NOTES
Nov., 1958 HClOd mixture.6 The HClO! oxidizes PuOz t o Pu(VI), thereby facilitatin dissolution. With this procedure, dissolution of the $hOz-Pu02 oxides was not particularly troublesome, but the CeOrPuOz oxides were difficult to dissolve and long heating times were required. qfter firing, the ThOz--PuOz samples were pale green and easily powdered. The CeOz-PuOn samples were sintered into a very hard, glassy lump, lavender in color. When the lump was ground to powder, the powder was reddishbrown. Dissolution of Pu metal in HC1 gives Pu(II1) ion, but this is oxidized slowly by air and by nitrate ion to Pu(IV), so that the solutions from which the mixed hydroxides were precipitated contained both Pu(II1) and Pu(IV) ions as well as Ce(1V) or Th(1V). The nature of the hydroxide precipitate produced from Pu solutions is not completely understood. Not only does Pu(IV) appear in the precipitate from solutions containing only Pu( 111) ions, but anions present in the solution, such as C1- or NOS-, are carried down with the hydroxide, and these cannot be washed out completely. Whatever the nature of the plutonium preci itate may be, however, ignition in air converts i t to pu&. X-Ray powder patterns were taken in a 114.6 mm. diameter powder camera using filtered copper K-radiation (wave 1 ngths, 0 1 ~ = 1.58051, cy2 = 1.54433, mean a = 1.5418 The lattice arameters were determined by graphical extrapolation o f the values found for the high angle lines on each pattern.
1467
t
8.)
5.361 0
1
1
EO
'
1
'
1
40
60
MOLE PER C E N T
I
'
80
I
I
100
PuOe.
Results All the mixed oxide samples showed the powder pattern of a single fluorite-structure phase, with the exception of a single sample (85% CeO2) which showed an unidentified extra line in the powder pattern. Samples of pure Thozand Ce02were also prepared by the above method. The lattice parameter for the Thoz, 5.597 A., agrees with Zachariasen's value.6 Our value for CeOz, 5.411 A., agrees with the results of some other investigator^.'-^ Lattice parameters and compositions of the solid solutions are presented in Table I and Fig. 1. The limits of error listed for the lattice parameters
parameter -m/o Pu02 relation is linear within the accuracy of the measurements. Acknowledgment.-The authors wish to acknowledge the assistance of Gladys E. Sturdy, who prepared the samples; Marian Gibbs, who measured the Debye films; and A. Zerwekh, who did the Pu assays.
TABLE I
VAPOR PRESSURE OF METHYLSILANE
ThOz-Pu02 SOLIDSOLUTION, FLUORITE STRUCTURE Lattice parameter (A, 25O) Mole % PuOt 0 5.598 f 0.001 15.0 5.568 f .004 26.0 5.5462 f .0004 36.9 5.526 f .001 46.7 5.502 f ,001 63.5 5.4693 f .0004 82.5 5.428 f .001 100.0 5.3960 f .0003
CeOz-PuOl SOLID SOLUTION, FLUORITE STRUCTURE 0 15.0 38.4 50.0 65.0 85.0 100.0
5.4112 f 0.0003 5.4083 f .0003 5.4054 f .0004 5.4040 f .0005 5.4005 f .0005 5.3976 f .0005 5.3960 f .0003
are estimated uncertainties in the graphical extrapolation. It is seen from Fig. 1 that the lattice ( 5 ) E. Wichers, et al., J . Research Nail. Bur. Standards, 33, 363 (1944)(6) W. H. Zachariasen. Phys. Rev., 73, 1104 (1948). (7)J. D. MoCullough, J . Am. Chsm. Soc., 72, 1386 (1950). (8)F. Hund, et al., 2. Elektrochem., 66, 61 (1952). (9) W. RUdorff and G. Valet, 2. anorg. allgem. Chem., 271, 257 (1953).
Fig. 1.-Lattice
parameter us. mole % PUOZ for solid solutions.
BY RAYW. SHADEAND G L ~ ND. N COOPER G'sdsral Elsctric Company Research Laboratory, Schenectady, New York Received June #I, 1068
Stock' has reported the vapor pressure of methylsilane from -130.5' to the normal boiling point, -56.9'. We have extended this range with measurements at several temperatures between - 29.0 and 47.2'. The results are shown in Table I, and are adequately fitted by the simple ClausiusClapeyron equation
.
log P (mm.) = 7.1454
- 919.05 T
This equation yields a value of 4205 cal./mole for the latent heat of vaporization. When these data are combined with those of Stock a plot of log P against 1/T shows a slight curvature, but a straight line is obtained when 1/(T 8) is used. Vapor pressures over the entire range from -130" to 47' may be calculated from the expression
-
log P = 7.0590
- 868.94 r8
with an average deviation of less than 2% from the measured values. (1) A. Stock and C. Somieski, BeT., 62, 695 (1919).
1468
NOTES TABLE I
VAPORPRESSURE OF METHYLSILANE t , "C. -29.0 0 24.0 35.7 40.5 47.2 P,mm. 2,340 6,310 11,110 14,800 16,670 18,920 Experimental Methylsilane was prepared by the reaction of methyltrichlorosilane with lithium aluminum hydride in di-n-butyl ether. "he crude product was analyzed by vapor-liquid partition chromatography and was found to contain approximately 0.5% each of dimethylsilane and trimethylsilane. It was redistilled through a low-temperature Podbielniak column rated a t one hundred plates and a center cut of the fraction boiling at -58" (700 mm.) was used in this work. No impurities could be detected in this fraction. The methylsilane was transferred to a small stainless steel cylinder equipped with two Bourdon gauges of different pressure ranges. The gauges were calibrated before and after the measurements were made. For measurements above room temperature the complete assembly was placed in a thermostated air chamber; for measurements below room temperature the cylinder was immersed in standard slush baths.
