Which of the following statements is/are incorrect ?

Options

A. Nitrobenzene will give meta-nitrotoluene on reaction with `CH_3Cl//AlCl_3`
B. Chlorobenzene will give meta-substituted product on electrophilic substitution since it exerts -I gt + M effect.
C. n-Propyl benzene can be easily obtained on Friedral crafts alkylation of benzene with n-propyl chloride.
D. Toluene can be obtained in better yield when excess of benzene with react with `CH_3Cl//AlCl_3`.

Explanation

To determine which statements are incorrect, let's analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement 1: Nitrobenzene will give metanitrotoluene on reaction with CH3Cl in presence of aluminum trichloride.**
- **Analysis:** Nitrobenzene has a nitro group (-NO2), which is a strong electron-withdrawing group. This group deactivates the benzene ring towards electrophilic substitution reactions. Therefore, when nitrobenzene is treated with CH3Cl in the presence of AlCl3, no reaction occurs, and thus metanitrotoluene is not formed.
- **Conclusion:** This statement is **incorrect**.

2. **Statement 2: Fluorobenzene will give metasubstituted product on electrophilic substitution since it exerts a -I effect greater than a +M effect.**
- **Analysis:** Fluorine is a halogen that exerts a +M (mesomeric) effect, which means it can donate electron density to the benzene ring, making it an ortho-para director. While it does have a -I (inductive) effect, the +M effect is stronger, leading to ortho and para substitution rather than meta substitution.
- **Conclusion:** This statement is **incorrect**.

3. **Statement 3: n-Propylbenzene can be easily obtained on Friedel-Crafts alkylation of benzene with n-propylchloride.**
- **Analysis:** Friedel-Crafts alkylation involves the formation of a carbocation from the alkyl halide. In the case of n-propyl chloride, the n-propyl carbocation (C3H7+) can rearrange to form a more stable carbocation (isopropyl cation). Therefore, n-propylbenzene is not obtained due to this rearrangement.
- **Conclusion:** This statement is **incorrect**.

4. **Statement 4: Toluene can be obtained in better yield when excess of benzene reacts with methyl chloride in presence of aluminum trichloride.**
- **Analysis:** When excess benzene is used in the reaction with methyl chloride and AlCl3, it helps to minimize polyalkylation and increases the yield of toluene. The presence of excess benzene favors the formation of the desired monoalkylated product.
- **Conclusion:** This statement is **correct**.

### Final Answer:
The incorrect statements are **1, 2, and 3**.