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
Answer and Explanation:
Isomers are compounds with the same formula (same numbers of atoms of each element) but different structure/connection. Let's try to eliminate some answer choices first that do not have the same formula. Choice 4 is 1-chloropropane and 2-bromopropane. Since the first compound contains chlorine (chloro) and the second compound contains bromine (promo), these can not be isomers. Now let's look at the parent chain names. In choice 2, propanoic acid contains 3 carbons ( prop=3) and pentanoic acid contains 5 carbons (penta=5). Therefore, we can eliminate choice 3 as well. Choice 1, methanol and methanal, has two different functional groups, alcohol and aldehyde and can be also eliminated. Therefore, choice 3 is the correct answer. 1-propanol and 2-propanol have exactly the same number of atoms of each element and only differ in the position of their alcohol (OH) group.
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