Electrostatic potential and a simple extended electric dipole model of hydrogen fluoride as probes of non-bonding electron pairs in the cyclic ethers 2,5- dihydrofuran, oxetane and oxirane

The electrostatic potential near to the oxygen atom in each of the cyclic ethers 2,5- dihydrofuran, oxetane and oxirane has been calculated by using a distributed multipole analysis (DMA) of each molecule. The electrostatic potential energy V() of a unit non-perturbing positive charge was calculated (via the DMA of the cyclic ether molecule) as a function of the angle  between the C2 axis of the cyclic ether and a vector of length r from the O atom to the unit charge. The resulting potential energy functions each has two equivalent minima. The angles min at the minima are compared with the angles 0 and e made by the O⋯H bond with the C2 axes in the cyclic ether⋯HF complexes, as determined by rotational spectroscopy and ab initio calculations at the CCSD(T)-F12c/cc-pVTZ-F12 level of theory, respectively. An electrostatic model of cyclic ether⋯HF complexes in which the DMA of the cyclic ether interacts with a simple extended electric dipole representation of HF is also used to calculate the variation of the potential energy VHF() of the HF molecule with . The angles min generated by this model are also compared with 0 and e. The extent to which the electrostatic potential and the extended electric dipole HF model can be used as probes for the directions of non-bonding electron pairs carried by O in these cyclic ethers is discussed.