Download Ch 12- 13 - Phillips Scientific Methods

Alkenes, Alkynes, and Aromatic
Compounds
(Chapter 12 and 13)
Alkenes and Alkynes

Unsaturated



contain carbon-carbon double and triple bond to
which more hydrogen atoms can be added.
Alkenes: carbon-carbon double bonds
Alkynes: carbon-carbon triple bonds.
Naming Alkenes and Alkynes
IUPAC nomenclature rules for alkenes
and alkynes are similar to alkanes.
 Step 1. Name the parent compound.
Find the longest chain containing the
double or triple bond, and name the
parent compound by adding the suffix
–ene or –yne to the name of the main
chain.

Step 2: Number the carbon atoms in the
parent chain, beginning at the end nearest to
the double or triple bond. If the multiple bond is
an equal distance from both ends, begin
numbering at the end nearer the first branch
point. The number indicates which carbon the
multiple bond is AFTER. (i.e. between 2 and 3 is
2-)
 Step 3: Assign numbers and names to the
branching substituents, and list the substituents
alphabetically.
Use commas to separate
numbers, and hyphens to separate words from
numbers.

Step 4. Indicate the position of the
multiple-bond carbon. If more than one
multiple bond is present, identify the
position of each multiple bond and use
the appropriate ending diene, triene,
tetraene, and so forth.
 Step 5. Assemble the name.

Naming Alkenes and Alkynes
When the carbon chain has 4 or more C atoms,
number the chain to give the lowest number to
the double or triple bond.
1
2 3 4
CH2=CHCH2CH3
1-butene
but-1-ene
CH3CH=CHCH3
2-butene
but-2-ene
2-butyne
but-2-yne

CH3C CCH3
Assigning Priority




Alkenes and alkynes are considered to have
equal priority
In a molecule with both a double and a triple
bond, whichever is closer to the end of the chain
determines the direction of numbering.
In the case where each would have the same
position number, the double bond takes the
lower number.
In the name, “ene” comes before “yne” because
of alphabetization.
Learning Check
Write the IUPAC name for each of the
following unsaturated compounds:
A.
CH3CH2CCCH3
CH3
CH3
B.
CH3C=CHCH3
C.
Answers:



2-pentyne
2-methyl-2-butene
3-methylcyclopentene (doesn’t need a “1”
before cyclopentene, because the double
bond must be in position 1)
Dienes, Trienes, Polyenes


Alkenes with more than one double bond are
named as alkadienes, alkatrienes, etc.
Compounds with several double bonds are
referred to more generally as polyenes
(Greek: poly, many)
CH2 =CHCH2 CH=CH2
1,4-Pentadien e
CH3
CH2 =CCH=CH2
2-Meth yl-1,3-b utadiene
(Isoprene)
1,3-Cyclopentad iene
Cis-Trans Isomerism
Methane is tetrahedral, ethylene is planar,
and acetylene is linear as predicted by the
VSEPR theory discussed earlier.

The
two carbons and the four atoms that make
up the double bond in alkenes lie in a plane.
Unlike carbon-carbon single bonds, rotation
around carbon-carbon double bond is not
possible. As a result, a new kind of isomerism is
possible for alkenes. Because rotation is not
possible around carbon-carbon double bonds,
there are two different kinds of 2-butenes. These
are known as cis-trans isomers.
Pick
up a kit.
butene
Build cis-2-butene and trans-2Chapter One
12
Cis and Trans Isomers


Double bond is fixed
Cis/trans Isomers are possible
CH3
CH3
CH = CH
cis
CH3
CH = CH
trans
CH3
Cis- and Trans- terminology
If alkenes have two different substituents at
each end of the C=C then they can exist as
stereoisomers because there is restricted
rotation of the double bond.
For example:



all terminal alkenes (begin or end with a C=CH2)
do not exist as cis- and trans- isomers.
all 1,1-symmetrically disubstituted alkenes (has
a C=CR2 unit) do not exist as cis- and trans-.
alkenes with the R-CH=CH-R unit can exist as
cis- and trans- isomers.

