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Acetaldehyde is an organic liquid that is colorless and has the chemical formula C2H4O, also written as CH3CHO. It is also mentioned as MeCHO. Ethanal is the IUPAC term for acetaldehyde. It has a strong smell and dissolves in water. Though many metals are not affected by Acetaldehyde, it has a narcotic effect that can irritate mucosal membranes. It might harm our liver. Alcohol breaks down and produces acetaldehyde when we consume it. It dissolves fully in water. Acetaldehyde is typically employed as an intermediary in the production of acetic acid, as well as in the production of medicines, flavoring compounds, colors, and other products.
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Key terms: Acetaldehyde, Ethanal, Organic compounds, Oxidation, Acetic acid, Alcohol, Metals, Mucosal membranes, Carbon, Hydrogen, Oxygen
Structure of Acetaldehyde
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The core structure of Acetaldehyde includes three types of compounds- Carbon, Hydrogen and Oxygen. Here is how the structure looks like-
Structure of Acetaldehyde
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| Acetamide | Acetone | Acetonitrile |
| Aldehydes, Ketones and Carboxylic | Uses of Carboxylic Acids | Physical Properties of Aldehydes, Ketones |
| Aldehydes | Cannizzaro reaction | Etard reaction |
| Nucleophilic Addition Reaction | Fehling’s Test | Tollen's Test |
Physical Properties of Acetaldehyde
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Here are the basic physical properties of Acetaldehyde-
- Acetaldehyde has a molecular weight/molar mass of 44.05 grams per mole.
- Acetaldehyde has a density of 0.784 grams per centimeter cube.
- Acetaldehyde also boils at a temperature of 20.2°C.
- Acetaldehyde melts at a temperature of -123.5°C.
Molecular Structure Of Acetaldehyde
Chemical properties of Acetaldehyde
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Here are the chemical properties of Acetaldehyde-
- Acetaldehyde and formaldehyde have a lot of the same chemical characteristics. As an electrophile, it is a precursor in the synthesis of organic compounds.
- One can obtain intermediates like pentaerythritol, which we can use in the synthesis of organic compounds, by the condensation reaction.
- Additionally, using a Grignard reagent in a process to create hydroxyethyl derivatives can be helpful. Building blocks like acetaldehyde are used to create heterocycles like amines and pyridines.
Acetaldehyde Analysis
Uses of Acetaldehyde
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Here are the common uses of Acetaldehyde-
- It served as an acetic acid precursor.
- It serves as a precursor for pentaerythritol, crotonaldehyde, and pyridine derivatives.
- It is used in the production of resin.
- In order to make polyvinyl acetate, it is used.
- It is employed in the production of medicines, fragrances, and disinfectants.
- The manufacture of compounds like acetic acid requires it.
Percentage of the uses of Acetaldehyde In Various Fields As Per 2020
Preparation of Acetaldehyde
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1. Ethyl alcohol oxidation
Acetaldehyde is produced via the oxidation of ethyl alcohol (CH3CH2OH) in the presence of acidified K2Cr2O7 or aqueous/alkaline KMnO4.
2. Dehydrogenation of ethyl alcohol via catalysis
Acetaldehyde is produced when ethanol undergoes catalytic dehydrogenation at 573 K when a copper catalyst is present.
3. Rosenmund ’s Reduction
Acetyl chloride can be reduced with H2 in the presence of palladium plated over barium sulfate, coupled with a little quantity of salt of sulfur or quinoline, to produce acetaldehyde. The catalyst developed by Lindlar is this mixture. Rosenmund's Reduction is the name of this reaction.
4. Wacker Process
By interacting with an aqueous solution containing cupric chloride and palladium chloride, ethene can be changed into acetaldehyde.
5. Preparation from Acetylene
Acetylene is hydrated to vinyl alcohol, which tautomerizes to acetaldehyde, a more stable molecule, in the presence of dilute H2SO4 and mercuric acid.
Preparation Of Acetaldehyde
Toxicity of Acetaldehyde
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Since acetaldehyde is ethanol's initial metabolite and a much more effective toxic than ethanol, acetaldehyde is at least partially responsible for ethanol's toxicity.
- Our bloodstream absorbs some of the acetaldehyde, harming our membranes and perhaps forming scar tissue.
- Additionally, it results in a hangover, a pounding heart, a headache, and an upset stomach. The largest effect on the brain is from acetaldehyde intoxication.
