A (very) Little Organic Chemistry
Carbon Chemistry
• Electronic structure leads to a variety of bonding possibilities
– Infinite number of p
possible combinations!
Organic Chemistry
Rule of thumb: Carbon typically forms four bonds!
– Four possible combinations of single, double & triple
– Stability and movement of bonds in carbon compounds.
Allotropic forms of carbon:
• Diamond - sp3
• Graphite - sp2
• Fullerenes (buckyballs & buckytubes) - "sp2"
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Classes of Carbon Compounds
Organic compounds are classified by functional group
– Group of atoms that has a characteristic structure and reactivity.
Class
Alkane
Formula
C-C and C-H single
bonds
Alkene
R2-C=C-R2
Alkyne
R-CC-R'
Alcohol
R-OH
Ether
R-O-R'
Structure
Properties
2
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More Functional Groups
Class
Formula
R-NH2,
R NH R'
R-NH-R'
Amine
Aldehyde
R-CHO
Carboxylic Acid
R-COOH
Ester
R-COO-R'
Amide
RCON-R’
Structure
Properties
• Because of common reactivity of functional groups, it is possible to
predict reactivity of organic compounds
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Functional Group Reactivity
EXAMPLE: Ester formation
• Esters can be formed by the dehydration reaction of an alcohol and
a carboxylic acid as shown below:
O
R
C
O
OH
+
R' OH
H+
R
C
O R'
H OH
+
• “R” can be any group
O
O
H3 C
OH
C
OH
H3C OH
+
H+
C
O CH3 + H OH
OH
O
C
H3 C
OH
+
H3C OH
H+
O
C
O CH3 + H OH
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2
Functional Group Reactivity
So, we can build larger, more complicated molecules by taking
advantage of functional group reactivity!
– Regardless of whether we
we're
re talking about small molecules like
methanol or huge molecules like proteins, behavior typically boils
down to functional group reactivity!
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Identification and Naming of Organic
Compounds
Two key criteria
1. Types of functional groups present
2. Length
g of carbon backbone
• Prefix tells length of carbon chain
• Virtually any organic compound can be named based on
rules developed from these criteria.
Name Molecular Formula Structural Formula Isomers
methane
CH4
CH4
1
ethane
C2H6
CH3CH3
1
propane
p
p
C3H8
CH3CH2CH3
1
butane
C4H10
CH3CH2CH2CH3
2
pentane
C5H12
CH3(CH2)3CH3
3
hexane
C6H14
CH3(CH2)4CH3
5
CH3(CH2)5CH3
9
heptane
C7H16
octane
C8H18
CH3(CH2)6CH3
18
nonane
C9H20
CH3(CH2)7CH3
35
CH3(CH2)8CH3
75
decane
C10H22
6
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Organic Nomenclature:
IUPAC Rules for Alkane Nomenclature:
1. Find and name the longest continuous carbon chain.
2 Identify and name groups attached to this chain.
2.
chain
3. Number the chain consecutively, starting at the end nearest a
substituent group.
4. Designate the location of each substituent group by an appropriate
number and name.
5. Assemble the name, listing groups in alphabetical order.
The prefixes di, tri, tetra etc., used to designate several groups of the
same kind, are not considered when alphabetizing.
Alkyl Substituents:
Group
CH3–
C2H5–
CH3CH2CH2–
(CH3)2CH–
Name
Methyl
Ethyl
Propyl
Isopropyl
Group
CH3CH2CH2CH2–
(CH3)2CHCH2–
CH3CH2CH(CH3)–
(CH3)3C–
Name
Butyl
Isobutyl
sec-Butyl
tert-Butyl
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Means of representing organic
compounds:
1. Molecular Formula: Identifies only number and types of atoms
present, no structural information.
Ex: C4H10
2. Structural Formula: Also gives structural information (Lewis
structure). Allows us to distinguish structural isomers.
– Structural isomers (aka constitutional isomers): Same
molecular formula, different structural formula (arrangements of
atoms).
Ex: C4H10 has two isomers  TWO DIFFERENT COMPOUNDS!
3 Condensed
3.
C d
d Formula:
F
l Hybrid
H b id off molecular
l
l and
d structural
t t l fformulae.
l
Attempts to provide some structural information.
4. Skeletal Formula: Shows carbon backbone and any non-H atoms
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4
Isomers
Isomers: different compounds with same molecular formula
Stereoisomers: isomers where connections are same, but
arrangement in space different
Constitutional Isomers: isomers where atoms are connected
differently
Enantiomers: stereoisomers that are mirror images
Diastereomers: stereoisomers that are not mirror images
EXAMPLE: C2H2Cl2 has 3 possible structures, only 2 are
diastereomers
9
Enantiomers
Molecules that have Enantiomers are Chiral
– Amino Acids are one Enantiomer
– Some bacteria use the amino acids of the other chirality to trick
their hosts
Enantiomers have similar physical properties (nearly identical)
– Interact differently with polarized light
– May have dramatically different reactivity
• Thalidomide
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5
Polymer Chemistry
“Big” molecules, but the result of several functional group reactions
•Monomer A
•+
•Monomer B
•Repeat Unit
•Repeat Unit
•Repeat Unit
•Repeat Unit
•Polymer
Polymer properties depend on several factors, including:
– the chemical composition of the monomer units,
– length of the chain,
chain
– the three dimensional arrangement of the chains in the solid,
– the branching in the chain,
– the bonding/interaction between chains,
Plasticizers:
Crosslinking:
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Polymerization Reactions
Two major classes of polymerization reactions: Addition and
Condensation
Addition Polymerization – no other products are formed
Examples: polyethylene and polystyrene
H
n
H
C
H
C
H
H
H
H
C
C
H
H
H
n
H
n
H
C
H
C
H
H
H
C
C
H
H
n
12
6
Polymerization Reactions
Condensation Polymerization – small molecules are produced as
byproducts
Example: Polytehylene Terephthalate (PETE)
O
HO CH2 CH2 OH
+
O
HO C
C OH
O
O
H O CH2 CH2 O C
C O
H
+
n H2O
n
• More condensation polymers – Polyamides (Nylon and Proteins)
OH
O
O
+
NH2
H2N
OH
O
NH2
O
O
OH
R
O
H2N
R
+
CH C
OH
N
+
H2O
n
H
H2N
C
R
CH
OH
R
O
O
CH C
NH2
CH
NH
O
C
+
H2O
13
OH
The Big Six
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