Enthalpies of formation for three- and eight- membered heterocyclic ethers (15
compounds) in gas state have been determined by different theoretical methods: levels of
theory B3LYP/6-31g(d), MP2/6-31g(d) and chemical composite methods (Gn and CBS)
via two approach’s: atomization energy (AE) and bond separations (BS). Median absolute
deviations (MAD) and standard deviations (SD) of calculated values from experimental
data have been determined for every using method’s. The bond separation method has the
smallest MAD at most of theoretical methods in comparison to the atomization energy
approach. The 6-31g(d,p) basis set doesn’t seen clear effect in the theoretical results.
Enthalpy of formation for three- and seven- membered heterocyclic theoethers (11
compound) in gas state have been determined by different theoretical methods: compo-site
methods (Gn, CBS) and two levels of theory B3LYP/6-31g(d) and MP2/6-31g(d) via
two
approaches: atomization energy (AE) and bond separation (BS). Median abs-lute
deviations (MAD) and standard deviations (SD) of calculation values from experi-ment
data have been determined for every used theoretical method. It has been observed that the
bond separation approach produce lower value of MAD in most of the theoretical methods
in comparison to the atomization energy approach; where the G3MP2 method produce
lower value of MAD, while the deviations corresponding to the two levels of theory
MP2/6-31g(d)//B3LYP/6-31g(d) and MP2/6-31g(d)//B3LYP /6-31g(d) is close to the
deviations of the composite methods. The 6-31g(d,p) basic set doesn't show substantial
effect in the theoretical results.
