Chapter 20: Problem 57
Toluene can be converted into benzaldehyde by oxidation with (1) \(\mathrm{KMnO}_{4}\) /alkali (2) \(\mathrm{CrO}_{2} \mathrm{Cl}_{2}\) (3) \(\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7} / \mathrm{H}_{2} \mathrm{SO}_{4}\) (4) \(\mathrm{O}_{2} / \mathrm{V}_{2} \mathrm{O}_{5}\)
Short Answer
Expert verified
(2) CrO₂Cl₂
Step by step solution
01
Identify the Correct Oxidizing Agent
Examine the provided oxidizing agents and their compatibility with converting toluene into benzaldehyde.
02
Analyze Option 1
KMnO₄ in alkaline medium typically oxidizes toluene all the way to benzoic acid, not benzaldehyde.
03
Analyze Option 2
CrO₂Cl₂ is known as the Etard reagent and is used specifically to oxidize toluene to benzaldehyde, making it a suitable choice.
04
Analyze Option 3
K₂Cr₂O₇/H₂SO₄ is a strong oxidizing agent that usually leads to the formation of benzoic acid, not benzaldehyde.
05
Analyze Option 4
O₂/V₂O₅, the conditions for catalytic oxidation, do not specifically oxidize toluene to benzaldehyde under normal conditions.
06
Conclude the Correct Option
Based on the analysis, the correct oxidizing agent to convert toluene into benzaldehyde is CrO₂Cl₂.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
benzaldehyde production
Benzaldehyde is an important chemical compound used in various industries, including perfumery and flavoring. The production of benzaldehyde typically involves the oxidation of compounds like toluene. Toluene is a methyl-substituted benzene, and when oxidized, it can yield benzaldehyde. Different oxidizing agents can be employed; however, some yield better results than others for this specific conversion. For instance, while \(\text{KMnO}_4\) in alkaline media usually results in the formation of benzoic acid, \(\text{CrO}_2\text{Cl}_2\) (the Etard reagent) selectively oxidizes toluene to benzaldehyde. The key is choosing the right reagent that stops the oxidation process at the formation of benzaldehyde and not proceed further to benzoic acid. This nuanced selection is crucial for producing high-quality benzaldehyde efficiently and effectively.
oxidizing agents in organic chemistry
Oxidizing agents are substances that gain electrons during a chemical reaction, causing another substance to be oxidized. In organic chemistry, they are used to modify the oxidation state of carbon atoms in molecules, making them crucial in transforming different functional groups.
Some commonly used oxidizing agents include:
Some commonly used oxidizing agents include:
- \text{KMnO}_4 (potassium permanganate)
- \text{CrO}_3 (chromium trioxide)
- \text{O}_2 (molecular oxygen)
- \text{K}_2\text{Cr}_2\text{O}_7 (potassium dichromate)
Etard reaction
The Etard reaction is a method used to oxidize aromatic methyl groups to aldehydes using \(\text{CrO}_2\text{Cl}_2\) (chromyl chloride). This reaction selectively converts toluene to benzaldehyde, avoiding further oxidation to benzoic acid. The general procedure involves mixing toluene with chromyl chloride, often in a solvent like carbon tetrachloride, at low temperatures.
Key steps in the Etard reaction:
Key steps in the Etard reaction:
- Mixing chromyl chloride with toluene
- Maintaining low reaction temperatures to avoid unwanted by-products
- Extracting and purifying the benzaldehyde formed