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1984
COMMUNICATIONS T O T H E EDITOR ADSORPTION AT THE DROPPING MERCURY ELECTRODE
as a normal electrode, but that the saturation current would be reduced; i. e., with a given proSir : tein concentration, the digusion current should be Despite the large quantity of work which has reduced by a constant fraction, which is independbeen carried out with capillary-active substances ent of the dye concentration. A series of polaroas maximum suppressors in polarographic analy- grams of the same system, this time with the prosis, a detailed consideration of their effect on the tein absent or held constant a t a comparatively diffusion current itself has apparently not been high concentration, showed a 70% reduction of made. One may find references in the litera- the saturation current, in the presence of protein, ture132Jto interference with the diffusion cur- but no change in the concentration of dye rerent, brought about by the use of capillary-active quired to reach saturation. materials, but no satisfactory explanation has The probable relation of these results to the been offered. phenomenon of maximum suppression is being Polarograms prepared from solutions which explored. A more detailed account of the work contained various concentrations of purified will be published later. horse albumin a t PH 8 and which were 1 X M GATESAND CRELLIN LABORATORIES OF CHEMISTRY in the dye p-hydroxyphenylazophenylarsonicacid, CALIFORNIA INSTITUTE OF TECHNOLOGY CALIFORNIA BERTRAM KEILIN 0.15 M in sodium chloride, and 0.02 M in veronal PASADENA, RECEIVED MARCH8, 1948 indicated that the diffusion current was suppressed to approximately 90% of its true value at a protein concentration of 1 X M and to an THE INFRARED SPECTRUM OF SPRUCE NATIVE asymptotic value of about 25% at 1 X M. LIGNIN It seems likely that the albumin, a capillary- Sir : active substance, is adsorbed on the growing Initial work on an extensive study of the applimercury drops, decreasing the surface available for reaction with the reducible molecules or ions cations of infrared spectroscopy to the problem and so decreasing the diffusion current. If so, of lignin structure has resulted in the establishthe fractional change of free surface and the con- ment of the spectrum of Brauns’ spruce native sequent fractional change in instantaneous diffu- lignin by several independent methods of sample sion current should a t any stage in the life of the preparation. Typical curves (obtained with a drop be a function of the change in the concentra- Perkin-Elmer Model 12-B recording spectrometion of protein. At moderately high concentra- ter using a sodium chloride prism) are shown in tions 01 protein, however, a monomolecular layer Fig. 1. The film method of sample preparation warwould be formed and an asymptotic diffusion rants a brief description. By filling a shallow current. would be attained corresponding to the remaining free surface between the adsorbed pro- cup comprised of a metal ring and salt plate base tein molecules. (Even in closest packing these with ethyl alcohol, adding a small proportion of large molecules might well leave holes large enough dioxane solution, and allowing evaporation to to permit the smaller molecules of reducible ma- take place slowly, the lignin was deposited as a terial to reach the electrode.) These considera- strongly adherent clear film. The films thus obtions are in qualitative agreement with the ex- tained were dried for sixteen hours in a vacuum perimental results; furthermore, for, protein con- desiccator before use. Of particular value is the centrations C, giving diffusion currents & not fact that dioxane is sufficiently transparent to too close to the asymptotic current for a given permit its use as a solvent in the important carconstant dye concentration, they lead to a theo- bonyl (1650-1850 cm.-l) and hydroxyl (3000retical relation similar to the equation log id = 3700 cm.-l) regions, as shown in Curve A. Two important points have been established : - kl C, kz which was found empirically. As the concentration of a reducible substance is (1) The infrared spectrum of native lignin in film increased beyond a critical value, the “diffusion form is essentially unchanged by as much as ten current constant” decreases and the current ap- hours of heating a t 100’. (2) The broad band proaches a saturation value. It might be ex- centered a t 3350 cm.-’ for film and Nujol dispected that an electrode covered over to a given persion and the shift of this band to higher freextent, say with a monomolecular layer of ad- quency in dioxane solution is indicative of strong sorbed large molecules, would reach saturation hydrogen bonding in lignin. Experiments on a t the same Concentration of reducible substance dilution and heating effects are planned which should yield valuable evidence as to the nature (1) Salac. Kvos, 64, 383 (1936). of this bond. (2) Brdicka, 2. Elckfrochem. 48, 278, 686 (1942). (8) Kolthoff and Aarnum, THISJOURNAL, 68, 520 (1941). An investigation of the spectra of related com-
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Frequency in crn.-l. Fig. 1.-Spruce native lignin: curve A, 3% solution in dioxane, 0.127 mm. cell; curve B, 10-15% dispersion in Nujol, smear on salt plate; curve C, film from dioxane-EtOH on salt plate (1900 ~ r n . - ~ 2 6 0crn.-l 0 section essentially transparent).
