44 8.5 Isomers

Practice questions

1. Which structures among those shown here are related to one another as constitutional isomers? Select all that belong in the set.
   1. 1. A five-carbon ring with two carbon double bonds located in alternative carbons.
      2. A four-carbon straight chain with a [latex]\ce{NH}[/latex] group located between the second and third carbon and a methyl group attached to the second and third carbons, each.
      3. A five-carbon straight chain with two carbon double bonds: one double bond between the first and the second carbon and the other third and the fourth carbon.
      4. A six-carbon straight chain with a [latex]\ce{NH_{2}}[/latex] attached to the last carbon.
2. What is the constitutional isomer of ethanol, [latex]\ce{CH_{3}CH_{2}OH}[/latex]?
   1. 1. A two-carbon chain with a hydroxyl group attached to [latex]\ce{CH_{2}}[/latex]:  [latex]\ce{CH_{3}CH_{2}OH}[/latex]
      2. A two-carbon chain with a hydroxyl group attached to [latex]\ce{CH_{2}}[/latex]: [latex]\ce{CH_{3}CH_{2}OH}[/latex]
      3. A two-carbon chain with an oxygen atom connecting two carbons: [latex]\ce{CH_{3}OCH_{3}}[/latex]
3. Is it true that this is a constitutional isomer of resorcinol, molecular formula [latex]\ce{C_{6}H_{6}O_{2}}[/latex]? The structure description: a benzene ring with two hydroxyl groups attached to carbons opposite to each other.
4. How many constitutional isomers does [latex]\ce{C_{5}H_{12}}[/latex] have?
   1. 1. 3
      2. None
      3. 2
      4. 4
5. How many constitutional isomers does [latex]\ce{C_{4}H_{10}O}[/latex] have?
   1. 1. 4
      2. 3
      3. 10
      4. 7
6. How many structural isomers does [latex]\ce{C_{3}H_{9}N}[/latex] have?
   1. 1. 3
      2. 2
      3. 4
      4. 7

Answers

1. b, d
2. c
3. True
4. a
5. 7
6. c