首页   按字顺浏览 期刊浏览 卷期浏览 Distribution of Methoxyl Groups in the Methylation of Starch Alkoxides Obtained by Meta...
Distribution of Methoxyl Groups in the Methylation of Starch Alkoxides Obtained by Metallation with Alkali Metal Naphthalene

 

作者: Gabriel Ezra,   Albert Zilkha,  

 

期刊: Journal of Macromolecular Science: Part A - Chemistry  (Taylor Available online 1969)
卷期: Volume 3, issue 8  

页码: 1589-1600

 

ISSN:0022-233X

 

年代: 1969

 

DOI:10.1080/10601326908051954

 

出版商: Taylor & Francis Group

 

数据来源: Taylor

 

摘要:

The distribution of the alkoxide groups obtained in the metallation of starch in dimethyl sulfoxide solution by alkali metal naphthalenes was studied. The starch alkoxide was reacted with methyl iodide, and the methylated starch was hydrolyzed and analyzed for glucose and O-methyl glucose derivatives. The metallation reaction was found to be random, as seen from the fact that at low alkoxide concentration (D.S = 0.6), 2,3,6-tri-O-methyl glucose was formed, while at relatively high alkoxide concentration (D.S. = 1.5) unreacted glucose was still present. At low alkoxide concentration (D.S. ⋍ 0.6) there was, to a certain extent, preferential metallation at the C2hydroxyl groups, and to a lesser extent at the C6hydroxyl groups, as seen from the relative molar ratios of about 10:4:1 of the 2-, 6-, and 3-O-methyl glucose derivatives obtained, respectively. An increase in the metallation at the C3hydroxyl occurred with increasing alkoxide concentration. The distribution of the methoxyl groups with the three alkali metals potassium, sodium, and lithium was similar; there were differences only in the ease of metallation of the starch by the various alkali metal naphthalenes and in the efficiency of the coupling reaction with methyl iodide.

 

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