Which is (are) correct out of the following:

Options

A. `CH_(2)=CH_(2)ltH-C-=C-h` (rate of electrophilic addition)
B. `ltH_(3)C-C-=C-CH_(3)` (rate of catalytic hydrogenation)
C. (rate of electrphilic substitution reaction)
D. (order of acidic strength)

Answer

To determine which statements are correct, let's analyze each one step by step.

### Step 1: Evaluate the first statement
**Statement:** Ethylene is less reactive than ethyne towards electrophilic addition reactions.

**Analysis:**
- Alkenes (like ethylene) are generally more reactive than alkynes (like ethyne) in electrophilic addition reactions. This is because alkenes form a more stable intermediate during the reaction compared to alkynes, which form a highly strained and unstable intermediate.
- **Conclusion:** This statement is **false**.

### Step 2: Evaluate the second statement
**Statement:** Cis-but-2-ene is less reactive than but-2-yne towards the rate of catalytic hydrogenation.

**Analysis:**
- In catalytic hydrogenation, alkynes are indeed more reactive than alkenes due to two main factors: lower steric hindrance and higher pi electron density in alkynes.
- Therefore, cis-but-2-ene (an alkene) is less reactive than but-2-yne (an alkyne) in this context.
- **Conclusion:** This statement is **true**.

### Step 3: Evaluate the third statement
**Statement:** Nitrobenzene is less reactive than toluene for electrophilic substitution reactions.

**Analysis:**
- In electrophilic substitution reactions, the presence of electron-donating groups (like the methyl group in toluene) increases the electron density of the benzene ring, making it more reactive towards electrophiles.
- Conversely, the nitro group in nitrobenzene is an electron-withdrawing group, which decreases the electron density, making it less reactive than toluene.
- **Conclusion:** This statement is **true**.

### Step 4: Evaluate the fourth statement
**Statement:** The ortho effect increases the acidity of benzoic acid when an ortho substituent is present.

**Analysis:**
- The ortho effect refers to the increased acidity of a carboxylic acid when an electron-donating group is present at the ortho position. This occurs because the substituent can stabilize the negative charge of the conjugate base through steric effects, making the acid more acidic.
- **Conclusion:** This statement is **true**.

### Final Conclusion
The correct statements are **B, C, and D**.