Organic Compounds containing Oxygen

Oxide is a binary compound of oxygen and another element. Oxygen forms oxides when it reacts with most of the elements in the periodic table. Often, one element will produce two or more oxides. The nature and properties of oxides vary greatly. 

Simple oxides (e.g., MgO, Al2O3) and mixed oxides (e.g., Pb3O 4 ) exist.

Simple oxides are classed according to whether they are acidic, basic, or amphoteric. Acidic oxide (e.g., SO2, Cl2O7, CO2, N2O5) is an oxide that reacts with water to form an acid. For example, when SO2 reacts with water, it forms H2 SO3, an acid.

 Epoxides are ethers in which three other atoms in a ring surround the oxygen atom. The oxygen-containing chemical compounds are Glycerol, formaldehyde, glutaraldehyde, citric acid, acetic anhydride, acetamide. 

Carbohydrates are organic molecules composed entirely of carbon, hydrogen, and oxygen. They are the most prevalent organic compound among the four primary types. There are thousands of distinct carbohydrates, but they all contain one or more monosaccharides, which are smaller units.

Proteins are organic compounds containing carbon, hydrogen, oxygen, nitrogen, and, in certain circumstances, sulphur. Amino acids are the smallest units that makeup proteins. Proteins are made up of 20 different types of amino acids.

Preparation

(i) Alcohols

• From Alkenes: In the presence of an acid, alkene interacts with water to generate alcohol. Alcohol is generated by following Markovnikov’s rule in the case of unsymmetrical alkenes.
• From Carbonyl compounds: LiAlH 4  is an extremely powerful reducing agent. This reagent is used to convert carboxylic acids into primary alcohols. 

(ii) Phenols

• From Cumene: Cumene is oxidised in the presence of air, resulting in cumene hydroperoxide. This hydroperoxide is now treated with dilute acid, resulting in the formation of phenol.
• From Haloarenes: Chlorobenzene reacts with NaOH at high temperatures and pressures, resulting in sodium phenoxide. After that, the phenoxide is acidified to form phenol. 

(iii) Ethers

• Williamson synthesis: Sodium phenoxide is formed when phenol is treated with sodium hydroxide in this process. After that, the phenoxide is transformed into ether.
• Dehydration of alcohols: At 413K, alcohol is dehydrated to ether in the presence of an acid such as H2 SO 4 .

(iv) Aldehydes

• Gattermann – Koch reaction: In this reaction, benzene is treated with carbon monoxide and hydrogen chloride in the presence of anhydrous aluminium chloride, and the product formed is benzaldehyde. This reaction is also known as the Gattermann-Koch reaction.
• From Acyl Chloride: The acyl chloride is treated with hydrogen in the presence of a palladium-barium sulphate catalyst in this reaction. The ‘Rosenmund reduction’ is another name for this reaction.

(v) Ketones

• From Nitriles: A ketone is produced when the nitrile is treated with the Grignard reagent.
• Friedel-Crafts Acylation reaction: A ketone is generated when benzene or substituted benzene is treated with an acyl chloride in the presence of anhydrous aluminium chloride. 

(vi) Carboxylic acids

• From primary alcohols: In the presence of oxidising agents such as alkaline KMnO 4 , primary alcohols are oxidised to corresponding carboxylic acids.

Chemical Reactions

Alcohols

• Dehydration: At 443K, alcohol is dehydrated in the presence of an acid, resulting in the formation of alkene. 
• Acylation of alcohols: In this reaction, alcohol is given an acyl group in the presence of pyridine.

Phenols

• Electrophilic aromatic substitution: When phenol is treated with dilute HNO3 at a low temperature, ortho and para nitrophenols are formed.
• Kolbe’s reaction: Phenol is reacted with sodium hydroxide to produce phenoxide in this process. After that, the phenoxide is treated with carbon dioxide to produce hydroxybenzoic acid.
• Reimer-Tiemann reaction: In this reaction, phenol is treated with chloroform in the presence of sodium hydroxide, followed by the attachment of a CHO group to the ortho position of phenol, resulting in salicylaldehyde.

Ethers

• Cleavage of C-O bond in ethers: In this reaction, hydrogen iodide is used to treat ether, resulting in alcohol and a tertiary halide formation. 
• Friedel-Crafts reaction: Anisole is treated with alkyl and acyl groups in these reactions, resulting in the alkyl and acyl groups being attached at the ortho and para positions, as illustrated in the reaction. This reaction takes place in the presence of anhydrous aluminium chloride catalysts. 
• Nitration: Anisole is treated with a mixture of strong sulphuric acid and nitric acid in this process, resulting in a mixture of ortho and para nitroanisole.

Aldehydes or Ketones

• Clemmensen’s Reduction: Aldehydes or ketones are treated with zinc amalgam and strong hydrochloric acid in this procedure. Aldehydes and ketones’ carbonyl groups are therefore converted to CH2 . 
• Intermolecular Cannizzaro reaction: In the presence of sodium hydroxide, two aldehyde molecules react to form alcohol and a carboxylic acid salt.

Carboxylic acids

• Reduction: In the presence of ammonia, carboxylic acids are converted to amides in this process.
• Decarboxylation: In the presence of LiAlH 4 , carboxylic acids are converted to corresponding alcohols in this process. When the sodium salts of these alcohols are heated with soda lime, they can be further reduced to hydrocarbons.

Uses

• Oxygen is used in oxyacetylene welding and is useful in normal respiration and combustion processes.
• Glycerol is used to treat constipation, improve athletic performance, and treat skin disorders.
• Citric acid is mostly employed as a flavouring and preserving ingredient, especially in soft drinks and candies, due to its acidic, sour taste.

Conclusion

The most abundant element in the Earth’s crust is Oxygen. The crust, atmosphere, and hydrosphere make up the Earth’s surface. Combustion processes, such as the burning of fuels, require oxygen. To breathe, plants and animals need oxygen from the air. Photosynthesis returns oxygen to the atmosphere that has been converted to carbon dioxide and water by metabolic processes in plants and animals. Since oxygen is the more electronegative element in these compounds, oxygen compounds with chlorine, bromine, and iodine are oxides.