An organic reaction occurs by using reagents called electrophiles and nucleophiles via the formation of some reactive intermediates called carbocations, carbanions, free radicals, carbenes, nitrenes, radical cations, and radical anions.
Which of the following contains nucleophiles only ?

Options

A. `PH_3, ROH, CH_2= CH_2`
B. `SnF_4, BeF_2, NH_3`
C. `Cr^(3 +), overset (Ө) N H_2, H_2 O`
D. `: C Cl_2, I^(Ө), H^(Ө)`

Answer

To determine which of the given options contains nucleophiles only, we need to understand what nucleophiles are. Nucleophiles are species that are electron-rich and have either lone pairs of electrons or a negative charge, allowing them to donate electrons to electrophiles.

### Step-by-Step Solution:

1. **Identify the Options**: We need to analyze each option provided in the question to check if they contain nucleophiles only.

2. **Analyze the First Set: pH3, ROH, CH2=CH2**:
- **pH3 (Phosphine)**: Phosphorus in pH3 has one lone pair of electrons, making it a nucleophile.
- **ROH (Alcohol)**: The oxygen in alcohol has two lone pairs of electrons, which also qualifies it as a nucleophile.
- **CH2=CH2 (Ethylene)**: The double bond in ethylene has a pi bond, and while it is not a classic nucleophile, it can act as one in certain reactions due to the presence of electrons in the pi bond.
- **Conclusion for First Set**: All three species can act as nucleophiles.

3. **Analyze the Second Set: SNF4, BEF2, NH3**:
- **SNF4 (Sulfur Tetrafluoride)**: This molecule has no lone pairs on sulfur and is electron-deficient, so it is not a nucleophile.
- **BEF2 (Beryllium Fluoride)**: Beryllium is electron-deficient as it does not complete its octet, making it a poor nucleophile.
- **NH3 (Ammonia)**: Ammonia has a lone pair of electrons on nitrogen, making it a nucleophile.
- **Conclusion for Second Set**: Since SNF4 and BEF2 are not nucleophiles, this option is incorrect.

4. **Analyze the Third Set: Cr3+, C+**:
- **Cr3+ (Chromium Ion)**: This ion is highly electron-deficient and does not have any electrons to donate, so it is not a nucleophile.
- **C+ (Carbocation)**: A carbocation is also electron-deficient and cannot act as a nucleophile.
- **Conclusion for Third Set**: Neither species is a nucleophile, making this option incorrect.

5. **Analyze the Fourth Set: CCl2 (Dichloromethane)**:
- **CCl2**: The carbon in CCl2 is electron-deficient due to the electronegativity of chlorine atoms, which pulls electron density away from carbon, making it a poor nucleophile.
- **Conclusion for Fourth Set**: This option also contains no nucleophiles.

### Final Conclusion:
After analyzing all the options, the only set that contains nucleophiles only is the **first set: pH3, ROH, and CH2=CH2**.

### Answer:
The correct answer is the first set: **pH3, ROH, CH2=CH2**.