1969 Volume 42 Issue 12 Pages 3565-3571
The rate constants of the hydrochloric acid-catalyzed rearrangement of N-methyldiaryltriazenes were determined in 95% aqueous ethanol in the presence of N-methylaniline. Electrondonating substituents on the diazo-part in triazene promoted the rearrangement. A Hammett plot of the rate constants gave a good straight line. The negative ρ-value (−3.63 at 30.0°C) and the large positive values of the entropy of activation suggested that the rate-determining step in this rearrangement is the dissociation of protonated triazene; this is in contrast with the case of the Friswell-Green mechanism. This theory was suppoted by such a solvent effect as that the rate decreased a little as the polarity of the solvent increased. The kinetic behavior of triazenes in the absence of N-methylaniline, and the incorporation of N-methyl-o-toluidine into the product in the rearrangement of 1-p-chlorophenyl-3-methyl-3-phenyltriazene (Id), were also discussed in connection with the above mechanism.
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