AbstractInfrared and Raman spectra of halogenated and nitrile substituted hydrocarbons have been studied in various phases including temperatures as low as 8 K by isolation in matrices of solid argon or krypton.
In the compounds :-
CH 2 =CH 2 CH 2 =CHD CH 2 =CH(CH 2 ) n -X
where n= 0,1,2 and X= CH 3 , Cl, Br and CEN
comparisons are made between the spectra in the gas and matrix isolated phases. The alkene out-of-plane vibrations are sensitive to rotation, aggregation and conformational change. The twist and wag modes show consistent differences between the gas and matrix phases which are discussed in terms of different anharmonicities.
Using a specially constructed temperature control unit evidence was obtained for rotation of ethene and ethene-d1 in the matrix.
The spectra of the larger molecules in the gas phase were measured (using Fourier Transform methods in some cases ) leading to the calculation of rotational constants which corresponded with those calculated for particular structures.
Discrimination between various matrix effects is achieved by comparing the rate of conversion from high to low energy forms under careful temperature control. In acrylonitrile the low energy form is the result of an intermolecular effect leading to polymeric aggregate, in chloroprene this is an intramolecular effect. Rate constants are reported in each case at 500:1 and 5000:1 dilution in argon and vibrational assignments are made to various high and low energy forms in matrices.
Finally a series of dichloro and dibromohexanes and octanes have been prepared and purified and their Raman and infrared spectra recorded in the liquid state. A modified manipulative method has been developed for introducing these compounds of relatively low volatility into inert gas matrices and recording their infrared spectra. Assignments of bands are made within a limited range in relation to their conformational preference as model compounds for head to head PVC and PVBr
|Date of Award||Oct 1984|