One of the most common chemical elements that make up the vast majority of chemicals is oxygen. Oxides, acids, bases, alcohols, phenols and other oxygen-containing compounds are studied in the course of inorganic and organic chemistry. In our article we will study the properties, as well as give examples of their application in industry, agriculture and medicine.
Oxides
The simplest in structure are binary compounds of metals and non-metals with oxygen. The classification of oxides includes the following groups: acidic, basic, amphoteric and indifferent. The main criterion for the division of all these substances is which element combines with oxygen. If it is metal, then they are basic. For example: CuO, MgO, Na 2 O - copper, magnesium, sodium oxides. Their main chemical property is the reaction with acids. So, copper oxide reacts with perchloric acid:
CuO + 2HCl -> CuCl2 + H2O + 63, 3 kJ.
The presence of atoms of non-metallic elements in the molecules of binary compounds indicates their belonging to acidic oxides, for example, hydrogen oxide H 2 O, carbon dioxide CO 2 , phosphorus pentoxide P 2 O 5 . The ability of such substances to react with alkalis is their main chemical characteristic.
As a result of the reaction, salts of two types can form: acidic or medium. This will depend on how much a mole of alkali reacts:
- CO2 + KOH => KHCO3;
- CO2 + 2KOH => K2CO3 + H2O.
Another group of oxygen-containing compounds, which include such chemical elements as zinc or aluminum, are referred to as amphoteric oxides. Their properties show a tendency to chemical interaction with both acids and alkalis. The products of the interaction of acid oxides with water are acids. For example, in the reaction of sulfuric anhydride and water, sulfate acid is formed. Acids are one of the most important classes of oxygen-containing compounds.
Acids and their properties
Compounds consisting of hydrogen atoms bound to complex ions of acid residues are acids. Conventionally, they can be divided into inorganic, for example, carbonate acid, sulfate, nitrate, and organic compounds. The latter include acetic acid, formic, oleic acid. Both groups of substances have similar properties. So, they enter into a neutralization reaction with bases, react with salts and basic oxides. Almost all oxygen-containing acids in aqueous solutions dissociate into ions, being second-order conductors. Determine the acidic nature of their environment, due to the excessive presence of hydrogen ions, using indicators. For example, purple litmus, when added to an acid solution, acquires a red color. A typical representative of organic compounds is acetic acid containing a carboxyl group. It includes a hydrogen atom, which determines the acid properties of the substance. It is a colorless liquid with a specific pungent odor, crystallizing at temperatures below 17 ° C. CH 3 COOH, like other oxygen-containing acids, is highly soluble in water in any proportion. Its 3 - 5% solution is known in everyday life as vinegar, which is used in cooking as a seasoning. The substance has also found its use in the production of acetate silk, dyes, plastics and some medicines.
Organic compounds containing oxygen
In chemistry, one can distinguish a large group of substances containing, in addition to carbon and hydrogen, also oxygen particles. These are carboxylic acids, esters, aldehydes, alcohols and phenols. All their chemical properties are determined by the presence in the molecules of special complexes - functional groups. For example, the general chemical formula of an alcohol containing only terminal bonds between atoms is ROH, where R is a hydrocarbon radical. It is customary to consider these compounds as derivatives of alkanes in which one hydrogen atom is substituted by a hydroxo group.
Physical and chemical properties of alcohols
The state of aggregation of alcohols is liquids or solid compounds. Among the alcohols, there are no gaseous substances, which can be explained by the formation of associates - groups consisting of several molecules connected by weak hydrogen bonds. This fact determines the good solubility of lower alcohols in water. However, in aqueous solutions, oxygen-containing organic substances - alcohols, do not dissociate into ions, do not change the color of indicators, that is, they have a neutral reaction. The hydrogen atom of the functional group is weakly bonded to other particles; therefore, it is able to leave the limits of the molecule in chemical interactions. In the place of free valency, it is replaced by other atoms, for example, in reactions with active metals or with alkalis - by metal atoms. In the presence of catalysts, such as a platinum network or copper, alcohols are oxidized by energetic oxidizing agents - potassium dichromate or potassium permanganate, to aldehydes.
