MCAT Chemical and Physical Foundations of Biological Systems Practice Exam 2026 – Comprehensive All-in-One Guide for Exam Success!

The root for an eight-carbon hydrocarbon chain is "oct-." In organic chemistry, the naming of hydrocarbons follows a systematic nomenclature based on the number of carbon atoms in the longest continuous chain.

For hydrocarbons, the prefixes corresponding to the number of carbon atoms are as follows:

- "meth-" for one carbon

- "eth-" for two carbons

- "prop-" for three carbons

- "but-" for four carbons

- "pent-" for five carbons

- "hex-" for six carbons

- "hept-" for seven carbons

- "oct-" for eight carbons

Since the question specifically asks for the root name corresponding to an eight-carbon chain, "oct-" is the correct choice, as it accurately reflects the presence of eight carbon atoms in the structure. Other options represent shorter chains, and thus do not apply to the eight-carbon hydrocarbon in question.