摘要:

It is shown that the exclusive 1,4-addition ofN-nitromethylphthalimide4ato unhindered α,β-unsaturated ketones and esters can be effected by non-nucleophilic bases, such as sodium hydride or potassium fluoride, in dimethyl sulfoxide. The phthalimido moiety can be removed from the adducts with hydroxylamine or 1,2-dianilinoethane to give the oximes or diphenylimidazolidines of 1,4-ketoaldehydes. The ethylene ketal5of 3-formylcyclohexanone could easily be recovered from the imidazolidine10, but it was not possible to transform11into 3-formylcyclohexanone under similar conditions. It is further shown that reactions, such as the Knoevenagel condensation, or the Paal–Knorr synthesis of pyrroles, can be achieved directly on the adducts without the need for isolating the unstable 4-formyl carbonyl compounds.N-Nitromethylphthalimide thus serves as a new formyl anion equivalent.

ISSN:0008-4042    

DOI:10.1139/v77-405

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

A study involving the biodegradation of (+)-usnic acid (1) by the microorganismMortierella isabellinais described. Three metabolic products, 6-acetyl-8,9bα-dimethyl-1,9b,2,3-tetrahydro-1α,7,9-trihydroxy-3-oxodibenzofuran (2, (+)-1α-hydroxy-2-desacetylusnic acid), (+)-2-desacetylusnic acid (3), and (+)-6-acetyl-8,9b α-dimethyl-1,9b-dihydro-2-acetoxy-3,7,9,trihydroxy-1-oxodibenzofuran (4, (+)-2-acetoxyusnic acid) are isolated and characterized. By means of radioactively labelled precursors, some information about the biodegradation sequence is derived.

ISSN:0008-4042    

DOI:10.1139/v77-406

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

A simple direct procedure to locate saddle points (transition states) on energy surfaces is described. The advantage of the method is that it may utilize effective unconstrained optimization techniques while convergence may occur only to saddle points and not to minima. Thus no further tests are needed to decide the nature of the critical point located. Both the simplex and conjugate gradients optimization techniques were applied within the framework of the proposed method (the X-method) and numerical tests were carried out on both 'mathematical' and 'chemical' model surfaces.

ISSN:0008-4042    

DOI:10.1139/v77-407

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The interaction of 1-hydroxy-9,10-anthrahydroquinones (1-HOAHQ) with boric acid in aqueous borate buffer solutions at pH9.5 causes a decrease in the anodic limiting current of the 1-HOAHQ and the simultaneous appearance of a new diffusion-controlled anodic wave at more positive potentials. This is attributed to the formation of a cyclic borate ester of the 1-HOAHQ involving the peri-hydroxyl groups. Ester formation is much slower but still complete when the boric acid – borate to 1-HOAHQ molar ratio exceeds 10–15. These esters are most stable at pH7.5–9.5 and completely unstable above pH12. 1,2-Dihydroxy-9,10-anthraquinones (1,2-diHOAQ) react with boric acid to give cyclic esters involving the 1- and 2-hydroxyl groups, but of lower stability than those from 1-HOAHQ. On reduction of a 1,2-diHOAQ in the presence of boric acid atpH9.5, cyclic borate esters involving the peri-hydroxyl groups are rapidly produced in preference to those involving the ortho-hydroxyl groups.

ISSN:0008-4042    

DOI:10.1139/v77-408

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The effect of a hexadecapole moment on the absorption by the translational vibrations of carbon-dioxide-type crystals has been calculated. If the qudrupole and hexadecapole moments have the same sign the absorption is relatively insensitive to the hexadecapole moment and the hexadecapole moment may reduce the integrated absorptivity to a minimum of about 0.85 of the value for the quadrupole moment alone. If the moments have opposite signs, the absorptivity can be increased significantly by a hexadecapole moment of the expected magnitude.

ISSN:0008-4042    

DOI:10.1139/v77-409

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Core-level binding energies of all atoms are reported for the methyl substituted disilyl and digermyl chalcogenides, (MenMH3−n)2E; where M = Si, Ge; E = O, S, Se, Te;n = 0, 1, 2, 3. Binding energies are also reported for the dimethyl series Me2E; where E = O, S, Se, Te; for the hydrides H2E; where E = O, S, Se; and for the methylhydrides MeEH; where E = O, S. Binding energy trends throughout these closely related series of compounds are discussed. The similarity of atomic charge patterns, deduced from the binding energies, for all molecules of a given silicon or germanium series are consistent with their ability to redistribute charge. The bonding mechanisms that make this possible are assessed.

ISSN:0008-4042    

DOI:10.1139/v77-410

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Concentration cells of the type M(Hg)|MX(1)||MX(2)|M(Hg), where M(Hg) is potassium amalgam or sodium amalgam, were investigated with three electrolytes, potassium bromide, potassium iodide, and sodium iodide. An attempt was made to determine the necessity and magnitude of liquid-junction potential corrections. Only in the case of sodium iodide are the ionic mobilities of cation and anion quite different in ethylenediamine, and liquid-junction potential corrections are necessary to obtain agreement between observed and calculated data. The limiting equations of Nernst and of Lewis and Sargent were found to be appropriate for calculating liquid-junction potentials in ethylenediamine, provided that calculated activities were used in these equations.

ISSN:0008-4042    

DOI:10.1139/v77-411

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Oxygen-18 exchange between gaseous carbon dioxide and water in liquid water–pyridine mixtures is used as a probe for changes in intermolecular forces when the composition of the system is changed from pure water to pure pyridine. In agreement with results obtained previously by other methods, it is found that the interaction energy of an 'average' water molecule with the medium decreases when the mole fraction of pyridine is varied from zero to unity. The experimental results are related to the vapour pressure isotope effect,P(H218O)/P(H216O), of the binary mixtures. The utility of the Stern – Van Hook – Wolfsberg equation for vapour pressure isotope effects has been investigated. In addition, a plot of the equilibrium constant of the oxygen-18 exchange reaction vs. the mole fraction of pyridine presents no evidence of the formation of stoichiometric pyridine–water complexes.

ISSN:0008-4042    

DOI:10.1139/v77-412

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The rates of the catalysed hydrolysis of bis(trifluoroethyl)sulfite have been measured in concentrated acid solutions at 25 and 35 °C in water and in an aqueous mixture containing 60.7%p-dioxane by weight. The results are analyzed in terms of a solvation model similar to that proposed by Bunnett, and the kinetic medium effect. The data indicate that the mechanism of the acid-catalysed hydrolysis is bimolecular and that catalysis by halide ions occurs only in acidified solutions.

ISSN:0008-4042    

DOI:10.1139/v77-413

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Molar excess enthalpies of acetonitrile + chloroform and of acetonitrile + chloroform-d1were measured at 298 K. The results for the former system were discussed in terms of an ideal associated solution model and the deuterium isotope effect was discussed.

ISSN:0008-4042    

DOI:10.1139/v77-414

出版商:NRC Research Press    

年代:1977

数据来源: NRC