Enthalpiesof combustion and vaporization at 298.1 5 K have been measured for five cyclic polyethers. Enthalpies of formation in the liquid and gaseous states have been derived : -AH,"(l)/kJ mol-l -AHc(g)/kJ mol-l lr3-Dioxan 377.5 f 1.1 338.4 f 1.1 1,4-Dioxan 355.1 f 0.9 316.5 f 0.9 1,3,6-Trioxacyclo-octane 516.0 f 1.2 467.2 f 1.2 1,4,7,1O-Tetraoxacyclododecane 696.8 f 2.1 631.1 f 2.1 1,4,7,10,13-Pentaoxacyclopentadecane 879.1 f 2.0 799.5 f 2.0The results for cyclic 1,3-and 1,4-polyethers are discussed in terms of apparent strain energies relative to aliphatic polyethers. It is shown that there is a constant contribution to the apparent strain from each 1,3-dioxa and 1,4-dioxa unit, provided that the reference system consists of compounds which have conformations similar to those of the cyclic polyethers.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.