270 MHz 'H NMR spectra were used to study the structure of end groups and terminal monomeric units in polybutadienes produced by radical polymerization, initiated with hydrogen peroxide and a series of substituted benzoyl peroxides. The hydroxyl or aroyl groups were found to be bonded to the methylene end group of the 1,4-cis-, 1.4-frans-or 1,2-butadiene terminal units. The terminal units are richer in 1,2-structures than the backbone due to the influence of hydroxyl or of the aroyl groups on the relative reactivity of carbons 1 and 3 in the allylic radical, formed by initiation. 1,2-Units at the chain ends and in the backbone are predominantly joined to 1 ,4-units; this results in a magnetic nonequivalence of the methylene protons in 1.2-structures. Data are also presented on the extent of radical decarboxylation during initiation by substituted benzoyl peroxides and also on the introduction of solvent fragments in polybutadienes obtained by initiation with hydrogen peroxide in alcoholic media. 4,20 CH=CHl 2 bands, 6 = 3,94 and 3,93 2 bands, 6 = 3,42 and 3.40 Multiplet Doublet, J = 6 Hz 2 bands, 6 = 3,28 and 3.27 2 bands, 6 = 4,21 and 4,19 2 bands, 6 = 4,70 and 4.68 2 bands, 6 = 4,81 and 4,79 2 bands, 6 = 3,29 and 3,27 2 bands, 6 = 4,21 and 4,19 2 bands, 6 = 4,lO and 4,68 2 bands, 6 = 4,79 and 4,77 Multiplet Doublet, J = 7 Hz Triplet, J = 7,3 HZ
