The decresing fugacity order of the following is:
i. `Me_(2)N - Nme_(2)`, ii. `MeNH-NHMe`
iii. `H_(2)N - NH_(2)`, iv. `NH_(3)`

Options

A. `(i) gt (ii) gt (iii) gt (iv)`
B. `(iv) gt (iii) gt (ii) gt (i)`
C. `(iv) gt (iii) gt (i) gt (ii)`
D. `(iii) gt (iv) gt (ii) gt (i)`

Explanation

To determine the decreasing fugacity order of the given species, we need to analyze their basic strengths since the fugacity order is inversely related to the basic strength. Here are the steps to find the solution:

### Step 1: Identify the Compounds
The compounds given are:
1. \( Me_2N - NMe_2 \) (Dimethylhydrazine)
2. \( MeNH - NHMe \) (Methylhydrazine)
3. \( H_2N - NH_2 \) (Hydrazine)
4. \( NH_3 \) (Ammonia)

### Step 2: Determine Basic Strengths
Basic strength is influenced by the number of electron-donating groups and the availability of lone pairs on the nitrogen atoms.

- **Dimethylhydrazine (i)**: Has two nitrogen atoms each bonded to two methyl groups. The methyl groups are electron-donating, which increases the basicity.
- **Methylhydrazine (ii)**: Has two nitrogen atoms, but only one is bonded to a methyl group. This makes it less basic than dimethylhydrazine.
- **Hydrazine (iii)**: Has two nitrogen atoms with no methyl groups. It is less basic than both dimethylhydrazine and methylhydrazine.
- **Ammonia (iv)**: Has only one nitrogen atom and no electron-donating groups. It is the least basic of all.

### Step 3: Rank the Basic Strengths
Based on the above analysis, we can rank the basic strengths from strongest to weakest:
1. \( Me_2N - NMe_2 \) (most basic)
2. \( MeNH - NHMe \)
3. \( H_2N - NH_2 \)
4. \( NH_3 \) (least basic)

### Step 4: Determine the Fugacity Order
Since the fugacity order is inversely related to the basic strength, we reverse the order:
1. \( NH_3 \) (best leaving group)
2. \( H_2N - NH_2 \)
3. \( MeNH - NHMe \)
4. \( Me_2N - NMe_2 \) (poorest leaving group)

### Final Fugacity Order
Thus, the decreasing fugacity order is:
\[ NH_3 > H_2N - NH_2 > MeNH - NHMe > Me_2N - NMe_2 \]

### Answer
The decreasing fugacity order of the given compounds is:
\[ NH_3 > H_2N - NH_2 > MeNH - NHMe > Me_2N - NMe_2 \]

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