Carbon-13 NMR assignments in 1,3-cyclohexadiene
Abstract Unambiguous 13 C-NMR assignments for the olefinic carbons of 1,3-cyclohexadiene (in CDCl 3 : δ C(1) = 126.02 ppm and δ C(2) = 124.30 ppm downfield from TMS) have been made by comparison with regioselectively synthesized 2-deuterio-1,3-cyclohexadiene (in CDCl 3 : δ C(1) = 125.88, δ C(3) = 124.22 and δ C(4) = 126.02 downfield from TMS). 1 H-NMR chemical shifts and splittings are shown for both compounds.
This paper deals with the behaviour of hydrolyse d Polyacrylamide solutions in the presence of chromium III. First, using potentiometry and spectroscopy, we study the complexation between chromium III and sodium acetate used as a low molecular weight model for the polymer. Then the same methods are applied to investigate the polymer—Cr(III) complexation and the results are discussed in conjunction with the nature of the physical states of the systems. Finally, we perform rheological measurements in the sol—gel transition regime in a range where the number of crosslinking points can be calculated unambiguously.