The process patented by Dewar and Redwood in 1889 consists in the use of a suitable still and condenser in free communication with each other - i.e.
In 1866 Sir James Dewar proposed an unsymmetrical form (II); while in 1867, A.
CH CH HC, N CH HC CH HC HC HC Hcch Hc Ch Ch Kekule t i Dewar Ladenburg One of the earliest and strongest objections urged against Kekule's formula was that it demanded two isomeric ortho-di-substitution derivatives; for if we number the carbon atoms in cyclical order from i to 6, then the derivatives 1.2 and 1.6 should be different.'
He admitted the possibility of the formulae of Kekule, Claus, Dewar and Ladenburg, although as to the last di-trimethylene derivatives should be possible reduction products, being formed by severing two of the prism edges; and he attempted to solve the problem by a systematic investigation of the reduced phthalic acids.
The relative merits of the formulae of Kekule, Claus and Dewar were next investigated by means of the reduction products of benzene, it being Baeyer's intention to detect whether double linkages were or were not present in the benzene complex.