Question

General formula for mono halogen derivatives of alkane is:
(A) ${C_n}{H_{n + 1}}X$
(B) ${C_n}{H_{2n}}{X_2}$
(C) ${C_n}{H_{2n - 1}}X$
(D) ${C_n}{H_{2n + 1}}X$

Answer 1

Halogens are chemical elements present in group seventeen of modern periodic table. The five elements present in group seventeen are fluorine, chlorine, bromine, iodine and astatine. Alkanes lose one hydrogen atom and gains a halogen atom.

Complete Step by step solution
In organic chemistry alkane is an acyclic saturated hydrocarbon. Alkane are also called paraffin. Alkane is made of hydrogen and carbon atoms. Alkane are arranged in a tree structure in which all carbon-carbon bonds are single bonds. Examples of alkane are as follows: methane made of one carbon atom and four hydrogen atoms bonded to carbon. Methane is the simplest form of alkane. Ethane is an alkane containing two carbons and having three hydrogens bonded to each carbon atom. Propane is an alkane having three carbon atoms and eight hydrogen atoms, where first and last carbon have three hydrogen atoms and the middle carbon atom has two hydrogen atoms attached.
So, by observing the above alkanes we can derive a general formula for non-cyclic alkane is
${C_n}{H_{2n + 2}}$ . By this general formula we can find the formula of any alkane, like for methane we have one carbon so the number of hydrogens will be 2n+2 that is 2(2)+2 that is one carbon atom and four methane atoms.
Mono halogenation of an alkane is a process of addition of one halogen atom to an alkane. Where halogen displaces the one hydrogen atom of alkane molecule and bonds with the carbon atom. When one halogen atom is added to alkane molecule it displaces one hydrogen atom from alkane which leads to reduction in one hydrogen atom. So, the general formula of monohalogenation of alkane is ${C_n}{H_{2n + 1}}X$ . Where X represents the halogen which can be fluorine, chlorine, bromine or iodine.
So, the correct answer is option D.

Note
General formula for cyclo-alkane is ${C_n}{H_{2n}}$ , similar to alkenes.
Haloalkanes are used as flame retardants, fire extinguisher, refrigerants, propellants, solvents and pharmaceuticals.