What is the number of $-CH_2-$ groups present in dodecane?

The molecular mass of a hydrocarbon is $86 \ g/mol$. What is the number of its possible structural isomers?

What do you mean by torsional strain?

Explain the isomerization reaction of alkanes.

Propane molecule on chlorination under photochemical conditions gives two dichloro products,$x$ and $y$. Amongst $x$ and $y$,$x$ is an optically active molecule. How many trichloro products (consider only structural isomers) will be obtained from $x$ when it is further treated with chlorine under photochemical conditions?

The number of possible monobromo products for the reaction of methylcyclohexane with $Br_2/hv$ is (excluding stereoisomers):