What chemical properties does sugar have?
Is this question correct from the viewpoint of chemistry?
To start with we should answer the second question. The fact is that sugars (carbohydrates) are an enormous class of the most varied compounds, which in their turn are divided into several classes.
Monosaccharides are compounds which consist of one molecule. They are monomers. They include glucose, fructose, galactose, maltose, and all kinds of less common compounds that consist of a greater or smaller number of carbon atoms (for example, pentoses, that are part of the nucleotides of DNA).
Disaccharides are compounds which consist of two monomer molecules. For example, sucrose.
Polymers consist of millions of monomers. For example, starch and cellulose.
This classification is important because each sub-group of these compounds is characterized by certain qualities which are not found in other sub-groups of sugars. So we should examine sugars (their chemical features) based on this classification, and it is not quite correct to discuss the chemical properties of sugar, as glucose, for example, may display quite different properties from sucrose or starch.
Chemical qualities of monomer carbohydrates.
We will examine them based on the example of glucose – the sugars present in the metabolism of human beings, animals and plants are of the greatest importance. Additionally, this compound is widely used in medicine and industry.
- Alcohol fermentation is the reaction that probably has the widest practical use. Yeast micro-organisms cause glucose molecules to transform into ethyl alcohol. Additionally, if lactic or butyric bacteria react with glucose, lactic or butyric acids will be formed.
- There is a qualitative reaction known as the silver mirror. As the aldehyde group is present in glucose, when it reacts with an ammonia solution of silver oxide, a silver residue will form (this will in fact be pure silver).
- The reaction of glucose with copper hydroxide is characteristic – the solution will change color from blue to red (the reason is that cuprous copper oxide forms). It is important to note that this reaction is only possible when the substances are heated – at room temperature the alcohol groups will cause the solution to turn dark blue (similar to the qualitative reaction with glycerin, a polyalcohol).
- Another reaction with practical significance is the hydrogenation of glucose to sorbitol, a hexahydric alcohol (again, this is possible because of the presence of the aldehyde group in the glucose molecule).
- And of course, we cannot forget the reaction of polymerization, when a huge number of molecules of glucose (or another monomer carbon) join together and starch is formed (or celluolose).
Chemical qualities of disaccharides
As it is widely believed by the general public that sugar is a white, crystalline substance that is sweet to the taste, we will examine the properties of sucrose. Essentially, no reactions that differ from glucose can be noted (as the aldehyde group is “joined”). The only difference is that under the influence of water, this substance will break down into glucose and fructose molecules.
Qualities of polymeric carbohydrates
The reaction of depolymerization is the breakdown of starch into glucose, and additionally there is a qualitative reaction of starch and iodine - it turns blue.
Carbohydrates (sugars) are a very wide group of substances, the qualities of which are determined by the number of “building blocks” in the compound. Here you'll find interesting experiments with sugar.