Organic Chemistry
Chapter 22
Vocabulary
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Organic Chemistry
Hydrocarbons
Saturated
Unsaturated
Alkanes
Alkenes
Alkynes
Cis-trans isomerism
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Carbonyl group
Ketones
Aldehydes
Carboxylic acids
Carboxyl group
Ester
Ether
Amine
Saturated vs. Unsaturated
Hydrocarbons
• Hydrocarbons are molecules composed of
carbon & hydrogen
– Each carbon atom forms 4 chemical bonds
– A saturated hydrocarbon is one where all C - C
bonds are “single” bonds & the molecule contains
the maximum number of H-atoms
– An unsaturated hydrocarbon is one where at least
1 C=C bond is double.
Prefixes for # of Carbons
1
Meth
6
Hex
2
Eth
7
Hept
3
Prop
8
Oct
4
But
9
Non
5
Pent
10
Dec
Alkanes
• Hydrocarbon chains where all the bonds between
carbons are SINGLE bonds
• Name uses the ending –ane
• Examples: Methane, Propane, Butane, Octane
• Formula: (CnH2n+2)
Straight-Chain Alkanes
• Straight-chain alkanes contain any
number of carbon atoms, one after the
other, in a chain pattern - meaning one
linked to the next (not always straight)
C-C-C
C-C-C-C etc.
Writing/drawing compounds
Line formula
Normal vs Branched Alkanes
• NORMAL alkanes consist of
continuous chains of carbon
CH2
CH2
CH3
CH2
CH3
atoms
• Alkanes that are NOT
continuous chains of carbon
atoms contain branches
CH3
CH2
CH
CH3
• The longest continuous chain
of carbons is called the
CH3
parent chain
Endings
• Attached carbon groups (substituents) end in
–yl
– Methyl CH3 – Ethyl CH3CH2– Propyl CH3CH2CH2 –
3-ethylpentane
Names of branches
• Carbon (alkyl) groups
– Methyl CH3 – Ethyl CH3CH2– Propyl CH3CH2CH2 –
Branched-Chain Alkanes
• Rules for naming –
1. Longest C-C chain is parent
2. Number so branches have lowest #
3. Give position number to branch
4. Prefix (di, tri) more than one branch
5. Alphabetize branches (not prefix)
6. Use proper punctuation ( - and , )
Designate the Location
• Designate the location (number of the carbon
on the parent chain) for each attached group
2-methyl
1
2
3
4
5
Name this compound
• 3,3-dimethylhexane
Some Simple Alkanes
• 2-methylpentane
• 3-ethylhexane
• 2,2-dimethylbutane
• 2,3-dimethylbutane
Branched-Chain Alkanes
• From the name, draw the structure, in a
right-to-left manner:
1. Find the parent, with the -ane
2. Number carbons on parent
3. Identify substituent groups (give lowest
number); attach
4. Add remaining hydrogens
Example 1: 2,2-dimethylpentane
2
4
• The parent chain is indicated by
CH2 5
CH2 3
1
the ROOT of the name CH3
CH2
“pentane”. This means there are CH3
5 carbons in the parent chain.
• “dimethyl” tells us that there are TWO
CH3
methyl branches on the parent chain.
A methyl branch is made of a single
carbon atom.
CH2
C
CH3
CH2
CH3
• “2,2-” tell us that BOTH methyl
CH3
branches are on the second carbon
atom in the parent chain.
4
1
3
5
Example 2: 3-ethyl-2,4-dimethylheptane
2
4
• The parent chain is indicated by
CH2 5
CH2 3
1
the ROOT of the name CH2
CH2
CH3
“heptane”. This means there are
7 carbons in the parent chain.
H2C 6
CH3
CH3
CH
CH
CH3
CH3
7
CH3
• “2,4-dimethyl” tells us there are
TWO methyl branches on the
parent chain, at carbons #2 and #4.
CH
CH2
CH2
• “3-ethyl-” tell us there is an ethyl
CH2
branch (2-carbon branch) on
CH3 carbon #3 of the parent chain.