In cis isomers, two methyl groups are
close together on the same side of the
double bond.


In trans isomer, two methyl groups are far
apart on opposite side of the double bond.
Both cis and trans isomers have the same
formula and connections between the atoms
but have different three dimensional structures
because the way the groups are attached to the
carbons.

Cis-trans isomerism occurs in an alkene
whenever each double bond carbon is bonded
to two different substituent groups. Cis-trans
isomerism is not possible if one of the double
bond carbons is attached to two identical
groups.
Cis / Trans


Another way of “viewing” this: The
orientation of the Carbon atoms of the
parent chain determines whether an
alkene is cis or trans.
Which is cis? trans?
Cis/trans in alkadienes, trienes


See exp. 12.4.
To determine the # of stereoisomers, use
the formula 2n
Applying Organic to
Biochemistry: Unsaturated
Fatty Acids


Fatty acids in vegetable oils are omega-6 acids
(the first double bond occurs at carbon 6
counting from the methyl group)
A common omega-6 acid is linoleic acid
CH3CH2CH2CH2CH2CH=CHCH2CH=CH(CH2)7COOH
6
linoleic acid, a fatty acid
Trans Fats


In vegetable oils, the unsaturated fats usually
contain cis double bonds.
During hydrogenation, some cis double bonds
are converted to trans double bonds (more
linear) causing a change in the fatty acid
structure

The more linear the chains, the closer together
and more “solid”. “Clogs” arteries
Triglycerides




Glycerol + 3 fatty acids = Triglyceride
We will do the reaction for how they are
formed in next unit (esterfication)
If an unsaturated fatty acid has multiple
bonds (polyunsaturated), enzymes in the
body can attach polar proteins and as a
result create HDL (high density
lipoprotein). Much better than LDL! (which
clogs arteries)
Polyunsaturated (best fat)
>monounsaturated > saturated
Trans Fats



In the US, it is estimated that 2-4% of our
total Calories is in the form of trans fatty
acid.
trans fatty acids behave like saturated fatty
acids in the body.
Many studies report that trans fatty acids
raise LDL-cholesterol. Some studies also
report that trans fatty acid lower HDLcholesterol
Fats and Atheroschlerosis


Inuit people of Alaska have a high fat diet
and high blood cholesterol levels, but a
very low occurrence of atherosclerosis and
heart attacks.
Fat in the Intuit diet was primarily from
fish such as salmon, tuna and herring
rather than from land animals (as in the
American diet).
Omega-3 Fatty Acids


Fatty acids in the fish oils are mostly the
omega-3 type (first double bond occurs at the
third carbon counting from the methyl group).
linolenic acid 18 carbon atoms
CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH


eicosapentaenoic acid (EPA) 20 carbon atoms
CH3CH2(CH=CHCH2)5(CH2)2COOH
Atherosclerosis




Plaques of cholesterol adhere to the walls of
the blood vessels
Blood pressure rises as blood squeezes through
smaller blood vessels
Blood clots may form
Omega-3 fatty acids decrease the “sticking” of
blood platelets (fewer blood clots)
Properties of Alkenes and
Alkynes
Nonpolar, insoluble in water, soluble in
nonpolar organic solvents.

Less dense than water as a result floats
on water.
London (van der Waals) forces between
molecules (weak)

Flammable

Nontoxic

Alkenes display cis-trans isomerism
whereas alkynes do not.

Both alkenes and alkynes are chemically
reactive.

