Paraffins, deuterated

A semi-quantitative treatment based upon the observation that, in the reactions of olefins with deuterium, the yields of deuterated paraffins often decrease logarithmically with increasing deuterium content, that is... 

The calculations with empirical potentials of the structure and dynamics of paraffin molecules adsorbed on graphite are presently being extended (27) to include the intermolecular interaction. This work together with elastic neutron diffraction experiments on deuterated paraffin films (see Sec. Ill) should provide a sounder basis for interpreting the inelastic neutron vibrational spectra. 

Burnett, L. J. and Muller, B. H. (1971). Deuteron quadrupole coupling constants in three solid deuterated paraffin hydrocarbons C2Dg, C4D1Q, C5D14. J. Chem. Phys. 55 5829. 

In order to have a reasonable starting set of peptide force constants, a complete analysis was done on NMA and its deuterated derivatives as well as on some nylons and their deuterated derivatives (JakeS and Krimm, 1971a). Force constants for the hydrocarbon portions of these molecules were transferred from the elegant work of Schachtschneider and Snyder (1963) on n-paraffins. A total of 125 NMA frequencies and 306 nylon frequencies were fit with a force field of 27 transferred and 84 refined force constants, with an average error of Aj ) = 4.3 cm" , and a total of 51 frequencies having an error greater than 10 cm". The ratio of observed frequencies to refined force constants, No/N[, was therefore 431/84 = 5.1. 

Third, n-allyl complexes are formed by palladium and cobalt analogous complexes of nickel and platinum are less stable, while ruthenium, rhodium, and iridium are not yet known to form them. In catalytic reactions the deuteration of cyclic paraffins over palladium has provided definite evidence for the existence of rr-bonded multiply unsaturated intermediates, while 7r-allylic species probably participate in the hydrogenation of 1,3-butadiene over palladium and cobalt, and of 1,2-cyclo-decadiene and 1,2-cyclononadiene over palladium. Here negative evidence is valuable platinum, for example does not form 7T-allylic complexes readily and the hydrogenation of 1,3-butadiene using platinum does not require the postulate that 7r-allylic intermediates are involved. Since both fields here are fairly well studied it is unlikely that this use of negative evidence will lead to contradiction in the light of future work. 

The hexenes form besides hydrogen the largest product group in the radiolysis of the paraffins. They can be formed by Reaction 1 and by disproportionation of hexyl radicals. The decrease of their G-value on deuteration is 1.5, the corresponding decrease of G( molecular hydrogen) is 1.6. This is additional proof for an isotope effect for Reaction 1. This reaction explains also the observation that the isomeric distribution of... 

The association of paraffins with the polyethylene surface may be directly observed under a different contrast condition. If one chooses the contrast such that the hairs are matched but, at the same time, both core and paraffins have strong contrast an interaction of the wax with the PE surfaces will appear in the scattering experiments as an increase of the effective thickness of the core. For these experiments the H1.5HH5DH sample was chosen. This sample has a protonated core and the required contrast is achieved by taking protonated paraffins in a nearly fully deuterated solvent. In this experiment the effects of two different paraffins C36 and C30 were studied. 

It is quite noticeable that these figures are very close to those known for melted paraffins of similar chain lengths. Then the development of NMR studies of deuterated moleoules and of NMR permitted to show that the amplitude of the deformations are about the same in all structures, ordered liquid crystals as well as in disordered micellar solutions. Thus there does not appear any definite correlation between one structure and the molecular behavior in it. The chains are about equally disordered in all structures, in spite of important changes of interfacial curvature and mean area per molecule at the interface. 

The main results of this experiment are shown in Figs. 5.5 and 5.6, where the measured values of Te and are reported as a function of temperature for proto-nated and deuterated solutions HK271-5CB and HK271-paraffin, respectively. The results for 1AAQ-5CB are qualitatively the same of HK271-5CB, and for them we refer the readers to paper [16], The main figures report, in semiloga-... 

Fig. 5.6 Semilog plot of Tr vs, 1 /T for protonated (filled squares) and deuterated (open circle. ) HK271-paraffin mixture. The dotted line is the prediction of SED model with slip boundary conditions. The Arrhenius activation energies of both data sets are consistent with that of SED, given in figure. Inset corresponding fluorescence lifetimes. Reprinted with permission from [16], Copyright 2002, American Institute of Physics...

In Fig. 5.9, the effect of deuteration on the (A) behavior for HK271 in 5CB and in paraffin is reported. It is seen that deuterated samples exhibit the same... 

Fig. 5.9 Effect of hydrogen-deuterium substitution on the quantum yield (A). The quantum yields of the protonated solutions have been rescaled so as to be superimposed at the lowest wavelengths. The data for the deuterated compounds have been kept in scale with the corresponding protonated ones. At A = 532 nm, the deuterated-protonated lifetime ratio is also shown for HK271 in 5CB and paraffin...

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