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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