Which compounds are isomers of each other?

January 2018 NY Regents Chemistry Exam

45 Which compounds are isomers of each other? (1) methanol and methanal (2) propanoic acid and pentanoic acid (3) 1-propanol and 2-propanol (4) 1-chloropropane and 2-bromopropane

Solution: Isomers are molecules with the same formula but different structure. We can look at Table R on the reference table which shows functional groups and examples of names with the correct ending. Table P shows the correct prefix for the number of carbons in a chain. We can eliminate choice 4 because one molecule has chlorine and another bromine. We can also eliminate choice 2 because prop means 3 carbons and pent mean 5 carbons. We can eliminate choice 1 because methanol(alcohol) has all single bonds and methanal (aldehyde) has a =O.1-propanol and 2-propanol are isomers of each other because they have the same formula (same number of carbons, hydrogens and oxygens) but different connection. In 1-propanol, the OH group is attached to carbon 1 while in 2-propanol, it is attached to carbon 2.

Answer: 3

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