Dec., 1950
NOTES
576.5
pyrithiamine is pure pyrithiamine, and that the substance described by Tracy and Elderfield was grossly contaminated with biologically inert material. Because confusion has arisen in the interpretation of the biological experiments with neopyrithiamine and pyrithiamine, some clarification might result if the name pyrithiamine were retained for the biologically active substance, in view of the facts just described. Possibly a designation such as pyrithiamine (neopyrithiamine) would indicate that the pure substance was employed rather than the old, impure preparation.
Kulka suggested the possibility of forming a salt of higher v d e n t nickel by the interaction of bromine and nickel dimethylglyoxime in an inert solvent. When bromine is added to the suspension of nickel dimethylglyoxime in carbon tetrachloride, a black solid is formed. When this product is filtered and allowed to dry, i t decomposes slowly and reverts to nickel dimethylglyoxime. The black solid dissolves in concentrated ammonium hydroxide to give a deep red solution such as is described by Feigl and Kulka. A generalization that has been made concerning the stabilization of valance is that if a given THEROCKEFELLER INSTITUTE. FOR MEDICAL RESEARCH coordirlating group stabilizes a valence state, NEW YORK21, NEWYORK RECEIVEDJUNE 19, 1950 than the more negative the group the greater is the stabilization effect. To restate this in different form, certain strongly coordinating The Preparation of New Compounds of Trivalent groups will displace the oxidation-reduction Nickel1 potential of an ion, and this displacement is BY LEONARD E. ED ELM AN^ greater with more negative groups. Therefore, the bromine reaction was tried Introduction with nickel a-benzildioxime and a trivalent nickel The stabilization of unusual valency states derivative was formed which was stable a t room b y coordination is a well-known phenomenon in temperature and decomposed slowly a t 100'. organic chemistry. Numerous examples of this A stable iodide has also been prepared. The phenomenon exist, such as di- and trivalent silver reaction of chlorine with nickel a-benzildioxime when coordinated with pyridine, trivalent cobalt in carbon tetrachloride results in the formation in the stable ammines, etc. Illustrations of com- of a purple solution which is unstable. pounds of metals a t stabilized lower states of oxidation are the nickel and manganese complex Experimental cyanides. A characteristic of this phenomenon a-Benzildioximonickelic(111) Bromide .-Three grams is the specificity of coordinating groups for various of nickel a-benzildioxime (recrystallized from benzyl metals. alcohol) was placed in 200 ml. of carbon tetrachloride. There is some evidence that coordination with Five grams of bromine was added with stirring for ten minutes. A dark brown product was formed which was the oxime group may be a stabilizing factor for filtered, washed with carbon tetrachloride and air-dried. the higher valency states of nickel. Hofmann and The compound is insoluble in water and in all organic Ehrhardt3 prepared the complex compound, liquids such as benzene, alcohols, ethyl ether, acetone and and carbon tetrachloride except pyridine. It forms a redtrisodium hexaformoximonickelate(III), solution in pyridine, from which it can be precipiDubsky and Kuras4the red crystalline compound, violet tated by the addition of water, or will crystallize upon nickel(II1) tribenzamidoxime. Feigl and Kulkaj slow evaporation of the solvent. Concentrated ammoconsidered the red solution formed by nickel nium hydroxide, dilute sodium hydroxide and sodium salts and dimethylglyoxime in ammoniacal solu- methylate in alcohol react to form a dark red compound is insoluble in water but soluble in alkaline media. tion in the presence of oxidizing agents such as which The compound slowly decomposes a t 100" to revert to bromine, nitrates, lead peroxide, etc., to be a the original orange-colored nickel a-benzildioxime. The solution of a compound of tetravalent nickel, loss in weight of the compound upon heating to constant dimethylglyoximonickelic(1V) oxide. They were weight was 13.5870, which is a measure of the bromine able to isolate this compound by precipitation content. A n d . Calcd. for NiC2&H22N4O4Br.: Ni, 9.51; Br, upon careful neutralization of its solution. 12.95; C, 54.5; H, 3.59. Found: Ni, 9.34; Br, 13.02; The present paper contains the description of C, 54.6; H, 3.62. stable compounds of higher valent nickel derivaa-Benzildioximonickelic(II1) Iodide.-Three grams of tives of oximes. The method of formation of recrystallized nickel a-benzildioxime was dissolved in 20 the tetravalent oxide prepared by Feigl and ml. of hot benzyl alcohol, 3 g. of iodine was added and the (1) Presented before the Division of Physical and Inorganic Chemistry of the American Chemical Society at the New York Meeting, September 1947. (2) Dental Research Associates, Inc., 608 California Avenue, Pittsburgh 2, Penna. (3) Hofmann and Ehrhardt, Bcr , 46, 1467 (1913); C. A , , 7,2577 (1913). (4) Dubsky and Kuras, Chcm. Zc?zfr., 102, I 2 0 4 5 (1931), C. A , , 26, 1708 (1931). (5) Feigl and Kulka. Bey., 67,958 (1924): C . A , , 18, 2663 (1924); A. Okac and M. Polster, Coll. Czechoslov. Chem. Comviuii., IS, 561 (1948).
mixture heated until crystallization started. The reaction mixture was cooled immediately and the product separated as glistening, bronze crystals. The solubility and stability characteristics are the same as the bromide. Anal. Calcd. for NiChH2&041: Ni, 8.85; I, 19.11; C, 50.64; H, 3.34. Found: Ni, 8.98; I, 19.30; C, 51.80; H , 3.48. Action of Chlorine on Nickel a-Benzildioxime .-Chlorine gas was passed for five minutes through a suspension of 5 g. of recrystallized nickel a-benzildioxime in 200 ml. of carbon tetrachloride. A darksolored solid and a purple solution formed. The reaction mixture was filtered.
