摘要:

The distribution of four branched chain octanols, 3-ethyl-3-hexanol, 4-ethyl-3-hexanol, 2-ethyl-4-methylpentanol, and 4-octanol, has been measured between dodecane and water. Measurements were made at alcohol concentrations in the dodecane of less than 0.1 mol/dm3, and as a function of temperature from 10 °C to 35 °C. From these distribution data, standard thermodynamic functions for transfer were calculated. Standard Gibbs energies of transfer from water to dodecane at 25 °C were in the range −14.1 to −15.1 kJ/mol, whereas the standard enthalpies of transfer at 25 °C varied from 29 to 39 kJ/mol. Thus, the change in the standard enthalpy tends to inhibit transfer, but a large standard entropy of transfer results in dodecane being the favoured phase.

ISSN:0008-4042    

DOI:10.1139/v85-130

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

In basic solution hydrogen peroxide reduces the hexacyanoferrate(III) ion to the Fe(II) complex. The stoichiometry and kinetics of this reaction have been examined. Both a stoichiometric reduction and a catalytic reaction leading to decomposition of the hydrogen peroxide occur. The latter is largely, but not completely, photochemical in origin. The data are consistent with the involvement of a common intermediate for the stoichiometric and the thermal catalytic reactions. It is suggested that this intermediate is formed by nucleophilic attack of the hydroperoxide ion or the superoxide radical on the carbon of a cyanide ligand.

ISSN:0008-4042    

DOI:10.1139/v85-131

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Standard free energies (ΔGt0) and entropies (ΔSt0) of transfer of HBr and HI from water to some aqueous solutions of 2-methoxy ethanol (ME) have been determined from emf measurements of the cells: Pt, H2(g, 1 atm)/HBr (m), solvent/AgBr–Ag and Pt, H2(g, 1 atm)/KOH (m1), KI (m2), solvent/AgI–Ag, respectively, at seven equidistant temperatures ranging from 15 to 45 °C. ΔGt0values of HBr and HI as well as of HCl obtained from literature, and particularly that of the individual ions obtained by tetraphenylarsonium tetraphenylboron (TATB) assumption, suggest that while H+is increasingly stabilized by cosolvent-induced larger "basicity", halide ions (X−) are increasingly destabilized by cosolvent-induced decreased "acidity" and the dielectric constant of the mixed solvents compared to that of water. Analysis of the variation of the observedTΔSt0(HX) and particularly of ΔY(= TΔSt0(H+) + TΔS0t.ch(X−), with composition, in the light of Kunduetal'ssemi-quantitative theory reveals that ME induces breakdown of three dimensional (3D) tetrahedral structures of water at water-rich compositions. This is being followed by an ordered region due to possible H-bonded cosolvent–water complexation and then the usual disordered region due to packing imbalance. Comparison of ΔY(HI)–composition profiles for aqueous mixtures oft-butanol (ButOH), ethylene glycol (EG), and 1,2-dimethoxy ethane (DME) also demonstrates that the remarkable enhancement of 3D water structures by the well known structure promoter ButOH gets succintly diminished when cosolvent ButOH is replaced by EG, ME, and DME, as is expected from structural and electronic considerations of the cosolvents.

ISSN:0008-4042    

DOI:10.1139/v85-132

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Standard free energies (ΔG0) and entropies (ΔS0) of autoionization of aqueous mixtures of 10, 30, 50, and 70 wt.% of 2-methoxy ethanol (ME) have been evaluated from the autoionization constants (Ks) of the solvents as determined from emf measurements of the cell Pt, H2(g, 1 atm)/KOH (m1), KBr (m2), solvent/AgBr–Ag at seven equidistant temperatures ranging from 15 to 45 °C. The observed increase in pKsand the related δ(ΔG0) (= sΔG0 − wΔG0) has been ascribed to be the effect of decreased dielectric constant, increased basicity and decreased acidity of the mixed solvents compared to that of water. Analysis of relative entropic contributions of autoionization,Tδ(ΔS0) (= T(sΔS0 − wΔS0)) and their chemical part,Tδ(ΔS0)chin the aqueous mixtures of ME as well as the closely related cosolvents like ethylene glycol (EG) and 1,2-dimethoxy ethane (DME), appears to suggest that unlike EG but like DME, ME has an overall structure breaking propensity of three dimensional (3D) tetrahedral structures of water. But the transfer entropies of water ΔSt0(H2O) derived thereof, for these cosolvents suggest that while the structural changes induced by protic EG are seemingly obseured due to the involved multiple acid-base equilibria with water, and that by aprotic DME are disturbed by the formation of strong hydrogen-bonded DME–H2O complexes around 4–14 mol% DME, quasi-aprotic ME appears to induce some order due to the possible formation of H-bonded ME–water complexes around 10–15 mol% ME.