Example 3: 2,3,3-trimethyl-4-propyloctane
• The parent chain is indicated by
the ROOT of the name - “octane”.
This means there are 8 carbons
in the parent chain.
3
5
4
2
6
7
1
8
CH3
2
1
3
5
4
6
7
• “2,3,3-trimethyl” tells us there are
CH3THREECmethyl branches
CH2 - one on
CH #2 andCH
CH2#3.
carbon
two on carbon
8
CH3
CH3
• “4-propyl-”
tellCH
us there
is CH
a propyl
2
2
branch (3-carbon branch)
CH2 on CH3
carbon #4 of the parent chain.
CH3
Example 4: Name the molecules shown!
CH3
• parent chain has 5 carbons “pentane”
CH
CH2
• two methyl branches - start
CH3
CH
CH3
counting from the right - #2 and #3
• 2,3-dimethylpentane
3
4
5
CH3
• parent chain has 8 carbons - “octane”
• two methyl branches - start counting
from the left - #3 and #4
• one ethyl branch - #5
• name branches alphabetically
5-ethyl- 3,4-dimethyl octane
Draw 2,2,4-trimethylpentane
Structural Isomerism
• Structural isomers are
molecules with the same
chemical formulas but different
molecular structures
CH2
CH2
CH3
CH2
CH3
n-pentane, C5H12
CH3
CH2
CH3
CH
CH3
2-methlbutane, C5H12
• However, carbons in butane (C4H10) can be
arranged in two ways; four carbons in a row (linear
alkane) or a branching (branched alkane). These
two structures are two isomers for butane.
Your Turn
• Draw all possible structural isomers of C5H12
Practice
IUPAC Rules for
Naming Branched Alkanes
– Find and name the parent chain in the hydrocarbon - this
forms the root of the hydrocarbon name
– Number the carbon atoms in the parent chain starting at
the end closest to the branching
– Name alkane branches by dropping the “ane” from the
names and adding “yl”. A one-carbon branch is called
“methyl”, a two-carbon branch is “ethyl”, etc…
– When there are more than one type of branch (ethyl and
methyl, for example), they are named alphabetically
– Finally, use prefixes to indicate multiple branches
CLASSWORK ASSIGNMENT
• Review section 22-1
– make notes on NONMENCLATURE OF
ALKANES and CYCLIC ALKANES
– Pay attention to sample exercises!
Alkenes & Alkynes
• Alkenes are
hydrocarbons that
contain at least one
carbon-carbon double
bond
• Alkynes are
hydrocarbons that
contain at least one
carbon-carbon triple
bond
• The suffix for the parent
chains are changed from
“ane” to “ene” and “yne”
– e.g. ethene, propyne
• the BONDS are
numbered like branches
so that the location of
the multiple bond may
be indicated
Alkenes & Alkynes: Examples
H2C
CH
CH2
H2C
H
C
HC
ethene
CH3
ethyne
propyne
butene
H2
C
CH
C
propene
2-pentyne
CH3 H3C
C
C
CH2
16
H3C
H2C
C
H
CH3
Aromatic Hydrocarbons
Cycloalkanes
• A cycloalkane is made of a hydrocarbon chain
that has been joined to make a “ring”.
H2
C
109.5° bond angle
CH2
CH3
CH3
n-propane
C3H8
H2C
60° bond angle
unstable!!
CH2
cyclopropane
C3H6
•Note that two hydrogen atoms were lost in forming the ring!
Aromatic Hydrocarbons
Cycloalkanes
• The two ends of the carbon chain are
attached in a ring in a cyclic hydrocarbon
– named as “cyclo- ____”
Aromatic Compounds and Benzene
Aromatic compounds contain benzene.
Benzene, C6H6 , is represented as a six carbon ring with 3
double bonds.
Two possible resonance structures can be drawn to show
benzene in this form.
