Thermodynamic analysis step effect

Unfortunately, the number of mechanistic studies in this field stands in no proportion to its versatility" . Thermodynamic analysis revealed that the beneficial effect of Lewis-acids on the rate of the Diels-Alder reaction can be primarily ascribed to a reduction of the enthalpy of activation ( AAH = 30-50 kJ/mole) leaving the activation entropy essentially unchanged (TAAS = 0-10 kJ/mol)" . Solvent effects on Lewis-acid catalysed Diels-Alder reactions have received very little attention. A change in solvent affects mainly the coordination step rather than the actual Diels-Alder reaction. Donating solvents severely impede catalysis . This observation justifies the widespread use of inert solvents such as dichloromethane and chloroform for synthetic applications of Lewis-acid catalysed Diels-Alder reactions. 

The thermodynamic analysis of an existing operation consists of three parts. The first part mainly assesses the thermodynamic performance of the current operation If found to be necessary, in the second part, targets for modifications are identified to reduce the cost of operation. The third part involves the assessment of the thermodynamics and economic effectiveness of the modifications. Exergy analysis can help in all three parts above. The main steps of exergy analysis are ... 

The results are appreciably different from those based on the analysis of the reactions of monosubstituted triphenylmethyl cations (McClelland et al., 1989). Obviously, this is due to the difficulties of correlating the substituent effects in a simple manner. The preferred results on the trisarylmethyl cation lead to the conclusion that both the forward process of the k ionization and the reverse process of the solvent-recombination step of the carbocation with various nucleophiles can be described to a good approximation by a Y-T a scale with an r value of the transition state which is essentially identical with the intrinsic r value of the thermodynamic stabilities. However, we will consider the triarylmethyl system further following similar analysis of a-arylethyl cations. 

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