摘要:

The nature of the products obtained from reactions of acetaldehyde with methanol have been investigated in neutral and acidic solutions by titration with iodine and sodium bisulphite, ultraviolet absorption, and infrared spectroscopy. In neutral and buffered solution the hemiacetal is the only important product; in the presence of a high concentration of hydrogen ions the acetal is produced nearly quantitatively.

ISSN:0008-4042    

DOI:10.1139/v52-061

出版商:NRC Research Press    

年代:1952

数据来源: NRC

摘要:

The effects of gelatin and chloride ion on deposition in a convection-free system were similar in most respects to those observed when convection currents were present. Gelatin concentrations up to and including 250 mgm. per liter and chloride concentrations of 4 and 45 mgm. per liter had no effect on concentration polarization. There was a difference, however, in the effect of the two addition agents on polarization other than concentration polarization.

ISSN:0008-4042    

DOI:10.1139/v52-062

出版商:NRC Research Press    

年代:1952

数据来源: NRC

摘要:

A homogeneous polyuronide hemicellulose has been prepared from a crude hemicellulose isolated from wheat straw holocellulose by hot water. The method of preparation consisted of fractional precipitation of the acetylated hemicellulose from chloroform solution by petroleum ether. Approximately 50% of the recovered fractions consisted of a polysaccharide made up of 28 moles ofD-xylose, 5 moles ofL-arabinose, and 3 moles of uronic acid and having anand a molar ratio, methoxyl: uronic anhydride, of approximately 1.0. Intrinsic viscosity measurements indicated a degree of polymerization of approximately 30. Separation of hexosans present in the original hemicellulose showed that they were not chemically combined with the main pentosan fraction. They were recovered admixed with short chain pentosan material containing a higher proportion of arabinose to xylose than the main homogeneous fraction.

ISSN:0008-4042    

DOI:10.1139/v52-063

出版商:NRC Research Press    

年代:1952

数据来源: NRC

摘要:

The carbon dioxide evolved when α-amino acids were heated for one hour at 85 °C. with ninhydrin was determined in a partially evacuated microdiffusion cell. Distillation of solvent from one chamber to the other was minimized by keeping the ionic concentrations of the reaction mixture and absorbing mixture approximately equal. The method was useful for samples of amino acids which liberated from 0.06 to 0.3 mgm. of carbon dioxide. The average deviation from the mean was somewhat less than 1% for samples liberating 0.2 mgm. of carbon dioxide. Use of the method for routine analysis of enzymatic digests resulted in substantial saving of time and material.

ISSN:0008-4042    

DOI:10.1139/v52-064

出版商:NRC Research Press    

年代:1952

数据来源: NRC

摘要:

Anthranilic acid is known to decarboxylate on being heated above its melting point, or on being boiled in water. We have found that the aqueous decomposition can be acid catalyzed, but that, after the concentration of added mineral acid approximates that of the anthranilic acid, the reaction rate decreases with increasing mineral acid concentration. A mass spectrometer study of the carbon dioxide produced in the decomposition has shown that C12-carboxyl anthranilic acid decomposes at the same rate as C13-carboxyl anthranilic acid. Thus, unlike all other organic acid decarboxylations in which an "isotope effect" has been searched for thus far, the decarboxylation of anthranilic acid does not show an "isotope effect". From the experimental facts available, it appears that the mechanism of the decarboxylation is best explained as bimolecular electrophilic substitution, with the attack of a proton being the rate determining step. While other possibilities are not entirely excluded, a proton attack on the α carbon of the zwitterion is the detailed mechanism suggested as being most probable.

ISSN:0008-4042    

DOI:10.1139/v52-065

出版商:NRC Research Press    

年代:1952

数据来源: NRC

摘要:

The addition of the elements of methoxymercuric acetate to 2-methyl-1-phenylpropene-1 occurs to give 2-methyl-2-methoxy-1-phenylpropylmercuric acetate. This structure could not be demonstrated by replacement of chloromercuri by halogeno because 2-methyl-1,2-dimethoxy-1-phenylpropane and 2-methyl-2-phenylpropanal or 3-phenylbutanone-2 were obtained instead of the expected halides. Indeed the 2-methyl-2-methoxy-1-phenylpropyl iodide which Tiffeneau, Orekhoff, and Lévy reported as the reaction product of 2-methyl-1-phenylpropene-1, mercuric acetate, and iodine in methanol is yet unknown, since their product actually comprised the di-ether and aldehyde described above. The structure proof of 2-methyl-2-methoxy-1-phenylpropylmercuric chloride has been accomplished by treatment with hydrazine hydrate. The isolation of 2-methoxy-2-methyl-1-phenylpropane and the two diastereomeric 2,5-dimethyl-2,5-dimethoxy-3,4-diphenylhexanes shows that this reaction has proceeded through intermediate formation of the 2-methoxy-2-methyl-1-phenylpropyl radical.

ISSN:0008-4042    

DOI:10.1139/v52-066

出版商:NRC Research Press    

年代:1952

数据来源: NRC

摘要:

A method of measuring density gradients caused by gravitational compression in gases near the critical region is described. Relative light scattering coefficients of ethane in bombs 40 cm. long increase, remain constant, or decrease in the downward direction, depending upon the mean filling density. These observations have been correlated with the variation of scattering coefficient with density, and show that appreciable density gradients exist. These observations are confirmed by parallel studies of condensation, and serve to explain the flat portion of the liquid–vapor coexistence curve found with a carefully purified system.

ISSN:0008-4042    

DOI:10.1139/v52-067

出版商:NRC Research Press    

年代:1952

数据来源: NRC