27
Terpenes (useful for Herbfest)

Terpene: a compound whose carbon skeleton
can be divided into five-carbon units identical
with the carbon skeleton of isoprene
CH3
CH2 =C-CH=CH2
2-Methyl-1,3-b utadien e
(Is op ren e)

head
tail
C
1 2
3
4
C-C-C-C
Isoprene u nit
Example of an important principle of the
molecular logic of living systems


Small subunits are combined (and modified) to
make larger molecules (polymerization, discussed
later)
In nature, reactions carried out by enzymes
(catalysts)
Examples of Terpenes
head
OH
formin g th is
bond makes
the ring
OH
tail
Myrcene
(Bay oil)
Geraniol
(Ros e and
other flow ers)
Limonen e
(Lemon
an d oran ge)
Menth ol
(Peppermint)
OH
OH
Farnes ol
(Lily-of-th e valley)
Vitamin A (retinol)
Kinds of Organic Reactions


Addition reactions: A substance add to the
multiple bond of an unsaturated reactant to
yield a saturated product that has only single
bonds. 4 types- hydrogenation, halogenation,
reaction with acids, hydration. See p. 363-370
Elimination reaction: In which a saturated
reactant yields an unsaturated product by
losing groups from two adjacent carbons. We
will do these in the next unit (alcohols to
alkenes). Not on this test
Chapter One
30



Substitution reaction: In which an atom or
group of atoms in a molecule is replaced by
another atom or group of atoms. Ex- alkanes or
aromatics (benzene)
Rearrangement reaction: In which a
molecule undergoes bond reorganization to
yield an isomer. Not on this test
Oxidation /Reduction: See next slide
Chapter One
31
Oxidation/Reduction




Oxidation-The loss of electrons (LEO or OIL)
and /or hydrogens by a compound. (Can also be
the gain of oxygen)
Reduction- The gain of e- (GER or RIG) and or
H’s by a compound. (Can also be the loss of O)
The more saturated a hydrocarbon is, the more
reduced it is. Alkanes are the most reduced.
Alkenes are more oxidized than alkanes (less H
bonds) and alkynes are more oxidized than
alkenes.
32
Redox Continued



Alkanes can become oxidized under strong
heat and a catalyst. This is what happens
in alkane “cracking”.
Alkanes (higher molecular wt)Alkenes
(lower molecular wt)
**Remember….alkanes are more reduced;
alkenes are more oxidized (alkynes even
more oxidized)
Chapter One
33
Reactions require Catalysts
Are used to initiate and lower activation energy of
reaction, but not used up in the rxn.
 Catalysts generally react with one or more reactants to
form intermediates that subsequently give the final
reaction product, in the process regenerating the
catalyst. The following is a typical reaction scheme,
where C represents the catalyst, X and Y are reactants,
and Z is the product of the reaction of X and Y:
 X + C → XC (1); Y + XC → XYC (2); XYC → CZ (3);
CZ → C + Z (4) Although the catalyst is consumed by
reaction 1, it is subsequently produced by reaction 4, so for
the overall reaction:
 X + Y → Z

Chapter One
34
Catalysts con’t







For reaction X+Y Z, where a catalyst is
used:
X + C → XC (1) (catalyst is “alone” at start)
Y + XC → XYC (2) (catalyst w/reactants)
XYC → CZ (3) (catalyst w/ products)
CZ → C + Z (4) (catalyst is “alone” at end)
Although the catalyst is consumed by
reaction 1,
it is subsequently produced by reaction 4,
X + Y → Z 35
so the overall reaction is:
Catalysts in Biochemistry: Enzymes-
(see Ch 23)







What to know for now:
Globular proteins; work on highly specific substrates (and
usually specific enantiomers); recyclable; lower activation
energy and increase rxn rate 109 – 1020 X
Usually named and classified by the rxn they catalyze
Active site vs allosteric site
Competitive inhibition (block active site) vs noncompetitive
inhibition (bind to another site and alter the tertiary
structure of enzyme, which changes the ‘shape’ of active
site)
Denatured by: high temp; altered pH; high salinity. Study
graphs p. 618-623. Expect a test question!
Feedback control: Study p. 625
Reactions of Alkenes and Alkynes

Addition of H2 to alkenes and alkynes:
Alkenes and alkynes react with hydrogen in the
presence of a metal catalyst such as palladium
to yield the corresponding saturated alkane
products – called hydrogenation. **Recall
unsaturated fats to saturated fats
Chapter One
37


