摘要:

The partial molal volumes ofn-alkanes andn-alkanols dissolved in benzene, ethanol, or cyclohexane are given with satisfactory accuracy by the equation previously developed for solutions in carbon tetrachloride, if certain parameters (the covolume, the volume increment for the hydroxyl group, and the volume decrement for somegaucheinteractions) are changed. Additionally, it is necessary to postulate a greater coiling of the alkyl chains when dissolved in cyclohexane.

ISSN:0008-4042    

DOI:10.1139/v79-469

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The partial molal volumesor 47 mono- or polycyclic alkanes, ethers, alcohols, ketones, and bromides have been determined in carbon tetrachloride at 25 °C.of most of these compounds can be calculated with moderate (±1–2%) accuracy using an equation containing parameters previously developed for acyclic compounds, and an additional cyclization parameterC, which is roughly linear with the numbernof atoms in the ring, fromn = 3 (C = +5.3 mL mol−1) ton = 10 (C = −21.0 mL mol−1). Substituted cyclohexanols and some polyfunctional compounds hadconsiderably lower than calculated.

ISSN:0008-4042    

DOI:10.1139/v79-470

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

not available

ISSN:0008-4042    

DOI:10.1139/v79-472

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Rate constants have been obtained for the acid-catalyzed N–H exchange ofN-methyl, 2,N-dimethyl, and 2,4,6,N-tetramethylbenzamide and the acid-catalyzed isomerization of the three correspondingN,N-dimethylbenzamides. The ratioincreases significantly with increased number oforthomethyl substituents. This is explained in terms of a suggestion of Perrin, that C—N bond rotation is not completely free in theN-protonated amide, since it must compete with a diffusion limited deprotonation reaction. The isomerization reaction, which requires such a rotation, is therefore slowed byorthomethyl substituents which hinder rotation, relative to the exchange reaction, which does not require rotation.

ISSN:0008-4042    

DOI:10.1139/v79-473

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The capsular polysaccharide antigen fromNeisseriameningitidisserogroup Z contains equimolar quantities of 2-acetamido-2-deoxy-D-galactose, glycerol, and phosphate. Carbon-13 nuclear magnetic resonance indicates that the polysaccharide is composed by a repeating unit of 1′-O-2-acetamido-2-deoxy-α-D-galactopyranosyl-glycerol joined through phosphate diester groups at O-3′ of glycerol and O-3 of the galactosamine residue. Assignments of the signals in the carbon-13 nuclear magnetic resonance spectrum were made by consideration of the previously assigned signals of related monomers and oligomers. When applied to a Karplus type relationship the values of the3J(13C–31P) coupling constants were consistent with the polysaccharide having an extended conformation.

ISSN:0008-4042    

DOI:10.1139/v79-474

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The mass spectra of several ring substituted acyclic styryl ketoximes and analogous ketones have been determined at 70 eV and also at low ionization voltages. The major fragmentation pathways for the oximes are loss of theorthosubstituent from the parent ion as well as loss of the hydroxyl and hydroxylamine radicals. Other fragmentation pathways include γ- and δ-cleavages as well as the McLafferty rearrangement. While there was a total absence of α-cleavage from the parent ions, the facility of loss of theorthosubstituents from the oxime molecular ions was compared with the same process occurring in the corresponding acyclic ketones, as well as the related cyclic derivatives, namely the substituted 2-benzylidinecyclohexanones and oximes. Stabilization of the resultant cyclized ion as well as steric factors are considered as factors favouring the cyclization process.

