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Acetic anhydride is an important organic compound. In chemistry, it is also known as acetic acid anhydride or ethanoic anhydride. Acetic anhydride was first synthesized in 1852 by the French chemist Charles Frederick Gerhardt by heating potassium acetate with benzoyl chloride.
The purpose of this article is to review the properties, reactions and applications of acetic anhydride. We will review its structure, chemical characteristics and physical properties, the main reactions in which acetic anhydride is involved and its interactions with other compounds.
The attention to acetic anhydride is due to its importance in our daily life and industry.
Physical and Chemical Properties of Acetic Anhydride
Acetic anhydride is a chemical compound with unique physical and chemical properties. The chemical formula of acetic anhydride (CH3CO)2O. It is a colorless, volatile and flammable liquid with a characteristic odor. The melting point of acetic anhydride is about -73°C, the boiling point is about 140°C. Molar mass of acetic anhydride is 102 g/mol, its density is 1.08 g/cm3.
Acetic anhydride dissolves well in organic solvents such as ethanol, diethyl ether, chloroform and benzene. When interacting with water, it forms acetic acid with the release of heat.
Synthesis of Acetic Anhydride
Acetic anhydride is produced in various ways. Consider the main methods to produce acetic anhydride.
Dehydration of Acetic Acid
One of the classical methods of acetic anhydride production is dehydration of acetic acid. This process can be carried out in many ways, but a common method is to produce acetic anhydride from acetic acid using a catalyst such as phosphorus oxide.
Another method of acetic anhydride production is oxidation. Acetic anhydride can be obtained by liquid-phase oxidation of acetaldehyde in air. Manganese acetate is used as catalysts.
Methyl Acetate Carbonylation
In industry, acetic anhydride is most often produced by the carbonylation of methyl acetate in the presence of a rhodium catalyst. The process takes place in the liquid phase.
Acyl Halide Acylation
Acetic anhydride is produced in the laboratory by the reaction of anhydrous sodium acetate with acetyl chloride.
Chemical Properties of Acetic Anhydride
Hydrolysis of Acetic Anhydride
Acetic anhydride reacts with water to form acetic acid. This reaction proceeds quickly and with the release of heat.
Preparation of acetic acid from acetic anhydride and water
Acylation Reaction of Alcohols with Acetic Anhydride
Acetic anhydride can react with alcohols and acylation occurs to produce acetates. This reaction is used to synthesize various acetates that are used in perfumery and pharmaceuticals.
Acylation of Amines with Acetic Anhydride
Acetic anhydride also reacts with amines to form aminoacetic esters. These aminoacetic esters are important in organic synthesis and can be used as intermediates in the manufacture of drugs and other biologically active molecules.
Acylation of Aromatic Hydrocarbons with Acetic Anhydride
Acetic anhydride is used to acylate aromatic hydrocarbons, for example, the reaction of benzene with acetic anhydride in the presence of a catalyst produces acetophenone.
Applications of Acetic Anhydride
Acetic anhydride has many industrial and research applications. Some of its main uses:
• Production of cellulose acetate, which is used in the production of films, varnishes, plastics and other materials.
• Synthesis of organic compounds including acetates, aminoacetic esters and other biologically active molecules.
• As an acylating agent in various chemical processes.
• In analytical chemistry for analysis.
Health Effects of Acetic Anhydride
Acetic anhydride can be a health hazard if handled or contacted incorrectly. In this chapter, we will look at important aspects of the health effects of acetic anhydride.
- Contact with skin and mucous membranes
Direct skin contact may cause irritation and burns. In case of skin contact, it is recommended to immediately wash the affected area with plenty of water and if necessary, seek medical attention. Prolonged contact with large amounts of acetic anhydride can cause severe burns.
Acetic anhydride in eyes can cause severe burns and damage to mucous membranes. In case of contact with eyes, rinse immediately with clean water for several minutes and seek immediate medical attention.
- Inhalation of vapors
Vapors of acetic anhydride irritate the respiratory system. Inhalation of vapors can cause a variety of symptoms including irritation of the nose, throat, lungs, coughing, difficulty breathing and headache. If vapors are inhaled for a long time, acute poisoning may occur, requiring immediate medical attention. People who work with acetic anhydride in industrial or laboratory environment may develop chronic diseases such as bronchitis or asthma.
When working with acetic anhydride, precautions must be taken, as it is a dangerous chemical compound. Improper handling may pose a health and safety hazard. In this chapter, we will review the basic safety precautions that should be taken when working with acetic anhydride.
- Personal protection
Before working with acetic anhydride, employees must be equipped with appropriate personal protective equipment, including:
- Safety goggles or face mask to prevent contact with eyes and face.
- Protective chemical resistant gloves to prevent skin contact.
- Protective clothing such as a laboratory coat to protect the body.
- Respirator or mask with a filter for respiratory protection.
- Storage of acetic anhydride
Acetic anhydride should be stored in special chemical containers designed for the storage of hazardous substances. Containers must be carefully closed. Storage should take place in well-ventilated areas, away from sources of heat and fire.
Spilled acetic anhydride can be removed with water and an alkaline solution.
Work with acetic anhydride should be carried out only in well-ventilated areas or in a fume hood. This will help prevent the accumulation of vapors in the air, which can lead to inhalation of harmful substances.
Acetic anhydride is an important chemical compound with many applications in various fields. In this article, we reviewed the basic reactions, properties and applications of acetic anhydride, its health effects and safety precautions when working with it.
This compound is highly reactive and is used in organic synthesis as an acylating agent. Its use requires safety precautions. Proper use of acetic anhydride allows it to be used effectively in organic synthesis, the production of pharmaceuticals, plastics, perfumes and other industrial processes.
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