^. The work as published appeared to be thoroughly sound. The comparatively novel tool—determination of molecular weight in solution—was used to support the apparently straightforward organic chemistry. To us nowadays the Kaufler formula is incredible, but in 1912 Cain® and his co-workers adopted it as the only way of accounting for their two (3,3'- and 3,5'-) dinitro-benzidines (/) and (//), NH, NO, NHj NOj (/) and in 1914 they obtained results^ which appeared to show that benzidine condensed with benzil as if it were an oriAo-diamine. In 1914 J. F. Thorpe®, in reviewing the whole subject, took the view that ' it is apparent that more evidence is desirable before the Kaufler formula can be accepted Yet there were no grounds for rejecting it outright. A similar view®, supported by experimental work, was expressed from another quarter at about the same time and later^ Cain's 1