S. WINSTEINAND ERNESTGRUNWALD
828
I, 1120; tran.i.-Ohc,0.305; trans-Br, 7.18 X trans-OCH8, ,5.28 X cis-OAc, 1.31 X low4; trans-Cl, 0.94 X lo-*; cis-OSOzCsHrBr, 1.6 X trans-C)S02CaH4Br,1.4 X 10-j. Variations in rate are largely due to variations in AH*'. The rate-determining ionization step appears to be largely a direct formation of the cycle I1 (rate constant ka) in the case of neighboting trans-I, Br, and OAc and predominantly the formation of carbonium ion I11 (rate constant k,) with neighA
I
x
> ds-cu < I1
dA > 4g-c:
) Spaeth and Koller, Bcr., 68, 12G9 (1925). (7) (a) Bateman, Church, Hughes, Ingold and Taher, J . Chcm. Soc., 970 (1940); (h) Hughes, Trans. Faraday Soc., 87, 603 (1941). ( 8 ) Hammett, "Physical Organic Chemistry," McGraw-Hill Book Co., Inc., New York, N. Y . , 1940, Chapters V and VI.
Feb., 1048
TIIE
ROLEOF NEIGIIBORING GROUPSI N
KATE CONSTANTS FOR
THE
l C5-G
