W. D. Walters

Bio: W. D. Walters is an academic researcher. The author has contributed to research in topics: Thermal decomposition. The author has an hindex of 1, co-authored 1 publications receiving 6 citations.

The Gas Phase Pyrolyses of Some Small Ring Hydrocarbons

Abstract: Publisher Summary This chapter discusses the thermal pyrolyses of a number of strained ring compounds. In most of the cases considered, there is good evidence that the processes are unimolecular. Plausible transition complexes and reaction paths are suggested in the chapter, which are based on the consideration of such factors as the kinetic parameters, stereochemistry of the reaction, and effect of substituents. In reactions of this type, the description of the transition complex is fraught with difficulties, since the absences of such things as solvent effects, which can be helpful in bimolecular reactions, limit the criteria. Often two types of transition complex may be equally good at accounting for the observed data. Sometimes, one complex will explain some of the data, while another is better able to account for the remainder. It is probable that in many cases the representation of the transition complex is too simple, biradical compared with expanded ring in the cyclopropane isomerizations, and that the true situation lies between the extremes, in exactly the same way as the simple Kekule formula do not represent all the properties of benzene.

Effect of pH on the thermal stability of potent roasty odorants, 3-mercapto-3-methylbutyl esters, in coffee drink.

Abstract: The effect of pH on the thermal stability of potent roasty odorants, 3-mercapto-3-methylbutyl esters, in coffee drinks was investigated. The concentration of 3-mercapto-3-methylbutyl formate in the coffee drink was drastically decreased during the heat processing. However, the residual ratio of this compound in the coffee drink adjusted to pH 5.0 was higher than that of pH 6.5. On the other hand, the residual ratios of 3-mercapto-3-methylbutyl acetate showed high values in the coffee drinks adjusted to both pHs. In the pH range of 3-7, the residual ratios of 3-mercapto-3-methylbutyl formate in aqueous model solutions varied depending on the pH value. It had a thermal stability maximum at pH 4.0, while 3-mercapto-3-methylbutyl acetate showed stability during heat processing over all the pH values tested. In addition, the residual ratios of the formate and acetate esters, which were composed of various alcohol derivatives, showed the same tendency as that of the 3-mercapto-3-methylbutyl esters. These results suggested that the low thermal stability and pH dependence of 3-mercapto-3-methylbutyl formate are based on the structure of the formate ester.

Initial state selection and intramolecular vibrational relaxation in reacting polyatomic molecules. Neopentylcyclobutane precursor

Abstract: In order to confirm and extend the kinetic and intramolecular vibrational relaxation features observed in the isopropylcyclobutane system (KR), the sub

Thermal unimolecular isomerization of 1,4-dimethylbicyclo[2.2.0]hexane, 1,4-dimethylbicyclo[2.1.1]hexane, and 1,4-dimethylbicyclo[2.1.0]pentane

Abstract: The thermal isomerization of the title compounds was studied in the vapor phase. Over the temperature range from 445.1 to 477.5°K, 1,4-dimethylbicyclo[2.2.0]hexane underwent a homogeneous unimolecular reaction to 2,5-dimethyl-1,5-hexadiene, the rate constants being represented by the equation: k = 1.86 × 1011 exp (−31000 ± 1800/RT) sec−1. Over the temperature range from 630.0 to 662.2°K, 1,4-dimethylbicyclo[2.1.1]-hexane also underwent a unimolecular isomerization to the same product, the rate constants being given by the equation: k = 8.91 × 1014 exp (−56000 ± 900/RT) sec−1. The pyrolysis of 1,4-dimethylbicyclo[2.1.0]pentane gave 1,3-dimethylcyclopentene-1 and 2,4-dimethyl-1,4-pentadiene in the ratio of 9:1. The former reaction was influenced by surface effects but the latter was not. The rate constants for the formation of 2,4-dimethyl-1,4-pentadiene fitted the equation: k = 1.66 × 1017 exp (−57400 ± 3100/RT) sec−1. The effect of the two methyl groups at the bridgehead positions in these molecules in influencing the rate of decomposition is discussed in terms of the non-bonded repulsive forces between the substituents.

Chapter 1 The Decomposition and Isomerization of Hydrocarbons

Abstract: Publisher Summary This chapter discusses the decomposition of substances, that is, the breakdown of a substance into smaller molecular fragments by the action of heat and of radiation Decomposition brought about by the action of heat alone is known as “thermal decomposition,” or “pyrolysis” Decomposition can also be brought about by radiations in an indirect way, the radiation being absorbed by a sensitizer, which in turn, induces reaction in another substance The chapter is concerned with the thermal, photolytic, photosensitized, and radiolytic decompositions of pure organic hydrocarbons As the action of heat on cyclic hydrocarbons usually leads to reactions that occur by simpler mechanisms than in the case with the other hydrocarbons, these reactions are considered first It deals with isomerization and decompositions The chapter discusses cistrans isomerization, in which there is twisting about a double bond It also examines the decompositions of non-cyclic hydrocarbons, and treats the effects of additives, such as inhibitors, on the various decompositions and isomerization