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Ch_322b_22.03 - Structural Features of Monosaccaharides...

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Structural Features of Monosaccaharides Some Historical Background By the late 19th century, the importance of a class of naturally occurring compounds called sugars was clear. The conversion of sugar into ethanol and CO 2 by living yeast cells had been demonstrated earlier in that century by Louis Pasteur. In 1892, Eduard Buchner showed that this fermentation could be carried out by a cell-free yeast extract. By the turn of the century, extensive studies were in progress on the metabolism of glucose. Structural studies on glucose (an aldohexose) and other carbohydrates were carried out by Emil Fischer (1852-1919) and his coworkers over a 30 year period that spanned the last part of the 19th century and the beginning of the 20th century. In 1875, the young Fischer (a student of von Baeyer) discovered phenylhydrazine and its reaction with sugars to form generally crystalline derivatives called osazones . This reaction became one of the cornerstones in Fischer's structural studies on monosaccharides. At the time this project began, the tetrahedral carbon was recognized (1874) and incorporated into the structural analyses.
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Earlier Structural Studies on (+)- Glucose Glucose is readily obtained from natural sources such as fruits. It is somewhat less sweet than sucrose (common table sugar, a dissacharide). It precipitates as a white solid in two forms: ! , mp 146 o C and " , mp 148-155 o C. The two forms show different (and unusual) rotatory power, although both are dextrorotatory.
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