What is the IUPAC name of CH3-CH2-CH(CH2-CH2-CH2-CH3)-CH(CH3)-CH3? (When two chains have the same length, choose the one with more substituents.)

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What is the IUPAC name of $CH X_{3} - CH X_{2} - CH (CH X_{2} - CH X_{2} - CH X_{2} - CH X_{3}) - CH (CH X_{3}) - CH X_{3}$ ? (When two chains have the same length, choose the one with more substituents.)

A5-ethyl-6-methylheptane
B3-ethyl-2-methylheptane
C2-methyl-3-ethylheptane
D3-(1-methylethyl)heptane

Answer: B

The longest chain has seven carbons, and there are two choices: one ends in the isopropyl group (giving 3-ethyl-2-methylheptane, two substituents) and one runs through the ethyl group (giving 3-(1-methylethyl)heptane, one substituent). The chain with more substituents is chosen. Numbering from the isopropyl end gives {2,3}, lower than {5,6}. Alphabetical order puts ethyl before methyl: 3-ethyl-2-methylheptane.

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What is the IUPAC name of CHX3​−CHX2​−CH(CHX2​−CHX2​−CHX2​−CHX3​)−CH(CHX3​)−CHX3​? (When two chains have the same length, choose the one with more substituents.)

Answer: B

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What is the IUPAC name of $CH X_{3} - CH X_{2} - CH (CH X_{2} - CH X_{2} - CH X_{2} - CH X_{3}) - CH (CH X_{3}) - CH X_{3}$ ? (When two chains have the same length, choose the one with more substituents.)