Organic Chemistry
Organic Chemistry:
The chemistry of carbon and
carbon-based compounds
Organic Chemistry in everyday life:
Smells & tastes: fruits, chocolate, fish, mint
Medications: Aspirin, Tylenol, Decongestants, Sedatives
Addictive substances: Caffeine, Nicotine, Alcohol, Narcotics
Hormones/Neurotransmitters: Adrenaline, Epinephrine
Food/Nutrients: Carbohydrates, Protein, Fat, Vitamins
Genetics: DNA, RNA
Consumer products: Plastics, Nylon, Rayon, Polyester
Hydrocarbons
 Simplest class of organic compounds
 Consist entirely of carbon and hydrogen
 Four major classes of hydrocarbons:
1. Alkanes — contain only carbon-hydrogen and carboncarbon single bonds
2. Alkenes — contain at least one carbon-carbon double
bond
3. Alkynes — contain a least one carbon-carbon triple bond
4. Aromatics — contain rings of six carbon atoms that can be
drawn with alternating single and double bonds

Alkanes are saturated hydrocarbons; alkenes, alkynes,
and aromatics are unsaturated hydrocarbons
Copyright 2007 Pearson Benjamin Cummings. All rights reserved.
Hydrocarbons
 Alkanes
– Names of all alkanes end in –ane, and their boiling points
increase with more carbon atoms present.
– The simplest alkane is methane.
– In larger alkanes, carbon atoms are joined in an unbranched
chain (straight-chain alkanes) where each carbon atom is
bonded to two other carbon atoms.
– Alkanes with four or more carbon atoms can have more than one
arrangement of atoms. Carbon atoms can form a single,
unbranched chain, or the primary chain of carbon atoms can
have one or more shorter chains that form branches.
– The systematic name for branched hydrocarbons uses the lowest
possible number to indicate the position of the branch along
the longest straight carbon chain in the structure.
Copyright 2007 Pearson Benjamin Cummings. All rights reserved.
Hydrocarbons
 Alkenes
– The simplest alkenes are ethylene and propylene.
– Names of alkenes that have more than three carbon atoms use
the same stems as the names of alkanes
but end in –ene.
– More than one structure is possible for alkenes that contain
four or more carbons.
– The number in the name of an alkene specifies the position of
the first carbon atom of the double bond. The name is
based on the lowest possible number starting from
either end of the carbon chain.
Copyright 2007 Pearson Benjamin Cummings. All rights reserved.
Hydrocarbons
 Alkynes
– The simplest alkyne is acetylene.
– The names of alkynes are similar to
those of the corresponding alkanes but
end in –yne.
Copyright 2007 Pearson Benjamin Cummings. All rights reserved.
Hydrocarbons

Cyclic hydrocarbons
– The ends of a hydrocarbon chain are connected to form a
ring of covalently bonded carbon atoms.
– Cyclic hydrocarbons are named by attaching the prefix
cyclo- to the name of the alkane, alkene, or alkyne.
– The simplest cyclic alkanes are cyclopropane and
cyclobutane
– Draw structures of cyclic alkanes by sketching a polygon
with the same number of vertices as there are carbon
atoms in the ring with each vertex representing a CH2
unit.
Copyright 2007 Pearson Benjamin Cummings. All rights reserved.
Hydrocarbons
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.
Hydrocarbons

