Question

On heating alkyl isocyanide to 250°C …………… is formed.

Answer 1

Hint: An isocyanide is an organic compound that contains the functional group $-N\equiv C$. It is the isomer of the corresponding nitrile, hence isocyano is the prefix. The organic fragment is linked via the nitrogen atom to the isocyanide group, not through the carbon. These are used for the synthesis of other compounds as building blocks.

Complete step by step answer:
An isocyanide (also called isonitrile or carbylamine) is an organic compound with functional group $-N\equiv C$. It is the isomer of the related nitrile $-C\equiv N$, hence the prefix is isocyano. The organic fragment is connected to the isocyanide group through the nitrogen atom, not via the carbon. They are used as building blocks for the synthesis of other compounds.
On heating alkyl isocyanide to 250° C, for a long time, more stable alkyl cyanide is formed through rearrangement.
\[R-N\equiv C\xrightarrow{{{250}^{o}}C}R-C\equiv N\]

Hence, on heating alkyl isocyanide to 250° C, for a long time, more stable alkyl cyanide is formed through rearrangement.

Additional Information:
Isocyanate is the functional group with the formula R-N=C=O. Organic compounds that contain an isocyanate group are referred to as isocyanates. An organic compound with two isocyanate groups is known as a di-isocyanate. Di-isocyanates are manufactured for the production of polyurethanes, a class of polymers.
Isocyanates should not be confused with cyanate esters and isocyanides, very different families of compounds. The cyanate (cyanate ester) functional group ($R-O-C\equiv N$) is arranged differently from the isocyanate group (R-N=C=O). Isocyanides have the connectivity $R-N\equiv C$, lacking the oxygen of the cyanate groups.

Note: Alkyl isocyanide is isomeric to alkyl cyanide.
Don’t get confused between isocyanate and isocyanide.
A rearrangement is a reaction in which the reactant and the products are constitutional isomers and the reactant is converted to the product by the migration of one or more ligands from one point of the reactant to another.