1. Sample Problem 12.1 Properties of Organic Compounds
Indicate whether the following properties are more typical of organic or inorganic compounds:
a. is not soluble in water
b. has a high melting point
c. burns in air
Solution
a. Many organic compounds are not soluble in water.
b. Inorganic compounds are more likely to have high melting points.
c. Organic compounds are more likely to be flammable.
Study Check 12.1
What elements are always found in organic compounds?
Answer
C and H

2. Sample Problem 12.2 Drawing Expanded, Condensed, and Line-Angle Structural Formulas for an Alkane
Draw the expanded, condensed, and line-angle structural formulas for pentane.
Solution
Step 1 Draw the carbon chain. A molecule of pentane has five carbon atoms in a continuous chain.
Step 2 Draw the expanded structural formula by adding the hydrogen atoms using single bonds to each of the carbon atoms.
Step 3 Draw the condensed structural formula by combining the H atoms with each C atom.

3. Sample Problem 12.2 Drawing Expanded, Condensed, and Line-Angle Structural Formulas for an Alkane
Continued
Step 4 Draw the line-angle structural formula as a zigzag line in which the ends and corners represent C atoms.
Study Check 12.2
Draw the condensed structural formula and give the name for the following line-angle structural formula:
Answer
CH3—CH2—CH2—CH2—CH2—CH2—CH3 heptane

4. Sample Problem 12.3 Naming Alkanes and Cycloalkanes
Give the IUPAC name for each of the following:
a. b.
Solution
a. A chain with eight carbon atoms is octane.
b. The ring of six carbon atoms is named cyclohexane.
Study Check 12.3
What is the IUPAC name of the following compound?
Answer
cyclobutane

5. Sample Problem 12.4 Structural Isomers
Identify each pair of formulas as structural isomers or the same molecule.
a b.
Solution
a. When we add up the number of C atoms and H atoms, they give the same molecular formula C4H10. The condensed structural formula on the left has a chain of four C atoms. Even though the —CH3 ends are drawn up, they are part of the four-carbon chain. The condensed structural formula on the right also has a four-carbon chain even though one —CH3 end is drawn down. Thus both condensed structural formulas represent the same molecule and are not structural isomers.
b. When we add up the number of C atoms and H atoms, they give the same molecular formula C6H14. The line-angle structural formula on the left has a five-carbon chain with a —CH3 substituent on the second carbon of the chain. The line-angle structural formula on the right has a four-carbon chain with two —CH3 substituents, one bonded to the second carbon and one bonded to the third carbon. Thus there is a different order of bonding of atoms, which represents structural isomers.

6. Sample Problem 12.4 Structural Isomers
Continued
Study Check 12.4
Why does the following formula represent a different structural isomer of the molecules in Sample Problem 12.4, part b?
Answer
This formula represents a different structural isomer because the —CH3 substituent is on the third carbon of the chain.

7. Sample Problem 12.5 Writing IUPAC Names for Alkanes with Substituents
Give the IUPAC name for the following alkane:
Solution
Step 1 Write the alkane name for the longest chain of carbon atoms.

8. Sample Problem 12.5 Writing IUPAC Names for Alkanes with Substituents
Continued
Step 2 Number the carbon atoms starting from the end nearer a substituent. Carbon 1 is the carbon atom nearer a methyl group, —CH3, on the left.
Step 3 Give the location and name for each substituent (alphabetical order) as a prefix to the name of the main chain. The substituents, which are bromo and methyl groups, are listed in alphabetical order (bromo first, then methyl). A hyphen is placed between the number on the carbon chain and the substituent name. When there are two or more of the same substituent, a prefix (di, tri, tetra) is used in front of the name. However, these prefixes are not used to determine the alphabetical order of the substituents. Then commas are used to separate the numbers for the locations of the substituents.

9. Sample Problem 12.5 Writing IUPAC Names for Alkanes with Substituents
Continued
Study Check 12.5
Give the IUPAC name for the following compound:
Answer
4-isopropylheptane

10. Sample Problem 12.6 Drawing Condensed Structures from IUPAC Names
Draw the condensed and line-angle structural formulas for 2,3-dimethylbutane.
Solution
Step 1 Draw the main chain of carbon atoms. For butane, we draw a chain or a zigzag line of four carbon atoms.
Step 2 Number the chain and place the substituents on the carbons indicated by the numbers. The first part of the name indicates two methyl groups —CH3: one on carbon 2 and one on carbon 3.

