Regiochemical effects on molecular stability: a mechanochemical evaluation of 1,4- and 1,5-disubstituted triazoles.
Poly(methyl acrylate) chains of varying molecular weight were grown from 1,4- as well as 1,5-disubstituted 1,2,3-triazoles. Irradiating acetonitrile solutions of these polymers with ultrasound resulted in the formal cycloreversion of the triazole units, as determined by a variety of spectroscopic and chemical labeling techniques. The aforementioned reactions were monitored over time, and the rate constant for the cycloreversion of the 1,5-disubstituted triazole was measured to be 1.2 times larger than that of the 1,4-disubstituted congener. The difference was attributed to the increased mechanical deformability of the 1,5-regioisomer as compared to the 1,4-isomer. This interpretation was further supported by computational studies, which employed extended Bell theory to predict the force dependence of the activation barriers for the cycloreversions of both isomers.
Department of Chemistry and Biochemistry, The University of Texas, Austin, Texas 78712, USA.
Johnathan N
JN
Brantley
Sai Sriharsha M
SS
Konda
Dmitrii E
DE
Makarov
Christopher W
CW
Bielawski