On an industrial scale. `H_(2)O_(2)` is prepared by auto-oxidation of:

Options

A. 2-Ethylanthraquinol.
B. 2-Ethylanthraquinone
C. 1-Ethylanthraquinol.
D. 1-Ethylanthraquinone.

Explanation

To solve the question regarding the industrial preparation of hydrogen peroxide (H₂O₂) through auto-oxidation, we can break down the process step by step:

### Step-by-Step Solution:

1. **Identify the Process**: The question asks about the industrial preparation of hydrogen peroxide via auto-oxidation. Auto-oxidation is a process where a compound is oxidized by oxygen from the air.

2. **Identify the Substrate**: The substrate used for the auto-oxidation process in the industrial production of H₂O₂ is 2-ethyl-anthraquinol. This compound is crucial as it undergoes a series of reactions to produce hydrogen peroxide.

3. **Reduction of 2-Ethyl-Anthraquinone**: Initially, 2-ethyl-anthraquinone is reduced to 2-ethyl-anthraquinol. This reduction is typically carried out using hydrogen gas (H₂) in the presence of a catalyst such as palladium (Pd).

4. **Oxidation of 2-Ethyl-Anthraquinol**: Once 2-ethyl-anthraquinol is formed, it is then exposed to air (which contains oxygen). The 2-ethyl-anthraquinol undergoes auto-oxidation back to 2-ethyl-anthraquinone, during which hydrogen peroxide (H₂O₂) is produced as a byproduct.

5. **Extraction of Hydrogen Peroxide**: The hydrogen peroxide formed during this reaction is then extracted from the mixture, usually by dissolving it in water, resulting in a solution of H₂O₂.

6. **Conclusion**: Therefore, the substrate that undergoes auto-oxidation to produce hydrogen peroxide on an industrial scale is 2-ethyl-anthraquinol.

### Final Answer:
On an industrial scale, H₂O₂ is prepared by the auto-oxidation of **2-ethyl-anthraquinol**.