11. Sample Problem 12.6 Drawing Condensed Structures from IUPAC Names
Continued
Step 3 For the condensed structural formula, add the correct number of hydrogen atoms to give four bonds to each C atom.
Study Check 12.6
Draw the condensed and line-angle structural formulas for 2-bromo-3-ethyl-4-methylpentane.
Answer

12. Sample Problem 12.7 Naming Alkenes and Alkynes
Write the IUPAC name for each of the following: a.
Solution a.
Step 1 Name the longest carbon chain that contains the double bond. There are five carbon atoms in the longest carbon chain containing the double bond. Replace the ane in the corresponding alkane name with ene to give pentene.

13. Sample Problem 12.7 Naming Alkenes and Alkynes
Continued
Step 2 Number the carbon chain starting from the end nearer the double bond. Place the number of the first carbon in the double bond in front of the alkene name.
Alkenes or alkynes with two or three carbons do not need numbers. For example, the double bond in ethene or propene must be between carbon 1 and carbon 2.
Step 3 Give the location and name for each substituent (alphabetical order) as a prefix to the alkene name. The methyl group is located on carbon 4.

14. Sample Problem 12.7 Naming Alkenes and Alkynes
Continued b.
Step 1 Name the longest carbon chain that contains the triple bond. There are six carbon atoms in the longest chain containing the triple bond. Replace the ane in the corresponding alkane name with yne to give hexyne.
Step 2 Number the carbon chain starting from the end nearer the triple bond. Place the number of the first carbon in the triple bond in front of the alkyne name.
Step 3 Give the location and name for each substituent (alphabetical order) as a prefix to the alkyne name. There are no substituents in this formula.

15. Sample Problem 12.7 Naming Alkenes and Alkynes
Continued
Study Check 12.7
Name each of the following:
a. b.
Answer
a. 2-pentyne b. 2-chloro-1-hexene

16. Sample Problem 12.8 Identifying Cis–Trans Isomers
Identify each of the following as the cis or trans isomer and give its name:
a. b.
Solution
a. This is a cis isomer because the two halogen atoms attached to the carbon atoms of the double bond are on the same side. The name of the two-carbon alkene, starting with the bromo group on carbon 1, is cis-1-bromo-2-chloroethene.
b. This is a trans isomer because the two alkyl groups attached to the carbon atoms of the double bond are on opposite sides of the double bond. This isomer of the five-carbon alkene, 2-pentene, is named trans-2-pentene.
Study Check 12.8
Give the name for the following compound, including cis or trans:
Answer
trans-3-hexene

17. Sample Problem 12.9 Writing Equations for Hydrogenation
Draw the structural formula for the product of each of the following hydrogenation reactions:
a. b.
Solution
In an addition reaction, hydrogen adds to the double bond to give an alkane.
a. b.
Study Check 12.9
Draw the condensed structural formula for the product of the hydrogenation of 2-methyl-1-butene, using a platinum catalyst.
Answer

18. Sample Problem 12.10 Hydration
Draw the condensed structural formula for the product that forms in the following hydration reaction:
Solution
In an addition reaction, hydrogen adds to the double bond to give an alkane.
For an asymmetrical alkene, the H— from water (H —OH) adds to the carbon with the greater number of hydrogen atoms, and the —OH bonds to the carbon with fewer H atoms.

19. Sample Problem 12.10 Hydration
Continued
Study Check 12.10
Draw the condensed structural formula for the product obtained by the hydration of 2-methyl-2-butene.
Answer

20. Sample Problem 12.11 Polymers
A firefighter/EMT arrives at a home where a premature baby has been delivered. To prevent hypothermia during transport to the neonatal facility, she wraps the baby in cling wrap. Draw and name the monomer unit and draw a portion of the polymer formed from three monomer units for cling wrap, which is polydichloroethylene (ethene).
Solution
Study Check 12.11
Draw the condensed structural formula for the monomer used in the manufacturing of PVC.
Answer

21. Sample Problem 12.12 Naming Aromatic Compounds
Give the IUPAC name for the following:
Solution
4-bromo-3-chlorotoluene
Study Check 12.12
Give the IUPAC and common name for the following compound:
Answer
1,3-diethylbenzene (m-diethylbenzene)