AbstractMost procedures for the estimation of critical values of oligomethylenes assume these critical values to depend only on the chain length n and/or the molecular weight M. In this work, we introduce new equations for estimating the critical values by inclusion of quantum chemical data calculated by a semiempirical SCF‐MOSCF‐MO: Self‐consistent field, molecular orbital. method (AM1). These models give a much superior prediction for the critical values such as the normal boiling point Tb, critical temperature Tc, critical pressure Pc, critical valume Vc, surface tension yb and enthalpy of vaporization ΔHvp of 18 oligomethylenes. The predictions for polyethylene (with infinite chain length) for the values of Tb, Tc, Pc, Vc, ΔHvp and yb are 1029.3 K, 1029.3 K, 1.013 bar, 15723.3 m3/mol, 0 KJ/mol and 0 mN/m, respectively.