Comprehensive force field for multiply-chlorinated hydrocarbons

A force field is presented that has been optimized for chlorinated hyrocarbons containing isolated, vicinal, and geminal secondary chlorines. For carbon--chlorine stretch modes, 74 frequencies in 10 molecules are reproduced with an average error of 4.5 cm-. This force field can therefore serve to study these conformation-dependent modes in multiply-chlorinated hydrocarbons.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28955/1/0000792.pd

Vibrational analysis of 2,3,4-trichloropentanes

One meso form and the racemic isomer of 2,3,4-trichloropentane have been synthesized, and their infrared and Raman spectra analysed on the basis of a general force field refined for multiply-chlorinated hydrocarbons. Previous results on 2,3-dichlorobutane have been incorporated in this study, thus providing a force field for detailed analyses of vicinally-chlorinated hydrocarbons.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28952/1/0000789.pd

Vibrational analysis of 2,2,3-trichlorobutane and a force field for 2,2-dichloropropane

The infrared and Raman spectra of 2,2,3-dichlorobutane have been analysed in terms of normal modes calculated from a force field for secondary dichlorides refined using this molecule as well as 2,2-dichlorobutane and 2,2-dichloropropane. A force field specific to the latter molecule is presented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28954/1/0000791.pd

Normal-mode analysis of infrared and Raman spectra of poly(vinyl fluoride)

Infrared and Raman spectra of samples of poly(vinyl fluoride) (PVF) have been recorded. The vibrational spectra have been analyzed by means of normal-mode calculations. A force field was derived by using 2-fluorobutane as a model compound. Crowder's force field for hydrofluorocarbons was employed as a starting point and subsequently refined in application to secondary fluorides. A planar zigzag, syndiotactic single-chain model of crystalline PVF was submitted to be analyzed by this scheme. A comparison of observed infrared and Raman bands with frequencies calculated for syndiotactic PVF shows that PVF produced by conventional free radical polymerization has an atactic structure, supporting the 19F-NMR results and conclusions reached by Koenig and Boerio. Band assignments in terms of atactic structure are proposed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30156/1/0000533.pd

Vibrational spectra of chlorinated poly(vinyl chloride).

In order to refine the force field for secondary chlorides which is applicable to chlorinated poly (vinyl chloride), CPVC, 2,3,4-trichloro-pentanes and 2,2,3-trichloro-butane were synthesized. To avoid trouble upon separation of a meso and racemic isomer mixture of 2,3,4-trichloro-pentanes, we used a new method to obtain each isomer exclusively. Each isomer was identified by NMR. However, to confirm the identification, one of the tosylates, which is a precursor to be converted to the meso form, was structurally determined by X-ray crystallography. The ir and Raman spectra were observed for both isomers of 2,3,4-trichloro-pentanes and 2,2,3-trichloro-butane at room temperature and in the crystalline states. The force constant refinement procedure was divided into two steps. In the first step, force constants related to adjacently chlorinated units such as -CHCl-CHCl-CHCl- were refined by using meso and racemic isomers of 2,3,4-trichloro-pentanes, meso and racemic isomers of 2,4-dichloro-pentanes, and two trans isomers (MRSM, MRRM) of 2,3-dichloro-butanes. In the next step, the force constants related to CCl\sb2 were refined by using trans and gauche isomers of 2,2-dichloro-butane, 2,2-dichloro-propane, and trans, gauche and gauche ($-$) forms of 2,2,3-trichloro-butane. The final refined force constants are tabulated. To validate the transferability of the refined force constants, the normal frequencies were calculated for 2-chloro-butane, 3-chloro-pentane, and syndiotactic, isotactic, and heterotactic isomers of 2,4,6-trichloro-heptanes, as well as syndiotactic PVC. The calculated bands well matched the observed bands. In particular, C-Cl stretches, which are sensitive to the conformation, were predicted within 5 cm\sp{-1}. The ir and Raman spectra of PVC and CPVC for the five different chlorine contents, 57.70%, 61.48%, 63.34%, 67.92%, and 70.92% were observed. To elucidate these spectra, normal mode analyses (NMA) were conducted for tetrad PVC fragments (010101010), and for CPVC fragments such as (010111010), (011111010), (0102010), (0121010), (0121110), (010202010), and (010202110). (Numerical designation was used for the three carbons in CPVC: CH\sb2 = 0, CHCl = 1, CCl\sb2 = 2). According to the NMA, CH\sb2 groups of the center r unit of r-r-m, and m-r-m heterotactic PVC tetrads were chlorinated in the early stages of the reaction.Ph.D.Molecular physicsPhysical chemistryPolymer chemistryPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/128251/2/8907013.pd