Question

Question: Using the general formula for alkanes

1. Predict the molecular formula of the${\mathbf{C}}_{\mathbf{27}}$straight chain alkane.
2. Predict the molecular formula of the alkanes containing 42 carbon atom with extensive branching.

Short answer

(a)Molecular formula of${\text{C}}_{\text{27}}$ straight-chain alkane is ${\text{C}}_{\text{27}}{\text{H}}_{\text{56}}$.

(b)Molecular formula of an alkane having 42 carbon atoms is ${\text{C}}_{42}{\text{H}}_{\text{86}}$.

Step-by-step solution

Alkanes

The general formula for alkanes is ${\text{C}}_{\text{n}}{\text{H}}_{\text{2n + 2}}$,where n is the number of carbon atoms present in molecule.

Explanation to part (a)

In part (a) there is 27 carbon atoms are present in molecular formula and according to above general formula number of hydrogens are 56 (2 x number of carbon atoms +2).

Explanation to part (b)

In part (b) there is 42 carbon atoms are present in molecular formula and according to above general formula number of hydrogens are 86 (2 x number of carbon atoms +2). Also extensive branching does not affect the molecular formula of alkanes.