Addition of Cl2 and Br2 to alkenes:
Halogenation
Alkenes react with the halogens Br2
and Cl2 to give 1,2-dihaloalkane.
Chapter One
38


Addition of HCl and HBr to alkenes:
Alkenes react with the hydrogen
bromide and hydrogen chloride to give
alkyl bromide or alkyl chloride product.
Chapter One
39

Markovnikov rule: In the addition of HX to an
alkene, the H becomes attached to the carbon that
already has the most H’s, and X becomes attached
to the carbon that has fewer H’s.
Chapter One
40
How does the rule work?


Reaction mechanisms will show us why
and how, always keeping in mind that
+ and - attract.
*Book- p. 365
How an Alkene Addition Reaction
Occurs

Reaction mechanism: A description of the
individual steps by which old bonds are broken
and new bonds are formed.




Electron flow is always from the electron-rich to the
electron-poor species.
The electron-rich species is a Lewis Base (must
have a lone pair or double bond) and is called the
“nucleophile”.
The electron-poor species is a Lewis Acid (must
have empty orbital) and is called the “electrophile”.
*For a review of orbitals and hybridization, see
links on my blog
Reaction mechanisms

Nucleophile= electron rich
Electrophile= electron poor
Carbocation: C with 3 bonds and + charge
Electron flow is always from nucleophile to
electrophile; from negative (anion) to positive
(cation); from alkene (double bond) to cation (or
partial pos charge)
Draw curved arrow from n’phile to e’phile

*Show www.leah4sci.com videos on following slides




H
O
H
Concepts and Terminology



Carbon hybridizes sp3 when forming single bonds.
But what about double bonds?
Watch this video: http://leah4sci.com/sp2sp-hybridization-bondangle-molecular-geometry-tutorial-video/ . *For a review on sp3,
watch this at home: http://leah4sci.com/sp3-hybridization-bondangle-molecular-geometry-tutorial-video/
*Helpful to watch all videos in this series:
http://leah4sci.com/organic-chemistry-video-library/organic-chemistrybasics-to-build-a-strong-orgo-foundation/
More Concepts and Terms

For alkenes (carbons w/ double bonds):




Sigma bond: one bond of double bond is considered
‘single’ (s orbitals)
Pi bond: is the other bond of db (p orbitals)
Carbocation- carbon atom with only 3 bonds,
therefore it has a positive charge
Watch in class: http://leah4sci.com/alkenereactions/
Carbocation Stability




Primary carbocation: carbocation is
bonded to one other carbon
Secondary carbocation: carbocation is
bonded to to 2 other carbons
Tertiary carbocation: carbocation is
bonded to 3 other carbons
General order of stability: 30>20>10
Hydrohalogenation: Addition of H-X
*Remember- Nucleophile (e- ‘rich’ and ‘loves’
positive charge) attacks Electrophile (epoor)
Steps Involved:


Reaction of pi (double) bond with H+ (of H-X),
concurrent separation of X- , and formation of
Markovnikov carbocation intermediate.
Attack on carbocation by X- to finish
formation of product
Reaction Mechanisms: Addition of H-X
(Hydrohalogenation)
Identify this mechanism – Starts with
alkene, ends with single halide…
X
H-X
Addition of H-X
Step 1: Reaction of pi bond with H+ (of HX), concurrent separation of X-, and
formation of carbocation intermediate.
H
X
H
+ X
Addition of H-X
Step 2: Attack of X- to finish formation
of product.
X
H
X
H
Addition of H-X
*Try this one by yourself, following steps of
last example:
Identify the mechanism…
Adding a Br and an H to an alkene…
H-Br
Br
Addition of H-X (Solution)
Step 1: Reaction of pi bond with H+ (of HX), concurrent separation of X-, and
formation of carbocation intermediate.
H Br
H
+ Br
Addition of H-X - Again
Step 2: Attack of X- to finish formation
of product.
Br
H
Br
H
Addition of HX – One more to try:
Identify the mechanism (show steps):
*Adding a chloride (and a H, which is not
drawn in) to an alkene. Remember
Markovnikov’s rule!
H-Cl
Cl
Addition of HX – Solution
Step 1: React the pi bond with H+ (of HX), separate off the X-, form the more
substituted carbocation intermediate.
H
H Cl
+
Cl
Addition of HX – Solution
Step 2: Attack of X- to finish formation
of product.
H
Cl
Cl
H
Classwork- Do now. I will be
around to check
Do problem 12.6 a and b from p.
364 (showing steps of
mechanism) and 12.7 (p. 366)
Homework: Complete worksheet
Homework Problems (from
worksheet)



