Nuclear magnetic resonance investigations of azo-hydrazone, acid-base equilibria of FD&C Yellow No 6

被引：10

作者：

Mazzola, EP ^{[1
]}

Turujman, SA ^{[1
]}

Bell, SJ ^{[1
]}

Barrows, JN ^{[1
]}

Bailey, JE ^{[1
]}

Mouchahoir, EG ^{[1
]}

Prescott, S ^{[1
]}

Archer, MD ^{[1
]}

Oliver, M ^{[1
]}

Reynolds, WF ^{[1
]}

Nielsen, KW ^{[1
]}

机构：

[1] UNIV TORONTO,DEPT CHEM,TORONTO,ON M5S 1A1,CANADA

来源：

TETRAHEDRON | 1996年 / 52卷 / 16期

关键词：

D O I：

10.1016/0040-4020(96)00205-0

中图分类号：

O62 [有机化学];

学科分类号：

070303 ; 081704 ;

摘要：

Azo-hydrazone, acid-base equilibria were examined for the water-soluble dye FD&C Yellow No. 6 (Y6), with the observation of dynamic NMR effects near, and at, pH 12, where the dye converts from a predominantly hydrazone tautomer (acidic to moderately basic pH) to a prevailing azo-anion resonance hybrid (high pH). Semilogarithmatic pH-C-13 chemical shift plots and a 2-bond, N-15(beta)-C-13(8a) coupling constants vs. pH relationship both indicate that the midpoint of the azo-hydrazone equilibrium occurs at ca. pH 12. Potentiometric titrations further indicate that the pK(a) of Y6 is ca. 12. These data suggest that the observed NMR line broadening is due to slow proton transfer between the hydrazone-NH and water. (C) 1996 Elsevier Science Ltd.

引用

页码：5691 / 5698

页数：8

共 24 条

[1] AZO-HYDRAZONE TAUTOMERISM OF HYDROXYAZO COMPOUNDS - A REVIEW [J].