H
H
H
H
H
H
H
H
H
H
H
H
Aromatic Hydrocarbons
• Benzene derivatives can have two or more
C
substituents:
– 1,2-dimethylbenzene
– 1,3-dimethylbenzene
– 1,4-dimethylbenzene
C
C
• Can use ortho for 1,2; meta for 1,3; and
para for 1,4 (page 711)
C
Isomers
With organic compounds
Isomers
• There is a lack of rotation around a carbon
to carbon multiple bond
– Two possible arrangements:
1. trans configuration - substituted groups on
opposite sides of double bond
2. cis configuration - same side
Geometric Isomers
Trans-2-butene
Substituted
groups are on
the same side
of the double
bond (in this
case, both are
above)
Substituted
groups are on
opposite sides
of the double
bond (in this
case, one is
above, the other
is below)
Cis-2-butene
Cis-Trans Isomers - Examples
cis-1,3-dimethylcyclobutane
cis-1,2-dichlorocyclohexane
2
CH2
6
H3C
CH
3
CH2
5
Cl
Cl
CH
1
CH3
4
trans-1-ethyl-2-methylcyclopropane
Reactions
With organic compounds
Alkanes
1. Combustion reactions
2C2H6(g) + 7O2(g)  4CO2(g) + 6H2O(g)
2. Substitution reactions
hv
CH4 + Cl2  CH3Cl + HCl
Methane
chloromethane
3. Dehydrogenation reactions
500C
CH3CH3 CH2=CH2 + H2
Ethane
ethene
Alkenes & Alkynes
1. Addition reactions
a. Hydrogenation
Catalyst
CH2 =CHCH3+ H2  CH3CH2CH3
Propene
Propane
b. Halogenation
CH2 =CHCH2CH2CH3 + Br2  CH2 BrCHBrCH2CH2CH3
Pentene
1,2-dibromopentene
c. Polymerization
Small molecules = large molecules
Aromatic
1. Substitution reactions
Catalyst = FeCl3
+ Cl2 
+ HCl
Functional Groups
With organic compounds
Functional Groups
Functional group: an atom or
group of atoms within a
molecule
Functional Groups
Alcohols
contain an -OH (hydroxyl) group
H H
:
-C-O-H
:
H-C-C-O-H
Fu nctional
group
H H
Ethan ol
(an alcohol)
CH3 -CH2 -OH
or
CH3 CH2 OH
Halides & Carboxylic Acids
contain an -X (Halogen) group
F, Cl, Br, I, At
contain a carboxyl (-COOH) group
:
Fu nctional
group
:O:
CH3 -C-O-H
:
O
C O H
or CH3 COOH or CH3 CO2 H
Acetic aci d
(a carboxy li c acid )
Aldehydes and Ketones
contain a carbonyl (C=O) group
O
O
C H
CH3 -C-H
Fu nctional A cetaldeh yd e
group
(an aldehyde)
O
O
C
Fu nctional
group
CH3 -C-CH3
Aceton e
(a ketone)
Amines
contain an amino group; nitrogen bonded to
one, two, or three carbon atoms
– an amine may by 1°, 2°, or 3°
Methylamine
(a 1° amine)
CH 3 N H
CH 3
Dimethylamine
(a 2° amine)
:
H
:
:
CH 3 N H
CH 3 N CH 3
CH 3
Trimethylamine
(a 3° amine)
Esters & Ethers
Ester: trapped carboxylic acid
O
: O:
:
Fun ctional
group
CH3 -C-O-CH2 -CH3
:
C O
Ethyl acetate
(an ester)
Ether: Trapped oxygen
Branches
CnH2n+2
CH4
C2H6
C3H8
Alkane
methane
ethane
propane
CnH2n+1
CH3
C2H5
–C3H7
CH3CHCH3
Alkyl group
Methyl
ethyl
propyl
methylethyl
Functional
Group
General
Formula
Name
Examples
alkanone
butan-2-one
O
O
C
R
C
-COOH
RCOOH
alkanoic acid
ethanoic acid
-COOR’
RCOOR’
ester
methyl ethanoate
ether
ethoxyethane
R-O-R’
R'
saturated ring
CnH2n
cycloalkane
cyclohexane
-X
-RX
haloalkane
chloroethane
alkanol
ethanol
amine
methylamine
alkanal
ethanal
-OH
-NH2
ROH
RNH2
(-CHO)
RCHO
Naming
Naming
Naming