Host selectivity considerations of compound (+)-(2R,3R)-1,1-4,4-tetraphenylbutane-1,2,3,4-tetraol (TETROL) in the presence of o-, m- and p-cresol guest isomers

摘要

In this work, (+)-(2R,3R)-1,1,4,4-tetraphenylbutane-1,2,3,4-tetraol (TETROL) was investigated for its feasibility as a host compound for its possible future employment in the separation of the cresol isomers (ortho-, meta- and para-cresol, o-, m- and p-Cr). Of the three, only m- and p-Cr were enclathrated by this host compound, and host:guest ratios were consistently 2:1. When TETROL was presented with equimolar mixed cresols, the host displayed significant selectivity for the para isomer, and a host selectivity order of p-Cr (64.9%) > m-Cr (23.8%) > o-Cr (11.3%) was observed. More notably, however, TETROL's selectivity for this isomer was enhanced (70.4%) when it was recrystallized from an equimolar binary mixture of m- and p-Cr, the two isomers that are the most onerous to separate by conventional means. Furthermore, TETROL remained selective for p-Cr even when this isomer was present in the mixture in low quantities relative to the meta isomer. Thermal analyses confirmed that p-Cr formed the more thermally stable complex with the host compared with the inclusion compound containing the m-Cr guest, and this correlated with the observed selectivity order.