1. Show the 2 step mechanism for the
reaction of 3-hexene with hydrochloric
acid and name product.
2. Show the 2 step mechanism of 2methyl-1-pentene with hydrobromic acid.
Name product
3. Show the 2 step mechanism of
ethylcyclohexene with hydroiodic acid.
Name product.


Addition of water to alkenes: Hydration
Alcohol is produced on treatment of the
alkene with water in the presence of a strong
acid catalyst, such as H2SO4. Markovnikov’s
rule can be used to predict the product when
water adds to an unsymmetrically substituted
alkene. Hydrated alkenes produce alcohols.
Chapter One
59
Try this one (overall reaction
only):


Draw a structural formula for the alcohol
formed by the hydration of 2-methylpropene.
*Do NOT have to name specific alcohols on
this test
One of you will come to board to show the
result
Answer:

2-methyl-2-propanol (do not have to
name it specifically for this test, but know
it’s an alcohol with hydroxyl functional
group)
Example #2 of Hydration: What
is the mechanism?
*Go back and review the section on catalysts
CH3 CH=CH2
Propene
+
H2 O
H2 SO4
OH H
CH3 CH-CH2
2-Propan ol
NOTE- you will not have to
name specific alcohols on this
test! Only identify them as
alcohols
**
Acid-Catalyzed Hydration
Steps Involved:



Reaction of pi bond with H+ (acid catalyst!)
resulting in Markovnikov carbocation
formation (note- the H+ is from a strong
acid, like HCl, H2SO4, etc)
Addition of H2O (this is where the OH is
coming from)
Removal of extra proton (H+) to finish
formation of –OH.
Mechanism for Hydration
(*Show leah4sci video on FC; show leah4sci.com video of partial
resonance?- Video 7: https://www.youtube.com/watch?v=zm1-gUxKr3g )
Video 6: https://www.youtube.com/watch?v=zm1-gUxKr3g
Step 1:
H2SO4
CH3 CH=CH2 + H+
*H+ is
from
H2SO4
H
CH3 CHCH2
A 2° carb ocation
intermediate
+
Step 2:
CH3 CHCH3
H
O+
CH3 CHCH3
+
:O-H
H
H
O+
CH3 CHCH3
An oxonium ion
:
Step 3:
H
:
*What is FC on O?
:
+
:
H
:OH
*What is FC on O?
CH3 CHCH3 + H+
*Bonds w/ HSO4- to
2-Propan ol regenerate catalyst
Try this one:



Show the mechanism of the hydration of
2-methyl-1-butene.
I will call someone up to the board 
Be sure to Review Exp 12.9 in book and
do problem 12.9
Alkene Polymers
Polymers: A large molecule formed by

the repetitive bonding together of many
smaller molecules called monomers. Many
simple alkenes undergo polymerization
reaction when treated with the proper
catalyst.
66
Polymerization

Polymerization is a VERY important reaction
of alkenes


polymer: Greek: poly, many and meros, part
monomer: Greek: mono, single and meros, part
nCH2 =CH2
Ethylene
initiator
(polymerization)
CH2 CH2 n
Polyethylene
Polymerization




