NOTES
700 PROTONATION I N N-METHYLACETAMIDE BY GIDEONFRAEXKEL~
Gates and Crellin Laboratoraes of Chemzstry, Calafornza Instztute of Technology, Pasadena, Calzfornza
AHARONLCJEWENSTEIN ARD N M R Laboratory, Reazmann Indtztute, Rehouoth, Israel
SAULMEIBOOII Bell Telephone Labs., Murray H z l l , S. J. Recewed Septembei 81,1960
I n a recent note by Spinner3 a discussion of the site of protonation in amides is given. In that note it is suggested that the n.m.r. evidence for 0protonation in K-methylacetamide and other amides is inconclusive. As we have shovn prev i o u ~ l y ,the ~ , ~N-methyl proton resonance of this molecule in very acidic solution consists of a symmetrical doublet presumably due to spin-spin interaction with a single N-hydrogen. Spinner, however, interprets this doublet as being due to non-equivalence of the methyl groups in different isomeric forms resulting from hindered rotation. We wish to point out that the symmetry of the doublet makes such an interpretation highly improbable as the equal intewity of the components would lead to the conclusion that the two isomeric forms have very nearly the same energy. Two experiments were performed t o shorn unambiguously that the splitting of the 3-methyl resonance in protonated N-methplacet~amide is due t o spin-spin interaction rather than a chemical shift. 1. The N-methyl resonance of a solution of Kmethylacetamide in 100% HzS04 consists of two equal lines while in 100% DzSOlthe same resonance consists only of a single line. 2. The separat#ion of the RI-methyl doublet in protonated N-methylacetamide is independent of the magnetic field (3.7 f 0.3 c.p.s. both at 33 and 60 Me.). It is therefore clear that K-methylacetamide protonates predominantly on oxygen. (1) Contribution No. 2580. (2) Department of Chemistry, The Ohio State University, Evans Chemical Laboratory, 88 W. 18th Avenue, Columbus 10, Ohio. (3) E. 6. Spinner, J . Phys. Chem., 64,275 (1960). (4) G. Fraenkel and C. Niemann, Proc. Nail. Acad. Sci. (U.S.), 1 4 , 688 (1958). ( 5 ) A. Berger, A. Loewenstein and 8. Meiboom, J. A m . Chem. SOC., 81, 62 (1959).
ANALYSIS OF T H E INTRINSIC VISCOSITY OF A POLMMER UNDERGOING SIMULTANEOUS CROSSLINKING A4ND DEGRADATION BY MALCOLM DOLE Department of Chemistry, Northwestern University, Euanston, Illinois Receiaed October 18, 1961)
The effect of simultaneous crosslinkine and derradation on the intrinsic viscosity of a” polym& has recently been considered theoretically in this country by Kilb,’b2 using the theory of Zimm and Kilb,3 and in Japan by S a i t ~I:, ~okutis and Inokuti
Vol. 65
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