Organic Chemistry

- Methanol (A) has a carbon in the oxidation state (since the hydroxyl group makes the carbon more reduced).
- Formaldehyde (B) has a carbon in the 0 oxidation state.
- Formic acid (C) has a carbon in the +2 oxidation state, as it is bonded to both an oxygen (via a double bond) and a hydroxyl group.
Conclusion:
Thus, the correct answer is:
Final Answer:

Step 1: Identify hallmark mechanism.
Halogenation of alkanes (e.g., methane) under light/heat follows a free radical chain mechanism.
Step 2: Outline the steps (example with ).
Initiation: (homolysis).
Propagation: Termination: Radical–radical coupling (e.g., ).
Step 3: Conclusion.
Thus, the process is free radical substitution.
Final Answer:

- Aniline (A): Aniline is an activating group and ortho/para-directing because the amino group donates electron density to the ring.
- Nitrobenzene (B): The nitro group is a deactivating group and meta-directing due to its electron-withdrawing nature.
- Chlorobenzene (C): The chlorine group is a mild activating group and ortho/para-directing due to its lone pairs, but it also withdraws electron density via induction.
- Allene (D): Allene has a central sp-hybridized atom, making it linear.
Step 2: Conclusion.
Thus, the correct matching is:
Final Answer:

Step 1: Analyze number of structural isomers.
- C4H10 (A): There are 2 structural isomers for butane.
- C5H12 (B): There are 3 structural isomers for pentane.
- C6H14 (C): There are 5 structural isomers for hexane.
- C7H16 (D): There are 9 structural isomers for heptane.
Step 2: Conclusion.
Thus, the correct matching is:
Final Answer: