Features of organic compounds
Elements of organic chemistry. Polymers
Features, theory of chemical structure and classification of organic compounds
Carbon compounds (except for the simplest ones) are called organic. These are either natural or artificially obtained substances. Organic chemistry is the study of the properties and transformations of organic compounds. This chapter deals with only a small part of the organic compounds that are important in technology.
Features of organic compounds
Organic compounds are very numerous and diverse, their number exceeds 4 million. The diversity of organic compounds is largely due to the ability of carbon atoms to form covalent bonds with each other. Due to the high strength of carbon-carbon bonds, chains are formed consisting of a large number of carbon atoms. Chains can be both open and closed (cycles). Carbon interacts with many other atoms. With hydrogen, carbon forms compounds called hydrocarbons. The diversity of organic compounds is also due to the phenomenon isomerism , which consists in the existence of substances of the same composition and molecular weight, but different in structure and spatial arrangement of atoms.
The features of organic compounds can also include the existence homologous series, in which each subsequent term can be derived from the previous one by adding one group of atoms defined for a given series. For example, in the homologous series of saturated hydrocarbons, such a group is CH2. The homologous series is characterized by a general formula, for example, C n H 2n+2 for saturated hydrocarbons. At the same time, there is a regular change in the physical properties of the elements as the number of groups increases.
Most organic compounds are characterized by a relatively low rate of chemical interactions under normal conditions. This is due to the high strength of the covalent bond carbon - carbon and carbon with other atoms and the relatively small difference in the bond energy of carbon with different atoms:
Communication with - H C-C C-Cl C-N C-S
Bond energy, kJ ………………………. 415 356 327 293 259
Electronegativity difference ……… 0.4 0.0 0.5 0.5 0.0
In a series of electronegativity values, carbon occupies an intermediate position between typical oxidizing and reducing agents, so the difference in the electronegativity of carbon with many other atoms is relatively small. Because of this, chemical bonds in organic compounds, as a rule, have low polarity. Most organic compounds are not capable of electrolytic dissociation.
The melting point of most organic compounds is relatively low (up to 100 - 200). At high temperatures, they burn in air mainly to carbon monoxide and water vapor.
17.1.2 The theory of the chemical structure of organic compounds by A.M. Butlerov In 1861, A.M. Butlerov formulated the main provisions of the theory of chemical structure.
1. The atoms in an organic molecule are interconnected in a certain order in accordance with their valency, which determines the chemical structure of the molecules.
2. Molecules with the same composition may have a different chemical structure and, accordingly, have different properties. Such molecules are called isomers. For a given empirical formula, a certain number of theoretically possible isomers can be derived.
3. Atoms in a molecule have mutual influence on each other, i.e. the properties of an atom may change depending on the nature of the other atoms of the compound. It should be noted that not only bound atoms experience mutual influence, but also those that are not directly bound to each other.
LIPIDS_ chemically, most lipids are esters of higher carboxylic acids and a number of alcohols. The most famous among them are fats. Each fat molecule is formed by a molecule of the trihydric alcohol glycerol and ester bonds of three molecules of higher carboxylic acids attached to it. According to the accepted nomenclature, fats are called triacylglycerols.
FUNCTIONS
1) structural,
2) protective,
3) thermo- waterproofing,
4) synthetic (component of many hormones),
5) energy,
6) storage function.
Lipids form a thermally insulating layer in the body, are part of the secretions of the sebaceous glands.
PROTEINS_Protein molecules are large, so they are called macromolecules. In addition to carbon, oxygen, hydrogen, and nitrogen, proteins can contain sulfur, phosphorus, and iron. Proteins differ from each other in number (from one hundred to several thousand), composition and sequence of monomers. The monomers of proteins are amino acids. The uniqueness of a protein is determined by the sequence of connecting certain amino acids. Protein molecules can form a primary, secondary, tertiary and quaternary structure.
Proteins perform many functions in the cell: enzymatic, transport, protective, etc.
Nucleic acids
/ \
RNA DNA
Nucleic acid molecules are long polymeric chains whose monomers are nucleotides. Each nucleotide consists of a nitrogenous base, a carbohydrate, phosphoric acid residues (one of three).
