1964 Reactivity of Halides in Sn2 Reactions 4645 a to sulfur, rather than ß to sulfur (where it would be closer to the halogen atom). The trends in chemical shifts noted for 14 and 15 are continued in the spectrum of the dibromo derivative 16.The CHBro singlet is at 1.37 p.p.m. and the quartet for the single ring hydrogen atom is at about 3.7 p.p.m. Peak B is shifted to 5.33, whereas peaks C and D remain essentially fixed [doublet centered at 5.SS (J = 7.0 c.p.s.)]. Peaks E and F are now resolved. as in the parent sultone 13, but are shifted downfield to 5.88 and 5.99 p.p.m. They are separated by a chemical shift ( = 0.11 p.p.m.) comparable in magnitude to that observed in 13 ( = 0.07 p.p.m.).Sultone 17 was prepared by the sulfonation of 1-/-butylcyclohexene.3 The structure assigned on the basis of the expected course of reaction3•4 is that shown. This assignment is supported by the p.m.r. spectrum, which can be compared with that of 13. Structurally, 17 differs from 13 by the fact that the cyclohexane ring has replaced one methyl group on each of the carbon atoms a and ß to oxygen. The structural features held in common (gem-dimethyl group a to oxygen, methyl group ß to oxygen, and single hydrogen atom 7 to oxygen) give rise to closely similar p.m.r. I). The chemical shifts observed in changing from 17 to 18 should be, and are, comparable to those in changing from 13 to 15. signals (TableAcknowledgment.-This work was generously supported by the Office of Ordnance Research under OOR Grant DA-ARO(D)-31-124-G19. We wish to thank Dr. K. W. Bartz, Humble Oil and Refining Co., Baytown, Texas, for checking some of the spectra and for several helpful discussions.

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NOTES 835 group and a N=C double bond.8 To the best of our knowledge, an analogous activation by a carbonyl group has not been observed before;9 indeed, on the whole, experience has shown that in such cases fluorine is the most easily replaceable substituent.3-Chlorophthalic anhydride did not react with potassium cyanide under the same operating conditions. EXPERIMENTAL 3-Chlorophthalic anhydride was prepared according to Newman and Scheurerz from 3-nitrophthalic anhydride10 and gaseous chlorine. The temperature of the bath was kept exactly at 250°, the liquid product poured into a mortar and, after it solidified, ground to a fine powder.It was not necessary to distill it; already in its crude stage it melted a t 118-124' and after trituration with anhydrous ether at 125-127'. The yield was 76%.5-Fluorophthalic anhydride. In a Claisen flask (for distillation of solid compounds) of 100-ml. capacity, 20 g. of anhydrous potassium fluoride" was covered with a layer of 20 g. of 3-chlorophthalic anhydride and the mixture heated a t 280-290° for 45 min. Distillation at 220-225', 80 mm. gave a clean fraction (11 g.), which solidified spontaneously and was recrystallized from 75 ml. of toluene, map. 160"; yield, 9 g. (50%).