Question

Methyl D- glucoside on reaction with $HI{O_4}$consumes two moles of reagent and produces the dialdehyde $A$ and mole of $HCOOH$. The result of this reaction proves that glucose has pyranose structure.

Answer 1

Hint: Saccharides: The unit structure of carbohydrates, are known as saccharides.
Pyranose structure: The saccharides which have six membered rings containing five carbon and one oxygen atom, are known as pyranose structure.

Complete step by step answer:
First of all we will discuss carbohydrates, saccharides, structures.
Carbohydrates: The sugar, starch and fibres found in fruits and vegetables, are known as carbohydrates. A carbohydrate is a molecule consisting of carbon, hydrogen and oxygen with hydrogen and oxygen ratio as $2:1$. So its empirical formula is as ${C_m}{({H_2}O)_n}$.
Saccharides: The unit structure by which carbohydrates are formed, known as saccharides. Saccharides are divided into four groups as: monosaccharide, disaccharide, oligosaccharide and polysaccharide.
Monosaccharide: These are the simplest carbohydrates which cannot be hydrolysed into smaller carbohydrates. For example: glucose, fructose.
Disaccharide: Two monosaccharides are joined together to form disaccharides. They are linked together by a covalent bond, known as glycosidic linkage. For example: sucrose, lactose.
Oligosaccharide:Carbohydrates containing three-ten molecules of saccharide, is known as oligosaccharide. For example: Raffinose
Polysaccharide: Carbohydrates containing more than ten molecules of saccharides, are known as polysaccharide. For example: starch.
Pyranose structure: The saccharides which have six membered rings containing five carbon and one oxygen atom, are known as pyranose structure.
Furanose structure: The saccharides which have five membered rings containing four carbon and one oxygen atom, are known as pyranose structure.
The molecular formula of glucose is ${C_6}{H_{12}}{O_6}$. The structure of glucose is pyranose which has six membered rings containing five carbon and one oxygen.

 The reaction is as follows:

Note:
Chiral carbon: Those carbons whose all the four valencies are filled by different atoms or molecules. D- and L- configuration are different. It is based on the position of the hydroxyl group present in the carbohydrate.