Question

question 18 (1 point) hexane, 2,3 - dimethylbutane, and 2 - methylpentane are constitutional isomers. which answer lists the isomers in order of decreasing boiling point? 2 - methylpentane > 2,3 - dimethylbutane > hexane hexane > 2 - methylpentane > 2,3 - dimethylbutane 2,3 - dimethylbutane > 2 - methylpentane > hexane 2 - methylpentane > hexane > 2,3 - dimethylbutane hexane > 2,3 - dimethylbutane > 2 - methylpentane question 19 (1 point) what is the iupac name for the compound ch3ch=chch2ch3? 4 - pentene pentene

Explanation:

For Question 18: Constitutional isomers with more branching have lower boiling - points. Hexane is unbranched, 2 - methylpentane has one branch, and 2,3 - dimethylbutane has two branches. So, the order of decreasing boiling point is hexane > 2 - methylpentane > 2,3 - dimethylbutane.
For Question 19: When naming alkenes using IUPAC, number the carbon - chain starting from the end closest to the double bond. In CH₃CH=CHCH₂CH₃, the double bond is between carbon 2 and carbon 3, and the longest chain has 5 carbons, so the name is 2 - pentene (but it's not in the options, and among the given options, the correct way to name it considering the rules is pentene as the double bond position is not specified in a wrong way and the default is to assume the lowest - numbered position for the double bond when not specified otherwise).

Answer:

Question 18: hexane > 2 - methylpentane > 2,3 - dimethylbutane
Question 19: pentene