摘要:

The kinetics of the reaction of ferroprotoporphyrin IX with CO have been studied in mixed glycerol–water solvents of high viscosity in order that the simultaneous influence of chemical activation and diffusion control of the reaction might be observed. Analyses of curved Arrhenius plots indicated that in the low temperature high viscosity limits the reaction is largely diffusion controlled. The deviation of the second order diffusion rate constants, from that predicted by simple theory for reaction between uniformly reactive spheres of equal radii, is a factor of 0.3 to 0.9, depending upon the solvent composition. A couple of other models for diffusion controlled reaction, ascribing these deviations to changes of steric requirements, were also examined.

ISSN:0008-4042    

DOI:10.1139/v77-561

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Free energies (ΔGt0) and entropies (ΔSt0) of transfer at 25 °C of the nonelectrolytep-nitroaniline from water to various alcohol + water mixtures have been determined from solubility measurements at seven temperatures from 10–40 °C. Increasing specific solute–solvent interactions have been proposed to interpret the nature of the ΔGt0-composition profiles and the enhanced structure of water in the water-rich mixed solvents has been correlated with maxima in the ΔSt0-composition profiles. The effectiveness ofp-nitroaniline as a useful probe for studying solvent structure has been pointed out.

ISSN:0008-4042    

DOI:10.1139/v77-562

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The infrared carbonyl stretching frequencies of acyl-substitutedp-tolyl, phenyl, andp-chlorophenyl benzoates, XC6H4COOC6H4Y, have been determined in carbon tetrachloride. Each of the substituted phenols generated an independentplot which was correlated precisely with the Hammett equation (r = 0.999–0.998). The values of ρXso obtained show no tendency to vary with the structure of the parent phenol and are all within ± 0.202 of the mean value of 13.899. Similar correlations were obtained with the Hammett plots made by varying the aryl moieties of the esters while holding the acyl portions constant. For the four sets (4–8) studied, the mean value of ρYis 8.964 ± 0.266. Using the slopes ofvs. σ correlations in the series studied, the transmissive factor for the ether bridge in carbon tetrachloride was calculated (π′ = 0.64). An expression relating substituents in both acyl and aryl moieties to the mono-substituted compounds suggests that substituents on the two different groups act reasonably independently of each other;For all esters studied the equationwas found to hold withr = 0.998.

ISSN:0008-4042    

DOI:10.1139/v77-563

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Trapped electron yields were measured by means of optical absorption spectroscopy for a hydrocarbon glass γ-irradiated at 77 K in the presence of an external electric field. It was observed that the yield of trapped electrons increased in the presence of an external electric field as compared with that in the absence of an external electric field. The experimental results were analyzed theoretically and interpreted as due to overall effects involving changes in geminate recombination times which were caused by an external electric field.

ISSN:0008-4042    

DOI:10.1139/v77-564

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The photochemically induced conjugate addition of simple alcohols to a variety of α-enones has been investigated. With hex-2-enopyranosid-4-uloses (1), the alkylations occur from the less-hindered side and are completely stereo- and regioselective. The resulting 1,4-ketoalcohols (2) are readily cyclized to α-cyclopropyl ketones which have been prepared by alternative, less desirable routes. Alkylative additions of hex-1-enopyran-3-uloses occur also although less readily and without stereospecificity, giving C-glycosides. 2-Cyclohexenone and carvone are also photoalkylated by methanol giving moderate yields of the 1,4-ketols. In the case of carvone, carvone camphor was not detected as a by-product. Steroidal α-enones and mesityl oxide both fail to be photoalkylated by methanol.

ISSN:0008-4042    

DOI:10.1139/v77-565

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Alcohols possessing an α-hydrogen, acetals, and aldehydes undergo photochemically induced conjugate addition to a variety of α-enones to give 1,4-ketols, 1,4-keto ketols and 1,4-diketones respectively. It appears that the aldehydes frequently succeed where acetals and alcohols fail, and acetals where alcohols fail. It is therefore possible to employ polyfunctional addenda and achieve addition at only one of the activated sites. The reactions are always regiospecific and are frequently completely stereoselective.

