摘要:

Methyl β-L-arabopyranoside-1-C14was hydrogenolyzed in the presence of copper chrome oxide catalyst at 250 °C, yielding an approximately equimolar mixture of optically inactivecis- andtrans-3,4-dihydroxytetrahydropyran-C14, together with 2,3-dihydroxypentane-C14. The latter was formed by reductive ring-opening of the tetrahydropyrandiols. Ether cleavage of each of the cyclic diols afforded 1,2,3,5-tetrahydroxypentane-C14in which the tracer was distributed about equally between carbons 1 and 5. Carbon-14 in the pentanediol was distributed in a similar manner. The results show that both the 2- and 4-hydroxyl groups of the original pentoside are prone to reductive cleavage, and thatcis- andtrans-glycol groups in the cyclic diols are formed by isomerization. They suggest that hydrogenolysis of the methoxyl group takes place initially, accompanied by isomerization, to give a mixture of tetrahydropyrantriols in which the 2- and 4-hydroxyl groups have equivalent reactivity.

ISSN:0008-4042    

DOI:10.1139/v59-181

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

The Freundlich isotherms for the adsorption of some ortho-alkylated phenols on carbon from cyclohexane solution have been determined. The minimum surface area covered by the adsorbed phenols is compared with the area of the molecules themselves. Large alkyl groups ortho to the hydroxyl group greatly reduce the adsorption.

ISSN:0008-4042    

DOI:10.1139/v59-182

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

A study has been made of the isolation of a lignin fraction from spruce and aspen wood meals using a low temperature (90–95 °C) acidolysis involving a dioxane–water (9:1) solvent medium containing the equivalent of 0.2Nhydrochloric acid. The effect of extraction time on the yield of precipitated lignin and ether-soluble material, and on the methoxyl content of these products, was investigated. For both species prolonged extraction times led to greater yields of lignin with lower methoxyl content.Further acidolysis of isolated spruce lignin led to no significant loss of methoxyl indicating the stability of this group to these reaction conditions. With increasing times of acidolysis of the aspen wood, a slow rise in the carbon–methyl/methoxyl ratio was observed for the isolated lignins. This is in agreement with earlier findings for the spruce lignin. The yields of vanillin and syringaldehyde from aspen lignin on alkaline nitrobenzene oxidation were much less than those from wood meal, and the relative yield of syringaldehyde was higher.It is suggested that this type of lignin may be only mildly modified during extraction and hence suitable for subsequent chemical investigation. The significance of the findings is discussed.

ISSN:0008-4042    

DOI:10.1139/v59-183

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

Optical absorption of the hydronium ion in the region 1.7 µ was measured in solutions of nitric acid and perchloric acid in the concentration range 0.01 to 4.0 moles per liter. Above 0.1 molar the absorption did not follow Beer's Law, being smaller than predicted from the low concentration behavior. This enhanced transparency is attributed to a "negative absorption" band, associated with the change in solvent structure, found in this spectral region.

ISSN:0008-4042    

DOI:10.1139/v59-184

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

The manner in whichL-arabinofuranose branches are arranged along the xylan chain of the pentosans has been examined. The approach used was based on the fact thatD-xylose units engaged in branching are resistant to periodate oxidation whereas other sugar residues are readily attacked. Selective degradation of oxidized portions of the polymer with phenyl-hydrazine or sulphurous acid enabled the isolation of fragments which corresponded to branch points in the original pentosans.D-Xylose and xylobiose were the major products obtained, and xylotriose a minor product. The results indicate thatL-arabinose branches of the polysaccharide occur sometimes on isolatedD-xylose residues, sometimes on two adjacentD-xylose units, less frequently on three, but not on four, five, etc., consecutiveD-xylose residues along the chain.

ISSN:0008-4042    

DOI:10.1139/v59-185

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

The infrared spectra of 14 trichloro- and trifluoro-acetamidine hydrochlorides were studied. It was concluded that protonation occurs at the imino nitrogen atom of the N-substituted amidines. Both nitrogens of the amidine grouping, C(=N)N, become electron-deficient due to resonance leading to the single structure (III), regardless of which of the tautomers is present in the equilibrium mixture, and of the number and type of substituents on the amidine nitrogen atoms. These findings predestine tofailureany attempts to isolate the two amidine tautomers, whenever amidinium salts are involved as intermediates.

ISSN:0008-4042    

DOI:10.1139/v59-186

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

It has been shown by infrared spectroscopic study that the alleged N-aryl-nitroacetamidines are in fact the salts of nitroacetonitrile with aromatic amines.

ISSN:0008-4042    

DOI:10.1139/v59-187

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

Steady-state equations are worked out for the case of a competitive inhibitor that is present in concentrations comparable with that of the enzyme; allowance is made for the inhibitor attached to the enzyme. Two cases are considered: in case 1 the enzyme and inhibitor form a simple addition complex, while in case 2 a molecule is split off. Methods of graphical analysis of rate data are described.

ISSN:0008-4042    

DOI:10.1139/v59-188

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

A study has been made of the kinetics of the α-chymotrypsin-catalyzed hydrolysis of methyl hydrocinnamate in the presence of various concentrations of methanol, of eserine, and of diisopropyl phosphorofluoridate (DFP). In 20% methanol the pH optimum, using a substrate concentration of 1.20 × 10−3M, is 7.8; in pure water it is 8.3; and at intermediate pH's the optimum varies between these values. No inhibition was observed with eserine. In aqueous solution the character of the inhibition by DFP differs from that in alcohol solutions; the inhibition is of the competitive type, and the inhibition constant varies with pH in essentially the same manner as does the rate of the reaction. This result suggests that DFP interacts with the same active groups on the enzyme as are responsible for the hydrolysis of the substrate. A specific mechanism for inhibition is suggested.

ISSN:0008-4042    

DOI:10.1139/v59-189

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

A new technique is described for detecting possible phase transitions of adsorbates. The method involves the measurement of length changes of the solid, but only solids for which the surface-to-volume ratio is large could be used with the present form of instrument because of its moderate sensitivity. Using this measurement an apparent phase transition for water adsorbed on porous Vycor glass has been detected at approximately −22 °C.

ISSN:0008-4042    

DOI:10.1139/v59-190

出版商:NRC Research Press    

年代:1959

数据来源: NRC