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Cane sugar is also called sugar cane. Sugars are biological compounds called biomolecules, and the name given for sugars is carbohydrates. Carbohydrates are usually made of carbon, hydrogen, and oxygen, covalently bonded by sharing electrons in various combinations and forming a wide range of sugars. The name given to carbohydrates or sugars in scientific terms is saccharides. Based on the number of saccharide units present, sugars can be categorised into monosaccharides, disaccharides, polysaccharides. The composition of the sugars, the complexity of the molecules, and the products formed on hydrolysis also differ for different sugars.
Sugars or carbohydrates make a good source of energy for every living being. The food we eat contains a lot of carbohydrate content, and the most common sugar we intake is glucose and fructose. Glucose is present in all staple foods like rice, roti, jowar, etc. Fructose is present in almost all fruits, and it is generally called fruit sugar. The sugar that we eat daily also contains fructose.
Types of sugar
Our body needs energy to perform any activity and biological and metabolic reactions. The energy required for activities is obtained by the food we intake. This food we intake needs to be rich in carbohydrates, our major energy source. These carbohydrates, on digestion, release energy and through which we can survive.
Carbohydrates can be classified into mono, di, tri, and polysaccharides based on the number of saccharide units present.
- Monosaccharides: The sugar compounds which contain only one unit of saccharide are called monosaccharides.
Examples of monosaccharides include glucose and fructose.
These monosaccharides on hydrolysing do not form any smaller unit sugars. They are converted into carbon dioxide and water.
- Disaccharides: The sugar compounds containing two saccharide units are called disaccharides.These units are linked by ∝- glycosidic linkage.
Examples of disaccharides include sucrose, maltose, and lactose.
Sucrose on hydrolysis gives one unit of glucose and one unit of fructose.
Maltose on hydrolysis gives two units of glucose.
Lactose on hydrolysis gives one unit of glucose and one unit of galactose.
- Trisaccharides: The sugar compounds containing three saccharide units are called trisaccharides.These units are linked by ∝- glycosidic linkage.
An example of trisaccharides is raffinose. Raffinose on hydrolysis gives one unit of glucose, one unit of galactose, and one unit of fructose.
- Polysaccharides: The sugar compounds containing many saccharide units are called polysaccharides.
An example of a polysaccharide is starch.
Sucrose (table sugar)
Table sugar is commonly known as cane sugar. Its scientific composition is o ∝-D-Glucopyranosyl (1-2)ß-D-fructofuranose.
Cane sugar sources are sugar cane, beetroot, fruits, vegetables, etc. Sucrose dissolves and separates into two units of sugar, and hence it is a reducing sugar. Sucrose is a dextrorotatory compound with specific rotation ∝ = +66.5. Dextro rotation is the turning of plane polarised light in the clockwise direction by the compound in the polarimeter. Sucrose on hydrolysis becomes a strong leaf rotatory compound.
Inversion of sugar
Sucrose on hydrolysis forms hydrolytic products, and this is called invert sugar. Sucrose is hydrolysed by an enzyme sucrase or dilute acids, which liberates one molecule of ∝D-Glucopyranose and ß-D-fructofuranose. The second molecule, ß-D-fructofuranose, is an unstable compound and gets converted into ß-D-fructopyranose immediately. This compound is a leaf rotatory compound with specific rotation (-92). This effect of converting a dextrorotatory compound (+66.5) to a leaf rotatory compound (-22.8) by hydrolysis is called the inversion of sugar. Inverted sugars are usually 33% sweeter than sucrose.
An example of an inversion of sugar is honey.
Kinetic study of inversion of sugar
Specific rotation in organic chemistry is the rotation of a polarised plane light by an optically active compound, a chiral compound, or an asymmetric compound per unit distance-concentration product when light passes through the compound.
Plane polarised light: It is the light that consists of waves in which the direction of vibration is observed to be the same for all the waves.
An asymmetric molecule has different groups around it and does not possess symmetry. When kept in a polarimeter, asymmetric molecules display the ability to rotate in a clockwise or anti-clockwise direction and can be known by a measurement called specific rotation. This is indicated by ∝. If the molecule rotates the light in a clockwise direction, its dextrorotatory compound is indicated by (d). If the molecules rotate the light in an anti-clockwise direction, its levorotatory compound is indicated by (l).
C12H22O11 + H2O + H+ → C6H12O6 + C6H12O6 + H+
Sucrose Glucose Fructose
(dextro-rotatory) (dextro-rotatory) (laevo-rotatory)
+66.50 +52.50 -920
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On hydrolysing the sucrose, slowly, a dextrorotatory compound turns to a laevorotatory compound. Due to this, the reaction is called the inversion of sucrose or cane sugar. This reaction follows first-order kinetics, where the reaction rate depends only on the concentration of sucrose. The chemical kinetics of the reaction can be studied by observing the angle of rotation of the compound at regular intervals of time in the polarimeter instrument, and the rate of the reaction can be studied.