ISSN:0008-4042    

DOI:10.1139/v77-566

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Cyclopropyl glycopyranosides which solvolyze via a stabilized cyclopropyl carbinyl-oxocar-bonium ion react under neutral conditions with nucleoside bases in nitromethane at 200 °C to give good yields of the corresponding cyclopropanated nucleosides. Under similar conditions hex-2-enopyranosides (which solvolyze by allyl-oxocarbonium ions) do not react. However, under catalysis by mercuric bromide or acetic acid, the corresponding 2′,3′ unsaturated nucleosides are formed although accompanied by appreciable amounts of 1′,2′-unsaturated-3′-nucleosides. Formation of the latter may be avoided if the hex-2-enopyranosides are first converted to the hex-2-enopyranosyl acetates by treatment with boron trifluoride and acetic anhydride. The derived acetates react with the nucleoside bases without catalysis to give anomeric mixtures of nucleosides, there being no trace of the unwanted 3′-nucleosides.

ISSN:0008-4042    

DOI:10.1139/v77-567

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Conjugate addition-alkylation reactions of lithium dialkyl cuprates to hex-2-enopyrano-4-ulosides (1), hex-3-enopyrano-2-ulosides (2), and hex-1-enopyrano-3-uloses (3) have been investigated. Extensive studies with1show that the homogeneous system using the soluble tri-n-butylphosphine copper(I) complex is less satisfactory than the heterogeneous medium in which copper(I) iodide is used. The use of Grignard reagents versus alkyl lithiums has also been investigated, the latter being found preferable. 1,2-Addition was observed in some cases, but conditions were developed to avoid formation of these side products.With α-enones1and2alkylation is completely stereoselective, the newly introduced alkyl group being in axial orientation. With3a complex mixture is obtained from which equatorial and axial adducts can be isolated in approximately equal amounts.

ISSN:0008-4042    

DOI:10.1139/v77-568

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The photophysical processes along with the photolysis of 4,4-diphenyl-γ-pyran (1) and 4,4-diphenyl-γ-thiopyran (2) are discussed in this paper. The solvent effect, the temperature effect, and the photolytic source intensity dependence of the yield of the secondary photoproduct are all among the experimental parameters investigated. It is shown that the first singlet–singlet electronic transition in molecules1and2is ππ*. in nature. The divinyl ether and divinyl thioether chromophore play a role in this transition and also directly contribute to the radiationless deactivation of the first excited singlet states of these molecules. On the other hand the energy of the first triplet ππ* state seems to be more localized in the phenyl groups of the molecules1and2.It is also shown that the photolysis of molecule1occurs by a monomolecular mechanism to produce a photoaldehyde which is also photolysed under prolonged irradiation. This aldehyde has also been shown to be a secondary photoproduct in the photoreaction sequence of 4,4-diphenyl-γ-pyran.

ISSN:0008-4042    

DOI:10.1139/v77-569

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

An approach to the study of the influence of electrolytes on adsorbed nonelectrolytes at liquid surfaces is described. The adsorption of tetrabutylammonium bromide (Bu4NBr) from aqueous solution to the interfaces with octane, decanol, and air has been determined. Results are presented for the effects of some inorganic salts (NaCl, NH4Br, and Na2CO3), and of Bu4NBr on monolayers of butanol at the air – aqueous solution interface, and of Bu4NBr on dodecanol adsorbed at the octane – aqueous solution interface. The interfacial salt effects differ from the bulk effects in the cases studied. The inorganic salts, which salt-out butanol (and alkanols generally) in aqueous solution, have little or no effect on adsorbed butanol. On the other hand, Bu4NBr which salts-in alkanols in bulk aqueous solution has a strong salting-out effect on dodecanol at the liquid–liquid interface; a similar but less marked effect is observed for butanol at the liquid–vapour surface. Salting-in of alkanols by Bu4NBr in bulk has previously been ascribed to hydrophobic interactions between cations and alkyl groups of the alkanol, whereas the surface effect is assumed to result from interactions between alcoholic OH groups and cations.

ISSN:0008-4042    

DOI:10.1139/v77-570

出版商:NRC Research Press    

年代:1977

数据来源: NRC