NOTES
4310
Results and Discussion The necessary values for covalent and packing radii were taken from Pauling,lO and they are given in Table 111. The values of Dgwith more particulars concerning how they were obtained are given in Table I1 and Figure 1. Table I11 radii, &----
-------Covalent
Single bond Double bond Triple bond
H
C
N
0
c1
0.30
0.77 0.62 0.55
0.74 0.62
0.72
0.99
r _ _ L -
Packing radii, A---
H
C
N
0
CI
1.15
1.65
1.5
1.4
1.8
Results of eq 3 were compared with experimental data of nine different binary solutions published by Filippov and Novoselova,6 Filippov, l 1 and Tsederberg. 12-14 Figure 2 shows Tsederberg's experimental data for the solution of water and ethanol compared with results of eq 1 and 3. Table I gives the maximum deviations of the values calculated by eq 1 and 3 from the experimental data, and it shows that in the case of eq 3 the maximum deviations do not exceed 4%. The reliability of used experimental data is 2-3%, The verification of generalized eq 5 has not been made because of the lack of experimental data. (11) L. P. Filippov, Vestn. Mosk. Univ., 6, 59 (1954). (12) N. V. Tsederberg, Tr. Mosk. Energ. Inst., 25, 13 (1955). (13) N. V. Tsederberg, Teploenergetika, 9, 42 (1956). (14) N. V. Tsederberg, Nauchn. Dokl. Vysshei Shkoly, Energ., 4, 189 (1958).
NOTES
Nitrogen-15 Magnetic Resonance Spectroscopy. Coupling Constants i n Hydrogen Cyanide
by Gerhard Binsch and John D. Roberts Gates and Crellin Laboratories of Chemistry,'t2 California Institute of Technology, Pasadena, California 91109 (Receiaed April 16, 1968)
Development of a promising new approach to the calculation of nuclear spin coupling constants,s capable of extension to atoms other than carbon and hydrogen, prompts us t o report the coupling constants in hydrogen cyanide-'5N which were measured in connection with a general study of spin coupling in nitrogen-15 labeled compound^.^ One and one-half grams of potassium cyanide-16N (96% W; R'Ierck Sharp and Dohme of Canada) was dissolved in 1.5 ml of water and 5 ml of 20y0 sulfuric acid added dropwise at room temperature. The liberated hydrogen cyanide was carried into a trap cooled t o -78" by a slow steam of nitrogen, After addition of the sulfuric acid was complete, the generating flask was first heated to 80" for 30 min and then to 105" for 15 min. The distillate containing the hydrogen cyanide was cooled to liquid nitrogen temperature and degassed. The hydrogen cyanide was then distilled into a bulb containing 5 g of Drierite and, after The Journal of Physical Chemistry
30 min at room temperature, condensed into an nmr tube which was sealed under reduced pressure. The proton nmr spectrum of the neat liquid taken immediately after preparation showed a sharp doublet centered at 3.60 ppm downfield from external TMS with a splitting of 8.7 f 0.1 Ha. The carbon-13 satellites (2 doublets) were separated by 274 i= 1 Hz. After 6 hr, a faint yellow color developed in the sample and the splitting of the main proton resonance and the carbon-13 satellites themselves disappeared-from then on only one single sharp line was observed. Apparently some catalytic agent formed, possibly associated with the oligomerization of hydrogen cyanide, which induced rapid intermolecular proton exchange. The corresponding coupling constants in acetylene are J l k ~= 248.7 Hz and J l k C H = 49.3 Hz.5 Multiplying J l a C C H in acetylene by the ratio y i 6 N / y l a C and assuming analogous bonding in acetylene and hydrogerr cyanide, one would predict 19.8 Hz for JWCHin (1) Contribution No. 3673. This paper is number VI11 in a series of papers on nitrogen-15 magnetic resonance spectroscopy. (2) Supported in part by Public Health Service Research Grant 11072-03 from the Division of General Medical Sciences. (3) J. A. Pople, J. W. McIver, Jr., and N. S. Ostlund, Chem. Phys. Lett., 1 , 465 (1967). (4) G. Binsch, J. B. Lambert, B. W. Roberts, and J. D. Roberts, J. Amer. Chem. Soc., 86, 5564 (1964). (5) R. M. Lynden-Bell and N. Sheppard, Proc. Roy. Soc., A269, 385 (1962).
