I.R. Lewis

Synthetic polyisoprenes studied by Fourier transform Raman spectroscopy

Abstract Fourier transform Raman spectra are presented for the cis -1,4 and trans -1,4 isomers of polyisoprenes Vibrational intensities are used to determine quantitatively the amounts of each isomer in the microstructure. Improvements over previous work are suggested for the quantitative assessment of 1,4 microstructure. Also, changes in the Raman spectrum due to oxidative degradation show that preferential oxidative degradation for the vinyl -3,4 units occurs. The α and β forms of trans -1,4 polyisoprene were studied the ν(CC) bands resolved were identified 4 cm −1 apart. A study of the copolymerization of methyl methacrylate with isoprene showed that the 1,4 form is the most favoured form produced on copolymerization. Accurate cis -1,4 and trans -1,4 microstructural information could not, however, be determined.

FT-Raman spectroscopic studies of metal oxalates and their mixtures

The Raman spectra of a number of Group I and II metal oxalates are presented. From quantitative spectroscopic studies of the pure compounds and of mixtures of calcium, potassium and magnesium oxalates, it has been demonstrated that each component can be determined in the prepared mixtures to better than 2%. Comparisons made with the Raman spectra of lithium and sodium oxalates indicate that there are characteristic differences in the observed spectra of the Group I metal oxalates and that several vibrational bands of C2O2−4 are sensitive to the cation, being shifted to lower wavenumbers as the cation mass increases from Li to K.

Raman and infrared spectroscopic studies of tris triphenyl phosphine chloride complexes of transition metals

Abstract In this work for the first time, Raman spectra are presented of tris triphenyl phosphine cobalt(I) chloride and tris triphenyl phosphine ruthenium(II) chloride. Infrared spectra are also provided for these complexes and infrared and Raman spectra of tris triphenyl phosphine copper(I) chloride are also provided for comparison. Assignments are made of the phosphine ligand vibrations in the vibrational spectra of these complexes in comparison with the free ligand triphenyl phosphine which identify the MX and MP vibrations; assistance in the skeletal assignments is achieved by comparison with the complex tris triphenyl phosphine rhodium(I) chloride.

Raman and FTIR spectroscopic studies of copolymers of methyl methacrylate with butadiene

Abstract The comprehensive characterization by Raman and IR spectroscopy of the products of the free-radically initiated copolymerization of methyl methacrylate with 1,3-butadiene is reported. Raman spectroscopy has been used to determine quantitatively the microstructure of the polymerized 1,3-butadiene units in the copolymers.

A vibrational spectroscopic study of tris triphenyl phosphine rhodium (I) chloride

Abstract In this work we report the first Raman spectrum of tris triphenyl phosphine rhodium (I) chloride. The vibrational spectrum of triphenyl phosphine has also been recorded under similar conditions to facilitate comparisons. FT-Raman spectra and diffuse reflectance mid-IR and far-IR spectra are presented and a full skeletal vibrational assignment is made.

Vibrational spectroscopic studies of iron(II) acetate

Abstract A Raman and infrared spectroscopic study of iron(II) acetate has been made. A comparison of the spectra of iron(II) acetate with an ionic acetate, such as sodium acetate, suggests that the compound does not contain acetate ions in the solid state and is best described as a partly dissociated bisacetatoiron(II) species. Comparison is made with the structure of nickel(II) acetate.

Vibrational spectra of diammine diisocyanatozinc(II) Zn(NCO)2(NH3)2 and dipyridyl diisocyanatozinc(II) Zn(NCO)2(C5H5N)2

Abstract The IR and Raman spectra of Zn(NCO) 2 (NH 3 ) 2 and Zn(NCO) 2 (C 5 H 5 N) 2 are reported. The substitution of pyridine for ammonia in Zn(NCO) 2 (NH 3 ) 2 enables the spectroscopic identification of the ν(ZnN) modes of the coordinated NCO ligands to be identified. The compounds have skeletal structures which are consistent with a C 2v molecular symmetry and there is no spectroscopic evidence of bridging NCO ligands.

Infrared and Raman spectra of monochloro- and monobromodisilanes, a scaled ab initio force field, intensities, atomic polar tensors and effective charges for Si2H5Cl

Abstract Infrared and Raman spectra are reported for Si 2 H 5 Cl, Si 2 D 5 Cl, Si 2 H 5 Br and Si 2 D 5 Br. These include approximate infrared intensities for Si 2 H 5 Cl. All the fundamentals of the chloro compounds, except the torsion, are securely assigned, and nearly all those of the bromo ones. The force field and spectral intensities of Si 2 H 5 Cl were calculated ab initio using a 6-31G ∗ basis set, and the force field scaled to fit the d 0 , d 5 and ν is SiH data, using 14 independent scale factors. Significant changes in normal coordinate occur on scaling. The SiH stretching part of this force field agrees well with an earlier harmonic local mode force field, although differences occur in the normal coordinates. The 6-31G ∗ atomic polar tensors for the H and Cl atoms indicate that the dipole derivatives for the SiH and SiCl bonds lie close to the bond directions. Both H and Cl atoms behave as if negatively charged in all motions. Comparisons of νSiH intensities and frequencies, effective charges and Mulliken atomic charges are made across the series SiH 4 -Si 2 H 6 -Si 2 H 5 Cl. These identify significant effects by chlorine on the gauche SiH bond, but virtually none on the trans one.

Raman spectroscopic studies of Pedigree Doll disease

Abstract A vibrational Raman spectroscopic analysis of the phenomenon known as ‘Pedigree Doll disease’ has been undertaken. The degradation of cellulose acetate dolls constructed in the 1940s and 1950s has been studied and explanations are proposed for their degradation.

Vibrational and NMR spectroscopic studies of a thiolsulphonate produced from the non-catalytic hydrogenation of polybutadiene

Abstract Mass spectrometry, 1 H NMR, 13 C NMR, 2D NMR, FT-IR and Raman spectroscopy have been used to establish the structure of a thiolsulphonate by-product in the non-catalytic hydrogenation process for polybutadiene, which makes use of p -toluene sulphonylhydrazide as a reaction intermediate. The formation of this product has not been reported previously under such conditions. Spectroscopic evidence is presented for the molecular structure.