Polarizabilities of Oxazoles:  Ab Initio Calculations and Simple Models

Abstract

Ab initio, electron correlated calculations of the equilibrium geometries, dipole moments, and static dipole polarizabilities are reported for 10 heteroaromatic five-membered rings: furan, oxazole, isoxazole, all four oxadiazoles, both oxatriazoles, and oxatetrazole. Our geometries and dipole moments agree well with available experimental microwave determinations. The polarizabilities are expected to be accurate to within 5%. Structural isomerism affects the dipole moments strongly but the dipole polarizabilities are rather insensitive to it. Uncoupled Hartree-Fock calculations indicate that as much as half the polarizability comes from the σ-electrons. Simple empirical formulas based upon atom-and bond-additive models correlate the calculated polarizabilities of 20 five-membered heteroaromatic rings (10 azoles and 10 oxazoles) quite well. * Fax 506-453-4981; e-mail: ajit@unb.ca. X Abstract published in AdVance ACS Abstracts, April 15, 1996.Figure 1. Oxazoles with MP2/C dipole moments shown to scale, with the arrowhead pointing to the negative end.

Dipole (hyper)polarizabilities of fluorinated benzenes: An ab initio investigation

“…[19]. As can be appreciated from the data collected in Table 4, D 1 a and D 2 a values are almost equivalent each other (within 0.11 a.u., 0.3%), consistently with the results previously obtained by Thakkar and co-workers on series of ring-like compounds [57][58][59][60]. On the other hand, the D 3 a data are much smaller than the corresponding D 1 a and D 2 a values, the largest datum in the series being predicted for 1,2,4,5-TeFB (4.30 a.u.…”

“…In the present work we report dipole moments (m), mean polarizabilities (hai), polarizability anisotropies (D 1 a, D 2 a, D 3 a), mean first-order hyperpolarizabilities (b vec ), which are rotationally invariant quantities [56][57][58][59][60]:…”

“…These results indicate that, for the series of fluorobenzenes the D 2 a value is ruled by an additive law. Additive models for electronic polarizabilities using number and type of atoms and bonds were previously explored on some series of heterocyclic compounds [58][59][60] [17,18]. Thus, we carried out a comparison between the calculated static and experimental dynamic a xx À a zz values ( Table 3).…”

Electronic and Vibrational Polarizabilities and Hyperpolarizabilities of Azoles: A Comparative Study of the Structure−Polarization Relationship

“…In this respect papers by Keshari et al, 4 El-Bakali Kassimi et al, [5][6][7] and Kamada et al 8 on heterocyclic structures are relevant. Keshari et al 4 present ab initio time-dependent coupled perturbed Hartree-FockRoothaan studies of basic heterocyclic structures, among them pyrrole, furan, and thiophene.…”

A coarse-grained density functional theory, chemical potential equalization and electric response in molecular systems

“…The environmental effects appear mainly through the atom-atom or bond parameters. The present work can thus augment the conventional ab-initio calculation of intermolecular potential [29] as well as simple additive models of molecular polarizability [30]. While a microscopic derivation of atomistic description of quantum systems has been presented here, work on its detailed numerical implementation and application is in progress and will be reported in future.…”