Hydrocarbons Quiz

1. Write down the IUPAC name of the following alkane and show the main chain and the ordering number!

     CH₃ – CH – CH – CH₂ – CH₂ – CH₂
                |      |
              CH₃   CH₂

                        |

                       CH₃

2. Write down the IUPAC name of the following alkene and show the main chain and the ordering number!

     CH₃ – C = C – CH₃
              |    |
             CH₃ C₂H₅

3. Write down the IUPAC name of the following alkyne and show the main chain and the ordering number!

     CH₃ – CH₂ – C ≡ C – CH – CH₂ – CH₃
                                            |
                                          CH₃

4. Write down the structural formula of the following hydrocarbon compound:

     3-ethyl-2,4-dimethylheptane

5. Which of the following isomers are chain isomers and position isomers?

     a. CH₃ – CH₂ – CH₂ – CH₂ – CH₂ – CH₂ – CH₃

     b.          CH₃
                    |

           CH₃ – C – CH₂ – CH₂ – CH₃

                    |

                   CH₃

     c. CH₃ – CH – CH₂ – CH – CH
                    |               |

                   CH₃          CH₃

     Chain isomer: ...
      Position isomer: ...

6. Which of the following isomers have geometric isomerism?

     a. CH₂ = CH – CH₂ – CH₃

     b. CH3 – CH = CH – CH2 – CH3

7. Complete the following hydrocarbon reactions:

     a.         H
                 |

           H – C – H   +   I₂
                 |

                 H

     b.   H    H
            |    |

            C = C   +   Br₂

            |    |

            H   H

Solutions:

1.  CH₃ – CH – CH – CH₂ – CH₂ – CH₂
                |      |
              CH₃   CH₂

                        |

                       CH₃
naming starts from the left (1-2-3-4-5-6 :: hexane)
you have 2-methyl, and 3-ethyl
∴ 3-ethyl-2-methylhexane (e comes before m)

2.     CH₃ – C = C – CH₃
                 |     |
                CH₃ CH₂
                        |
                       CH₃
break down C₂H₅ into CH₂ and CH₃
naming starts from the left CH₃ - C = C, then down to CH₂ - CH₃ to make it the longest chain (2-pentene). *2 -> double bond   *ene -> alkene
you have 2-methyl and 3-methyl which becomes 2,3-dimethyl.
∴ 2,3-dimethyl-2-pentene.

3. CH₃ – CH₂ – C ≡ C – CH – CH₂ – CH₃
                                           |
                                         CH₃
naming starts from the left
∴ 5-methyl-3-heptyne

4. CH₃ – CH – CH – CH – CH₂ – CH₂ – CH₃
               |     |      |
            CH₃  CH₂ CH₃
                      |
                     CH₃
(naming starts from the left)
For those of you who are still confused on how to write the chains, I start by writing a line of C's as long as main chain is (in this case, heptane = 7). Then I add the branches: ethyl to number 3, and methyl to numbers 2 and 4.

5. Chain isomer: a and b, a and c
     Position isomer: b and c

6. b

7. a.              H

                     |

           H – I – C – I – H
                     |

                     H

   b.          H   H

                 |   |

          Br – C – C – Br

                 |   |

                 H   H