Use parentheses around the repeating monomer
unit
Subscript, n, indicates that this unit repeats n times
Show that a polymer chain can be reproduced by
repeating the enclosed structure in both directions
Example: section of polypropene (polypropylene)
monomer un its show n in red
n
CH3
CH3
CH3
CH3
CH2 CH-CH2 CH-CH2 CH-CH2 CH
CH3
CH2 CH n
Part of an extended polymer chain
The repeating un it
Monomer
Formula
CH2 =CH2
Common
N ame
ethylene
CH2 =CHCH3
propylene
CH2 =CHCl
CH2 =CCl2
Polymer N ame(s ) and
Common Uses
polyethylen e, Polyth ene;
break-resistan t containers
polypropylene, Hercu lon;
textile and carp et fib ers
vinyl chlorid e poly(vinyl ch loride), PV C;
cons truction tubing
1,1-dichloropoly(1,1-d ichloroethylene);
ethylene
Saran Wrap is a cop olymer
w ith vinyl chlorid e
CH2 =CHCN
acrylon itrile
CF2 =CF2
tetrafluoroethylene
polyacrylonitrile, Orlon;
acrylics and acrylates
polytetrafluoroethylene, PTFE;
Teflon , nonstick coatin gs
CH2 =CHC6 H5
CH2 =CHCOOC2 H5
styrene
ethyl acrylate
polystyrene, S tyrofoam; insulation
poly(eth yl acrylate); latex paints
CH2 =CCOOCH3
CH3
methyl
methacrylate
poly(methyl methacrylate), Lucite,
Plexiglas; glass s ubs titu tes
Note:


I will only require you to know a couple of
these for this test……most notably,
ethylene and propylene. Maybe 1 or 2
more…..vinyl chloride?
Anyone doing doing a polymerization for
Herbfest? If so, be sure and include the
monomer in your lab report/paper and on
your board.

If your active ingredient is a terpene, find out which
enantiomer (R or S) or if it’s a racemic mixture
(combination of the 2). You will understand what
these both mean SOON!
Polymerization of vinyl chloride (chloroethene) to PVC
Polyethylene

Low-density polyethylene (LDPE)




Highly branched polymer, so chains do not pack
well—weak London Force interactions
Softens and melts above 115°C
Primarily used for packaging for trash bags
High-density polyethylene (HDPE)


Little branching, so chains pack well--London
dispersion forces between them are stronger
Higher melting point and stronger than LDPE
Used for squeezable jugs and bottles
FYI-Codes for Plastics
(don’t expect
you to know)
5 PP
Polymer
poly(eth ylen e
terephthalate)
high-den sity
polyethylen e
poly(vinyl
ch loride), PV C
low -density
polyethylen e
polypropylene
6 PS
polystyrene
7
all other p lastics
Cod e
1 PET
2 HD PE
3 V
4 LD PE
Common Uses
soft drin k bottles, hous ehold
ch emical b ottles , films, textile fib ers
milk and w ater jugs, grocery bags,
sq ueezable bottles
sh amp oo bottles, pip es, show er curtains,
vinyl siding, w ire in sulation, floor tiles
sh rin k w rap , tras h and grocery bags,
san dw ich b ags , squ eeze bottles
plas tic lids, clothin g fibers, bottle cap s,
toys , diaper linings
styrofoam cu ps, egg carton s, disp os able
uten sils, packaging materials, app lian ces
various
Nomenclature Review:
Name These
CH3
C
H
CH3
C
Cl
CH2 CH3
CH2 CH3
C C
H
Cl
Ch 13: Aromatic Compounds
and Benzene
Aromatic compounds contain benzene.
Benzene, C6H6 , is represented as a six carbon
ring with 3 alternating double bonds.
Two possible can be drawn to show benzene in
this form.
H
H
H
H
H
H
H
H
H
H
H
H
Aromatic Compounds
and the Structure of Benzene



In the early days the word aromatics was
used to described many fragrant
molecules isolated from natural sources.
Today the term aromatic is used to
describe benzene like molecules.
Benzene is a flat, symmetrical molecule
with the molecular formula C6H6.
It has alternating three carbon-carbon
double and three single bonds.