NOTES hydrogen cyanide which is about twice too large. Similar anomalously small coupling constants involving 16Nhave previously been r e p ~ r t e d ;examples ~ include (C~HF,)~C="NH, C6H5CH='5N'3CH3, C6H513CH= 15iSCH3,and CH3l3C=l6N. The common denominator for these cases seems to be a carbon-nitrogen multiple bond. It will be interesting to see whether these anomalies can be rationalized on the basis of the Fermi contact mechanism for nuclear spin-spin coupling. The commonly assumed linear relationship6 between the per cent of s character of carbon orbitals and coupling constants between directly bonded 13Cand H, s = O . ~ O J % H , predicts 55% s character for the carbonhydrogen bond of hydrogen cyanide, slightly more than in acetylene. This conclusion is in qualitative agreement with the idea that the p character of the C=N bond should be greater than for the C s C bond of acetylene because nitrogen is more electronegative than carbon. This would mean more s character for the CH bond in hydrogen cyanide. (6) N. Muller and D. E. Pritchard. J . Chem. Phvs.. 31. 768 (1959): N: Muller, ibid., 36,359 (1962); C.' Juan and H. S , Gutowsky, ibid.; 37,2198 (1962).
The Crystal Structure of Benzophenone by Everly B. Fleischer,' Nako Sung, and Stuart Hawkinson Department of Chemistry, University of Chicago, Chicago, Illinois 60637 (Received December 81,1967)
Benzophenone is used in many types of organic and physical-organic experiments.2 We report here the crystal structure of benzophenone determined by threedimensional X-ray diffraction. The X-ray data were collected on a benzophenone crystal grown from hexane by slow evaporation. The cell constants ofobenzophenone are a = 10.30, b = 12.15, c = 8.00 A and the space group is P212121 with four molecules per unit cell (doalCd = 1.208 g/cm3; dobsd = 1.20 g/cm3). The 866 independent reflections were collected employing Cu K a radiation with a GE XRD5 diffractometer.3 The structure was solved by using the orientation of the molecule as determined from magnetic measurements2 and translating the molecule in the xy plane until a minimum R was determined for the Fhao's. The molecular translation in the direction followed directly from packing considerations. The structure was refined by full-matrix least-squares and Fourier difference techniques. The final weighted R factor [R = (zwlFo- Fc(2/zWFo2)'/2] for all refleetions is 5.3%. The weighting scheme used was w =
4311
11.23
A
Figure 1. Bond parameters for benzophenone. Average standard deviations in bond distances are 0.01 A ; in bond angle 0.5". The 1". bond angles in benzene rings are 120
1.0 for all Fhkz> 4.5 and w = 0.10 for FhRz< 4.5, where on this scale 2.0 is the smallest Fhk,considered to have a measurable value. The refinement was anisotropic and included hydrogen atoms. The coordinates of benzophenone are given in Table I, and Figure 1 gives the numbering system and important bond parameters of the molecule. The bond distances are as expected in the molecule and no special comment about them is necessary. The benzene rings are both planar. The dihedral angle between the two benzene rings is 56". Table I : Fractional Coordinates for Benzophenone Structure' Atom
z
2/
E
C(1) C(2) C(3) C(4) C(5) C(6) (37) C(8) C(9) CUO)
0.2147 ( 5 ) 0.1170 (5) 0,0109 (6) -0.0011 (6) 0.0945 (5) 0.2036 (4) 0.3003 ( 5 ) 0.2648 (3) 0.4402 (5) 0.5104 (6) 0.6439 (6) 0.7034 (6) 0.6352 (6) 0.5018 (5)
0.0282 (3) -0.0512 (5) -0.0312 (5) 0.0667 (6) 0.1499 (5) 0.1283 (4) 0.2176 (4) 0.3141 (3) 0.1935 (4) 0.2713 (5) 0.2526 (5) 0.1621 (5) 0.0866 (5) 0.1010 (4)
0.2165 (8) 0.2344 (8) 0.3315 (8) 0.4172 (9) 0.4001 (7) 0.3019 (6) 0.2786 (7) 0.2891 (6) 0.2442 (6) 0.1516 (7) 0.1263 (9) 0.1930 (9) 0.2812 (9) 0.3082 (7)
Wl) W2) (313) C(14)
a Standard deviations of coordinates in parentheses. gen atoms are not included.
Hydro-
(1) Alfred P. Sloan Fellow. (2) For example, R. W. Brandon, G. L. Class, C. E. Davoust, C. A. Hutchinson, Jr., B. E. Kohler, and It. Silbey, J. Chem. Phys., 43, 2006 (1965). (3) The observed and calculated structure factors for benzophenone have been deposited as Document No. NAPS-00082 with the ASIS National Auxiliary Publication Service, C/O CCM Information Sciences, Inc., 22 West 34th St., New York, N. Y. 10001. A copy may be secured by citing the document number and remitting $1.00 for microfiche or $3.00 for photocopies. Advance payment is required. Make checks or money orders payable to: ASIS-NAPS. T h e hydrogen positions and temperature factors are also with these data,
Volume 7 2 , Number 12
iVoaember 1968
