Kober chromogen

In the course of the isolation of new Kober chromogens from pregnancy urine, Marrian and his colleagues (Loke et al, 1957) obtained a phenolic... 

A reaction in which oestrogens (Kober chromogens), when heated with sulphuric acid, yield an orange-yellow complex which can be estimated fluorimetrically or colorimetrically. 

A few analytical methods have been selected as being of particular interest to organic chemists. The spectrophotometric determination of oxo-steroids as their glyoxalyl derivatives is mentioned on p. 331. The Kober reaction and its modifications,in which a phenolic steroid is heated with moderately concentrated sulphuric acid to generate chromogenic materials, is still not fully understood. Oestradiol 3-methyl ether, with 78 % sulphuric acid, gives a mixture including isomers of the 17-methyl-18-nor structure (776), and the derivative (777) with an... 

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