Question

Which reagents oxidize ethyl alcohol to acetaldehyde and acetic acid? Why are two different reagents required for these conversions?

Short answer

Answer: To oxidize ethyl alcohol to acetaldehyde, a mild oxidizing agent like Pyridinium Chlorochromate (PCC) is used because it selectively oxidizes primary alcohols to aldehydes without further oxidation to carboxylic acids. For the conversion of ethyl alcohol to acetic acid, a strong oxidizing agent such as Potassium Permanganate (KMnO4) or Potassium Dichromate (K2Cr2O7) in an acidic medium is required, as they can completely oxidize primary alcohols to carboxylic acids. Two different reagents are needed because the oxidation of ethyl alcohol to acetaldehyde is a partial oxidation, while the oxidation of ethyl alcohol to acetic acid is a complete oxidation.

Step-by-step solution

Write the chemical reactions

First, we must write the chemical reactions for the conversion of ethyl alcohol to acetaldehyde and acetic acid. The conversion of ethyl alcohol to acetaldehyde can be represented by the following reaction: Ethyl alcohol (C2H5OH) -> Acetaldehyde (CH3CHO) + 2H The conversion of ethyl alcohol to acetic acid can be represented by the following reaction: Ethyl alcohol (C2H5OH) + 2O -> Acetic acid (CH3COOH) + H2O

Identify the reagents

Next, we need to identify the reagents that can bring about these reactions. For the conversion of ethyl alcohol to acetaldehyde, we can use a mild oxidizing agent, like Pyridinium Chlorochromate (PCC). The reaction with PCC can be represented as follows: C2H5OH + PCC -> CH3CHO + 2H + (Cr^3+) + (PyHCl) For the conversion of ethyl alcohol to acetic acid, we need a strong oxidizing agent, such as Potassium Permanganate (KMnO4) or Potassium Dichromate (K2Cr2O7) in an acidic medium. The reaction with KMnO4 in an acidic medium can be represented as follows: C2H5OH + 2KMnO4 + 4H2O -> CH3COOH + 2Mn^2+ + 2K+ + 6H2O (or) C2H5OH + K2Cr2O7 + 4H2SO4 -> CH3COOH + Cr2(SO4)3 + K2SO4 + 7H2O (using H2SO4 as the acidic medium)

Explain why two different reagents are required

Two different reagents are required for these conversions because the oxidation of ethyl alcohol to acetaldehyde is a partial oxidation, while the oxidation of ethyl alcohol to acetic acid is a complete oxidation. Mild oxidizing agents such as PCC are used for partial oxidation reactions as they can selectively oxidize primary alcohols to aldehydes, without further oxidizing the aldehyde to a carboxylic acid. This selectivity makes PCC suitable for the conversion of ethyl alcohol to acetaldehyde. Strong oxidizing agents such as KMnO4 or K2Cr2O7 are required for complete oxidation reactions, as they can oxidize primary alcohols all the way to carboxylic acids. In this case, the ethyl alcohol is completely oxidized to acetic acid.