Provide the structures of chain isomers of $C_6H_{14}$ that contain two methyl groups,along with their $IUPAC$ names.

(N/A) The molecular formula $C_6H_{14}$ corresponds to an alkane. Chain isomers with two methyl groups are:
$(i)$ $CH_3-C(CH_3)_2-CH_2-CH_3$: The longest chain has $4$ carbon atoms,and there are two methyl groups at the $2^{nd}$ position. Its $IUPAC$ name is $2,2-Dimethylbutane$.
(ii) $CH_3-CH(CH_3)-CH(CH_3)-CH_3$: The longest chain has $4$ carbon atoms,and there are methyl groups at the $2^{nd}$ and $3^{rd}$ positions. Its $IUPAC$ name is $2,3-Dimethylbutane$.