Aqueous carbon dioxide with 2,2'-dichlorodiethylamine gives 3-(2-chloroethyl)-2-oxazolidinone. At 37°over the pH range of 6.3-7.5 and buffered with 5 X 10-4 to 170 X 10-4 M carbon dioxide, the half-lives of the pseudo-first-order reactions vary from 1.5 to 35 min. Rate and equilibrium constants bearing on the formation of the oxazolidinone have been determined. Ring closure from the carbamate anion, (CICHiCHzjzNCOz-, is the rate-controlling step, ks = 10™16 ™ 10 3 sec-1; closure from the zwitterion, (ClCHíCF^NH+COr, and reactions involving the aziridine are kinetically unimportant. The pKE of 2,2 '-dichlorodiethylamine hydrochloride, measured by pH titration and confirmed by the kinetic results, is 6.41 at 37°.(1) Support by a Sterling-Winthrop Research Fellowship and a Stauffer Chemical Fellowship is gratefully acknowledged.(2) (a) H.

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