Choose the false statement

Options

A. `-NH_(2)` is strongly activating while `-NHCOCH_(3)` is activating
B. `-NO_(2)` is strongly deactivating while `-CHO` is deactivating
C. `-NHCOR` and `-CHO` are m - directing
D. `-CF_(3)` and `-COR` are m - directing

Answer

To determine which statement is false, we need to analyze the options provided regarding the activating and deactivating effects of various substituents on aromatic rings. Let's go through the statements one by one.

### Step 1: Analyze the First Statement
**Statement:** NH2 is strongly activating while NHCOCH3 is activating.

- The **NH2** group (amino group) has a lone pair of electrons that can be donated to the aromatic ring, increasing the electron density. This makes it a strongly activating group and ortho-para directing.
- The **NHCOCH3** group (acetanilide) also has a lone pair on nitrogen, but this lone pair is partially delocalized into the carbonyl (C=O) bond, reducing its ability to donate electrons compared to NH2. Therefore, it is activating but not as strongly as NH2.

**Conclusion:** This statement is true.

### Step 2: Analyze the Second Statement
**Statement:** NO2 is strongly deactivating and CHO is deactivating.

- The **NO2** group (nitro group) is a strong electron-withdrawing group due to resonance and inductive effects, making it strongly deactivating.
- The **CHO** group (aldehyde) is also an electron-withdrawing group, but it is less strong than NO2. It is still considered deactivating.

**Conclusion:** This statement is true.

### Step 3: Analyze the Third Statement
**Statement:** NHCOR and CHO are meta directing.

- The **CHO** group is indeed meta directing because it withdraws electron density from the ortho and para positions, making them less favorable for electrophilic substitution.
- However, the **NHCOR** group (where R can be an alkyl group) is actually ortho-para directing due to the presence of the lone pair on nitrogen, which can donate electron density to the ring.

**Conclusion:** This statement is false.

### Step 4: Analyze the Fourth Statement
**Statement:** CF3 and COR are meta directing.

- The **CF3** group (trifluoromethyl) is a strong electron-withdrawing group due to the electronegativity of fluorine, making it meta directing.
- The **COR** group (carbonyl) is also electron-withdrawing and thus meta directing.

**Conclusion:** This statement is true.

### Final Conclusion
The false statement is the **third statement**: "NHCOR and CHO are meta directing." The NHCOR group is actually ortho-para directing due to the lone pair on nitrogen.