THE DECARBOXYLATION O F MALONIC ACID I N PHENOL, THIOPHENOL AND ANISOLE BY LOUIS WATTSCLARK
Vol. 62
reaction in several basic type solvents containing nucleophilic elements other than nitrogen inasmuch as relatively few such compounds have been studied previously.*+ Preliminary experiments having revealed,that decarboxylation of malonic acid takes place readily in phenol, thiophenol and anisole, the kinetics of the reaction in these three solvents was investigated. Results of this investigation are reported herein. Experimental Reagents.-( 1 ) Reagent Malonic Acid, 100.0% Assay,was used in these experiments. (2) Solvents: (a) phenol, Reagent Grade, b.p. 181.8" (755 mm.); (b) thiophenol, b.p. 169' (755 mm.); (e) anisole, Reagent Grade, b.p. 153.8" (760 mm.). Each sample of each solvent was distilled a t atmospheric pressure directly into the dried reaction flask immediately before the beginning of each decarboxylation experiment. Apparatus and Technique.-The kinetic experiments were conducted in a constant temperature oil-bath (-lr0.05") by the technique previously described .5 Temperatures were determined by means of a thermometer calibrated by the U. S. Bureau of Standards. I n each experiment a 0.1857-g. sample of malonic acid (the amount required to produce 40.0 ml. of COS at STP on complete reaction) was introduced in the usual manner into the reaction flask containing 50 ml. of solvent saturated with dry COa gas.
Results and Discussion The decomposition of malonic acid in anisole was studied at four different temperatures between Contribution from the Department of Chemistry, Saint Joseph College, 134 and 151'; in phenol at six different temperaEmmitsburg, Maryland tures between 141 and 168"; in thiophenol at four Received June 89, 1968 different temperatures between 139 and 161". Kinetic data have been presented previously The experiments were carried out twice at each on the decarboxylation of malonic acid in thirty- temperature. The experimental data were conthree basic type solvents, including twenty-five verted to standard conditions and milliliters of aromatic mines, l s 2 one alicyclic amine, four aro- evolved gas was plotted against time for each matic nitro compounds,8 a s~lfoxide,~ a ~ 0 1 ~ 0 1 temperature. ,~ Values of ~t:(corrected volume of gas) and an alkyl phosphate.6 All the data presented corresponding to different values of t were obtained support the mechanism for the reaction proposed from the resulting isotherms. When log (a - x) by Fraenkel and co-workers,6 namely, that an TABLE I electrophilic carbonyl carbon atom of the malonic acid coordinates with a nucleophilic atom of a APPARENTFIRST-ORDER RATE CONSTANTS FOR THE DEmolecule of solvent forming a transition compIex CARBOXYLATION OF MALONIC ACIDIN PHENOL, THIOPHENOL which suffers cleavage. In order for the reaction AND ANISOLE Cor. temp. k x 10' to ensue by this mechanism, a solvent is needed, Solvent ("C.) (sec. -9 apparently, which is capable of furnishing a pair of Phenol 141.26 3.67 Z!Z 0.02 electrons to the electrophilic reagent, but which is 145.00 4.85f .05 not sufficiently basic to cause ionization of the 153.01 9 . 0 7 - .04 malonic acid. (It has been shown that in strongly 156.49 13.61 f .05 basic solvents in which one hydrogen atom of the 159.07 14.95 f .05 malonic acid ionizes decomposition of the acid 167.63 28.25 f .IO malonate ion is involved.6 If both hydrogen atoms Thiophenol 138.85 1.73 f 0 . 0 5 ionize no decomposition at all takes place.') The 147.46 4 . 1 3 f -05 reaction appears capable, therefore, of being of use 156.24 10.02 f .02 in the study of the structure and properties of 160.50 1 5 . 0 0 f .02 various basic type solvents, and also of contributAnisole 134.26 0.77 f 0.01 ing to a greater understanding of the principles 138.85 1 . 1 8 f .04 of kinetics. Additional motivation for further 147.46 2 . 5 4 f .04 investigation of the reaction is the importance of 151.45 3 . 6 3 f .03 the malonic acid decomposition in synthesis. It was thought worthwhile to investigate the (where a is the maximum theoretical volume of (1) L. W. Clark, THIS JOURNAL, 62, 79 (1958). CO,) was plotted against t straight lines were ob(2) L. W. Clark, ibid., 62, 500 (1958). tained in each case for the first 75% of the reaction. (3) L. W. Clark, ibid., 62, 368 (1958). (4) L. W . Clark, ibid., 60, 825 (1956). The average values of k obtained from the slopes ( 5 ) L. W. Clark, ibid., 60, 1150 (1956). of the logarithmic plots are shown in Table I. ( 6 ) G.Fraenkel, R. L. Belford and P. E. Yankwich, J . Am. Chem. When log k was plotted against 1/T for each solSOC.,76, 15 (1954). vent straight lines resulted. The parameters of the (7) G.A. Hall, Jr., ibid., 71, 2691 (1949).
t