- Memory is hampered, and there are problems with brain function.
Previous Year Questions
- The number of pi-bonds present in benzoic acid molecules are… (MHT CET 2019)
- Transesterification is the process of… (NEET 2007)
- A is a lighter phenol and B is an aromatic carboxylic acid… (NEET 1992)
- 1-phenyl ethanol can be prepared by the reaction… (NEET 1997)
- In a set of reactions propionic acid yielded a compound… (NEET 2006)
- A compound A has a molecular formula… (NEET 1994)
- Among acetic acid, phenol and n-hexanol which is one of the following…(NEET 1993)
- A strong base can abstract an α-hydrogen from… (NEET 2008)
- The relative reactivities of acyl compounds towards nucleophilic… (NEET 2008)
- Aldehydes and ketones will not form crystalline derivatives with… (NEET 1994)
- Benzoic acid may be converted into ethyl benzoate… (NEET 2000)
- Carboxylic acids have higher boiling points than aldehydes… (NEET 2018)
- Clemmensen reduction of a ketone is carried out in the presence… (NEET 2011)
- Consider the following compounds… (NEET 2007)
Things to Remember
- Acetaldehyde is soluble in alcohol, benzene, naphtha, gasoline, xylene, ether, and turpentine.
- Acetaldehyde is an inflammable liquid with no apparent color.
- It smells suffocating.
- Although it is non-corrosive to many metals, it can irritate mucous membranes when it has a narcotic effect.
Also Read:
| Other Articles Related To This Chapter | ||
|---|---|---|
| Carboxylic Acid | Activation Energy Formula | Electron Gain Enthalpy |
| Ester Hydrolysis | Decarboxylation Reaction | Methyl Ethyl Ketone |
| Benzaldehyde | VSEPR Theory | Preparation of Aldehydes |
Sample Questions
Ques 1. Describe acetaldehyde. (3 marks)
Ans. Acetaldehyde can be found in a variety of plants, ripe fruits, vegetables, tobacco smoke, gasoline, and engine exhaust.
- This substance is frequently employed in the production of acetic acid, fragrances, dyes, and medications as a flavoring agent and as an intermediary in the metabolism of alcohol.
- Acetaldehyde's chemical formula is CH3CHO.
Ques 2. What impact does acetaldehyde have on the liver? (3 marks)
Ans. One of the key players mediating the fibrogenic and mutagenesis effects of alcohol on the liver is acetaldehyde, a highly toxic metabolite. Mechanistically, acetaldehyde encourages the formation of adducts, which causes DNA damage and functional impairments of important proteins, including enzymes, and promotes mutagenesis.
Ques 3. What distinguishes acetaldehyde from formaldehyde? (3 marks)
Ans. Iodoform testing will distinguish between acetaldehyde and formaldehyde. 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 in formaldehyde.
Ques 4. Will acetaldehyde withstand the Tollen's Test? (4 marks)
Ans. Tollen's test determines whether a particular material contains an aldehyde functional group or an alpha-hydroxy ketone functional group. It makes use of a Tollen's reagent, which is produced by mixing ammonia and silver nitrate.
Acetaldehyde will result in a positive Tollen test because it has the functional group -CHO (aldehyde). The silver metal reduces and creates a coat of metallic silver when heated with the reagent, proving that the test was successful.
Ques 5. Can acetaldehyde be a highly effective reducer? (4 marks)
Ans. A reducing agent is one that goes through oxidation but also reduces other substances. Strong oxidizing agents, such as potassium permanganate, readily oxidize acetaldehyde. Using potassium dichromate or other gentle oxidizers, carboxylic acids are produced. It will have fewer other species since it has a greater oxidation potential. It diminishes Fehling's solution, Benedict's solution, and the Tollen reagent, for instance.
Ques 6. Can acetaldehyde result in a positive iodoform test result? (3 marks)
Ans. The iodoform test is a very reliable way to find out if methyl ketone groups are present in an unknown chemical. The chemical name for acetaldehyde is CH3CHO. It will cause a positive iodoform test because it has the COCH3 group (methyl ketone group). It is important to keep in mind that it is the only aldehyde that results in a positive test.
Ques 7. What distinguishes acetone from acetaldehyde most significantly? (3 marks)
Ans. Both acetone and acetaldehyde are colorless liquids. The main difference between acetaldehyde and acetone is that the former has a functional group called -CHO (aldehyde) while the latter has a functional group called -CO (ketone).
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