Activation energy amides

Polymerization Solvent. Sulfolane can be used alone or in combination with a cosolvent as a polymerization solvent for polyureas, polysulfones, polysUoxanes, polyether polyols, polybenzimidazoles, polyphenylene ethers, poly(l,4-benzamide) (poly(imino-l,4-phenylenecarbonyl)), sUylated poly(amides), poly(arylene ether ketones), polythioamides, and poly(vinylnaphthalene/fumaronitrile) initiated by laser (134—144). Advantages of using sulfolane as a polymerization solvent include increased polymerization rate, ease of polymer purification, better solubilizing characteristics, and improved thermal stabUity. The increased polymerization rate has been attributed not only to an increase in the reaction temperature because of the higher boiling point of sulfolane, but also to a decrease in the activation energy of polymerization as a result of the contribution from the sulfonic group of the solvent. 

Hindered rotation around the P-N bond has been observed at low temperature in tetrasubstituted phosphorus amides [28]. For PhjPNJSiMCjJj, two different Me3Si groups are observed below -65 °C, the calculated activation energy for P-N rotation being 10.2 Real moT [29]. Chiral phosphinous amides with stereogenic phosphorus atoms have been prepared [30,31 ]. 

Electronic effects. Nucleophilic attack is favoured by electron-withdrawing groups on the amide and the acyloxyl side chains. Interpolated bimolecular rate constants at 308 K for the series of para-substituted /V-acetoxy-/V-butoxybenzamides 25c, 26b-g and 26i (Table 5) gave a weak but positive Hammett correlation with a constants ip = 0.13, r = 0.86).42,43 These Sn2 reactions are analogous to those of aniline and substituted pyridines with phenacyl bromides, which have similar Arrhenius activation energies and entropies of activation in methanol (EA= 14-16 kcal mol-1, AS = — 27 to —31 calK-1 mol-1) and 4-substituted phenacyl halides afforded a similar Hammett correlation with pyridine in methanol (cr, p — 0.25).175... 

A new, more general, way to combine ab initio quantum mechanical calculations with classical mechanical free-energy perturbation approach (QM/FE approach) to calculate the energetics of enzyme-catalysed reactions and the same reaction in solution has been reported." The calculated free energies were in fairly good agreement with the experimental data for the activation energies of the first test case, amide hydrolysis in trypsin and in aqueous solution. 

The fate of A-alkoxy-Af-aminoamides from Af-methylaniline and Af-acyloxy-Af-alkoxy-amides has been modelled at semiempirical, ab initio and density functional levels of theory " . B3LYP/6-31G calculations predicted the HERON rearrangement of the model intermediate 214 to methyl formate (173) and l,l-dunethyldiazene (220) to be exothermic by 5.5 kcalmoG and have an activation energy of 21.4 kcalmoG in the gas phase (Scheme 32). 

In addition the films were amorphous, but this result indicates that the activation energy of the deposition may be lowered significantly when amide precursors are used. The reason is facile transamination reactions. In this sense, the amide [Ga(NMe2)3]2 is not a true SMP for GaN but a good choice for depositing amorphous GaN at very low temperatures. 

Computational studies showed that the nature of the reactive species in the oxidation of trimethylamine, iodide ion, and dimethyl sulfide with lumiflavin is a C4 a-hydroperoxide complexed with water. The other two species, C4 a-hydroperoxide and C4 a-peroxide, yielded higher activation energies.237 Kinetic and spectroscopic studies on the effect of basic solvents, ethers, esters, and amides, on the oxidation of thianthrene-5-oxide with substituted peroxybenzoic acids indicated the involvement of the basic solvent in the transition state of the reactions. A solvent parameter, Xtc, based on the ratio of the trans to the cis form of thianthrene-5,10-dioxide, has been introduced.238... 

Depending on the analyses of structure-activity relationships and electrochemical studies [158,162], the indole nucleus is the reactive center of interaction with oxidants due to its high resonance stability and very low activation energy wall towards the free-radical reactions. However, the methoxy and amide side chains are also important for indole s antioxidant capacity [169]. 

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