Identify the incorrect characteristic of carbenes,: `CR_2`

Options

A. contain carbon atom with only six valence electrons
B. nutral specis
C. very reactive
D. normally neocleophylic

Answer

To identify the incorrect characteristic of carbenes, we need to analyze the properties and behavior of carbenes systematically.

### Step-by-Step Solution:

1. **Definition of Carbene**:
- Carbenes are neutral species containing a carbon atom that is bonded to two other atoms and has two unshared valence electrons. The general formula for a carbene is \( CR_2 \), where \( R \) can be hydrogen or any other substituent.

**Hint**: Remember that carbenes have a unique structure with two bonds and two lone electrons.

2. **Electron Configuration**:
- The electron configuration of carbon is \( 1s^2, 2s^2, 2p^2 \). In carbenes, the carbon atom has a total of 6 electrons in its valence shell (4 from the two bonds and 2 from the lone pairs).

**Hint**: Focus on the valence shell electron count to understand the reactivity of carbenes.

3. **Reactivity of Carbenes**:
- Carbenes are known to be highly reactive due to their electron deficiency. They often seek to complete their octet by reacting with other molecules.

**Hint**: Consider how electron deficiency influences the behavior of molecules.

4. **Electrophilic Nature**:
- Due to the presence of only 6 electrons in the valence shell, carbenes act as electrophiles. They are attracted to electron-rich species to complete their octet.

**Hint**: Recall that electrophiles are electron acceptors, which is crucial for understanding carbene behavior.

5. **Nucleophilic Behavior**:
- The statement that carbenes act as nucleophiles is incorrect. Nucleophiles are electron-rich species that donate electrons, while carbenes, being electron-deficient, cannot behave as nucleophiles.

**Hint**: Differentiate between electrophiles and nucleophiles based on their electron characteristics.

6. **Conclusion**:
- The incorrect characteristic of carbenes is that they act as nucleophiles. The correct behavior is that they act as electrophiles due to their electron deficiency.

### Final Answer:
The incorrect characteristic of carbenes is that they act as nucleophiles.