The Relative Efficiency of Some Polymerization Inhibitors

NOTES 90s what modified process, whereby the vapors of nicotinic acid were passed through a heated column of thorium dioxide, gave a comparable yield of the ketone. This was identified by analysis of the dipicrate. The same result was obtained when aluminum oxide was used in place of thorium dioxide. UC0'0 Downloaded by HENKEL KGAA on August 18, 2009 Published on May 1, 1946 on http://pubs.acs.org | doi: 10.1021/ja01209a504 Experimental &p'-Dipyridyl Ketone.-A Pyrex tube, 25 inches long, closed at one end, was charged with 20 g. of nicotinic acid, followed by 100 g. of thorium dioxide. The outlet was connected with a descending condenser and the receiving flask was immersed in an ice-bath. Nicotinic acid was slowly distilled through the thorium oxide layer which was kept a t 300" during the process. The distillate was collected, and pyridine and water were boiled o f f at atmospheric pressure, leaving a dark residue which was extracted with ether. After the ether was evaporated, this extract yielded 0.4 g. of a viscous oil. The dipicrate, formed in alcoholic solution and recrystallized from alcohol, was in dark green plates; m. p. 135". Anal. Calcd. for C I I H ~ N ~ O . ~ C ~ H ~ N 42O , : H, C, ~ 99; 2 17. Found C, 4300, H, 2.02. RESEARCH LABORATORY ASSOCIATES RALPH EVANS L. 250 EAST43RD STREET NEWYORK17, N. Y. RECEIVED JANUARY 31, 1946 The Relative Efficiency of Some Polymerization Inhibitors' BY ROBERT L. FRANK AND CLARK E. ADAMS Considerable losses often occur in the preparation of vinyl monomers due to their ease of polymerization, especially during distillation. The present comparison of inhibitors was undertaken to prevent such losses. Equal weights (0.20 g.) of a number of compounds were added to 2.0-ml. samples of three monomers, styrene, 3,4-dichlorostyrene, and 5ethyl-%vinylpyridine, each freshly distilled. These monomers were chosen for their tendency toward ready polymerization. Each sample wassealed in a LO X 110-mm. test-tube and allowed to stand in a refluxing water-bath. No effort was made to exclude oxygen from the tubes, but all were of the same size and had approximately the same air space above the monomer-inhibitor mixtures. The fluidity of the samples was periodically compared with the initial fluidity by means of the flow-times when the tubes were inverted. The heating time required to show a difference in flowtime is given in Table I as the "inhibition period." A t the "total time of polymerization" the samples were too viscous t o give a measurable flow time. There appears to be no great variation in the order of inhibitory strength from one monomer to (1) This inve5tigation wab carried out under the sponsozship 01 the OlEce of Rubher Reserve, Reconstruction Finance Corporation, in connwtion w t h t b O o v r m m m t Synthetic Rubher Program. ~ Vol. 68 another. A good inhibitor for one monomer is likely to be good for another. TABLE 1 EFFECT INHIBITORS OF ON POLYMERIZATION Inhibition period, Inhibitor Picric acid Trinitrobenzene 2,5-Dihydroxy-l,4 benzoquinone 1,4-Naphthoquinone 1,I-Benzoquinone Chloranil 9,lO-Phenanthraquinone I-Butylcatechol 4-Amino-1-naphthol Hydroquinone Phenyl-p-naphthylamine Triphenyl phosphite Control a Sa 299 299 hr. DCS" VEP' 39 120 72 i4 S stands for styrene; DCS for 3,?-dichlorostyrene; VEP for 5-ethyl-2-vinylpyridine. One fact that stands out in the present study is that phenyl-&naphthylamine and t-butylcatechol, two widely used inhibitors, are among the poorest in inhibitory action a t least for the monomet's tried. Picric acid and trinitrobenzene are now being used in this Laboratory with great success during distillation of a wide variety of monomers, Some question has arisen concerning the possible hazard from explosion of polynitro compounds, but the use of traces should involve no danger.2 Picric acid should probably not be used, however, in metal containers. (2) Cf. Belyaev and Yuzefovich, Comfit. rend. acad. sci. (URSS), 27, 133 (1940); C. A , , S4, 7607 (1940). NOYES CHEMICAL LABORATORY CNIVERSITY ILLINOIS OF URBANA, ILLINOIS RECEIVED MARCH 194ti 11, Anils as "Open Models" of a Modified Atebrin BY HENRY GILMAN SAMUELMASSIE, AND P. JR. I n a recent study' concerned with some quinolines patterned as so-called open models of atebrin, [I], it was shown that a compound like 6methoxy - 2-(3' - chlorophenyl) - 4 - [(a- methyldiethylaminobuty1)-amino]-quinoline, [II ], was active in experimental avian malaria infections. H-N-C!H( CHs) (CHI)3 ?J(CrHb)2 (1 1 H-N-CH I (C Ha) (CHy ) 3 N(C2Hr)8 I cH30-o? OdC1 \N - [I11 (1) Cilrnan and Spatz, THIS O U R N A L , 66, 621 (1944). J