AIM study on the transferability of the oxygen atom in linear ethers

The integrated values of the electron population, electron energy, nucleus- electron potential energy interaction, dipole moment and volume of the oxyg en atoms, and the main properties of the O-C bond critical points, were det ermined by employing the theory of atoms in molecules and 6-31++G**//6-31G* wave functions for a series of 25 unbranched alkyl monoethers. These resul ts were used to assess the degree of approximate transferability of the oxy gen atom along this series in terms of the particular alkyl radicals bonded to it. It has been found that a set of six different oxygen atoms is neces sary to classify all the computed values. It can be established that the ox ygen atoms bonded to propyl and larger radicals can be treated, in practice , as a transferable fragment, while those bonded to at least one smaller ra dical are specific. Though the total HF energy and the available experiment al heats of formation are well fitted by a traditional additivity scheme th at distinguishes only among O, CH2, and CH3 units, it has been found that t he energy properties are influenced by the size of the molecule.