Final answer:
The isomer of C7H16 with an ethyl branch is called 3-ethylpentane. Other isomers with a five-carbon chain and three methyl substituents include 2,2,3-trimethylbutane and 2,2,4-trimethylbutane. For C4H6 alkyne isomers, they are 1-butyne and 2-butyne.
Step-by-step explanation:
The student is asking for the name of the isomer of C7H16 that contains an ethyl branch on the parent chain. Among the nine isomers of heptane (C7H16), one that contains an ethyl group (C2H5-) as a substituent on the main chain is 3-ethylpentane. This isomer has a five-carbon chain with an ethyl group attached to the third carbon atom.
Answering part (b) of the question, the isomers that contain a five-carbon chain with three methyl substituents are 2,2,3-trimethylbutane and 2,2,4-trimethylbutane. These isomers are part of the numerous possible structures that can be derived from the heptane molecular formula.
Regarding the query about alkyne isomers of C4H6, the student would need to look at the potential connectivity of the carbon atoms, ensuring the correct number of hydrogens are placed to satisfy the valency of each carbon. There are two isomers possible: 1-butyne, with the triple bond at the end of the chain, and 2-butyne, with the triple bond between the second and third carbon atoms.