The correct answer is option 3. \(CrO_3 | H_2SO_4\).
Jones reagent is a powerful oxidizing agent used in organic chemistry for the conversion of primary and secondary alcohols to carbonyl compounds (aldehydes and ketones). The reagent consists of a mixture of chromic trioxide (\(CrO_3\)) and concentrated sulfuric acid (\(H_2SO_4\)). The general reaction involved is: \[ R-CH_2-OH \rightarrow R-CHO \] for primary alcohols, and \[ (R)_2-CHOH \rightarrow R_2-CO \] for secondary alcohols, where \(R\) represents an alkyl group.
Here's a step-by-step explanation:
1. Formation of Chromic Acid (Chromate(VI)) from Jones Reagent: In the presence of sulfuric acid, chromic trioxide (\(CrO_3\)) reacts to form chromic acid (\(H_2CrO_4\)): \[ CrO_3 + H_2SO_4 \rightarrow H_2CrO_4 \]
2. Oxidation of Alcohols: The chromic acid is a powerful oxidizing agent and can oxidize primary and secondary alcohols. The mechanism involves the transfer of oxygen to the alcohol, resulting in the formation of a carbonyl compound. For primary alcohol, the oxidation leads to the formation of an aldehyde: \[ R-CH_2-OH \overset{\text{Jones Reagent}}{\longrightarrow} R-CHO \] For secondary alcohol, the oxidation leads to the formation of a ketone: \[ R_2-CHOH \overset{\text{Jones Reagent}}{\longrightarrow} R_2-CO \]
3. Color Change: During the reaction, the orange-colored Jones reagent changes color to blue-green, indicating the reduction of chromium(VI) to chromium(III).
4. Advantages of Jones Reagent: Jones reagent is useful for selective oxidation of alcohols without over-oxidation to carboxylic acids, making it a valuable tool in synthetic chemistry. It is particularly effective for oxidizing alcohols that are not easily oxidized by other reagents like potassium permanganate (\(KMnO_4\)) or potassium dichromate (\(K_2Cr_2O_7\)).
In summary, Jones reagent (\(CrO_3 | H_2SO_4\)) is a potent oxidizing agent that plays a crucial role in the conversion of alcohols to carbonyl compounds, providing a valuable method for synthetic chemists to achieve specific oxidation reactions in organic synthesis. |