FUNCTIONS
1) catalytic
2) building
3) transport
4) protective
5) motor
6) energy
7) hormonal
8) receptor
CARBOHYDRATES_substances with the general formula Cn(H2O)m, where n and m can have different values. They are the primary products of photosynthesis and the initial products of the biosynthesis of other organic substances in plants. Carbohydrates come in 3 varieties, they are biopolymers, there are homopolysaccharides (starch, chitin, glycogen, cellulose), heteropolysaccharides (pectin, murein, heparin)
FUNCTIONS:
1. energy (with the breakdown of 1 g of carbohydrate = 17.6 kJ of energy)
2. structural (shells of plant cells)
3. storage (reserve nutrients - starch, glycogen, cellulose) (organic acids, alcohols, amino acids, etc.), and are also found in the cells of all other organisms.
Reply
All substances that contain a carbon atom, in addition to carbonates, carbides, cyanides, thiocyanates and carbonic acid, are organic compounds. This means that they are able to be created by living organisms from carbon atoms through enzymatic or other reactions. Today, many organic substances can be synthesized artificially, which allows the development of medicine and pharmacology, as well as the creation of high-strength polymer and composite materials.
Classification of organic compounds
Organic compounds are the most numerous class of substances. There are about 20 types of substances here. They are different in chemical properties, differ in physical qualities. Their melting point, mass, volatility and solubility, as well as their state of aggregation under normal conditions, are also different. Among them:
- hydrocarbons (alkanes, alkynes, alkenes, alkadienes, cycloalkanes, aromatic hydrocarbons);
- aldehydes;
- ketones;
- alcohols (dihydric, monohydric, polyhydric);
- ethers;
- esters;
- carboxylic acids;
- amines;
- amino acids;
- carbohydrates;
- fats;
- proteins;
- biopolymers and synthetic polymers.
This classification reflects the features of the chemical structure and the presence of specific atomic groups that determine the difference in the properties of a substance. In general terms, the classification, which is based on the configuration of the carbon skeleton, which does not take into account the features of chemical interactions, looks different. According to its provisions, organic compounds are divided into:
- aliphatic compounds;
- aromatic substances;
- heterocyclic compounds.
These classes of organic compounds can have isomers in different groups of substances. The properties of the isomers are different, although their atomic composition may be the same. This follows from the provisions laid down by A. M. Butlerov. Also, the theory of the structure of organic compounds is the guiding basis for all research in organic chemistry. It is put on the same level with Mendeleev's Periodic Law.
The very concept of chemical structure was introduced by A. M. Butlerov. In the history of chemistry, it appeared on September 19, 1861. Previously, there were different opinions in science, and some scientists completely denied the existence of molecules and atoms. Therefore, there was no order in organic and inorganic chemistry. Moreover, there were no regularities by which it was possible to judge the properties of specific substances. At the same time, there were also compounds that, with the same composition, exhibited different properties.
The statements of A. M. Butlerov in many ways directed the development of chemistry in the right direction and created a solid foundation for it. Through it, it was possible to systematize the accumulated facts, namely, the chemical or physical properties of certain substances, the patterns of their entry into reactions, and so on. Even the prediction of ways to obtain compounds and the presence of some common properties became possible thanks to this theory. And most importantly, A. M. Butlerov showed that the structure of a substance molecule can be explained in terms of electrical interactions.
The logic of the theory of the structure of organic substances
Since, before 1861, many in chemistry rejected the existence of an atom or a molecule, the theory of organic compounds became a revolutionary proposal for the scientific world. And since A. M. Butlerov himself proceeds only from materialistic conclusions, he managed to refute the philosophical ideas about organic matter.
He managed to show that the molecular structure can be recognized empirically through chemical reactions. For example, the composition of any carbohydrate can be determined by burning a certain amount of it and counting the resulting water and carbon dioxide. The amount of nitrogen in the amine molecule is also calculated during combustion by measuring the volume of gases and releasing the chemical amount of molecular nitrogen.
If we consider Butlerov's judgments about the chemical structure, which depends on the structure, in the opposite direction, then a new conclusion suggests itself. Namely: knowing the chemical structure and composition of a substance, one can empirically assume its properties. But most importantly, Butlerov explained that in organic matter there is a huge number of substances that exhibit different properties, but have the same composition.
General provisions of the theory
Considering and investigating organic compounds, A. M. Butlerov deduced some of the most important patterns. He combined them into the provisions of the theory explaining the structure of chemicals of organic origin. The provisions of the theory are as follows:
- in the molecules of organic substances, atoms are interconnected in a strictly defined sequence, which depends on valence;
- chemical structure is the direct order according to which atoms are connected in organic molecules;
- the chemical structure determines the presence of the properties of an organic compound;
- depending on the structure of molecules with the same quantitative composition, different properties of the substance may appear;
- all atomic groups involved in the formation of a chemical compound have a mutual influence on each other.
