Order parameters, aliphatic hydrocarbons

A further difficulty arises during preparative electrolyses in aprotic solvents because of the bulk pH change which commonly occurs. Thus cathodic reductions often require proton abstraction from the solvent in order to yield stable products, while many anodic oxidations, mcluding those of aromatic and aliphatic hydrocarbons, give rise to a quantitative yield of proton and the consequent changes in the pH. of the electrolysis media would be expected to lead to a variation in the products with the duration of the electrolysis. Unfortunately, the pH can be a very difficult parameter to control in aprotic solvents and most work reported in the literature has been carried out in unbuffered conditions. In the case of oxidations, organic bases, e.g. pyridine, have... 

The order parameters of aliphatic hydrocarbons solubilized in a lamellar liquid crystal were determined from NMR data. The variation of order parameters along the hydrocarbon chain with varying amounts of hydrocarbon solubilized supports a model with the main part of the hydrocarbon forming a layer between the amphiphilic layers with only a small amount of it penetrating between the amphiphilic molecules. 

Although the concentration of fluorine is the most important quantity in the control of the reaction rate and must be maintained within certain limits, in practice the stoichiometry, the molecular fluorine to substrate H-atom molar ratio, is used to determine the reaction parameters leading to a successful and efficient perfluorination. AF is most successful when sublimable solids are introduced into the hydrocarbon evaporator unit of the aerosol fluorinator as solutions by a syringe pump. This now common procedure emphasizes the individual molecule s isolation as it is fluorinated using AF. No intermolecular reactions between solute and solvent have been observed Choice of the solvent is important as it must not boil at a temperature below the melting point of the solute in order to prevent solid deposition in the tubes feeding the evaporator. It must also fluorinate to a material easily separable from the solid reactant after perfluorination. In most cases it has been found that aliphatic hydrochlorocarbons are excellent choices, but that carbon tetrachloride and chloroform and other radical-scavenging solvents are not (sec ref 6). 

Potential energy calculations have been employed in a description of the dynamic structure of adamantane and the nature of the order-disorder phase transition, as well as the mechanism of self-diffusion in the molecular solid. Theoretical calculations on the acid-catalysed hydrolysis of aliphatic esters lend support to the use of Taft , values as a measure of steric effects of alkyl groups correlation of with relative rate data (log k,., ) is discussed as well as that with steric energy parameters (from force-field calculations), which are found to parallel AAH values. " The same authors have outlined a new source of data of use in the estimations of van der Waals strain in hydrocarbons (including norbornane and adamantane). 

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