2.E: Unsaturated and Aromatic Hydrocarbons (Exercises)

Additional Exercises

1. Classify each compound as saturated or unsaturated.

   1. 
   2. CH₃C≡CCH₃

2. Classify each compound as saturated or unsaturated.

   1. 
   2. 

3. Give the molecular formula for each compound.

   1. 
   2. 

4. When three isomeric pentenes—X, Y, and Z—are hydrogenated, all three form 2-methylbutane. The addition of Cl₂ to Y gives 1,2-dichloro-3-methylbutane, and the addition of Cl₂ to Z gives 1,2-dichloro-2-methylbutane. Draw the original structures for X, Y, and Z.

5. Pentane and 1-pentene are both colorless, low-boiling liquids. Describe a simple test that distinguishes the two compounds. Indicate what you would observe.

6. Draw and name all the alkene cis-trans isomers corresponding to the molecular formula C₅H₁₀. (Hint: there are only two.)

7. The complete combustion of benzene forms carbon dioxide and water:

   C₆H₆ + O₂ → CO₂ + H₂O

   Balance the equation. What mass, in grams, of carbon dioxide is formed by the complete combustion of 39.0 g of benzene?

8. Describe a physiological effect of some PAHs.

9. What are some of the hazards associated with the use of benzene?

10. What is wrong with each name? Draw the structure and give the correct name for each compound.

    1. 2-methyl-4-heptene
    2. 2-ethyl-2-hexene
    3. 2,2-dimethyl-3-pentene

11. What is wrong with each name?

    1. 2-bromobenzene
    2. 3,3-dichlorotoluene

12. Following are line-angle formulas for three compounds. Draw the condensed structure and give the name for each.

    1. 
    2. 
    3. 

13. Following are ball-and-stick molecular models for three compounds (blue balls represent H atoms; red balls are C atoms). Write the condensed structural formula and give the name for each.

    1. 
    2. 
    3. 

Answers

1.  

   1. unsaturated
   2. unsaturated

 

3.  

   1. C₆H₁₀
   2. C₄H₈

 

5. Add bromine solution (reddish-brown) to each. Pentane will not react, and the reddish-brown color persists; 1-pentene will react, leaving a colorless solution.

 

7. 2C₆H₆ + 15O₂ → 12CO₂ + 6H₂O; 132 g

 

9. carcinogenic, flammable

 

11.  

    1. number not needed
    2. can’t have two groups on one carbon atom on a benzene ring

 

 

13.  

    1. CH₃CH=CHCH₂CH₂CH₃; 2-hexene
    2. 
    3.