Improvements in the Zimmermann reaction are effected by using methanol as a solvent for the reagents employed in the reaction in place of ethanol or aqueous ethanol. The advantages are as follows. Considerably lower blanks are obtained; extraneous chromogens are negligible at the wavelength of measurement, so that no correction procedure or extraction process is required; high concentrations of potassium hydroxide may be used at an elevated temperature leading to good sensitivity and a considerably shortened reaction time; and finally, the potassium hydroxide is stable for long periods under good storage conditions. A steroid with keto (oxo) groups at positions 3, 11, and 20, but not at 17, failed to give any coloured product.
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