All classes of organic compounds are built according to the principles of this theory. Having laid the foundations, A. M. Butlerov was able to expand chemistry as a field of science. He explained that due to the fact that carbon exhibits a valence of four in organic substances, the variety of these compounds is determined. The presence of many active atomic groups determines whether a substance belongs to a certain class. And it is precisely due to the presence of specific atomic groups (radicals) that physical and chemical properties appear.
Hydrocarbons and their derivatives
These organic compounds of carbon and hydrogen are the simplest in composition among all the substances of the group. They are represented by a subclass of alkanes and cycloalkanes (saturated hydrocarbons), alkenes, alkadienes and alkatrienes, alkynes (unsaturated hydrocarbons), as well as a subclass of aromatic substances. In alkanes, all carbon atoms are connected only by a single C-C bond, which is why not a single H atom can be built into the composition of the hydrocarbon.
In unsaturated hydrocarbons, hydrogen can be incorporated at the site of the double C=C bond. Also, the C-C bond can be triple (alkynes). This allows these substances to enter into many reactions associated with the reduction or addition of radicals. All other substances, for the convenience of studying their ability to enter into reactions, are considered as derivatives of one of the classes of hydrocarbons.
Alcohols
Alcohols are called organic chemical compounds more complex than hydrocarbons. They are synthesized as a result of enzymatic reactions in living cells. The most typical example is the synthesis of ethanol from glucose as a result of fermentation.
In industry, alcohols are obtained from halogen derivatives of hydrocarbons. As a result of the substitution of a halogen atom for a hydroxyl group, alcohols are formed. Monohydric alcohols contain only one hydroxyl group, polyhydric - two or more. An example of a dihydric alcohol is ethylene glycol. The polyhydric alcohol is glycerol. The general formula of alcohols is R-OH (R is a carbon chain).
Aldehydes and ketones
After alcohols enter into reactions of organic compounds associated with the elimination of hydrogen from the alcohol (hydroxyl) group, a double bond between oxygen and carbon closes. If this reaction takes place at the alcohol group located at the terminal carbon atom, then as a result of it, an aldehyde is formed. If the carbon atom with alcohol is not located at the end of the carbon chain, then the result of the dehydration reaction is the production of a ketone. The general formula of ketones is R-CO-R, aldehydes R-COH (R is the hydrocarbon radical of the chain).
Esters (simple and complex)
The chemical structure of organic compounds of this class is complicated. Ethers are considered as reaction products between two alcohol molecules. When water is cleaved from them, a compound of the R-O-R sample is formed. Reaction mechanism: elimination of a hydrogen proton from one alcohol and a hydroxyl group from another alcohol.
Esters are reaction products between an alcohol and an organic carboxylic acid. Reaction mechanism: elimination of water from the alcohol and carbon groups of both molecules. Hydrogen is split off from the acid (along the hydroxyl group), and the OH group itself is separated from the alcohol. The resulting compound is depicted as R-CO-O-R, where the beech R denotes radicals - the rest of the carbon chain.
Carboxylic acids and amines
Carboxylic acids are called special substances that play an important role in the functioning of the cell. The chemical structure of organic compounds is as follows: a hydrocarbon radical (R) with a carboxyl group (-COOH) attached to it. The carboxyl group can only be located at the extreme carbon atom, because the valency C in the (-COOH) group is 4.
Amines are simpler compounds that are derivatives of hydrocarbons. Here, any carbon atom has an amine radical (-NH2). There are primary amines in which the (-NH2) group is attached to one carbon (general formula R-NH2). In secondary amines, nitrogen combines with two carbon atoms (formula R-NH-R). Tertiary amines have nitrogen attached to three carbon atoms (R3N), where p is a radical, a carbon chain.
Amino acids
Amino acids are complex compounds that exhibit the properties of both amines and acids of organic origin. There are several types of them, depending on the location of the amine group in relation to the carboxyl group. Alpha amino acids are the most important. Here the amine group is located at the carbon atom to which the carboxyl group is attached. This allows you to create a peptide bond and synthesize proteins.
Carbohydrates and fats
Carbohydrates are aldehyde alcohols or keto alcohols. These are compounds with a linear or cyclic structure, as well as polymers (starch, cellulose, and others). Their most important role in the cell is structural and energetic. Fats, or rather lipids, perform the same functions, only they participate in other biochemical processes. Chemically, fat is an ester of organic acids and glycerol.