Benzene’s relatively lack of chemical reactivity is
due to its structure. Unlike alkenes, benzene
does not undergo addition reactions
There are two possible structures with
alternating double and single bonds.




Experimental evidence suggest that all six
carbon-carbon bonds in benzene are identical.
The properties, including the above one, of
benzene can only be explained by assuming
that the actual structure of benzene is an
average of the above two possible equivalent
structures-known as resonance.
Simple aromatic compounds like benzene are
non-polar, insoluble in water, volatile, and
flammable.
Unlike alkenes, several aromatic hydrocarbons
are toxic. Benzene itself is implicated as a
cancer causing chemical.
Aromatic Compounds in Nature
and Health
Many aromatic compounds are common in nature
and in medicine.
CHO
COOH
COOCH3
CH3
CH3
CH3CHCH2
CHCOOH
OCH3
OH
Aspirin
Vanillin
Ibuprofen
Naming Aromatic Compounds
Aromatic compounds are named with benzene as the
parent chain. One side group is named in front of the
name benzene.
- No number is needed for mono-substituted benzene
since all the ring positions are identical.
CH3
methylbenzene
(toluene)
Cl
chlorobenzene
Naming Aromatic Compounds
When two groups are attached to benzene, the
ring is numbered to give the lower numbers to the
side groups. The prefixes ortho (1,2), meta (1,3-)
and para (1,4-) are also used. O,M,P
Cl
CH3
Cl
CH3
Cl
CH3
1,2-dimethylbenzene
1,3-dichlorobenzene
(ortho-dimethylbenzene)
(meta-dichlorobenzene)
(para-chloromethylbenzene)
M-dichlorobenzene
P-chloromethylbenzene
O-dimethylbenzene
1-chloro-4-methylbenzene
Some Common Names
Some substituted benzene rings also use a common
name. Then naming with additional more side
groups uses the ortho-, meta-, para- system.
CH3
OH
CH3
Cl
Toluene
(Methylbenzene)
meta-chlorotoluene
(meta-chloromethylbenzene)
phenol
(hydroxybenzene)

Many substituted aromatic compounds have
common names in addition to their
systematic names.
Learning Check
Select the names for each structure:
Cl
a. Chlorocyclohexane
b. Chlorobenzene
c. 1-chlorobenzene
CH 3
CH 3
a. Meta-xylene
b. Meta-dimethylbenzene
c. 1,3-dimethylbenzene
Learning Check
Write the structural formulas for each of the
following:
A. M-dichlorobenzene
B. Ortho-chlorotoluene
Attached Groups
(*only know the ones
on the left)

Phenyl
4-phenyl-1-butene

Benzyl
Benzyl alcohol

Nitro -NO2
Refer to nomenclature
packet for order of priority!
2,4,6-trinitrotoluene
Reactions of Aromatic
Compounds
Unlike
alkenes which undergo addition
reactions, aromatic compounds undergo
substitution reactions. That is, a group y
substitutes for one of the hydrogen atoms
on the aromatic ring. Some examples are
given below:
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Nitration reaction: Substitution of a

nitro group (NO2-) for a ring hydrogen.
Halogenation reaction: Substitution of

a halogen (Cl or Br) for a ring hydrogen.
Sulfonation reaction: Substitution of a

sulfonic (SO3H-) group for
hydrogen. (*not on this test)
a
ring
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Learning check:


Show the chlorination of benzene
* Remember……benzene undergoes
substitution, like alkanes
Chapter Summary






Alkenes contain carbon-carbon double bonds.
Alkynes contain carbon-carbon triple bonds.
Aromatic compounds contain six carbons in a
ring arrangement with three double and three
single bonds alternating between carbon atoms.
Alkenes are named using the family ending –
ene, while the alkynes use the family ending –
yne.
Alkenes and alkynes generally undergo addition
reactions and aromatic compounds generally
undergo substitution reactions.
Reaction mechanism: A description of the
individual steps by which old bonds are broken
and new bonds are formed.
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