ISSN:0008-4042    

DOI:10.1139/v79-475

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The kinetics of formation of the metalloporphyrin Cu(II)–ENP is dependent on the pH due to the protonation of the pyrrol nitrogen atoms and the protonation of the diamino groups of the side chains. The degree of protonation of these side chains also influences the degree of association of the prophyrin and the metalloporphyrin in solution. The order of reaction with respect to the porphyrin is not unity, a consequence of an inhibition by the reaction product; this inhibition operates via the formation of a new species, a mixed complex of porphyrin–metalloporphyrin of low reactivity.The order of reaction with respect to Cu(II) is also not unity, a consequence of the chelation of Cu(II) by the diamino groups of the side chains. The presence of Cu(II) ligands influence both the reaction kinetics and the nature of the final reaction product. [Journal translation]

ISSN:0008-4042    

DOI:10.1139/v79-476

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Nitrosyl chloride reacted with 1,5-cyclooctadiene andtrans,trans,trans-1,5,9-cyclododecatriene in methylene chloride by thecis-addition to give chloronitroso alkenes withcisandthreo(trans) configuration, respectively. These enantiomorphicC-nitroso compounds were isolated as a single compound for the former, and a mixture for the latter, ofdland (or)mesodimers, the presence of which was readily monitored by13C nmr spectroscopy. The former can assume a conformation to place the π-bonds of the nitroso and olefinic groups in interacting vicinity and undergo an acid catalyzed intramolecular electrophilic cyclization to give bicyclic hydroxylamines which are readily air oxidized to the corresponding nitroxide radicals. Rearrangement in acetic anhydride – methylene chloride afforded good yields of the stable bicyclic hydroxyl-amine acetates which served as precursors to generate the corresponding nitroxides under mild conditions. Photoaddition ofN-nitrosopiperidine to 1,5-cyclooctadiene also partly afforded thecis-aminonitroso adduct which underwent the intramolecular addition to give hydroxylamines. Thethreo(trans)-chloronitroso alkenes failed to cyclize in similar fashion under comparable conditions. Nitrosylchloride added exclusively to thetrans-double bond oftrans,cis-1,5-cyclo- decadiene without regiospecificity but was believed to follow the stereospecificcis-addition; this chloronitroso compound also underwent the acid catalyzed transannular reaction to give similar hydroxylamines that were not isolated in pure states.

ISSN:0008-4042    

DOI:10.1139/v79-477

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Photolysis of nitramines in a neutral solvent generated nitrogen dioxide and aminyl radicals which abstracted a hydrogen but did not add to a π-bond. In dilute acidic solution, the aminyl radicals generated from the photolysis were protonated to the corresponding aminium radicals that preferentially added to π-bonds rather than abstracted a hydrogen. However, complex mixtures of addition products were obtained when nitramines were photolysed in the presence of cyclohexene under nitrogen. The plethora of the products is believed to arise from the complex behavior of nitrogen dioxide in solution; for example, (i) nitrogen dioxide may react asO- orN-radical, (ii) nitrogen dioxide exists in equilibrium with nitrogen tetraoxide, and (iii) both oxides can react as oxidizing or radical trapping agents. Under oxygen, the oxidative addition of nitramines to cyclohexene gave 1-dialkylamino-2-nitratocyclohexenes which could be treated with lithium aluminium hydride to give good yields of the corresponding amino alcohols. The quantum yields of nitramine disappearance indicated that the photolysis followed short chain processes either in neutral or acidic conditions. The decrease in quantum yield at >2NH2SO4is believed to be due to a reduced reactivity of aminium radicals in a highly acidic environment. The probable mechanisms of these photolytic radical chain processes are discussed.

ISSN:0008-4042    

DOI:10.1139/v79-478

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Kinetic equations, applicable to A-1, A-SE2, and A-2 reactions in concentrated aqueous acids, are derived. The variation in reaction rate with varying acid concentration is treated in terms of the "excess acidity" of the medium (X-function), rather than in terms of Hammett-type acidity functions or the water activity. The parameters obtained are the medium-independent rate constantk0, in the aqueous standard state, as an intercept, and a slope parameterm≠hydration parameters (r-values) are also obtained, for A-2 reactions. The equations derived are shown to apply to A-1 acetal hydrolyses, A-SE2 electrophilic aromatic substitutions, and mixed A-2/A-1 ester hydrolyses. In a general discussion of available methods for analyzing rate data in these media, it is shown that theX-function method encompasses most, if not all, of the others, and that classical acidity functions are no longer necessary.

ISSN:0008-4042    

DOI:10.1139/v79-479

出版商:NRC Research Press    

年代:1979

数据来源: NRC