J. Org. Chem. 1992,57,1045-1047 boxylate anion and 1.1 equiv of 1&6 crown ether in DMF. The solution was allowed to stir overnight in order to completely dissolve the salt and was then used immediately. The 0.1 M solution of KC104 was prepared similarly. Second-order rate constante, k", were obtained from plots of kob VB concentration of the nucleophile. Typically five concentrations of nucleophile were used from 0.02 to 0.1 M however, for some faster reactions lower concentrationswere employed. Generally plots of k h va nucleophile were linear with intercepts of zero; however, some plots appeared to show a small amount of upward curvature at higher nucleophile concentrations. The experimental point for the higheat nucleophile concentration never deviated more than 25% from the line defined by lower concentrations of nucleophile.
Acknowledgment is made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, for partial support of this work and to the University of Maryland for an institutional DRIF grant. We thank Dr. R. M. Pollack and Dr. D. Creighton for helpful discussions. W S t m NO. 1% 18052-27-2; Ib, 126644-72-2;IC, 126644-71-1; Id, 98525-64-5; DMF, 68-12-2; (CH3)&Si(CH3)2C1,18162-48-6; PhOH, 108-95-2; 4ClC&OH, 106-48-9; 3-C1C&OH, 108-43-0; 3-0zNC&OH, 554-84-7;CH&OzK, 127-082;HCOZK, 590-29-4; ClCHzCOZK, 7748-25-6; ClzCHCOzK, 19559-59-2; F3CC02K, 2923-16-2.
1045
Scheme I. Synthesis of Stereoisomers of the m-Nitro Analogue of Chloramphenicol n
0
tography for chloramphenicol in tissues at
