Chapter 20, Problem 2STP

Interpretation Introduction

Interpretation: The correct name for 3-methyl-4-isopropylpentane needs to be determined.

Concept introduction: The complete name for alkane is n-octane, the n indicating a straight-chain alkane.

Answer to Problem 2STP

B. 2,3,4-trimethylhexane.

Explanation of Solution

Rules for Naming Alkanes

1. Find the longest continuous chain of carbon atoms. This chain (calledthe parent chain) determines the base alkane name.
2. Number the carbons in the parent chain, starting at the end closest to any branching (the first alkyl substituent). When a substituent occurs the same number of carbons from each end, use the next substituent (if any) to determine from which end to start numbering.
3. Using the appropriate name for each alkyl group, specify its position on the parent chain with a number.
4. When a given type of alkyl group occurs more than once, attach the appropriate prefix (di- for two, tri- for three, and so on) to the alkyl name.
5. The alkyl groups are listed in alphabetical order, disregarding any prefix.

The structure of 3-methyl-4-isopropylpentane is therefore, the correct name for 3-methyl-4-isopropylpentane is 2,3,4-trimethylhexane since methyl group is starting 2^nd parent carbon and since it is the next substituent from branching chain.

Conclusion

For a branched hydrocarbon, the longest continuous chain of carbon atoms gives the root name for the hydrocarbon.