NOTES
1958
Vol. 64
system, such as that involved in iodine coordination, pheric pressure and a t 1360 atm., and the volume these weak interactions have little effect on the AH change of activation in ml./mole. The rate oonvalue. These effects are slight compared to the stants were reproducible within 3% and the corenergies of bond formation, can be overcome in responding error in AV* is 0.5 ml. All volume part by rearrangement, and are manifested in the changes are very small in comparison t,o the molar entropy ~ h a n g e . ~ volumes, and it seems that racemization of these This study indicates that intensity values are compounds does not involve extensive desolvation. not reliable criteria for basicity when steric effects may be operative in the system under consideration TABLE I although sometimes they have been showna to Compd. Solvent T,OC. ka lip AV* parallel both basicity and reactivity in systems I DMF 114.8 0.0548 0.0553 - 0 . 2 free from steric interactions. .I66 -0.8 I1 DMF 50.8 ,159 Acknowledgment.-The authors gratefully ac.lo1 1.9 51.5 ,111 I1 EtOH knowledge the financial support given by the ReI1 EtOH-"*OH 51.5 .308 .288 2.0 search Corporation and the very helpful discussion I11 DMF 114.5 .I32 ,129 0.5 of the problem with Dr. T. L. Brown. Although the salt of I1 racemizes somewhat faster than the free acid the volume changes are T H E EFFECT OF PRESSURE ON T H E essentially equal. The carboxyl group evidently RESTRICTION OF ROTATION ABOUT does not contribute to the restriction of rotation. SINGLE BONDS Previous experiments have shown that the mesomeric effect of electron-withdrawing groups pura BY DONALD R. MCKELVEY AND K. R. BROWER to the nitrogen atom causes an increase in the Department of Chemistry, New Mezico Institdm of Mining und Techrate of racemization by stabilization of the planar nology, Campus Statran, Socorro. New Mezieo intermediate.s The same phenomenon should Receioed June 9'7, lS60 occur in t,he racemization of 11, but the resulting Detailed calculations of the geometry and strain polarization does not cause sufficient electrostricenergy of the transition states for the racemization tion of solvent to be reflected in the volume change of a number of optically active biphenyls' lead to of activation. the conclusion that the chief mode of deformation Experimental is bending of the single bonds which hold the interBromomesity1ene.-The method of Smith was used.' fering groups. Since very little stretching should Bromonitromesity1ene.-To a mixture of 14 ml. of acetic occur, there is no reason to expect that internal anhydride and 14 ml. of acetic acid was added 12 ml. of geometrical changes would produce a measurable white fuming nitric acid a t -15". The resulting solution increase in volume in the transition state. On the was added slowly to a mixture of 60 g. of bromomesitylene and 85 ml. of acetic anhydride while the temperature was other hand it is likely that a significant part of the maintained a t - 15' by addition of Dry Ice. The reaction restriction of rotation arises from solvation of the mixture was allowed to reach room temperature and was polar interfering groups. It recently has been re- poured into 300 ml. of water. The organic layer was ported that the rates of racemization of biphenyls diluted with ether, washed with 5% sodium hydroxide solution, dried, and distilled a t a pressure of 1 mm. The having ionic or polarized interfering groups are fraction boiling from 120-140' was collected and crystalstrongly dependent on the solvent and added lized from ethanol. The yield was 30 g. (41%), m.p. salts.2 If a considerable amount of electrostricted 51-53'; rec. m.p. 54". N-Benzenesulfonyl-N-carboxymethyl-3-bromomesidine .solvent is released during the activation process it bromonitromesitylene was reduced, benzenesulfonyshould be possible to detect a decrease in rate with The lated, and carboxymethylated by a sequence of steps increasing pressure. used in another ~ynt~hesis.5The yield was 17 g., m.p. This preliminary survey reports the volume 218-219'. Therec0rdedm.p. i~216.0-217.5".~ N-Benzenesulfonyl-N-carboxymethyl-l-amino-2-methylchange of activation for the racemization of d-Nprocedure of Adams and Sundstrom3 benzenesulfonyl-N - carboxymethyl - 3 - bromomesi- naphthalene.-The was used with modifications described in ref. 5. dine (I), d-N-benzenesulfonyl-N-carboxymethyl-1N-Benzenesulfonyl-N-carboxymethyl-l-amino-2,4-diamino-2,4-dimethyl-6-nitrobenzene(11) and d-N- methyl-6-nitrobenzene.-The procedure of Sdams and benzenesulfonyl - N carboxymethyl - 1 - amino 2- Gordon7 was used with modifications described in ref. 5. of Racemic Mixtures.-The cinchonine salts methylnaphthalene (111). The solvent used for of Resolution the acids were prepared by dissolving each acid together I and I11 was dimethylformamide, whereas I1 with the stoichiometric amount of cinchonine in approxiwas racemized in dimethylformamide, ethanol, and mately six parts of hot ethanol. The crystals which sepaethanol containing twice the amount of ammonium rated after several days of refrigeration were recrystallized ethanol, and the optically active acids were retrieved hydroxide required to neutralize the acid. The from by the methods described in the preceding references. volume change of activation was calculated from The d - N - benzenesulfonyl-N-carboxymethyl-3-bromomethe equation sitylene obtained in this way had [ a ] 2 6 ~ + 27.9' in DMF whereas the reported values is I ~ ] P ~ 4D 22.1". The other -RT ( 8 In k / 6 P ) ~= AV*
-
-
acids had rotations in agreement with the literature values.
in which k is the reaction rate constant. The results are shown in Table I which lists the conditions, the rate constants in hr.-l a t atmos(1) F. R. Waetheimer. J . Chem. Phys., 16, 252 (1947); K. E. Howlett, J . Chum. Soc., 1055 (1960). (2) J. E. Lefflsr and B. 11 Graybill, THISJOURNAL, 63, 1457, 1461 (1959).
