Correct order of -I effect is :

Options

A. `-NR_(3)^(+)gtORgtF`
B. `Fgt-NR_(3)^(+)gt-OR`
C. `-NR_(3)^(+)gtFgtOR`
D. `ORgt-NR_(3)^(+)gtF`

Answer

To determine the correct order of the -I (negative inductive) effect, we need to analyze the electron-withdrawing ability of different groups. The -I effect is a result of the electronegativity of atoms or groups attached to a carbon chain, which can pull electron density away from the rest of the molecule.

### Step-by-Step Solution:

1. **Understand the Inductive Effect**:
The inductive effect refers to the permanent polarization of a sigma bond due to the electronegativity difference between atoms. The -I effect specifically refers to the electron-withdrawing nature of certain groups.

**Hint**: Recall that electronegative atoms or groups can attract electrons towards themselves, leading to a -I effect.

2. **Identify the Groups**:
In this case, we are considering groups such as NR3+, F (fluorine), and OR (alkoxy group). We need to evaluate their electronegativities.

**Hint**: Look at the periodic table to compare the electronegativities of nitrogen, fluorine, and oxygen.

3. **Rank the Groups by Electronegativity**:
- **NR3+**: The positively charged amine group (NR3+) has a strong electron-withdrawing effect due to the positive charge.
- **F (Fluorine)**: Fluorine is the most electronegative element, thus it has a strong -I effect.
- **OR (Alkoxy Group)**: The alkoxy group (OR) is less electronegative than fluorine and has a weaker -I effect.

**Hint**: Remember that a positive charge increases the electron-withdrawing ability of a group significantly.

4. **Establish the Correct Order**:
Based on the electronegativities and the strength of the -I effect:
- NR3+ > F > OR

Therefore, the correct order of the -I effect is NR3+ > F > OR.

5. **Choose the Correct Option**:
From the given options, the one that matches our derived order is option 3: NR3+ > F > OR.

**Hint**: Always double-check the options provided to ensure your derived order matches one of them.

### Final Answer:
The correct order of -I effect is: **NR3+ > F > OR** (Option 3).