Name an ortho-and para-directing deactivating group.

Answer

To answer the question "Name an ortho- and para-directing deactivating group," we can follow these steps:

### Step 1: Understand the Terms
- **Ortho- and Para-Directing**: This refers to substituents on a benzene ring that direct incoming electrophiles to the ortho (adjacent) and para (opposite) positions relative to themselves.
- **Deactivating Group**: A substituent that decreases the reactivity of the benzene ring towards electrophilic substitution reactions.

### Step 2: Identify Characteristics of the Group
- An ortho-para directing group must increase the electron density at the ortho and para positions.
- A deactivating group must lower the overall reactivity of the benzene ring.

### Step 3: Consider Examples
- **Halogens**: Chlorine (Cl), Bromine (Br), and Iodine (I) are examples of groups that are ortho-para directing due to their ability to donate electron density through resonance (due to their lone pairs).
- However, they also exhibit a -I (inductive effect) because they are electronegative, which pulls electron density away from the benzene ring, thus deactivating it.

### Step 4: Conclusion
- The group that fits both criteria (ortho-para directing and deactivating) is **Chlorine (Cl)**. It directs electrophiles to the ortho and para positions due to its resonance effect (plus R effect) but deactivates the ring due to its electronegativity (minus I effect).

### Final Answer
**Chlorine (Cl)** is an example of an ortho- and para-directing deactivating group.

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