'The purple-colored filtrate decomposed and deposited .L tion constants of the acids. Since there is s o t i i t ' dark solid which was insoubIe in the carbon tetrachloride controversy over this constant in the literature, The residue could be extracted with chloroform to yield inore purple 5olutioi1, vhirh tlso drcotnposed in a it.!\ we have redetermined this constant for hypobroIt was found possible to add sufficient chlorine to ,I \ample of nickel a-benzildioxime to diwolvc it coinpletel, but this solution was also unstable. Hydrolysis of ar -Benzildioximonickelic(In) Bromide. Approximately 1 g. of a-benzildioximonickelic(I11) bromide was stirred in 50 ml. of cold concentrated ammonium hydroxide. A maroon-colored compound formed which \\as somewhat soluble in the ammonia solution. The product was filtered, washed vr.ith distilled mater, and itlied in ct desiccator The product decomposes slowly to give nickel cu-benzildioxime. I t is slightly soluble in dioxane but insoluble 111 uater and in organic liquids such as benzene, carbon tetrachloride, diethyl ether, ethanol and acetone. Action of Bromine on Other Nickel-oximes.-Besides ru-benzildioxime and dimethylglyoxime, other nickeloxime derivatives were treated with bromine in carbon tetrachloride solution. These include ar-furildioxime, cyclohexanedionedioxime, glyoxalglyoxime, diacetylinonodxime monophenylhydrazide and ethylenediaminebis-diacetyldioxime. The last of these gave a stable bromide and the glyoxalglyodme gave an unstable deriv'i tive The other compouiid~ were decomposed Itv the I Irornine. RECFIVFI)3 T 4 3~3 , 1050
The 6-Phenylphenacyl Ester of Phenylacetic Acid 1)raL.e and Sweeney' reported 63" (dec.) as the melting point of the p-phenylphenacyl ester of phenylacetic acid. In the course of undergraduate instruction we recently had occasion to prepare this ester and found it to melt a t 88.2-88.8' (cor.). Five preparations2 showed the same melting point. Experimental p-Phenylphenacyl Phenylacetate .--This compound was prepared by the standard method.3 The light tan crude product was recrystallized three times from ethanol (once \I tth charconl) . The pure white analytical sample melted 88 3 88 8' icor.) to a completely colorlesi mc.lt. ..lncil. Cctlctl for C&,d) . c', 7'1 03. 11. 7 10 i ' o c i i ~ l . C, 79 -I{;H , iti0 '\i
1
nr.iir
Two ot these ii 5 ImuIicl\
acid. Shilow and Gladchikova2 found by lectrometric titration that a t 20' = 2.Ori x I O and according to the same method, AHOCL a t 30" = 3.16 X lo-*. While the latter value is in good agreement with the results of other ~ n v e s t i g a t o r sand ~ , ~ is also close to the figure obtained by Skrabal and Berger6 from the kinetics of the hypochlorite decomposition (viz., 5.6 X IO-* a t 25'), the correctness of the above value of I ~ H O Bwas ~ questioned by SkrabaLG He calculated from data on the rate of decomposition of hypobromite depending upon the $H, the much a t 25'. lower value of 2 X The following method was used for the deterinination of the dissociation constant of the hypobromous acid : T o a hypochlorite solution, kept a t ct pH approximately equal to its p K , the equivalent amount of bromide was quickly added and the change of the pH was accurately measured by Iiiedns of a glass electrode. Since, upon the addition of the bromide, all the hypochlorite was con1-erted to hypobromite,' the observed ApH according to the Henderson-Hasselbach formula was in good approximation, equal to the A,PK of hypochlorous and hypobromous acid. In Table I, the results of a series of experiments &re given, In these experiments, the solutions used were prepared by a method previously tlescribed.' The bromide was added to the hypochlorite solution while the electrodes were iiniiiersed in that solution. The final PH was establtshed within a few seconds after the addition of t h e hronude7,9and remained constant for more t h m 1:) niinutes. 'The solutions were analyzed for hypochlorite before, and for hypobromite inimediately after, the addition of the bromide according to the method already describeds; no change i n the oxidation capacity was found, the hypochlorite being quantitatively converted t o iiious
lllllmtes.
M
iiiii
%e11
i I'
llrV
pirfornird
I
III,
I,JI XUI
64, . x i - + l
1 lie R4,r