Aromatic Hydrocarbons
– Alkanes, alkenes, alkynes, and cyclic hydrocarbons are called
aliphatic hydrocarbons.
– Aromatic hydrocarbons are also called arenes and are obtained
by the distillation and degradation of highly scented resins
from tropical trees.
– The simplest aromatic hydrocarbon is benzene.
– The chemical behavior of aromatic compounds differs from the
behavior of aliphatic compounds.
– The general name for a group of atoms derived from an alkane is
an alkyl group, and the name of the alkyl group is derived
from the name of the alkane by adding the suffix –yl.
– Groups of atoms derived from aromatic hydrocarbons are aryl
groups.
– In general formulas and structures, alkyl and aryl groups are
abbreviated as R.
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.
Hydrocarbons
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.
Hydrocarbons
• Alcohols
– Replacing one or more hydrogen atom of a hydrocarbon
with an –OH group gives an alcohol and is
represented as R-OH.
– The simplest alcohol is methanol (systematic name) or
methyl alcohol (common name).
– The simplest alcohol derived from an aromatic
hydrocarbon is phenol.
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.
Drawing Organic Structures
Shortcuts make structures easier & faster to draw
Butane: C4H10
Lewis Structure
H
H
H
H
H
C
C
C
C
H
H
H
H
Carbon Atoms
H
Condensed Structures
CH3 CH2 CH2 CH3
CH3CH2CH2CH3
CH3(CH2)2CH3
Line Structure
• Only shows bonds
• C atoms assumed at each end
and intersection of bonds
• H atoms not shown
• Assume 4 bonds to each C
• Fulfill C’s 4 bonds by adding H’s
Types of Organic Compounds
Classified according to functional group
Alkane
Alcohol
Carboxylic acid
O
OH
OH
Alkene
Ether
Amine
NH2
O
Alkyne
C
Ketone
Amide
O
O
C
NH2
Haloalkane
Aldehyde
Amino acid
O
O
Cl
Br
H
H2N
OH
Big Idea in Organic Chemistry
Structure controls Function
Each functional group has predictable reactivity
Alkanes or Paraffin
• All C atoms are tetrahedral and sp3 hybridized
(only C-C single bonds)
• General formula = CnH2n+2 (CH4, C2H6, C3H8, C4H10, etc.)
• Can have linear or branched alkanes
C5H12
CH3
1°
3°
H3C
C
CH2 CH3
H
2°
• Same molecular formula, different structure: structural isomers
• Branches are called substituents
Primary (1°) carbon atom: bound to one other C atom
Secondary (2°) C atom:
bound to 2 other C atoms
Tertiary (3°) C atom:
”
3
”
Quaternary (4°) C atom:
”
4
”
Names of Linear Alkanes and Alkyl Substituents
# of
C atoms
Alkane
1
CH4
2
CH3CH3
3
CH3CH2CH3
4
CH3CH2CH2CH3
methane
ethane
propane
butane
5
pentane
6
hexane
7
heptane
8
octane
9
nonane
10
decane
Alkyl substituents
-CH3
-CH2CH3
-CH2CH2CH3
methyl
ethyl
propyl
etc.
Root: number of C atoms
Suffix: functional group
(-ane for alkanes)
(-yl for alkyl groups)
H H H H
H
H C H
H
H
H H H H
Methane
CH4
Butane
C4H10
H H H H
H
R?
C C C C H
C H
R
?
C C C C H
H
H H H H
Methyl
-CH3
Butyl
-C4H9
Where R = any other C atom or arrangement of C atoms
First Ten Hydrocarbons: Properties
Name
Number of
Carbon Atoms
Molecular
Formula
Melting
Point, oC
Boiling
Point, oC
# of
Isomers
Methane
1
CH4
-182.5
-161.5
1
Ethane
2
C2H6
-183.2
-88.6
1
Propane
3
C3H8
-187.7
-42.1
1
Butane
4
C4H10
-138.3
-0.5
2
Pentane
5
C5H12
-129.7
36.1
3
Hexane
6
C6H14
-95.3
68.7
5
Heptane
7
C7H16
-90.6
98.4
9
Octane
8
C8H18
-56.8
125.7
18
Nonane
9
C9H20
-53.6
150.8
35
Decane
10
C10H22
-29.7
174.0
75
Properties of Alkanes
Nonpolar → only London Dispersion Forces IMF
Larger molecular weight → Stronger London dispersion forces
Compound
Methane
Formula
CH4
MW
16
Boiling point (°C)
-164
Ethane
Propane
Butane
C2H6
C3H8
C4H10
30
44
58
-88.6
-42.1
-0.5
Pentane
C5H12
72
+36.0
Linear Alkanes:
1 - 4 C atoms: gas at room temp
5 - 15 C atoms: liquid at room temp
>15 C atoms: solid at room temp
Fractional
Distillation of
Crude Oil
Kelter, Carr, Scott, Chemistry A World of Choices 1999, page 429
Naming Branched Alkanes (IUPAC)
Octane
4-ethyl
6
8
7
2
5
4
3
4-ethyl-3,5-dimethyloctane
1
3-methyl and 5-methyl = 3,5-dimethyl
1. Root name: name of longest continuous C chain (parent chain)
Two equally long? Choose the one with more branches
2. Number C atoms in chain, starting at end with first branch
3. Identify substituents, give each a number (C it is connected to)
