Aqueous Solutions Of Amides Research Articles

Free Radicals in U.V.-irradiated Aqueous Solutions of Substituted Amides: An E.S.R. and Spin-trapping Study

The radicals produced by reactions of hydroxyl radicals with alkyl substituted ureas and amides in aqueous solutions have been investigated. Hydroxyl radicals were produced by U.V. photolysis of H2O2 and the short-lived amide and urea radicals were spin-trapped by t-nitrosobutane and identified by e.s.r. For all N-alkyl derivatives of urea and acetamide, and for N,N-dimethyl propionamide and N,N-diethyl formamide, only radicals centred on N-alkyl groups were detected. Radicals situated only on alkyl groups attached to the carbonyl carbon were observed for dimethyl acetamide, trimethyl acetamide and butyramide. However, for N,N-dimethyl butyramide, N, N-diethyl butyramide, N-methyl propionamide and N, N-diethyl propionamide, free radicals were formed which were localized on the alkyl group attached to the amide carbon as well as those attached to nitrogen. The hydrogen atom bound to the carbonyl carbon was abstracted in N-ethyl formamide. Acyl radicals formed by C-N scission due to direct U.V. photolysis of N, N-dimethyl butyramide and N,N-dimethyl propionamide were also detected.

Ultrasonic and Volumetric Investigation of Aqueous Solutions of Amides

Abstract The ultrasonic velocity and density of aqueous solutions of N-methylformamide, N,N-dimethylformamide, and N,N-dimethyIacetamide have been measured at 25 and 35 °C over the entire concentration range. The compressibility, excess compressibility, partial molar compressibility, partial molar volume, and pressure dependence of the partial molar volume have been calculated. The concentration dependences of the velocity and density are highly nonlinear, and the velocity maxima are observed in all the amide solutions at ca. 20 mol%. Minima in the partial molar volume exist in solutions of DMF and DMAA, but not in that of MFA. On taking account of the results for viscosity, the velocity maxima are ascribed to the complex formation, and the minima in the partial molar volume, to the competition between the volume increase due to the complex formation and the volume decrease due to the breaking-down of the water structure. The pressure dependence of the partial molar volume shows that amides and water have strong interactions, even in the low-mole-fraction regions for each component.

Calorimetric studies of the interactions of guanidinium hydrochloride and potassium iodide with model amides in aqueous solution.

AbstractThe enthalpies of transfer, ΔHtr, of a series of amides from water to aqueous solutions of either guanidinium hydrochloride (GuHCl) or potassium iodide were obtained from calorimetric measurements at 25°C. The amides were studied at molalities around 10−2 m while salt molalities ranged from 0–10 m. The amides investigated were Ac‐Gly‐NHMe, Ac‐Gly‐Gly‐NHMe, Ac‐Ala‐NHMe, and Ac‐Leu‐NHMe. Use of an additivity assumption allowed the calculation of group contributions to ΔHtr in these two salt systems for the methyl group, leucyl side chain, and the peptide backbone unit. Values of the entropy of transfer were also obtained. The great ability of GuHCl to randomize protein structures appears to arise from effects on polar and nonpolar groups, which are characterized by enthalpies and entropies of transfer not substantially different from those with KI, a salt comprised of ions of comparable size and polarizability. The difference in the sign of the free energies of transfer of nonpolar groups from water to MX solutions, negative for GuHCl and positive for KI, is the result of these small differences in enthalpies and entropies of transfer. Variations in water structure produced by differences in ionic properties rather than a mode of action for GuHCl very different from that of other salts characterizes its superior denaturing ability.

Physical-chemical Properties of Substituted Amides in Aqueous Solution and Evaluation of Their Potential Use as Solubilizing Agents

The tetramethyl-substituted amides of pimelamide, suberamide, azelamide, and sebacamide markedly enhance the solubility of glutethimide in aqueous solution. Partition studies, surface tension measurements, and light-scattering measurements strongly suggest that the amides are associating at infinitely dilute concentrations and further aggregation of these associated molecules occurs with the possible formation of micelles at concentrations slightly higher than that observed for surfactants. The CMC' s were identified at 0.41, 0.20, 0.031, and 0.11 M for pimelamide, suberamide, azelamide, and sebacamide, respectively. The solubility of glutethimide was increased significantly above the critical concentrations and, from the nature of the solubility curves, a micellar type of solubilization appears to be dominant.

NMR studies of the structure of aqueous amide solutions

An extensive investigation has been made concerning the structure of a series of aqueous amide solutions using nuclear magnetic resonance techniques. Changes in spectral parameters as a function of solution composition and temperature were used to determine the effect of the intrinsic amide molecule structure on the structure of water and the solution as a whole.

Sites of attack of hydroxyl radicals on amides in aqueous solution. II. Effects of branching .alpha. to carbonyl and to nitrogen

Sites of attack of hydroxyl radicals on amides in aqueous solution. II. Effects of branching .alpha. to carbonyl and to nitrogen

Intermediates produced in the flash photolysis of acetone and amides in aqueous solution

Intermediates produced in the flash photolysis of acetone and amides in aqueous solution

Thermochemical Properties of Some Carboxylic Acids, Amines, and N-Substituted Amides in Aqueous Solution.

Thermochemical Properties of Some Carboxylic Acids, Amines, and N-Substituted Amides in Aqueous Solution.

Sites of attack of hydroxyl radicals on amides in aqueous solution

Sites of attack of hydroxyl radicals on amides in aqueous solution

Hydrolytic and Associative Behavior of Aromatic Amides in Aqueous Solution

Rate constants for alkaline hydrolysis (in 0.1N NaOH) of aromatic amides such as nicotinamide, benzamide, phenylacetamide, cinnamamide, and their corresponding N-alkyl substituted analogs were determined at 25°and 90°in order to investigate the effect of molecular structure on the stability of these amides against hydroxyl ion attack. Stability constants of these aromatic amide complexes with theophylline and 8-methoxycaffeine at 25°were also computed from phase-solubility data. The results have shown that cinnamamides are most stable against hydroxyl ion attack and formed the most stable complexes with the alkylxanthines while phenylacetamides are least stable in alkaline hydrolysis and least associative with alkylxanthines among benzene derivatives. Both hydrolytic behavior and associative tendency of these amides are discussed in relation to the extent of conjugation of the amide group with the rest of the molecule.

Properties of amides in aqueous solution. I. Viscosity and density changes of amide-water systems. An analysis of volume deficiencies of mixtures based on molecular size differences (mixing of hard spheres)

Properties of amides in aqueous solution. I. Viscosity and density changes of amide-water systems. An analysis of volume deficiencies of mixtures based on molecular size differences (mixing of hard spheres)

Dielectric properties and structure of aqueous amide solutions

Dielectric properties and structure of aqueous amide solutions

236. Catalysis by ion-exchange resins. Part I. The hydrolysis of amides in aqueous solutions

236. Catalysis by ion-exchange resins. Part I. The hydrolysis of amides in aqueous solutions