Draw the structural formula for each of the following. a. 3 -isobutylhexane b. 2,2,4 -trimethylpentane, also called isooctane. This substance is the reference (100 level) for octane ratings. c. 2 -tert-butylpentane d. The names given in parts a and c are incorrect. Give the correct names for these hydrocarbons.

Draw the hexane chain with six carbon atoms, and then attach an isobutyl group, which contains four carbons, to the 3rd carbon of the hexane chain. Hexane: \(-CH_{3}CH_{2}CH_{2}CH_{2}CH_{2}CH_{3}\) Isobutyl: \(-CH_{2}CH(CH_{3})_{2}\) Result: \(CH_{3}CH_{2}CH(-CH_{2}CH(CH_{3})_{2})CH_{2}CH_{2}CH_{3}\)

Draw the pentane chain with fives carbon atoms, and then attach three methyl groups to carbons 2 and 4. Pentane: \(-CH_{3}CH_{2}CH_{2}CH_{2}CH_{3}\) Methyls: \(-CH_{3}\) Result: \(-CH_{3}-C(CH_{3})_{2}CH_{2}C(CH_{3})_{2}CH_{3}\)

Draw the pentane chain and then attach a tert-butyl group (with four carbons) to the 2nd carbon of the pentane chain. Pentane: \(-CH_{3}CH_{2}CH_{2}CH_{2}CH_{3}\) tert-Butyl: \(-C(CH_{3})_{3}\) Result: \(-CH_{3}C(CH_{2}CH_{2}CH_{2}CH_{3})C(CH_{3})_{3}\)

a. We need to change the name of 3-isobutylhexane to its correct IUPAC name, which should be 3-methylheptane. For 3 -isobutylhexane, check the order of carbons: Longest chain: \(CH_{3}CH_{2}CH_{2}CH_{2}CH_{2}CH_{2}CH_{3}\) (Heptane) Position 3: \(-CH_{2}CH(CH_{3})_{2}\) (Methyl group) Correct Name: \(CH_{3}CH_{2}CH(-CH_{2}CH(CH_{3})_{2})CH_{2}CH_{2}CH_{2}CH_{3}\) (3-methylheptane) c. We need to change the name of 2-tert-butylpentane to its correct IUPAC name, which should be 2,2,3-trimethylbutane. For 2 -tert-butylpentane, check the order of carbons: Longest chain: \(-CH_{3}CH_{2}CH_{2}CH_{3}\) (Butane) Position 2: \(-C(CH_{3})_{3}\) (Two methyl groups) Position 3: \(-C(CH_{3})\) (One methyl group) Correct Name: \(-CH_{3}C(CH_{2}CH_{3})C(CH_{3})_{3}\) (2,2,3-trimethylbutane)