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CHEM 111 Chapter Notes - Chapter 13: Cycloalkene, Elastomer, AlanineExam


Department
Chemistry
Course Code
CHEM 111
Professor
Prof
Study Guide
Final

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55
CHAPTER 13 | Organic Chemistry: Fuels, Pharmaceuticals, and Materials
13.1. Collect and Organize
Given the carbon-skeleton structures in Figure P13.1 of four hydrocarbons, we are to determine the degrees of
unsaturation present in each.
Analyze
An unsaturated hydrocarbon contains one or more carbon–carbon double or carbon–carbon triple bonds. These
compounds have less than the maximum amount of hydrogen for each carbon atom. A double bond has one
degree of unsaturation and a triple bond has two degrees of unsaturation.
Solve
(a) This structure has one double bond. It has one degree of unsaturation.
(b) This structure has two double bonds. It has two degrees of unsaturation.
(c) This structure has neither double nor triple bonds. It is a saturated hydrocarbon with no degrees of
unsaturation.
(d) This structure has one double and one triple bond. It has three degrees of unsaturation.
Think about It
Because the structure in (d) has three degrees of unsaturation, it will combine with 3 molecules of hydrogen
(H2) to form a saturated hydrocarbon.
13.2. Collect and Organize
Of the four structures shown in Figure P13.2, we are to identify the ones that are structural isomers of each
other.
Analyze
Structural isomers have the same chemical formula but different arrangements of the atoms.
Solve
Structure a has the chemical formula CH3CH2CH2CH(CH3)2or C6H14.
Structure b has the chemical formula CH3CH2CH(CH3)CH2CH3or C6H14.
Structure c has the chemical formula (CH3)2CHCH(CH3)2or C6H14.
Structure d has the chemical formula (CH3)2CHCH2CH2CH3or C6H14.
These are all potentially isomers of each other, but we have to check to see if any of these are indeed line
structures of the same molecule. Notice that a and d are the same if we rotate one of them by 180˚ on the page.
Therefore, structures a, b, and c are structural isomers.
Think about It
Although structural isomers have the same chemical formula, they have different chemical and physical
properties.
13.3. Collect and Organize
From the structures of fragrant oils in Figure P13.3, we are to identify those that contain the alkene functional
group.
Analyze
An alkene functional group is a carbon–carbon double bond.
Solve
Both pine oil and oil of celery contain a C C bond and so are classified as alkenes.

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56 | Chapter 13
Think about It
Camphor is not an alkene but it does have a C O double bond. This functional group is a ketone.
13.4. Collect and Organize
Of the molecules acrylonitrile, capillin, and pargyline (Figure P13.4), we are to determine which one does not
contain an alkyne functional group.
Analyze
An alkyne has a carbon–carbon triple bond with sp-hybridized carbon atoms.
Solve
Both capillin and pargyline have the C C functional group (capillin has two of these groups!), but
acrylonitrile does not.
Think about It
The C N group in acrylonitrile is the nitrile functional group and is distinct from the alkyne group.
13.5. Collect and Organize
Of the four hydrocarbons shown in Figure P13.5, we are to identify those that are aromatic.
Analyze
Aromatic compounds have planar, hexagonal rings of 6 sp2-hybridized carbon atoms with alternating single
and double bonds.
Solve
Compounds b and d are aromatic.
Think about It
Aromatic compounds have a special stability due to resonance.
13.6. Collect and Organize
Of the molecules benzyl acetate, carvone, and cinnamaldehyde (Figure P13.6), we are to determine which ones
contain an aromatic ring in their structures.
Analyze
An aromatic ring is a planar, six-membered ring composed of sp2-hybridized carbon atoms with alternating
single and double bonds.
Solve
To find the aromatic rings, we focus on the hexagonal rings in each molecule. Carvone’s six-membered ring
has only one double bond, not the requisite three double bonds plus three single bonds. Benzyl acetate and
cinnamaldehyde do have six-membered rings with sp2-hybridized carbon atoms and, therefore, they both
contain an aromatic ring.
Think about It
Aromaticity can be present in smaller and larger ring systems as well, as long as the number of electrons in the
p orbitals (or
S
system) is equal to 4n + 2 where n = 1, 2, 3, 4, etc.
13.7. Collect and Organize
For the molecules in Problem 13.6 we are asked to identify the other functional groups aside from the aromatic
rings.

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Organic Chemistry: Fuels, Pharmaceuticals, and Materials |57
Analyze
The other typical functional groups include alkenes (C C), alkynes (C C), alcohols (ROH), ethers
(ROR), aldehydes [R(C O)H], ketones [R(C O)R'], carboxylic acids [R(C O)OH], esters
[R(C O)OR'], and amides [R(C O)NH2].
Solve
Benzyl acetate contains an ester group. Carvone contains two alkene groups and a ketone group.
Cinnamaldehyde contains an alkene and an aldehyde group.
Think about It
The wide variety of functional groups possible in organic compounds means that there are many combinations
of functional groups in organic chemistry. This gives rise to a seemingly endless array of different substances
with potentially useful properties.
13.8. Collect and Organize
For the three polymers shown in Figure P13.8, we can examine their molecular structures to determine which
has the strongest intermolecular forces.
Analyze
As chlorine atoms are placed on the polymer backbone the polarity of the backbone increases, so dipole–dipole
forces increase.
Solve
(c) Poly(vinylidene chloride) has the strongest intermolecular forces.
Think about It
Adding Cl atoms to the backbone also increases the strength of the weaker dispersion forces between the
polymer chains.
13.9. Collect and Organize
From the structure of dihydroxydimethylsilane (Figure P13.9) we are to draw the condensed structure for the
repeating monomeric unit in Silly Putty.
Analyze
The condensation reaction of dihydroxydimethylsilane combines the monomers of Si(CH3)2(OH)2 to create a
larger molecule, losing water as a by-product. The –OH groups on the monomer will combine to produce the
OSiO– linkage for the polymer backbone.
Solve
Si OH
HO
CH3
CH3
Si OHHO
CH3
CH3
+Si OHO
CH3
CH3
Si OH
CH3
CH3
Continuing this reaction produces a long-chain polymer with the condensed structure
Think about It
These types of siloxane polymers have found uses in soft contact lenses, oils, and greases.
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