ISSN:0008-4042    

DOI:10.1139/v85-133

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Infinitely extended, periodic, bent chains of methanol and water molecules have been investigated with the aid of theabinitiocrystal orbital method. Results on equilibrium geometries, stabilization energies, and other ground state properties are compared with the corresponding data obtained on monomers and homodimers. We also confront our computed results with experimental vapor phase and solid state data. Deviations from additivity of intermolecular interactions and the change of molecular properties from vapor phase monomer to molecules embedded in a periodic lattice are pointed out and compared to analogous effects as observed in other hydrogen bonded polymers. A few remarks on the evaluation of effective molecular dipole moments in molecular crystals are included as well.

ISSN:0008-4042    

DOI:10.1139/v85-134

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The rates of hydrolysis of 1-substituted 2,7,8-trioxabicyclo[3.2.1]octanes and 2,8,9-trioxabicyclo[3.3.1]nonanes (R = H, CH3, C6H5) have been determined at two temperatures in dioxan/water (60:40 by volume). These new results confirm the behaviour generally observed in the hydrolysis of orthoesters which have a favourable conformation to hydrolyze under stereoelectronic control.

ISSN:0008-4042    

DOI:10.1139/v85-135

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

During the synthesis of γ-lactones bearing a phosphonic acid group at the γ-position, difficulties were encountered generating the free phosphonic acids from corresponding esters. A protecting group used for carboxylic acids was adapted to phosphonic acids, making this transformation easy.

ISSN:0008-4042    

DOI:10.1139/v85-136

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Starting from tetrachloroacetone1and (carbomethoxymethylene)triphenylphosphorane4, the title compound16was prepared in five steps in 44% yield. Spectroscopic and chromatographic data indicated that this material was identical to a potent mutagen isolated from kraft pulp chlorination effluent. Various mutantSalmonellatyphimuriumstrains (TA 98, 100, and 1537) behaved similarly when incubated with either16or the isolated mutagen.

ISSN:0008-4042    

DOI:10.1139/v85-137

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Recently published correlations between heat of formation and structure of gas-phase ions have been used to assign formation threshold structures to [C5H7O]+ions produced by methyl radical loss from molecular ions of mesityl oxide, 5-hexene-2-one, 3-methylcyclopentanone, and 2-cyclohexenol. An unambiguous structure assignment has been made for the [C5H7O]+daughter ion from mesityl oxide. For the three other precursors two common formation-threshold structures consistent with the thermochemical data are proposed.

ISSN:0008-4042    

DOI:10.1139/v85-138

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Theoretical calculations on the fluoroacetones and their conjugate acids exhibit an inverse dependence of the proton affinity on the number of fluorine substituents. The good correlation between increasing proton affinity and decreasing ionization potential is attributed to the observation that the ionization of a nonbonding electron is essentially localized at a single atom whieh is also the site of protonation. The best quantitative agreement between the theoretical and experimental proton affinities is obtained at the 6-31G* level, while the STO-3G basis set leads to a satisfactory account of the additivity of fluorine substituents. The calculations corroborate the experimental interpretation of the preferred conformations ofp-fluoroacetone molecules in terms of the presence of an intramolecular hydrogen bond between the carbonyl proton and the F on the adjacent carbon. Only one type of equilibrium conformation is predicted for the fluorinated acetones, whereas two types of equilibrium conformations are predicted for the conjugate bases.

ISSN:0008-4042    

DOI:10.1139/v85-139

出版商:NRC Research Press    

年代:1985

数据来源: NRC