Question

Which of the following is the first and simplest alkane?
(A)- Ethane
(B)- Methane
(C)- ${{C}_{2}}{{H}_{2}}$
(D)- $CC{{l}_{4}}$

Answer 1

Hint: For the first alkane, it should have only one central carbon atom, surrounded by hydrogen atoms and also only single covalent bonds present in it.

Complete step by step solution:
The alkanes are organic compounds in which the compounds have single covalent bonds between the carbon and hydrogen atom. Each carbon forming four bonds and each hydrogen forming only one bond in the compound. They are thus saturated hydrocarbons.
So, in the long straight-chain alkane, the general molecular formula becomes ${{C}_{n}}{{H}_{2n+2}}$ , where n is the number of carbon atoms present in the alkane. Then, the simplest alkane will be the compound having at least one carbon atom.

Hence, the option (B) methane, with one carbon atom bonded to four hydrogen atoms is the first and simplest alkane.

Additional information:
The alkanes are nonpolar in nature due to the small difference in the electronegativities of carbon and hydrogen atom, so it is soluble in only non-polar organic solvents.
Also, with the increase in the length of the chain, that is, increase in the molecular weight of the alkane, its boiling and melting point increases gradually.

Note: Hydrocarbons are compounds consisting of only carbon and hydrogen atoms, single covalently bonded in it.
Also, the ethane is the next alkane after methane, with two carbon atoms and six hydrogens in it. Whereas ${{C}_{2}}{{H}_{2}}$ is an unsaturated alkene hydrocarbon, with a double-bond present in it.
And the $CC{{l}_{4}}$ is formed by the replacement of the hydrogen atoms in methane by the chlorine atom. Thus, forming the tetrachloromethane, with only C-Cl bonds in it.