Acetaldehyde – C2H4O

Acetaldehyde is the chemical name for the organic molecule C2H4O. Another name for acetaldehyde is MeCHO. It is miscible with benzene, alcohol, turpentine, gasoline, xylene, and naphthalene. It is a combustible liquid with no color. It has a suffocating smell. Although it doesn’t corrode many metals, it can irritate mucous membranes and have a narcotic effect.

The production of acetic acid, perfumes, medications, flavoring agents, colors, and other products uses acetaldehyde extensively. Acetaldehyde is harmful when applied externally for extended periods of time. The earliest record of acetaldehyde was made in 1774 by the Swedish chemist and pharmacist Carl Wilhelm Scheele.


Formula And Properties Of Acetaldehyde

The formula for acetaldehyde is C2H4O or CH3CHO. The properties consist of the following:

Molecular Weight/Molar Mass44.05 g/mol
Density0.784 g/cm3
Boiling Point20.2 °C
Melting Point-123.5 °C

Application of Acetaldehyde (C2H4O)


  • Served as acetic acid’s precursor.
  • Utilized in the production of medicines, perfumes, and disinfectants.
  • Used to make polyvinyl acetate.
  • Utilized in the production of resin.
  • It serves as a precursor to pentaerythritol, crotonaldehyde, and derivatives of pyridine.
  • Used in the production of chemicals such as acetic acid.

Acetaldehyde (CH3CHO) Synthesis

Preparation from Acetylene

When vinyl alcohol is exposed to a solution of diluted H2SO4 and mercuric acid, acetylene becomes hydrated and transforms into the more stable molecule acetaldehyde.


Catalytic Dehydrogenation of Ethyl Alcohol

Acetaldehyde CH3CHO

At 573 K, acetaldehyde is produced by the catalytic dehydrogenation of ethyl alcohol in the presence of a copper catalyst.

Wacker Process

Acetaldehyde CH3CHO

An aqueous solution comprising palladium chloride and cupric chloride can react with ethylene to produce acetaldehyde.

Pd was converted back into PdCl2 in this reaction by CuCl2.

2CuCl2 + Pd → PdCl2 + 2CuCl

It is atmospheric oxygen that reoxidizes cuprous chloride to CuCl2 when HCl is present.

4CuCl + 4HCl +O2 → 4CuCl2 + 2H2O

Oxidation of Ethyl Alcohol

Oxidation of Ethyl alcohol

Acetaldehyde is produced when ethyl alcohol (CH3CH2OH) is oxidized in the presence of acidified K2Cr2O7 or aqueous or alkaline KMnO4.

Rosenmund’s Reduction

Acetaldehyde CH3CHO

Acetaldehyde can be made by reducing acetyl chloride with H2 in the presence of palladium plated on barium sulfate and a small amount of quinoline or sulfuric acid salt. The catalyst developed by Lindlar is this mixture. We refer to this reaction as Rosenmund’s reduction.

The Chemical Characteristics of Acetaldehyde (CH3CHO)

Acetaldehyde reacts with Hydrazine

Chemical Characteristics

The nitrogen atom of phenylhydrazine functions as a nucleophile, attacking the electrophilic carbon of acetaldehyde and removing water to produce acetaldehyde phenylhydrazone.

Acetaldehyde reacts with NaOH (Sodium Hydroxide)

Chemical Characteristics

When NaOH experiences aldol condensation, acetaldehyde (A) is formed. Heating this beta-hydroxyacetaldehyde yields alpha-beta-unsaturated aldehyde.

Acetaldehyde reacts with HCN (Hydrogen Cyanide)

Chemical Characteristics

Compounds known as hydroxynitriles are created by adding hydrogen cyanide across the carbon-oxygen double bond in aldehydes and ketones. As an illustration, ethanal, an aldehyde, yields 2-hydroxypropanenitrile.

Toxicity Of Acetaldehyde

At least some of the toxicity of ethanol is caused by its first metabolite, acetaldehyde, which is a much more potent toxin than ethanol itself. A portion of the acetaldehyde enters your circulation and damages your membranes, sometimes leaving scar tissue behind.

In addition, it gives rise to a hangover, headache, racing heart, and an unsettled stomach. The most significant effect on the brain is acetaldehyde intoxication. It creates problems with brain function and memory. Acetaldehyde is categorized as a possible human carcinogen due to a lack of research on the disease in humans and animal studies that demonstrate laryngeal tumors in hamsters and nasal cancers in rats.

Acetaldehyde is a major toxic metabolite that is one of the key culprits mediating the fibrogenic and mutagenic effects of alcohol in the liver. Acetaldehyde increases the formation of adducts, which damage DNA and affect the functionality of vital proteins like enzymes. This process also promotes mutagenesis.


What is acetaldehyde?

Acetaldehyde can be found in a variety of plants, ripe fruits, vegetables, fuel, tobacco smoke, and motor exhaust. This substance is frequently used in the production of acetic acid, perfumes, dyes, and medicines as a flavoring agent and as an intermediary in the metabolism of alcohol.

Where is acetaldehyde used?

Acetaldehyde is used as an additive in a variety of products, including gelatine hardening, fruit and fish preservatives, and flavoring agents. In addition, acetaldehyde is utilized in the production of vinegar, yeast, and other products for fruit and fish preservation.

What distinguishes acetaldehyde from formaldehyde?

You can distinguish between formaldehyde and acetaldehyde with the iodoform test. In response to the yellow precipitate, methyl ketones produce potassium hydroxide and iodine. Acetaldehyde, iodine, and KOH bond to the carboxylic acid to produce sodium salt. Iodoformity is not screened for using formaldehyde.

What are the health consequences of acetaldehyde?

Irritation of the respiratory system, skin, and eyes is a consequence of acute (short-term) acetaldehyde exposure. Chronic (long-term) acetaldehyde poisoning symptoms are similar to those of alcoholism.

Is acetaldehyde going to pass Tollen’s test?

Tollen’s test determines whether a particular material has an aldehyde or an alpha-hydroxy ketone functional group. It makes use of a Tollen reagent, which is produced by mixing silver nitrate with ammonia. Acetaldehyde will produce a positive result on the Tollen test because it contains the functional group CHO (aldehyde). The test was successful when the silver metal was reduced and formed a coat of metallic silver when heated with the reagent in acetaldehyde.

How does the liver react to acetaldehyde?

Acetaldehyde, a significant toxic metabolite, is primarily responsible for mediating the fibrogenic and mutagenic effects of alcohol on the liver. Mechanistically, acetaldehyde encourages the creation of adducts, which impair the functionality of important proteins, such as enzymes, and damages DNA, which encourages mutagenesis.


To sum up, acetaldehyde (C2H4O) is an adaptable organic compound with a variety of chemical and industrial uses. It is an important part of many processes, from the synthesis of plastics and resins to its use as a flavoring and fragrance agent, thanks to its diverse applications and synthesis methods. Acetaldehyde’s importance in various industries can be attributed to its chemical characteristics and reactivity, which emphasize its value in the fields of manufacturing and chemistry.

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