Arrange decreasing order of reactivity of these compounds for nucleophilic substitution reaction.
(1) `CH_3-CH_2-O-underset(O)underset(||)overset(O)overset(||)S-CF_3`
(2) `CH_3-CH_2-O -TsCl`
(3) `CH_3-CH_2-Cl`
(4) `CH_3-CH_2-Br`
Select the correct answer from the codes given below

Options

A. 3,4,1,2
B. 3,4,2,1
C. 1,2,3,4
D. 1,2,4,3

Answer

To determine the decreasing order of reactivity of the given compounds for nucleophilic substitution reactions, we need to analyze the leaving groups in each compound. The reactivity in nucleophilic substitution reactions is influenced by the stability of the leaving group; the better the leaving group, the more reactive the compound will be.

### Step-by-Step Solution:

1. **Identify the Compounds and Their Leaving Groups:**
- (1) `CH_3-CH_2-O-underset(O)underset(||)overset(O)overset(||)S-CF_3`: Leaving group is `O-S-CF3`.
- (2) `CH_3-CH_2-O-TsCl`: Leaving group is `OTs` (tosylate).
- (3) `CH_3-CH_2-Cl`: Leaving group is `Cl` (chloride).
- (4) `CH_3-CH_2-Br`: Leaving group is `Br` (bromide).

2. **Rank the Leaving Groups:**
- The ability of a leaving group to depart is influenced by its stability. The order of leaving group ability is:
- `O-S-CF3` (from the first compound) is a very good leaving group due to the resonance stabilization provided by the sulfonate group.
- `OTs` (from the second compound) is also a good leaving group due to its sulfonate nature.
- `Br` is a better leaving group than `Cl` because bromide is larger and more stable than chloride.
- `Cl` is the least stable leaving group among the four.

Thus, the order of leaving groups from best to worst is:
- `O-S-CF3 > OTs > Br > Cl`

3. **Determine the Reactivity Order:**
- Since the reactivity of the compounds is directly related to the stability of the leaving groups, we can arrange the compounds based on their leaving groups:
- Compound (1) with `O-S-CF3` is the most reactive.
- Compound (2) with `OTs` is next.
- Compound (4) with `Br` follows.
- Compound (3) with `Cl` is the least reactive.

Therefore, the decreasing order of reactivity for nucleophilic substitution is:
- (1) > (2) > (4) > (3)

### Final Answer:
The correct order of decreasing reactivity for the nucleophilic substitution reaction is:
**(1) > (2) > (4) > (3)**