Q.Describe the hybridisation and bonding of the carbon and nitrogen atoms in $\text{CH}_3-\text{N}{\equiv}\text{C}$ (methyl isocyanide), and contrast this with the bonding in $\text{CH}_3-\text{C}{\equiv}\text{N}$ (methyl cyanide/acetonitrile).

In $\text{CH}_3-\text{C}{\equiv}\text{N}$, the nitrile carbon is $sp$-hybridised and forms one $\sigma$ and two $\pi$ bonds to nitrogen, a genuine carbon-nitrogen triple bond directly analogous to an alkyne's $\text{C}{\equiv}\text{C}$; nitrogen's lone pair points straight outward along the molecular axis, uninvolved in bonding to carbon. In $\text{CH}_3-\text{N}{\equiv}\text{C}$, methyl is instead bonded to nitrogen, and the terminal carbon is best represented by the resonance structure $\text{CH}_3-\overset{+}{\text{N}}{\equiv}\overset{-}{\text{C}}$ -- carbon carries a formal negative charge and a lone pair of its own, giving it carbene-like character. This exposed carbon lone pair is chemically very reactive (the structural basis of isocyanide chemistry used in multicom …

Draw the resonance structure of the isocyanide explicitly to locate the carbene-li …

Describing both compounds as having 'identical' triple bonds -- the isocyanide's terminal-carbon lone pair is a genuine …