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Chapter 11
Organic Chemistry
Organic chemistry is the study of carbon compounds excluding CO, CO2, CS2,
bicarbonates, carbonates and cyanides. Upon completion of this chapter, your students
should be able to:
1.
2.
3.
4.
5.
6.
7.
8.
Write the general formula for and provide examples for each of the following
organic functional groups
a. alkane
b. alkene
c. alkyne
d. cycloalkane
e. aromatic
f. alcohol
g. ether
h. aldehyde
i. ketone
j. carboxylic acid
k. ester
l. amine
Use IUPAC rules to name
a. alkanes
b. alkenes
c. alkynes
d. aromatics
Draw and name all of the possible isomers given the chemical formula of an
alkane.
Use the following groups in naming organic compounds
a. methyl
b. ethyl
c. n-propyl
d. n-butyl
e. isopropyl
f. t-butyl
g. amino
h. fluoro
i. chloro
j. bromo
k. iodo
l. nitro
m. vinyl
Define what a free radical is and show by a chemical equation the steps in which
chlorine can be used to generate free radicals.
Give an example of a substituted alkane that is optically active.
Use cis and trans to specify geometric isomers in alkenes.
Use the terms olefin, unsaturated and addition reaction to describe the properties
and reactions of alkenes.
9.
Justify polarity and expected boiling point trends for geometric isomers.
10.
Describe the concept of resonance in aromatic compounds.
11.
Suggest why aromatic compounds under go substitution reactions rather then
addition reactions.
12.
Give the chemical formulas for
a. wood alcohol (methanol)
b. ethyl alcohol (ethanol)
c. rubbing alcohol (2-propanol or isopropanol)
d. ethylene glycol
13.
State how a condensation reaction is characterized.
14.
Define carbonyl and show by example the difference in chemical structures of
aldehyde and ketone.
15.
Write the chemical structure for acetic acid, the acid found in vinegar.
16.
Write a chemical equation that demonstrates saponification of an ester.
17.
Describe what is meant by octane number of gasoline and give two examples of
antiknocking agents that have been used (tetraethyllead and MTBE)
Section 24.1
Classes of Organic Compounds
Your author suggests that over 13 million organic compounds are known. In order
for your students to begin to understand this huge field, it is important that they become
familiar with several of the major functional groups. The chemical behavior of most
organic compounds is determined by the functional groups that are present. In addition,
the functional groups dictate the correct name of the compound.
Section 24.2
Aliphatic Hydrocarbons
Hydrocarbons, organic compounds containing only carbon and hydrogen, are
classified as aliphatic or aromatic. Aromatic compounds contain the benzene ring. The
aliphatics are the alkanes, alkenes, cycloalkanes, and alkynes.
The recommended nomenclature for organic compounds is a series of prefixes and
suffixes joined together. The prefix meth- refers to one carbon, eth- to two carbons,
prop- to three carbons, etc. The suffix -ane suggests only single carbon bonds, -ene
carbon-carbon double bonds and -yne carbon-carbon triple bonds. It may be easier for
your students to understand the numbering system for organic compounds if you use
halogens on various positions of straight-chain molecules before you begin branching.
For example
BrCH2CH2CH2CH2CH3
CH3CHCH2CH2CH3
1-bromopentane
2-bromopentane
Br
CH3CH2CHCH2CH3
Br
3-bromopentane
BrCH2CHCH2CH2CH3
1,2-dibromopentane
Br
Br
3,3-dibromopentane
CH3CH2CCH2CH3
Br
Once your students are comfortable with placing bromine on various positions, then
combine Br and Cℓ. Finally, after they have mastered that, begin substituting methyl or
ethyl groups. Your students should understand that a straight-chain alkane is not really
straight in nature. An analogy is that a piece of string wadded into a ball would be
considered a straight chain because it has no branches.
One can demonstrate the halogenation of alkanes by using a "black light". The
procedure is to add a few drops of bromine dissolved in carbon tetrachloride to two test
tubes containing an alkane such as hexane. The solutions will be an amber color. If one of
the tubes is placed under the ultraviolet light for about fifteen minutes, the amber color of
the bromine solution will dissipate indicating that the Br2 has reacted with the alkane. The
solution that is not exposed to ultraviolet light will remain amber-colored.
We encountered optical isomerism in our study of coordination compounds. It is easy
to show, by using molecular models, optical isomers in organic chemistry. To do this,
assemble two CHFCℓ Br models. These two models need to be identical. Now interchange
any two atoms on one of the models. The result is a nonsuperimposable mirror image of
the first model. These two compounds would be optical isomers and would rotate planepolarized light differently.
You may wish to point out to your students that cycloalkanes have the same general
formula as alkenes, CnH2n; however, they have considerably different reactivities. An easy
demonstration is to add a few drops of aqueous potassium permanganate to two or three
milliters of cyclohexane and to hexene. The cyclohexane will not react, but the double
bond in the hexene will react with the potassium permanganate to convert the purple
solution to a brown precipitate of manganese dioxide. This same demonstration can be
used to show that toluene (methylbenzene) does not contain carbon-carbon double bonds
as is found in hexene. The toluene will behave similarly to cyclohexane and not react with
potassium permanganate.
Section 24.3
Aromatic Hydrocarbons
Your students have seen benzene, the simplest aromatic compound, previously when we
discussed resonance and delocalized molecular orbitals. It has been shown earlier that
aromatic compounds do not usually react via addition reactions as those compounds
containing carbon-carbon double or triple bonds do, rather aromatic compounds prefer
substitution reactions. As your author points out, many of the polycyclic aromatic
compounds are carcinogens thus must be handled with special care.
Section 24.4
Chemistry of the Functional Groups
Your author suggests that ethanol can be converted to acetic acid using acidified
dichromate. This is a very visual reaction in that the orange dichromate solution is
converted to a forest-green solution upon reaction with ethanol. This is the same principle
that alcohol breathalizer tests are based on. It should be noted that the suffix for alcohol
is -ol.
When ethanol is oxidized, it can form ethanal (acetaldehyde) or acetic acid. The
suffix for aldehyde is -al. The accepted suffix for ketone is -one. A very common ketone
found in industry is methylethylketone (MEK). It is used as a solvent in a variety of
applications including solvents for paints and coatings.