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The third group of compounds to be considered in Table IV is benzyl chloride and cy, a,a-trichlorotoluene. The rate of the C&&,CHzC1 reaction is faster than expected for the CHzCl group as an aliphatic substituent, when compared with 6-chloroethanol. We conclude, therefore, that the aromatic nucleus is activated toward a nucleophilic attack by electron withdrawal, both by inductive and by resonance effects. The chlorine atom, on the other hand, is also activated by the aromatic nucleus.lyThe interiction of eaq-with C6H6CC13, on the other hand, is in greater part a direct interaction with the chlorine atoms.lg In fact, this rate is slower than that with c h l~r o f o r m .~ This is attributed to a withdrawal of electrons from the aromatic nucleus resulting in partial deactivation of the -CC13 group.lY This last case is another example of a direct reaction of eaqwith a substituent. The use of our eaqrate constants as a measure of electron density in the nucleus is therefore limited to substituents which do not readily interact directly with eaq-.It is interesting to find that comparable rate constants are obtained for the naphthalene and benzyl chloride + esol-reactions in water and in ethanol, As the anionic product is a sparingly solvated species, this result corroborates the conclusion that the solvation of the electron in both solvents is comparable.20In conclusion, it can be stated that the hydrated electron may be considered as the most elementary nucleophile as well as the simplest reducing agent. The rules that apply to the eaqreaction are governed by the same parameters that determine aromatic substitu-tion13 and the information gained from the eaqreactivity may be applied to aromatic chemistry in general. It is gratifying to observe that the Hammett's freeenergy relationship holds up to the limit of diffusioncontrolled processes.Acknowledgment.-We wish to acknowledge the highly valued help of Dr. S. Gordon, the technical assistance of ,Miss P. Walsh, and the cooperation of Messrs.Several optically active diaryl sulfoxides have been prepared by treating optically active ( -)-menthyl ( -)arenesulfinates with arylmagnesium bromides.The optical rotatory dispersion curves and ultraviolet spectra of the sulfoxides and the sulfinate esters were determined and are discussed.This reaction is shown to produce optically pure sulfoxides. Sulfoxides can be synthesized by treating sulfinate esters with Grignard reagents4 If the sulfinate esters are optically active a t sulfur, optically active sulfoxides are formed. The first example of the use of this method was reported in a preliminary comm~nication.~ (+)-Ethyl p-tolyl sulfoxide (2) was prepared by the reaction of (-)-menthyl (-)-p-toluenesulfinate (1) with ethylmagnesium iodide. 0 0 I RMgX I .

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9) A reviewer suggested that the Hammett value is too small in absolute magnitude if carbonium ion formation is rate determining, but is consistent with urethan formation.The Journal of Organic Chemistry urethan formation is the simplest explanation, it is still disturbing that urethan cannot be isolated at low temperatures in most cases. If, on the other hand, the mechanisms are different for consumption of isocyanate, it might be concluded that three nitro groups have approximately the same effect in the urethan reaction as they would have in the amide-producing reaction.It is interesting to note that 4-toluenesulfonyl isocyanate (I) is slightly less reactive than is benzenesulfonyl isocyanate3 toward triphenylmethanol (II).(The rate constants are 0.209 and 0.296, respectively, at 100°.) Apparently, the methyl group destabilizes the transition state (which may have partial negative charges on the carbon or nitrogen of the isocyanate) or the subsequent ions. As expected from the above result, we have found that 4-chlorobenzenesulfonyl isocyanate is considerably more reactive than is I toward hindered phenols.10

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