A Nuclear Magnetic Resonance Study of the Structure and

0. L. CHAPMAN, R. W. KING,W. J. WELSTEAD, JR.,

4968 [ CONTRIBUTION

F R O M THE

DEPARTMENT O F CHEXISTRY, I O W A

STATE

,4ND

USIVERSITY

Vol. 86

T. J. MURPHY

O F S C I E N C E AND

TECHNOLOGY, AMES, IOWA]

A Nuclear Magnetic Resonance Study of the Structure and Mutarotation of Sugar Osazones in Dimethyl Sulfoxide Solution' BY 0. L. CHAPMAN, ROYW. KING,W. J . WELSTEAD, JR.,

AND

T. J. MURPHY

RECEIVED JLXE 15, 1964 Study of the nuclear magnetic resonance spectra of sugar osazones and appropriate model compounds in dimethyl sulfoxide leads to the conclusion t h a t sugar osazones possess chelate structure I. Mutarotation of sugar osazones is shown to be the result of equilibration of the osazone with an isomer. The nuclear magnetic resonance spectrum of the isotner shows t h a t it still possesses an aldimine C-H b u t t h a t it no longer possesses a chelate ring. The mutarotation process involves rupture of the chelate ring and concomitant geometric isomerization about the CQ-S bond.

Evidence has been presented that sugar phenylosazones contain a chelate ring both in solution and in the crystal.2-6 Mester3.6 has favored the chelate structure I on the basis of similarities in properties of glucose phenylosazone (I, R = C4H904)and glucose l-methylH,

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phenyl-2-phenylosazone (11, R = C4H904). Wolfrom, Fraenkel, Lineback, and Komitsky4 have favored chelate structure 111 for tetraacetylglucose phenylosazone on the basis of nuclear magnetic resonance studies in deuteriochloroform. Crystalline xylose p-bromophenylosazone shows an arrangement of carbons and nitrogens analogous to I in a two-dimensional X-ray analysis.5 We have examined the structure and mutarotation of sugar osazones in dimethyl sulfoxide solution. Dimethyl sulfoxide is a particularly useful solvent for such studies because of the solubility of sugar osazones in this solvent and the reduced rate of exchange of protons bound to heteroatom^.^^^ This reduced rate of exchange permits observation of spin-spin splitting of hydroxyl protons (which facilitates assignments) and produces sharp N- H resonance lines.'f8 Structure of Sugar 0sazones.-Examination of the n.m.r. spectra (Table I) of certain model compounds is necessary before turning to the sugar osazones. Biacetyl bisphenylhydrazone ( I T ) in dimethyl sulfoxide shows a single sharp resonance a t 6 9.25.9 The pres(1) Portions of this work were described: Abstracts, l-l.5th National hieeting of t h e American Chemical Society, S e w York, N . V . , Sept , 1963, p. 3 6 Q . ( 2 ) T h e chelate structure for osazones was first suggested by r,. F . Fieser and hi. Fieser. "Organic Chemistry," 2nd Ed., D . C. Heath and Co., Boston. hlass , 1550, pp. 369-372. (3) Iahm. S Furberg, a n d C. S. Peterben, .4c!a C h e m S c n $ i i f . , 17, 559 (19633. (6) I,. N e s t e r and A. hiajor. J . A m Clieiii. Soc., 79, 8232 (1957). King, t b i d , 86, 1236 11964) (7) 0 I.. Chapman and I