Quantum chemical calculation of force and electrooptical parameters and steric characteristics of electronic interactions in haloethers

Abstract

oromethyl ether (VI); R I = CH2CH2CI , R 2 = CH 3 - 2-chloroethyl methyl ether (VII); R I = CH3, R 2 = C6H s - anisole (VIII); R I - CH2CI, R 2 = C6H ~ - phenyl chloromethyl ether (IX); R l = CHCI2, R 2 = C6H ~ pheny! dichloromethyl ether (X); R l = CH3, R 2 = C6HsCH 3 - p-methylanisole (XI); R l = CH2CI, R 2 = C6H~CH 3 - p-tolyl dichloromethyl ether (XII); R l = CHCI 2, R 2 = C~H~CH 3 - p-tolyl dichloromethyl ether (XIII). The calculation was done on theES-1046 computer using the program package in [6, 7]. As the initial values of the bond lengths and bond angles, we took the experimental data obtained by electron diffraction in[8, 9], which were then optimized. The force constants were calculated for the equilibrium geometry of the molecules. The potential function was approximated by a fourth-degree polynomial, and the fourth-order and third-order terms were included only for the bond stretching coordinates. The electrooptical parameters were calculated in terms of the MINDO/3 charge model. For large molecules, a number of coordinates in the alkyl and phenyl fragments were fixed and only the parameters of the ether group were calculated. The values of the force constants and electrooptical parameters calculated by the quantum chemical method were scaled using the factors which were fixed for each bond type; these factors were determined based on experimental data from IR spectra, and were assumed to be invariant in the series of studied molecules and for different conformations of the compounds. The calculation results, together with the "experimental" values of the force constants and the electrooptical parameters, obtained by solving the inverse spectral problem, are presented in Table i. On the whole, we observe good agreement between the experimental and calculated values of the molecular parameters. This is evidence that the force and electric fields we obtained earlier in [4, 5] are correct. Analysis of the calculation results shows that in methyl chloromethyl ether, as a result of the n-o* interaction of the unshared electron pair of the oxygen atom and the antibonding orbital of the C-C1 bond, alternation of the Ci-O and C2-O bond lengths occurs,