Reaction Products of Chloral with cis-1,4-Polyisoprene

Abstract

In an earlier note the fixation of chloral onto cis-1,4-polyisoprene (natural or synthetic) in the presence of a catalyst such as AlCl3 or BF3 was discussed. A similar combination with glyoxal has already been mentioned. The fixation of chloral produces macromolecular products with a level of fixation of not higher than n=30 (n, number of reagent molecules attached to a chain of 100 C5H8 units). These compounds contain hydroxyl groups, the infrared bands of which appear at 3,300–3,500 cm−1, while the chlorines are identified at 570, 620, 680, 730, and 1,080 cm−1; these bands can be attributed to side chains —CHOH—CCl3. Also, the band which is characteristic for the cis configuration remains in the spectrum, but has decreased in comparison with the blank; the broadening of the peak at 1,640 cm−1 and the presence of a band at 860 cm−1 indicate the appearance of vinylidene double bonds not located in the chain. This observation is in agreement with our earlier work. The presence of side chains —CHOH—CCl3 is confirmed by the reactivity inherent to these functional groups. The expected reactions take place but are limited by the formation of a three dimensional network resulting in insoluble compounds. Thus, a modified polyisoprene (n=15) loses only 60% of its chlorine by heating to 130° C in xylene solution in presence of finely dispersed sodium. It is difficult to eliminate the remaining chlorine because the radicals formed by the —CCl3 groups produce crosslinking. Phenyllithium produces similar effects to those of sodium, in addition a certain number of phenyl groups are added and result in bands found at 1,495–1,580 cm−1. The presence of hydroxyl groups is also verified by reaction with acetyl chloride. Bifunctional reagents such as adipoyl dichloride or hexamethylene diisocyanate produce crosslinking reactions which become evident by rapidly increasing insolubility.