(3) R. Adams and K. V. Y . Sundstrom. J . A m . Chern. Soc., 7 6 , 5474 ( 1954). (4) "Organic Syntheses," Coll. 1'01. New York, N. Y.,1950, p. 95.
11, John Wiley and Sons, Inc.,
(5) R. Adams and K. R. Brower, J . Ana. Chem. Sac., 78, 663 (195G). (6) R. Adams and M. J. Gortatoweki, ibid., 79, 5525 (1957). (7) R. Adams and J. R. Gordon. ibid., 78, 2458 (1950).
Dec.. 1960
COMMUNICATIONS TO THE EDITOR
Racemization Procedure .-Solutions having initial rotations of 2-6' were heated in a constant temperature bath until the rotation had decreased by one-half. The rotations were measured with a Kern polarimeter, and the re-
1959
producibility was f0.03'. The high pressure apparatus and sample holder already have been described.* (8) K.
R. Brower, J . Am. Cham. Soc., 80, 2105 (1958).
COMMUNICATIONS TO THE EDITOR TRIMERIC BISMUTH(1) : AN X-RAY DIFFRACTION STUDY OF SOLID AND MOLTEN BISMUTH(1) CHLOROALUMINATE
tained' a t this laboratory from measurements of optical absorp6ion.
t
sir:
50 This report summarizes an X-ray diffraction study of molten, polycrystalline, and monocrystalline BiA1C14 which indicates the occurrence of a trimer of bismuth atoms separated by 3.04 A. in the configuration of an equilateral triangle. The compound was prepared as previously described. l X-Ray diffraction patterns of the powder and melt were measured with monochromatized M o K a radiation in the range of (4?r/X) sin 0 less than 16. The powder pattern included diffuse as well as Bragg scattering. The patterns were interpreted, by procedures described elsewhere12m3 to yield the radial pair distribution functions shown in Fig. 1. The principal feature of both functions, a prominent sharp peak a t about 30.0 A. partially resolved from another a t about 3.4 A., requires the existence of a bismuth polymer. Further analysis, to be described in detail elsewhere, led to the probable configuration (Bi3)3+. The figure demonstrates by means of synthetic peaks that the proposed model is consistent with the observed distributions. Single crystals of BiA1C14have been shown4 to be rhombohedral with space group R3c, a = 12.12 A., 0 .I 2 3 4 5 6 a = 58' 23', 2 = 6. This cell accounts for the powder pattern of BiAlCL, thereby demonstrating f , A. the identity of the two materials. Equivalent bis- Fig. 1.-Radial pair distribution functions for BiAlCL, solid muth atoms a t a separation of 3 A. can be accomand melt, from X-ray diffraction data. modated in this cell only if related by the triad axis; DIVISION thus the symmetry of the crystal also indicates the CHEMISTRY OAKRIDGENATIONAL LABORATORY H. A. LEVY existence of a trimer. OAK RIDGE,TENNESSEE M. A. BREDIG FOR THE U.S.A.E.C. M. D. DANFORD The finding of the trimer (Bi3)3+casts consider- OPERATED CORPORATION P. A. AGRON able doubt on an earlier tentative propo~al,~ based BY UNIONCARBIDE RECEIVED OCTOBER12, 1960 on cryoscopic and vapor pressure data, of a species (BQ2+ in the system Bi-BiC1,. Recent measure(7) C. R. Boston and G. P. Smith, Jr., personal communication, to ments6 of e.m.f. in molten Bi-BiCL solutions also be published. suggest the species (Bi3)3+ in this system. Additional evidence of polymer formation has been obSORPTION O F GASEOUS HYDROGEN (1) -1. D. Corbett and R. K. hIcMullm, J. A m . Chem. Soc.. 7 8 , 2906 CHLORIDE BY NYLON AND PROTEINS
50r
(1956). (2) H.-4. Levy, P. A. Agron and M. D. Danford, J. Chem. Phys., 30, 1486 (1959); 31, 1458 (1959). (3) H. A. Levy, P. 4. Agron. hl. -4.Bredig and M. D. Danford, Annals of the h'ew Y o r k Academy of Scaences, 79, 762 (1960). (4) H..4. Levy, P. A. Agron and R. D. Ellison, t o be reported. ( 5 ) M. A. Bredig, THIS JOURNAL, 63, 978 (1959). (6) L. E. Topol, S. J. Yosim and R. A. Osteryoung. Xeeting American Chemical Society, New York, N. Yo, 1960,division of Physical Chemistry. Abstracts p. 6-6.
Sir: I n the course of work published in 1956' it was noticed that when Nylon with sorbed hydrogen chloride was exposed to water vapor or liquid water, it lost its tensile strength, felt sticky to the (1) L. 13. Reyerson and L. E. Peterson, THISJOURNAL,60, 1172 (1956).
