Points to Remember:
- Acetic acid (CHâCOOH) preparation involves various chemical reactions.
- Different starting materials require different reaction pathways.
- Understanding the chemical properties of each reactant is crucial.
- Safety precautions must be followed during chemical synthesis.
Introduction:
Acetic acid, also known as ethanoic acid, is a ubiquitous organic compound with the formula CHâCOOH. It’s a weak acid, found in vinegar and used extensively in various industries, from food preservation to chemical synthesis. This response will outline the preparation of acetic acid from five different precursors: acetonitrile (CHâCN), ethanol (CâHâ OH), acetamide (CHâCONHâ), methylmagnesium halide (Grignard reagent, CHâMgX), and ethyl acetate (CHâCOOCâHâ ). The methods employed will vary depending on the starting material’s chemical properties.
Body:
i) From Acetonitrile (CHâCN):
Acetonitrile can be hydrolyzed to acetic acid. This reaction typically involves heating acetonitrile with a strong acid catalyst, such as sulfuric acid (HâSOâ), or a base catalyst, such as sodium hydroxide (NaOH). The acid-catalyzed hydrolysis proceeds via an intermediate imidic acid, which readily tautomerizes to acetamide and then undergoes further hydrolysis to acetic acid. The base-catalyzed hydrolysis is a direct conversion.
- Reaction: CHâCN + 2HâO –(H⺠or OHâ»)–> CHâCOOH + NHâ
ii) From Ethanol (CâHâ OH):
Ethanol can be oxidized to acetic acid. This can be achieved
through several methods:- Biological Oxidation: Acetic acid bacteria (e.g., Acetobacter aceti) can oxidize ethanol to acetic acid in the presence of oxygen. This is the traditional method used in vinegar production.
Chemical Oxidation: Strong oxidizing agents like potassium permanganate (KMnOâ) or potassium dichromate (KâCrâOâ) can oxidize ethanol to acetic acid. However, these methods often lead to the formation of byproducts.
Reaction (Chemical Oxidation): CâHâ OH + [O] –(KMnOâ or KâCrâOâ)–> CHâCOOH + HâO
iii) From Acetamide (CHâCONHâ):
Acetamide undergoes hydrolysis to yield acetic acid. This reaction is similar to the hydrolysis of acetonitrile, requiring either acidic or basic conditions. Acid hydrolysis typically uses dilute sulfuric acid, while base hydrolysis uses sodium hydroxide.
- Reaction: CHâCONHâ + HâO –(H⺠or OHâ»)–> CHâCOOH + NHâ
iv) From Grignard Reagent (CHâMgX):
The Grignard reagent, CHâMgX (where X is a halide), reacts with carbon dioxide (COâ) to form a magnesium salt, which upon acidification yields acetic acid.
- Reaction: CHâMgX + COâ â CHâCOOMgX –(Hâº)–> CHâCOOH + MgXOH
v) From Ethyl Acetate (CHâCOOCâHâ ):
Ethyl acetate undergoes hydrolysis to produce acetic acid and ethanol. This reaction is catalyzed by either acids (e.g., sulfuric acid) or bases (e.g., sodium hydroxide). Acidic hydrolysis is reversible, while basic hydrolysis is irreversible.
- Reaction: CHâCOOCâHâ + HâO –(H⺠or OHâ»)–> CHâCOOH + CâHâ OH
Conclusion:
Acetic acid can be prepared from various starting materials via different reaction pathways. The choice of method depends on factors like cost-effectiveness, availability of reactants, and desired purity of the product. Biological oxidation of ethanol is a sustainable and environmentally friendly approach, particularly for vinegar production. However, for large-scale
industrial production, chemical methods might be more efficient. Further research into optimizing these methods, focusing on minimizing waste and maximizing yield, is crucial for sustainable and cost-effective acetic acid production. The development of greener and more efficient catalytic systems for these reactions remains an area of active research, aligning with principles of sustainable development and environmental protection. CGPCS Notes brings Prelims and Mains programs for CGPCS Prelims and CGPCS Mains Exam preparation. Various Programs initiated by CGPCS Notes are as follows:-