RATES OF REACTIONS OF OZONE WITH CHLORINATED AND CONJUGATED OLEFINS

The absolute values of the second-order rate constants for the reactions of ozone with chloroethylenes and allyl chloride have been determined in carbon tetrachloride solution at room temperature (25 ±pM 1°dg). The rate of ozone attack decreases strongly as the number of chlorine atoms in the olefin molecules is increased. The large variation in the values of the rate constants for the chloroethylenes, from 1.0 1. mole-1 sec-1 for C2C14 to 1200 1. mole-1 sec-1 for C2H3Cl, is believed to be primarily due to a predominantly electrophilic role of ozone in its reactions with these olefins. A pronounced additional trend is shown by the three isomeric dichloroethylenes: trans-1,2-C2H2Cl2 is about 16 times moee reactive than cis-1,2-C2H2Cl2, while 1,1-C2H2CI2 is the least reactive of the three isomers. These trends are discussed in terms of the electronic and steric effects and are compared with the behavior of other 1,3 dipoles in their cycloadditions to olefins. Relative rates of ozonation of 1,3-C4H6 and styrene have been determined by competition with 1-pentene. The two conjugated olefins do not show a strongly increased reactivity and in this respect differ from the behavior reported for some other 1,3-dipolar cycloadditions. © 1968, American Chemical Society. All rights reserved.