Question

15 points) You are given a carbohydrate to analyze. It behaves as a reducing sugar with a Tollen's test. When you exhaustively methylate it with alkaline CH3l and then hydrolyze with strong acid, you get the following in an equal molar ratio (1:1); 2,3,4,6-tetra-o-methylgalactose 2,3,6-tri-O-methylglucose You try reacting it with different glycosidases, and get the following results: a-galactosidase: No reaction B-galactosidase: produces galactose and glucose (1:1) as products a-glucosidase: No reaction B-glucosidase: No reaction . (2 point) Based upon these results, what is the sugar (use common name, if there is one). Is is classified as a monosaccharide, disaccharide, or polysaccharide? Explain how you are confidence in your answer.

Answer 1

we need to work from back to front to solve this Problem. 2, 3, 4, t-tera-o-methylgalactone in CH₂CH CH₂OCH? Hscola oh Koch HY H KH Ý OCH₃ 2,3; 6-tri-o-methyl Glucose is CH2OCH 3 ң оң HOY OCHI Let's combine the above two molecules such that resulting compound behaved as reducing agent with Tollens reagent and

Note: A compound with hemi acetal group or aldehyde aca ai reducing agent with Tollens reagent. Therefore we need to combine above two molecules much that there is one free hemiacetal group. H - CH2 OCH3 KOCH HY hemiacetal group CHzo go Reaponeible for reducing KOCH HY behavious with Tollens rear ! н оска .. CH₂OCH3 0.01 TH ☺ H OCH3 we can remove -CH₃ ground to write the structure before methylation with CH₃ I

CH₂o14 a oH 2 ç alucone unit 2014 CHOH B-Gartyserandre bye L W B.- Galactosidare breaks this band to produce al Glucone and galactose. Galactine unit

The sugar is a dissacharide and its common name is Lactone because it contains Galactone and Glucone cnica with Bul>4 glycosidic linkage . The compound breake its B-1.74 aly conidic band only with B-galacto liday but not with the ot glycosidaxes given in the question. Therefore y 100 7. confident that the sugar il Lacture herefore I am