Density functional calculations of enthalpies of hydrogenation, isomerization, and formation of small cyclic hydrocarbons

Abstract

Density functional molecular orbital calculations using a high-level basis set on cyclic hydrocarbons (C≤5) make less severe demands on computer resources than the G2 family of ab initio calculations, and give results that are only slightly less accurate than G2. We present results for B3LYP/6-311+G(3df,2p) calculations at the MP2(full)/6-31G(d) geometry on 30 cyclic and eight acyclic hydrocarbons having two, three, four, or five carbon atoms. The arithmetic mean absolute deviation from 26 experimental results for Δ f H 298 is 2.1 kcal mol −1.