Propane, reaction with deuterium

One way to introduce a deuterium or tritium atom into a specific location in a molecule is through the acid—base reaction that takes place when a very strong base is treated with D2O or T2O (water that has deuterium or tritium in place of its hydrogens). For example, treating a solution containing (CH3)2CHLi (isopropyllithium) with D2O results in the formation of propane labeled with deuterium at the central atom ... 

The Reaction of Cyclopropane and of Propane with Deuterium over Metals of Group... 

In all the experiments involving deuterium to be described here, there was an extensive formation of HD by exchange processes, and this necessitated the use of large excesses of deuterium to prevent its further reaction. Nevertheless, its introduction into the deuterium always caused the proportions of the various deuteropropanes to vary as the reactions proceeded, and they were therefore taken only to small conversion wherever possible. Extrapolation procedures were then used to arrive at the distribution of deuterium among the propanes at zero conversion, and results in subsequent tables are quoted as such. The propanes are expressed as fractions of those containing from two to eight deuterium atoms the yields of propane-do and propane-di from reactions with cyclopropane were normally very small, but in reactions with propane, that of propane-di was sometimes considerable. 

The exchange of propane with deuterium was very much slower than the addition reaction of cyclopropane, but by the use of longer times, the process has been studied at 100, 150, and 200°. Propane-di (and to a lesser extent propane-dg) was formed to an appreciable extent in the very early stages of the reaction, but since their subsequent rate of formation was low, their proportion decreased as the reaction proceeded. However, the relative proportions of the other propanes remained constant, and some results are given in Table II. These distributions differ from those obtained with cyclopropane only in that A is somewhat smaller and shghtly temperature-dependent, but the values of 8a and Sb are constant and the same as for... 

It is also clear that accumulated chemical evidence on warmed products may in some instances permit reasonable, although not optimum, deductions about low-temperature reactions. For example, it seems clear from experiments with deuterium that addition of hydrogen atoms to some olefins followed by abstraction does occur at 77°K, while with some other olefins this abstraction is not apparent [ ]. From the propylene reaction with D rather than with H atoms, it was established that virtually all of the propane was formed by... 

The acid-induced reaction of aryldiazomethanes with olefins gives arylcyclo-propanes in addition to olefins and esters. The cyclopropanes are formed stereo-specifically and their yields are largest in reactions with olefins which on cation addition give secondary carbonium ion centres. The use of deuteriated acids leads to partial incorporation of deuterium in the cyclopropane adducts, whereas the use of [a- H]-phenyldiazomethane leads to partial loss of deuterium, suggesting a slow proton transfer from the acid to the diazo-compound a carbenoid rather than a free carbene appears to be involved. 

Hydrogen abstraction from propan-2-ol and propan-2-ol- /7 by hydrogen and deuterium atoms has been studied by pulsed radiolysis FT-ESR. A secondary kinetic isotope effect was observed for H (D ) abstraction from the C—H (C—D) bonds. The results were compared with ab initio data. In similar work, the kinetic isotope effects in H and D abstraction from a variety of other alcohols in aqueous solvents have been measured. It was found that, compared with the gas phase, the reactions exhibit higher activation energies in agreement with the ability of solvation to decrease the dipole moment from the reactant alcohol to the transition state. 

Similar results have been obtained for methane 12) and for ethane 19). The values quoted in Table II also illustrate the point that the distribution of deuterium between hydrogen and propane differs from the value expected for a random distribution. With the ratio of pressures used, the expected percentage for the mean deuterium content of the hydrocarbon would be 33.3, which is substantially less than the experimental value of 40.9 %. This type of deviation is also found with other hydrocarbons, but it does not affect the validity of using classical theory for the calculation of the interconversion equilibrium constants in studies of mechanism of exchange reactions. More accurate values for these equilibrium constants are necessary, however, if one is interested in the separation of isotopes by chemical processes. 

Deuterium isotope effects in the reactions of 2-nitroso-2-methyl propane with formaldehyde, glyoxylate, glyoxylic acid, pyruvic and phenylglyoxylic acid... 

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