Which statement is incorrect.

Options

A. Fluoro benzene can be synthesized in the laboratory from aniline by diazotisation followed by heating with `HBF_(4)`
B. Quarternary Ammonium hydroxides having `beta -` hydrogen atom give hlfmann elimination on pyrolysis.
C. on reaction with `HNO_(2)` produces
D. Benzyl amine on reaction with `NaNO_(2)//HCl` followed by `beta-` Naphthol in slight basic medium forms a coloured dyo.

Explanation

To determine which statement is incorrect, let's analyze each statement one by one based on the information provided in the video transcript.

### Step-by-Step Solution:

1. **Statement 1**: "Fluorobenzene can be synthesized in laboratory from aniline by diazonation followed by heating with HBF4."
- **Analysis**: This statement is correct. The process described is known as the Sandmeyer reaction. Aniline reacts with sodium nitrite (NaNO2) and hydrochloric acid (HCl) to form a diazonium salt. This diazonium salt can then react with HBF4 to yield fluorobenzene.
- **Conclusion**: Statement 1 is correct.

2. **Statement 2**: "Quaternary ammonium hydroxide having beta hydrogen atom gives Hoffman elimination on pyrolysis."
- **Analysis**: This statement is also correct. Quaternary ammonium compounds can undergo Hofmann elimination when heated (pyrolysis). In this reaction, a beta hydrogen is abstracted, leading to the formation of an alkene.
- **Conclusion**: Statement 2 is correct.

3. **Statement 3**: "This reactant on reacting with HNO2 produce this type of product."
- **Analysis**: The statement describes the reaction of a compound with HNO2, leading to the formation of a diazonium salt and subsequent rearrangement to form a stable carbocation. This is consistent with known reactions involving diazonium compounds.
- **Conclusion**: Statement 3 is correct.

4. **Statement 4**: "Benzylamine on reacting with NaNO2 HCl followed by beta naphthalene in slightly basic medium forms a colored dye."
- **Analysis**: This statement is incorrect. When benzylamine reacts with NaNO2 and HCl, it forms a diazonium salt. However, the subsequent reaction with beta naphthalene does not lead to the formation of a colored dye. The product formed is not a dye because the necessary functional groups for dye formation are not present in the resulting compound.
- **Conclusion**: Statement 4 is incorrect.

### Final Answer:
The incorrect statement is **Statement 4**.

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