sample, recrystallized twice from acetone-isooctane, was obtained as colorless glistening platelets, m. p. 78-79'. Anal. Calcd. for CsH90N: C, 73.43; H, 6.16; THEINSTITUTE OF PAPERCHEMISTRY APPLETON,WISCONSIN EDWARD J. JONES N, 9.52; mol. wt., 147.2. Found: C, 73.20; H, RECEIVED APRIL3, 1948 6.23; N, 9.58; mol. wt., 139 (Rast). A suspension of the lactam (0.5 g.) in 5 ml. of N sodium hydroxide was warmed with shaking t o A NOVEL SYNTHESIS OF A @-LACTAM 70-80'. After ten to twelve minutes the solution Sir: became completely clear. From the cooled acidiIn the course of an investigation of amino acid derivatives, a unique synthesis of the /3-lactam of fied solution crystalline N-phenyl-palanine (0.25 N-phenyl-&alanine was discovered. The re- g., m. p. 59-60') was recovered by ether extraction, action between an isocyanate and diazomethane evaporative distillation, and crystallization from does not seem to have been studied previously, carbon disulfide-ligroin. No depression in meltWe have found that in the case of phenyl iso- ing point was observed for a mixture with authencyanate two methylene units are added in a re- tic N-phenyl-P-alanine (m. p. 58-59'), prepared action analogous to the formation of cyclobuta- from aniline and P-iodopropionic acid by the method of Bischoff and M i n k 2 none from ketene and diazomethane.' This appears to be the simplest P-lactam re0 ported; other known representatives of this class // of compounds have a t least two substituents on CBH~NCO 2CHtNz +CeHbN-C 2Nz I 1 the ring.3 It is of interest to note the ease of CHz-CHs hydrolysis in the present case as compared to more To a solution of 2.38 g. (0.02 mole) of freshly highly substituted p-lactams or normal amides. distilled phenyl isocyanate in 25 ml. of anhydrous The reaction between diazomethane and other isoether was added 109 ml. of a 0.46 M cold ethereal cyanates and isothiocyanates has been investisolution of diazomethane (0.05 mole) dried over gated and will be reported shortly, sodium. Within about two minutes a vigorous reWe are indebted to Dr. John D. Roberts for action commenced with evolution of nitrogen and valuable suggestions and to Swift and Company the simultaneous deposition of an amorphous for support of a fellowship for one of us (P.T.T. 1. orange precipitate. After twenty hours at 0-5' DEPARTMENT OF CHEMISTRY JOHNC. SHEEHAN the solution was separated from insoluble ma- MASSACHUSETTS INSTITUTE OF TECHNOLOGY terial (0.9 g.), and concentrated under reduced CAMBRIDGE 39, MASSACHUSETTS PATRICK T. Izzo pressure to a brown, viscous oil (1.8 g.). EvapoRECEIVED APRIL15, 1948 rative distillation a t 80-120' and 1 mm. gave 0.59 (2) C . A. Bischoff and N. Mintz, Ber., 16, 2351 (1892). g. (20%) of the colorless crystalline p-lactam of (3) H. Staudinger and S.Jelagin, ibid., 44, 373 (1911) ; Staudinger, N-phenyl-P-alanine, m. p. 74-76'. An analytical ibid., 60, 1038 (1917); H.Breckpot, Bull. SOC. chim. Bclg., a i , 424 pounds, of lignin derivatives, and of lignin from other sources and as the result of industrial processing is in progress.
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(1) P. Lipp and R. Kbter, Be?., 64, 2823 (1931).
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(1923);
E.Gilman and M. Speeter, TRIEJOURNAL, M,2255 (1943).
