1706
Vol. 77
COMMUNICATIONS TO THE EDITOR
grtnic acids by washing with dilute aqueous sodium carbonate and then with water, the benzene solution was allowed to evaporate a t room temperature. The 0.160 g.. (69%) of oxide, m.p. 66-67', which remained was crystallized at 0" from 40-60' petroleum ether, yielding analytically pure material, m.p. 67.5-68.0'.
Anal. Calcd. for CBHIRrzO: C, 38.14; €1, 3.13. Found: C, 25.56; H, 3.28. DEPARTMENT OF CHEMISTRY UNIVERSITY O F &I'SCONSIN MADISON, WISCONSIN
-
COMMUNICATIONS T O T H E E D I T O R SALT EFFECTS ON NON-ELECTROLYTES IN PARTIALLY AQUEOUS MIXED SOLVENTS1 Sir :
Previous work on kinetic salt effects2*ahad led us to the belief that salt effects on non-electrolytes in mixed, partly aqueous solvents might be quite different from corresponding effects observed in water. This belief has been borne out by some data recently obtained from solubility measurements in 50% dioxane a t 25', as tabulated in Table I. TABLE I Non-electrolyte
Benzoic Acid
a-Naphthoic Acid
Naphthalene
Solvent
Water4
50% Dioxane
Water6 50% Dioxane
k
Salt
NaCl HC1 KCl KI HC1 KI NaC1 KCl NaCl KC1 NaCl KCl
0.182 ,121 ,093 ,041 .011 ,017 - .12 .15 ,260 ,204 - .09 - .08
-
The data show that the salting order of various electrolytes in 50% dioxane is quite different from that generally observed in water.s This can be seen by comparing the values of k in Table I, which So were obtained by plotting log - versus CS and S measuring the slope. A positive k is associated with salting-out while a negative k results from salting-in of the non-electrolyte by the salts present. For example, NaCl and KC1, which in water are usually better salting-out agents than HCl and K1, in 50% dioxane actually cause salting-in. A qualitative understanding of the effect of the mixed solventon the salting order of electrolytes may be reached on the basis of the preferential hydration of the electrolytes. i Consider, for example, the effects due to KC1.1 I n water, hydration of KC1 leaves less solvent for the non-electrolyte to dissolve in; hence, salting-out. I n 50% dioxane, pref-
erential solvation by water leaves an effective solvent richer in dioxane. When the non-electrolyte solubility increases with dioxane content, the net effect may be salting-in. The solubility data for naphthalene and CY- naphthoic acid in Table I1 suggest this as a partial explanation. TABLEI1 Dioxane,
Solubility
Nonelectrolyte
5%
(g /IO0 ml )
u-X'iphthoic Acitl
40
ii0
0 80 2 91 7 57
40 50
0 14 0 79
50
Saphthalene
The present data suggest that previous treatments of kinetic salt effects as colligative functions of ionic strength, or even on the basis of the Setschenow equation, may be oversimplified in partly aqueous solvents. CHEMISTRY DEPT. ARTHURF. BUTLER FLORIDA STATE UNIVERSITY ERNESTGRU~YWALD FLORIDA TALLAHASSEE, RECEIVED FEBRUARY 10, 1955 AN INVESTIGATION OF T H E HYPOTHETICAL ION PAIR INTERMEDIATE IN T H E REARRANGEMENT OF 9-DECALYL HYDROPEROXIDE BENZOATE USING OXYGEN-IS
Sir: Recently, ion pairs have been considered as intermediates in a variety of organic reaction^.^^^.^ The degree of separation of the ions in many of these reactions, particularly those ion pairs which have been dubbed "intimate" or "internal," has remained obscure. We wish t o report the results of an oxygen-18 tracer study of the rearrangement of the benzoate of 9-decalyl hydroperoxide (I), a reaction which has the properties of an intimate ion pair r e a c t i ~ n . ~ . ~ Benzoyl chloride-018, prepared from benzoic acid-018, was allowed to react with 9-decalyl hydroperoxide to form I. I was rearranged in both methanol and acetic acid to give 1-benzoyI1,A-epoxycyclodecane (111) which was reduced with lithium aluminum hydride to benzyl alcohol
(1) This paper is based on research done under contract Nonr (1) S. Winstein, E. Clippinger, A. H. Fainberg and G. C. Robinson, 988(02) with the Office of Naval Research. ( 2 ) W. C. Coburn, Jr.. E. Grunwald and H. P. Marshall, THIS Chem. and Ind., 664 (1954) (2) E. Grunwald, A n a l . Chem., 26, 1698 (1954). JOURNAL, 76, 5735 (1353). (3) H. L. Goering, J . P. Blanchard and E. E. Silversmith, THIY (3) L. C. Baternan, M. G. Church, E. D. Hughes, C. K. Ingold J O U R N A L , 76, 5409 (1954). and N, A. Taher, J . Chem. SOC.,973 (1940). (4) P. D. Rartlett and J. I.. Kice, ibid., 76, 5581 (19.73). (4) F. A. Long and W. F. McDevit, Chem. Reus., 61, 119 (1352). ( 5 ) R. L. Goering and A. C. Olson, ibid., 76,5863 (1953). ( 5 ) M. A. Paul, THIS JOUBNAL, 74, 5274 (1952).
