Structural formula is a graphic representation of a substance

It has long been accepted in chemistry that the composition of any substance should be written in abbreviated form, using symbols and indices (numbers). The record in this form is called the "empirical" formula. So, for example, the composition of phosphoric acid is reflected in such a form - H ₃ PO _4. From this record it follows that the phosphoric acid molecule consists of three hydrogen atoms, one - phosphorus, and four - oxygen. However, it is not clear how the elements are interconnected, i. E. Information is incomplete. To eliminate this gap, the structural formula of the substance is used.

This connection record has a great deal of informativeness, because With its help, it is shown schematically how and in what sequence the elements of matter are interconnected. In this case, each covalent bond (a pair of electrons) is represented by a dash and corresponds to one unit of valence.

For example, oxygen has a valence of two, it is surrounded by two dashes, hydrogen is a valence one, therefore, one dash, five phosphorus, five dashes. Based on this writing, we can assume the chemical properties of substances, classify them and systematize them.

Structural formula can be written in full and abbreviated form. When the record is expanded, all links between atoms are indicated, and when written in abbreviated form - no.

The most graphic and significant is the graphic representation of compounds in organic chemistry. After all, the properties of substances depend not only on the number of atoms and molecules, but also on the order of their connection. This phenomenon was called "isomerism" (branching of the carbon chain).

So, for example, the structural formula of ethane suggests that all carbon valencies are occupied, and it can not add other atoms to itself. From this it is clear that C ₂ H ₆ is a representative of the ultimate hydrocarbons, the bonds in the molecule are covalent, there are no free electrons, therefore for ethane only substitution reactions are possible and r Of sight.

The structural formula of the substance also indicates the functional groups of carbohydrates: the alkyl group in alcohols, the aldehydic for the aldehydes, and the benzene nucleus for aromatic compounds. In addition, using a schematic image, it is easy to "see" the presence of characteristic bonds of limiting hydrocarbons - a single covalent bond. Unsaturated: ethylene - one double bond, diene - two double bonds, triple - acetylene.

The structural formula of fructose is an example of spatial isomerism. This carbohydrate has the same quantitative and qualitative composition as glucose. In solutions comes at once in several forms. From the graphical fructose formula, it can be seen that it contains ketone and hydroxyl groups, i.e. This substance has the "dual" properties of alcohols and ketones. This formula also allows us to establish that this ketone-alcohol is formed by the residues of cyclic a-glucose and pentose (fructose).

Thus, the structural formula is a graphic representation of a substance by means of which one can learn about the arrangement of atoms in a molecule, taking into account the type of bond and their features.