WAEC Chemistry 2019 Paper

Concept:The IUPAC name is obtained by selecting the longest carbon chain and naming all substituent groups attached to that chain.Explanation:The given structure is $\mathrm{CH_3C(CH_3)_2CH_2CH_2CH_3}$.It can be understood as $\mathrm{CH_3-C(CH_3)_2-CH_2-CH_2-CH_3}$.Identify the longest continuous chain of carbon atoms.The longest chain contains five carbon atoms, so the parent alkane is pentane.The central carbon has two methyl groups, $-\mathrm{CH_3}$, attached to it.When numbering the pentane chain, these two methyl groups are both on carbon $2$.Two identical methyl groups are shown by the prefix di, so the substituent part is $2,2$-dimethyl.Hence, the complete IUPAC name is $2,2$-dimethylpentane.Answer:D. 2,2-dimethylpentane