Among $\mathrm{Me}_{3}\mathrm{N}, \mathrm{C}_{5} \mathrm{H}_{5} \mathrm{N}$ and MeCN (Me $=$ methyl group)…
Among $\mathrm{Me}_{3}\mathrm{N}, \mathrm{C}_{5} \mathrm{H}_{5} \mathrm{N}$ and MeCN (Me $=$ methyl group) the electronegativity of $\mathrm{N}$ is in the order
To determine the order of electronegativity of nitrogen \((\mathrm{N})\) in different compounds, let's analyze the given compounds:
1. \(\mathrm{Me}_3 \mathrm{~N}\) (Trimethylamine):
- In trimethylamine, nitrogen is bonded to three methyl groups. Methyl groups are electrondonating through inductive effects. As a result, the nitrogen in \(\mathrm{Me}_3 \mathrm{~N}\) will have reduced electronegativity due to the electron-donating effect of the methyl groups.
2. \(\mathrm{C}_5 \mathrm{H}_5 \mathrm{~N}\) (Pyridine):
- In pyridine, nitrogen is part of an aromatic ring system. The lone pair on nitrogen in pyridine is less available for donation or attraction due to resonance with the ring, leading to relatively high effective electronegativity compared to nitrogen in aliphatic amines.
3. MeCN (Methyl Cyanide or Acetonitrile):
- In acetonitrile, nitrogen is bonded to a carbon that is triple-bonded to another carbon. The presence of the triple bond in MeCN (which is highly electronegative) significantly pulls electron density away from nitrogen, making the nitrogen more electronegative compared to its state in trimethylamine.
Electronegativity Order:
1. MeCN: The nitrile group \((\mathrm{C} \equiv \mathrm{N}\)) has a high electronegativity effect due to the triple bond with carbon, making nitrogen the most electronegative.
2. \(\mathrm{C}_5 \mathrm{H}_5 \mathrm{~N}\) : Nitrogen in the pyridine ring is more electronegative than in trimethylamine but less than in acetonitrile.
3. \(\mathrm{Me}_3 \mathrm{~N}\) : In trimethylamine, the nitrogen is least electronegative because of the electrondonating methyl groups.
Correct Order:
(1) \(\mathrm{MeCN}>\mathrm{C}_5 \mathrm{H}_5 \mathrm{~N}>\mathrm{Me}_3 \mathrm{~N}\)