The photobromination of methanol has been studied with C02 added to suppress wall reactions.The chain reaction involving the step Br + CH30H +CH20H+ HBr (6) may be terminated in various ways and the observed rate law varies with the relative concentrations of bromine and methanol. Under certain conditions, the rate law agrees with termination by Br+Br+ M +BQ+ M y and assuming an absolute value for k15, it is found that k6 = 2 6 5 X 1010 Ti exp (-6200/RT)cm3 mole-1 sec-1. The steric factor for reaction ( 6) is 5 x 10-3. The dissociation energy D(H-CH20H) is calculated to be 6 92 kcal mole-1.
Equilibrium constants for the systems containing propanolf propanal, and butanol+ butanal were derived from measurements of the composition of mixtures obtained when the vapours were passed with hydrogen over a catalyst held at a measured temperature. Equations expressing the changes in Gibbs energy, enthalpy and entropy of the reactions over a range of temperature were calculated from the measurements, with the aid of heat capacity data. By coupling thermodynamic data for the reactions with thermodynamic data for the appropriate alcohol, the standard heats of formation of liquid propanal and butanal were calculated to be -552.64 and -556.90 kcal mole-1 respectively, and the standard entropies of liquid propanal and butanal were calculated to be 48.2 and 59.4caldeg-1. mole-1 respectively. The above values for the heats of formation agree with values derived from heat-of-combustion measurements ; the value for propanal indicates an unusual thermochemical stability in this compound. The value derived for the standard entropy of butanal agrees with a published value obtained by low-temperature calorimetry, but the value derived for the entropy of propanal (ideal gas) does not agree with a published value obtained by statistical mechanics.
Equilibrium constants Kp for the systems containing propan-2-01 + propan-2-one, butan-2-01 + butan-2-one and pentm-3-01+ pentan-3-one were derived from measurements of the composition of mixtures obtained when the vapours were passed with hydrogen over a catalyst held at a measured temperature. Equations expressing the free-energy, enthalpy and entropy changes for the reactions over a range of temperature have been derived from observations by the use of published heatcapacity data. The results are compared with such published thermodynamic data as exist.Thermodynamic quantities for the ideal gas now recorded and not previously measured include the standard entropies of butan-2-01 (85.69 cal deg-1. mole-1) and pentan-3-01 (91.35 cal deg-1. mole-1) and the standard heat of formation of pentan-3-01 (-75.38 kcal mole-1).
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