Ch. 31 Carbohydrates - Core Points

JEE Syllabus

Carbohydrates:
Classification;
mono and di-saccharides (glucose and sucrose);
Oxidation, reduction,
glycoside formation and hydrolysis of sucrose.
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1. Carbohydrates means "hydrates of carbon".
These are poly-hydroxylated-aldehydes or poly-hydroxylated-ketones. The general formula is C-x(H-2O)-y

2. Carbohydrates are classified as:
Monosaccharides, Oligosaccharides, Polysaccharides

3. Glucose is a monosaccharide and it forms a six membered ring of five carbon atoms and one oxygen atom.

4. When acqueous solution of glucose is treated with sodium amalgam or sodium borohydride, it is reduced to sorbitol (or glucito) a hexahydric alcohol.

5. Mild oxidizing agents such as bromine water, silver oxide, sodium hypobromite etc. oxidize glucose ot gluconic acid converting -CHO group to -COOH group.


6. The important members belonging to disaccharides are sucrose, maltose and lactose.

7. On hydrolysis these give two molecules of monosaccharides.

8. Sucrose in comination with water (hydrolysis) gives glucose and fructose.

9. Sucrose is composed of alpha-D-glucose and beta-D-fructose. These units are held together by alpha, beta-glycosidic linkage between C1 (carbon 1) of the glucose unit (pyranose ring) and C2 of the fructose unit (furanose ring).


10. Reducing sugars are easily oxidized to give carboxylic acid.