Abstract
The behavior of estrone methyl ether (V) in strong acid was studied, in order to elucidate the mechanism of the Kober color reaction. When V was dissolved into concentrated sulfuric acid, a maximum absorption gradually appeared at 465 nm which was then transferred to 452 nm with elapse of time. On the other hand, 3-methoxy-17α-methylestra-1, 3, 5 (10), 9 (11)-tetraen-17β-ol (XIIIb) immediately gave the chromophoric cation χ-465 (VIIb) in concentrated sulfuric acid. Similarly, 3-methoxyestra-1, 3, 5 (10), 9 (11)-tetraen-17β-ol (XIIIa) gave the cation χ-364 (XIVa) which changed in turn to χ-465 (VIIa). Sulfonation gradually occurred at C (2)s of VIIa and VIIb in the same acid to give the corresponding cations XIXa and XIXb ; the maximum absorption at 465 nm altered to 452 nm. The mechanism of the conversion of V into the C (2)-sulfonated χ-465 (XIXa) was elucidated from these behavior of XIIIa and XIIIb in concentrated sulfuric acid.
