OXIBASE SCALE AND DISPLACEMENT REACTIONS .18. REACTION OF MERCAPTOETHYLAMINE WITH METHYL IODIDE AND WITH ETHYL TOSYLATE

The reaction of mercaptoethylamine (MEA) with methyl iodide to give the mono-S-methyl derivative has been studied in aqueous solution as a function of pH and temperature. The rate expression is – d[CH3I]/dt = k2[CH3I][H3N+CH2CH2S-] + A:4[CH3I][H2NCH2CH2S-] with only the thiolate forms of MEA being kinetically important. The data have been used to calculate the oxibase scale parameters of each thiolate anion. The factors influencing the reactivity of MEA as an antiradiation drug are discussed. The reaction of MEA with ethyl tosylate in aqueous buffer solutions has been studied over the pH range of 5-12 from 25 to 53° The product is S-ethyl MEA. The oxibase scale parameters of the various forms of MEA are obtained. The relationship of these data to the antiradiation drug is discussed. It is concluded that all of the existing theories would be correlated with the oxibase scale. A prediction has been made concerning the design of better drugs. While some of the discussion is quite speculative, the theories do explain the experimental data. © 1969, American Chemical Society. All rights reserved.