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
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 Paraffins
• 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)
• 2 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
Chemical Bingo: Naming Review
• There are 27 structures or names drawn
on the next slide. Select 24 of them to be
placed on your bingo card.
• Because of space issues, I would number
each bingo square and then list the names
or structures on a separate sheet of paper
• If I give you a name, you must match it to
a structure. If I give you a structure, you
must match it to a name
• Any bingo winner will be awarded 1 bonus
point on the quiz (5% pts)
Chemical Bingo: Alkanes
R
isopropyl
sec-butyl
tert-butyl
isobutyl
decane
nonane
2,3,4,5-tetramethylhexane
3,4-diethylhexane
3,5-diethyl-4-isopropylheptane
R
R
4-tert-butyl-3,5-dimethylheptane
4-ethyl-2,2,3,5,6,6-hexamethylheptane
Any isomer of C5H12
Any isomer of C6H14
Any isomer of C7H16
R
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
CH4 + Cl2  CH3Cl + HCl
Mechanism (chain reaction):
Step 1
Type of Step
Cl2 ⇌ Cl· + Cl · (Free Radicals) 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
Textbook Resource
Chemistry: An Intro to General,
Organic and Biological Chemistry
by Timberlake (Green/Tan Book)
Sections 10.1-10.6 already covered
Currently Section 11.2 (Haloalkanes)
Can be used as an outside reference
Naming Practice: Haloalkanes
Two equal numbering options?
Number based on alpha order
Cl
6
1
2
5
3
4
4
2
5
3
1
6
F
F
Cl
5-chloro-2-fluorohexane
2-chloro-5-fluorohexane
Br
2-chloro-4-fluoro-2,3-dimethylpentane
I
Br
Cl
2-bromo-3-ethyl-4-iodopentane
2-bromo-4-chloro-3-isopropylpentane
Radical Halogenation: Predict the Product
Cl
?
?
?
Cl + HCl OR
+ Cl2 →
1-chloropropane
2-chloropropane
Cl
OR
3-chloropropane?
Remember that any H on the alkane can be replaced by a halogen
+ Br2 →
Br
1-bromo-2-methylbutane
OR
Br
2-bromo-2-methylbutane
Radical Halogenation: Predict the Product
+ Br2 →
Br
1-bromo-2-methylbutane
Br
OR
Br
2-bromo-2-methylbutane
Br
OR
OR
Br
2-bromo-3methylbutane
1-bromo-3methylbutane
1-bromo-2methylbutane
Structural Isomers
What are the possible structural isomers of C3H7Br?
Br
Br
1-bromopropane
2-bromopropane
What are the possible structural isomers of C4H9Cl?
Cl
Cl
1-chlorobutane
2-chloro-2-methylpropane
Cl
2-chlorobutane
Cl
1-chloro-2-methylpropane
Structural Isomer Practice
On piece of your own paper, draw AND name
ALL of the isomers with the following formulas:
Formulas
C 4H 9I
C3H6Cl2
C5H11Br
C4H8Cl2
# isomers
4
4
8
9
To be honest, there may be more…this is what I
found, so try and prove me wrong! Extra Credit to
anyone who can find more structures…
Some of your drawings may look different, but they are
only different structures (isomers) if they also have
different names
Structural Isomers: C4H9I
II
1-iodobutane
I
2-iodobutane
I
I
2-iodo-2-methylbutane
1-iodo-2-methylbutane
Structural Isomers: C3H6Cl2
Cl
Cl
Cl
Cl
1,1-dichloropropane
Cl
Cl
1,3-dichloropropane
1,2-dichloropropane
Cl
Cl
2,2-dichloropropane
Structural Isomers: C5H11Br
Br
Br
1-bromopentane
Br
3-bromopentane
2-bromopentane
Br
1-bromo-3-methylpentane
Structural Isomers: C5H11Br
Br
Br
1-bromo-2-methylbutane
Br
1-bromo-2,2-dimethylbutane
2-bromo-3-methylbutane
Br
2-bromo-2-methylbutane
Structural Isomers: C4H8Cl2
Cl
Cl
Cl
1,1-dichlorobutane
Cl
1,2-dichlorobutane
Cl
Cl
Cl
1,3-dichlorobutane
Cl
1,4-dichlorobutane
Structural Isomers: C4H8Cl2
Cl
Cl
Cl
Cl
1,1-dichlorobutane
1,2-dichloro-2-methylpropane
Cl
Cl
2,2-dichlorobutane
Cl
Cl
Cl
1,3-dichloro-2-methylpropane
Cl
2,3-dichlorobutane