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Chapter 24—Organic Chemistry II: Shapes, Selected Reactions, and Biopolymers


MULTIPLE CHOICE
1. Which of the following is a pair of constitutional (or structural) isomers?
a. 1-bromobutane and 1-bromopentane
b. benzene and cyclohexane
c. 1-bromobutane and 2-bromobutane
d. ethanol and methanol
e. cis-2-butene and trans-2-butene
ANS: C
OBJ: Identify the pair of structural isomers given the compound names.
TOP: Constitutional Isomers
2. Below are five pairs of constitutional isomers. One pair has different functional groups.
Which pair has the different functional groups?
a.




b. CH2=CHCH=CHCH3 and CH2=CHCH2CH=CH2
c. CH3CH2OH and CH3OCH3
d.


CH3CH2CH2CH3 and
e.


CH3CH2CH2Br and
ANS: C
OBJ: Identify the structural isomers with different functional groups given the structural
formulas.
TOP: Constitutional Isomers
3. Which of the following is a constitutional isomer of 2-pentanone that has a different
functional group?
a. 3-pentanone
b. 2-butanone
c. 2-pentanal
d. pentanal
e. 2-pentanol
ANS: D
OBJ: Identify the name of a constitutional isomer given the name of one of the isomers.
TOP: Constitutional Isomers

,4. Which of the following compounds does not have a constitutional isomer with a different
functional group?
a. propanone (acetone)
b. 3-pentanone
c. ethanol
d. dimethyl ether
e. ethanal (acetaldehyde)
ANS: E
OBJ: Identify the name of the compound that does not have a constitutional isomer with a
different functional group.
TOP: Constitutional Isomers
5. Which of the following statements about constitutional isomers is false?
a. Constitutional isomers have the same molecular formula.
b. Constitutional isomers have different structural formulas.
c. Constitutional isomers always have the same boiling point.
d. Constitutional isomers differ in the order in which their atoms are bonded.
e. Sometimes constitutional isomers have different functional groups present.
ANS: C
OBJ: Identify the incorrect description of constitutional isomers.
TOP: Constitutional Isomers
6. What are the two types of stereoisomers?
a. geometrical and optical
b. optical and positional
c. geometrical and positional
d. geometrical and functional group
e. chiral and optical
ANS: A
OBJ: Identify the two types of stereoisomers.
TOP: Stereoisomers
7. Which of the following is a chiral molecule?
a. CH3CBr2Cl
b. CBrCl2I
c. CH3CHBrCH2CH3
d. (CH3)2CHCl
e. CH2BrI
ANS: C
OBJ: Identify the chiral molecule given condensed structural formulas.
TOP: Stereoisomers
8. Does the following compound have any asymmetric carbons? If so, which one (or ones)?

, a. 1
b. 3
c. 2
d. 1 and 2
e. 1, 2, and 3
ANS: B
OBJ: Identify the asymmetric carbons given the structural formula.
TOP: Stereoisomers
9. Which of the following compounds can have geometrical isomers?
a. 1,1-dichloroethene
b. 2,3-dichloropropene
c. 1,2-dichloropropane
d. 1,2-dichlorocyclobutane
e. 3-ethyl-3-hexene
ANS: D
OBJ: Identify the name of the compound which has geometrical isomers.
TOP: Stereoisomers
10. Which statement concerning optical isomers is false?
a. Optical isomers have identical physical properties, except for their interaction with
polarized light.
b. A racemic mixture is a single sample containing equal amounts of the two optical isomers
of a compound.
c. Each optical isomer of a compound rotates polarized light by equal amounts but in
opposite directions.
d. A racemic mixture does not rotate the plane of polarized light because the effects of the
two isomers exactly cancel.
e. Optical isomers react exactly the same with any particular compound.
ANS: E
OBJ: Identify the incorrect description of optical isomers.
TOP: Stereoisomers
11. Which one of the following statements about the isomers of butane is false?
a. Butane has staggered and eclipsed conformational isomers.
b. Butane and isobutane are geometric isomers.
c. The staggered conformation of butane is more stable than the eclipsed conformation.
d. Staggered and eclipsed conformations are not constitutional isomers.
e. Butane and isobutane do not have optical isomers.
ANS: B
OBJ: Identify the incorrect description of isomers of butane.
TOP: Stereoisomers

, 12. Cyclohexane can assume two different geometries, chair and twist boat. What is the
relationship between these two forms?
a. optical isomers
b. geometric isomers
c. structural isomers
d. conformational isomers
e. constitutional isomers
ANS: D
OBJ: Identify an example of conformational isomers.
TOP: Conformations
13. Which of the following statements concerning isomers and conformations is false?
a. Conformations of a compound differ in the extent of rotation about one or more single
bonds.
b. A staggered conformation is slightly more stable than the eclipsed conformation.
c. At least one chemical bond must be broken and reformed to convert one isomer into
another.
d. In the staggered conformation, there is less repulsive interaction between H atoms on
adjacent C atoms.
e. The chair and twist boat forms are two isomers of cyclohexane.
ANS: E
OBJ: Identify the incorrect description of isomers and conformations.
TOP: Conformations
14. Conversion of one form of a molecule into another form by rotation about a C C single bond
occurs very rapidly at room temperature. These different forms of the molecule are known as
____.
a. constitutional isomers
b. optical isomers
c. geometric isomers
d. conformations
e. enantiomers
ANS: D
OBJ: Recognize the definition of conformations.
TOP: Conformations
15. What are the products of the reaction of ethanol and metallic sodium?
a. CH3CH2CH2CH2 and NaOH
b. CH3CH2OCH2CH3, NaH, and NaOH
c. CH3CH2O−, Na+, and H2
d. CH3CH3 and NaOH
e. CH3O−, Na+, and H2
ANS: C
OBJ: Identify the products given the reactants.
TOP: Reactions of Brønsted-Lowry Acids and Bases
16. Which of the following classes of organic compounds has the greatest acid strength?
a. phenols
b. alcohols
c. carboxylic acids
d. amines
e. substituted ammonium ions