One of the most common chemical elements included in 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, Na2O - oxides of copper, magnesium, sodium. Their main chemical property is the reaction with acids. So, copper oxide reacts with chloride 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 H2O, carbon dioxide CO2, phosphorus pentoxide P2O5. The ability of such substances to react with alkalis is their main chemical characteristic.
As a result of the reaction, s alts of two types can be formed: acidic or medium. This will depend on how many moles of alkali react:
- 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. In their properties, there is 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 associated with complex ions of acid residues are acids. Conventionally, they can be divided into inorganic, for example, carbonic acid, sulfate, nitrate, and organic compounds. The latter include acetic acid, formic, oleic acids. Both groups of substances have similar properties. So, they enter into a neutralization reaction with bases, react with s alts andbasic oxides. Almost all oxygen-containing acids in aqueous solutions dissociate into ions, being conductors of the second kind. It is possible to determine the acidic nature of their environment, due to the excessive presence of hydrogen ions, using indicators. For example, purple litmus turns red when added to an acid solution. A typical representative of organic compounds is acetic acid containing a carboxyl group. It includes a hydrogen atom, which determines the acidic properties of the substance. It is a colorless liquid with a specific pungent odor, crystallizing at temperatures below 17 °C. CH3COOH, like other oxygen-containing acids, is perfectly soluble in water in any proportions. Its 3 - 5% solution is known in everyday life under the name of 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 limiting bonds between atoms is ROH, where R is a hydrocarbon radical. These compounds are usually considered as derivatives of alkanes, in which onethe hydrogen atom is replaced by a hydroxo group.
Physical and chemical properties of alcohols
Aggregate state of alcohols are liquids or solid compounds. There are no gaseous substances among alcohols, which can be explained by the formation of associates - groups consisting of several molecules connected by weak hydrogen bonds. This fact also 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 bound to other particles, therefore, in chemical interactions it is able to leave the molecule. At the same 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 platinum mesh or copper, alcohols are oxidized by vigorous oxidizing agents, potassium bichromate or potassium permanganate, to aldehydes.
Esterification reaction
One of the most important chemical properties of oxygen-containing organic substances: alcohols and acids is a 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, andisoamyl nitrite is a protector of coronary artery spasms. The esterification reaction equation is as follows:
CH3COOH+C2H5OHCH3COOC2H5+H2O
In it, CH3COOH is acetic acid, and C2H5OH is the chemical formula of alcohol ethanol.
Aldehydes
If a compound contains a –COH functional group, then it belongs to aldehydes. They are presented as products of further oxidation of alcohols, for example, with oxidizing agents such as copper oxide.
The presence of a carbonyl complex in the molecules of formic or acetaldehyde determines their ability to polymerize and attach atoms of other chemical elements. Qualitative reactions that can be used to prove the presence of a carbonyl group and the belonging of a substance to aldehydes are the silver mirror reaction and the interaction with copper hydroxide when heated:
Acetaldehyde, which is used in industry to produce acetic acid, has received the greatest use - a large 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 linked together by hydrogen bonds. The compounds dissociate into hydrogen cations and acid residue anions and are weak electrolytes. An exception is the first representative of a series of limitingmonobasic acids - formic, or methane, which is a conductor of the second kind of medium strength. The presence of only simple sigma bonds in molecules indicates the limit, but if the 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 are part of liquid fats - oils, for example, oleic acid. The chemical properties of oxygen-containing compounds: organic and inorganic acids are largely similar. So, they can interact with active metals, their oxides, with alkalis, and also with alcohols. For example, acetic acid reacts with sodium, oxide and caustic soda to form a s alt - sodium acetate:
NaOH + CH3COOH→NaCH3COO + H2O
A special place is occupied by compounds of higher carboxylic oxygen-containing acids: stearic and palmitic, with a trihydric saturated alcohol - glycerin. They belong to esters and are called fats. The same acids are part of the sodium and potassium s alts as an acidic residue, forming soaps.
Fats and soaps
Important organic compounds that are widely distributed in wildlife and play a leading role as the most energy-intensive substance are fats. They are not an individual compound, but a mixture of heterogeneous glycerides. These are compounds of the limiting polyhydric alcohol - glycerin, which, like methanol and phenol, contains hydroxyl functional groups. Fats can be hydrolyzedheating with water in the presence of catalysts: alkalis, acids, oxides of zinc, magnesium. The products of the reaction will be glycerol and various carboxylic acids, further 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
Coming up with the classes of oxygen-containing compounds, let's focus on phenols. They are represented by the phenyl radical -C6H5, connected to one or more functional hydroxyl 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 production of dyes and phenol-formaldehyde resins.
In our article, we studied the main classes of oxygen-containing compounds, and also considered their chemical properties.
