Analysis of the telomerization of acrylic acid by mercaptans, 1 - Telomerization of acrylic acid by thioglycolic acid; Influence of the natural of the solvent on the value of the transfer constant and k(p)/k(te)1/2

The telomerization of acrylic acid (AA) with thioglycolic acid (TGA) initia ted with 2,2'-azoisobutyronitrile (AIBN) was first investigated in organic medium (THF, 65 degreesC). The kinetic study of this telomerization led to the determination of the TCA transfer constant (C-r = 3.2) and to the ratio k(p)/rootk(te) equal to 0.48 L-1/2.mol(-1/2).s(-1/2). Then, the same study was performed both in aqueous medium and in water/THF mixture in order to investigate the solvent effect on the transfer constant. From these works i t is emphasised that the nature of the solvent plays an important role on t he kinetics parameters. First, this research underlined an increase of the k(p)/rootk(te) value by raising the water proportion in water/THF mixtures. Then, the kinetic study showed the highest value for the k(p)/rootk(te) co nstant, equal to 2.48 L-1/2.mol(-1/2).s-(1/2) when the telomerization proce eded in water. Consequently, the value of C-T, which is directly influenced by the k(p)/rootk(te) constant, presented a decrease from CT = 3.2 in THF to a value equal to 0.5 in water. By this way, the a ideal,, case of telome rization (C-T = 1) was reached for a mixture of solvents; 80% water/20% THF (v/v). [GRAPHICS]