Ketal reference structure

Peaks at m/e 113 and 85 have been found in the mass spectra (12) of other O-isopropylidene ketals of sugars, as well as in Figure 7. Since these shift to m/e 119 and to m/e 88 and 91 in the mass spectrum of 10a as they did for the d6-analogs in Reference 12, the structures, 17, 18, and 19 from Reference 12 are shown as possible explanations. The peak at m/e 85 (91) could alternatively be from m/e 113 (119) by loss of carbon monoxide (28 mass units) from the six-membered-ring of structure 17b. 

Monosaccharides are sweet-tasting solids that are very soluble in water. Noncarbohydrate low-calorie sweeteners such as aspartame have been developed as sugar substitutes. Pentoses and hexoses form cyclic hemiacetals or hemiketals whose structures can be represented by Haworth structures. Two isomers referred to as anomers (the a and p forms) are produced in the cyclization reaction. All monosaccharides are oxidized by Benedict s reagent and are called reducing sugars. Monosaccharides can react with alcohols to produce acetals or ketals that are called glycosides. 

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