Esterification reaction
One of the most important chemical properties of oxygen-containing organic substances: alcohols and acids is the reaction leading to the production of esters. It is of great practical importance and is used in industry for the extraction of esters used as solvents in the food industry (in the form of fruit essences). In medicine, some of the esters are used as antispasmodics, for example, ethyl nitrite dilates peripheral blood vessels, and isoamyl nitrite is a protector of coronary artery spasms. The esterification reaction equation has the following form:
CH3COOH + C2H5OH <- (H2SO4) -> CH3COOC2H5 + H2O
In it, CH 3 COOH is acetic acid, and C 2 H 5 OH is the chemical formula of ethanol alcohol.
Aldehydes
If the compound contains a functional group —COH, then it refers to aldehydes. They are presented as products of the further oxidation of alcohols, for example, by such oxidizing agents as copper oxide.
The presence of the carbonyl complex in the molecules of formic or acetic aldehyde determines their ability to polymerize and to attach atoms of other chemical elements. Qualitative reactions that can be used to prove the presence of a carbonyl group and the substance to belong to aldehydes are the reaction of a silver mirror and the interaction with copper hydroxide when heated:
The most widely used is acetaldehyde, which is used in industry to produce acetic acid - a lot of tonnage product of organic synthesis.
Properties of oxygen-containing organic compounds - carboxylic acids
The presence of a carboxyl group — one or more — is a hallmark of carboxylic acids. Due to the structure of the functional group, dimers can form in acid solutions. They are interconnected by hydrogen bonds. Compounds dissociate into hydrogen cations and anions of the acid residue and are weak electrolytes. An exception is the first representative of a number of saturated monobasic acids - formic, or methane, which is a conductor of the second kind of medium strength. The presence in the molecules of only simple sigma bonds indicates extremeness, but if substances have double pi bonds in their composition, these are unsaturated substances. The first group includes such acids as methane, acetic, butyric. The second is represented by compounds that make up liquid fats - oils, for example, oleic acid. The chemical properties of oxygen-containing compounds: organic and inorganic acids are very similar. So, they can interact with active metals, their oxides, with alkalis, as well as with alcohols. For example, acetic acid reacts with sodium, oxide and sodium hydroxide to form a salt - sodium acetate:
NaOH + CH3COOH → NaCH3COO + H2O
A special place is occupied by compounds of higher carboxylic oxygen-containing acids: stearic and palmitic, with a triatomic saturated alcohol - glycerol. They belong to esters and are called fats. The same acids are part of sodium and potassium salts as an acid residue, forming soaps.
Fats and Soaps
Important organic compounds that are widespread in wildlife and play a leading role as the most energy-intensive substances are fats. They are not an individual compound, but a mixture of dissimilar glycerides. These are compounds of the limiting polyhydric alcohol - glycerol, which, like methanol and phenol, contains hydroxyl functional groups. Fats can be hydrolyzed - heated with water in the presence of catalysts: alkalis, acids, zinc oxides, magnesium. The reaction products are glycerin and various carboxylic acids, which are subsequently used for the production of soap. In order not to use expensive natural edible fats in this process , the necessary carboxylic acids are obtained by oxidizing paraffin.
Phenols
Finishing up with the classes of oxygen-containing compounds, let us dwell on phenols. They are represented by the phenyl radical —C 6 H 5 attached to one or more hydroxyl functional groups. The simplest representative of this class is carbolic acid, or phenol. As a very weak acid, it can interact with alkalis and active metals - sodium, potassium. A substance with pronounced bactericidal properties - phenol is used in medicine, as well as in the manufacture of dyes and phenol-formaldehyde resins.
In our article, we studied the main classes of oxygen-containing compounds, and also examined their chemical properties.