Two or more identical substituents: use prefixes (di-, tri-, tetra-, etc.)
4. List substituents alphabetically before root name
Do not alphabetize prefixes
5. Punctuation: commas separate numbers from each other
hyphens separate numbers from names
no space between last substituent & root name
Common Names of other Alkyl Substituents
Remember that R = any carbon chain
R
3 carbons
CH CH3
R
CH3
isopropyl
alphabetized as “i”
“iso” indicates symmetry
R
CH2 CH CH3
R
isobutyl
CH3
4 carbons
2o
R
alphabetized as “i”
CH CH2 CH3 R
2o
CH3
sec-butyl
alphabetized as “b”
Secondary carbon
CH3
R
3o
C
CH3
CH3
R
3o
tert-butyl
alphabetized as “b”
Tertiary carbon
Naming Practice
Expanded Structure
H H H
Line Structure
H
H C C C C H
H H
H
H C H
H
butane
2 - methylbutane
Naming Practice
H H CH3
H
C C C
6
1
52
43
CH3
Line Structure
H H C H
3
4
H C H
25
H C H
16
H
4,4-dimethylhexane
3,3-dimethylhexane
Lowest sum of numbers
is correct
Isomers
The fat dog shook himself, and then rolled over on the
wet rug.
OR
The dog shook the fat rug, then rolled over and wet on
himself.
These two statements use the same words...
but have very different meanings!
Likewise, isomers may have the same formula, but
have very different structures…
Structural Isomers of C4H10
2-methylpropane
or
Structural Isomer Practice
• On piece of your own paper, draw AND name
ALL of the isomers for the following alkanes:
# isomers
Formulas
Pentane C5H12
3
Hexane C6H14
5
Heptane C7H16
9
Some of your drawings may look different, but they are
only different structures (isomers) if they also have
different names
If you complete that, try to draw and name all of the
isomers for octane (C8H18). There are 18 of them!
Structural Isomers: Pentane (C5H12)
pentane
2-methylbutane
2,2-dimethylpropane
Structural Isomers: Hexane (C6H14)
hexane
2,3-dimethylbutane
2-methylpentane
2,2-dimethylbutane
3-methylpentane
Structural Isomers: Heptane (C7H16)
heptane
2,2-dimethylpentane
2-methylhexane
2,3-dimethylpentane
3-methylhexane
Structural Isomers: Heptane C7H16
2,4-dimethylpentane
3-ethylpentane
3,3-dimethylpentane
2,2,3-trimethylbutane
Comparing Structural Isomers
C5H12
Structure
(Same formula, different structure)
Name
Boiling point (°C)
pentane
36.0
2-methylbutane
27.9
2,2-dimethylpropane
9.5
More branching → weaker London dispersion forces
BP/MP of Linear alkanes > BP/MP of branched alkanes
Reactions of Alkanes
Combustion
• exothermic reaction
• alkanes used as fuel source
13/
2
C4H10 + ___
4 CO2 + ___
5 H2O
O2  ___
Incomplete Combustion with insufficient O2 produces CO
• Poor ventilation, cigarettes
C4H10 +
9/
___
2
4 CO + ___
O2  ___
5 H2O
CO is poisonous because it binds to the hemoglobin
in the blood, preventing the absorption of O2
Radical Halogenation Terms
Mechanism
How the reaction occurs through multiple steps
(most reactions actually occur in many steps)
Chain Reaction
Reactions that occur on their own after some
initiating event
Free Radicals
Atoms that have one free electron—highly
reactive
Radical Halogenation Terms
• Initiation Step
– Step where a bond is split by heat/light,
producing free radicals
• Propagation Step
– Step where free radicals react with nonradicals, producing more free radicals and
continuing the “chain reaction”
• Termination Step
– Step where free radicals react with each
other, producing non-radicals and terminating
the “chain reaction”
Reactions of Alkanes
Radical Halogenation of Alkanes
Mechanism (chain reaction):
Step 1
Cl2 ⇌ 2 Cl· (Free Radicals)
Type of Step
Initiation
Step 2
Cl· + CH4  CH3· + HCl
Propagation
Step 3
CH3· + Cl2  CH3Cl + Cl·
Propagation
Step 4
Cl· + Cl·  Cl2
Termination
h
Overall reaction: CH4 + Cl2  CH3Cl + HCl
 chloromethane
Why not 1-chloromethane?
Halogenated product is a haloalkane
Naming: halogen atom is a substituent, replace –ine ending with –o
-F fluoro
-Cl chloro
-Br bromo
-I iodo
Radical Halogenation of Alkanes
Halogen substitutes for hydrogen in alkane →multiple results
Cl2
CH4

Compound
CH3Cl
CH2Cl2
CHCl3
CCl4
Cl2
CH3Cl

Cl2
CH2Cl2

Cl2
CHCl3

CCl4
IUPAC Name
chloromethane
dichloromethane
Common Name
methyl chloride
methylene chloride
trichloromethane
tetrachloromethane
chloroform
carbon tetrachloride
All are liquids at room temperature
• Heavy Cl atoms increase LDF
• Polar C-Cl bonds – can have polar molecules