Arrange decreasing order of reactivity of these compounds for nucleophilic substitution reaction
(I) `CH_(3)CH_(2)-O-overset(O)overset(||)underset(O)underset(||)S-CF_(3)`
(II) `CH_(3)-CH_(2)-OTs`
(III) `CH_(3)-underset(OH)underset("| ")"CH"-OH`
(IV) `CH_(3)-underset(C_(6)H_(5))underset("| ")"CH "-OH`

Options

A. III > IV > I > II
B. III > IV > I > II
C. I > II > III > IV
D. I > II > IV > III

Answer

To determine the decreasing order of reactivity of the given compounds for nucleophilic substitution reactions, we need to analyze each compound based on the mechanism (SN1 or SN2) and the stability of the leaving groups.

### Step-by-Step Solution:

1. **Identify the Mechanism**:
- The compounds provided are likely to undergo SN2 reactions since they involve primary and secondary carbons. In SN2 reactions, the rate depends on the strength of the leaving group and the partial positive charge on the carbon.

2. **Analyze Each Compound**:
- **Compound I: `CH₃CH₂-O-S-CF₃`**
- The leaving group here is `S-CF₃`. The CF₃ group is a strong electron-withdrawing group, which stabilizes the leaving group, making it a good leaving group. Thus, this compound is likely to be very reactive.

- **Compound II: `CH₃-CH₂-OTs`**
- The leaving group is `OTs` (tosylate), which is a very stable leaving group due to resonance stabilization. This compound is also reactive but not as much as Compound I.

- **Compound III: `CH₃-CH₂-OH`**
- Here, the leaving group is `OH`, which is a poor leaving group unless converted to a better leaving group (like `OTs`). Therefore, this compound is less reactive compared to Compounds I and II.

- **Compound IV: `CH₃-C₆H₅-CH(OH)`**
- The leaving group is `OH` again. However, the presence of the phenyl group can stabilize the positive charge through resonance when the nucleophile attacks, but `OH` is still a poor leaving group. Thus, this compound is the least reactive among the four.

3. **Rank the Compounds**:
- Based on the analysis:
- Compound I is the most reactive due to the strong leaving group.
- Compound II follows due to the good leaving group (OTs).
- Compound III is next, as `OH` is a poor leaving group.
- Compound IV is the least reactive due to the same poor leaving group but with additional resonance stabilization.

### Final Order of Reactivity:
**I > II > III > IV**