770
Additions and Corrections
The product structure of D6h is (the decompositions of most common point groups are given in ref 5)
n a h 8 The supergroup is appropriate for the attempt to separate isomers (at least at reasonable temperatures) while the point group is appropriate for the low temperature NMR.
The groups of eq 4 and 5 are isomorphic since they have the same product structure of primative groups having the same orders. The question naturally arises as to when the supergroup is the appropriate group to use in describing a system. The answer to this depends either upon the energy barrier for the isodynamic operation in relation to the energy of the experiment being performed’ or upon the mean lifetime of a conformation in relation to the time scale of the experiment. In the case of cyclohexane, for example, no enantiomers of cis-1,2-dibromocyclohexanecan be isolated; however, at low temperatures the axial and equatorial protons of cyclohexane itself can be observed as distinct NMR sig-
Acknowledgments. Financial support from the National Science Foundation (Grant No. GP-38740X) is gratefully acknowledged. References a n d Notes (1) J. E. Leonard, G. S. Harnrnond, and H. E. Simmons, J. Am. Chem. SOC., 97, 5052 (1975). (2) G.Polya, Helv. Chim. Acta, 19, 22 (1936). (3) H. C. Longuet-Hlgglns, Mol. Phys., 6 , 445 (1963). (4) S. L. Altrnann, Proc. R. SOC.London, Ser. A,, 298, 184 (1967). (5) S. L. Altrnann, Phil. Trans. R. Soc., Ser. A, 255, 216 (1963). (6)J. F. Gllles and J. Philipott, lnt. J. Quantum Chem., 6, 225 (1972). (7) R. L. Flurry, Jr., J. Mol. Spectrosc.,56, 68 (1975). ( 8 ) F. R. Jensen, D. S. Noyce, C. H. Sederholrn, and A. J. Berlin, J. Am. Chem. Soc., 84, 386 (1962).
ADDITIONS AND CORRECTIONS
1972, Volume 76 N. Dennis Chasteen a n d Melvin W. Hanna: Electron Paramagnetic Resonance Line Widths of Vanadyl(1V) a Hydroxycarboxylates. Page 3952. Parallel and perpendicular subscripts were omitted. In the second column, the bottom line should read ‘Values for g and A I were , . .”. Equation 4 should read wo = gllPoH/h
A 2 + A I ~ M+ -$-. ..
The fourth line from the bottom should read “We derived g and A ,I . . .”
The Journal of Physical Chemistry, Vol. 80, No. 7, 1976
Page 3956. Equation 11 should read “a” = Dennis Chasteen
. . . -N. ”
1975, Volume 79 Wayne M. Marley a n d Peter M. Jeffers: Shock Tube Cis-Trans Isomerization Studies. IV Page 2085. The correct value for km(l,3-pentadiene)in line 3 of the Abstract is 1013.6exp (-53,000/4.58T). The activation energy is correctly reported as 53 kcal/mol in the body of the paper.-Peter M. Jeffers
