With the molecular formula $\left({\mathrm{C}}_4{\mathrm{H}}_8{\mathrm{Cl}}_2\right)$, how many compounds are possible excluding stereoisomers and branching of alkyl groups.

Given molecular formula indicates that the molecule has 4 C atoms, 8 H atoms and 2 Cl atoms. There are number of isomers possible but those isomers that have linear carbon chain are six.