Conclusion

We have completed our study of the organic chemistry course. Let us give a brief summary. Organic chemistry — is the chemistry of carbon compounds. Thanks to the atom's unique structure, in which the valence level is exactly half filled, carbon atoms readily bond with one another via fairly strong covalent bonds, forming linear and branched chains and rings. These structures may contain only single bonds, and may also include multiple (double and triple) bonds. A special case is presented by aromatic compounds, which contain rings with alternating single and double (conjugated) bonds. If the carbon skeleton is supplemented with hydrogen atoms, we are dealing with hydrocarbons, of which there is an inexhaustible variety.

Despite the enormous diversity of hydrocarbon structures, their properties are fairly limited in number. Hydrocarbons burn, which accounts for their practical use as energy sources. The most stable hydrocarbons — alkanes and arenes — undergo substitution reactions, in which the carbon skeleton is preserved while hydrogen atoms can be replaced by other atoms, in particular by halogen atoms. Alkane molecules can be cracked at high temperatures and pressures into hydrocarbon molecules of lower molecular weight. These processes are widely used in the processing of natural hydrocarbon feedstock.

Unlike alkanes and arenes, hydrocarbons whose molecules contain double and triple bonds (alkenes, alkadienes, and alkynes) readily undergo addition reactions, leading to the formation of alkanes (hydrogenation), halogen derivatives (halogenation, hydrohalogenation), alcohols (hydration), and polymers (polymerization). Aromatic hydrocarbons also undergo addition reactions, forming cycloalkanes.

At this stage of studying organic chemistry, the chemistry of hydrocarbons is limited to these properties. The chemical properties of organic compounds whose molecules include, besides carbon and hydrogen atoms, atoms of other elements are considerably more varied. Oxygen atoms in organic compounds form part of functional groups: the hydroxyl —OH, the aldehyde —CHO, and the carboxyl —COOH. Alcohols and phenols, whose molecules contain hydroxyl groups, display weak acidic properties, which allow them to react with alkali metals (alcohols) and even with alkalis (phenols).

The truest acids are the carboxylic acids, whose molecules contain carboxyl groups. They change the color of indicators and react with alkalis, active metals, salts, and metal oxides. Acids also enter into esterification reactions with alcohols to form esters. Fats are representative esters; they are formed from the trihydric alcohol glycerol and higher fatty acids, the most important of which are — palmitic, stearic, oleic, linoleic, and linolenic.

Aldehydes, whose molecules contain the —CHO group, are an important class of organic compounds, but at this stage of studying organic chemistry we have limited ourselves to learning about the ability of aldehydes to be oxidized to carboxylic acids (the «silver mirror» reaction) and to be reduced to alcohols. The aldehyde group is found in the molecules of many carbohydrates, glucose in particular. Carbohydrates — are bifunctional organic compounds; their molecules include, alongside the aldehyde group, hydroxyl groups. Glucose is a pentahydric aldehyde-alcohol and displays chemical properties characteristic of both polyhydric alcohols and aldehydes. This example shows that knowledge of the structure of organic molecules makes it possible to explain and even predict their properties, which makes the targeted synthesis of substances possible.

The molecules of the simplest carbohydrates (monosaccharides) readily undergo intramolecular cyclization. The rings, in turn, form disaccharide molecules (maltose, sucrose) and polysaccharide macromolecules (cellulose, starch) through intermolecular dehydration.

In studying oxygen-containing organic compounds, we encountered among them substances that are part of living organisms. These are carboxylic acids, fats, and carbohydrates, which form the basis of the plant and animal world. Our acquaintance with the «chemistry of the living» was broadened by the study of nitrogen-containing organic compounds, which brought us to proteins — the substances from which animal organisms, including ourselves, are built. We saw that the nitrogen atom in the amino group gives substances basic properties. Amino acids — are organic amphoteric compounds, whose molecules contain a basic —NH2 and acidic —COOH groups. Intermolecular dehydration of amino acids leads to peptides, which are what proteins are.

Knowledge of the fundamentals of organic chemistry has allowed us to understand the basics of the chemistry of high-molecular-weight compounds, which are formed as a result of polymerization and polycondensation reactions of organic substances.

A brief review of the material studied shows that organic chemistry occupies a special place not only among the chemical sciences but among all the natural sciences. It allows us to judge the structure and properties of the substances that make up the surrounding world of living nature, and also to understand the significance of the achievements of chemical science in meeting the needs of modern society for substances without which it simply could not exist.