Download 7 Organic 2

Organic Part 2
Hydrocarbons
1. Alkanes:
all single bonds
2. Alkenes:
C
C
saturated v. unsaturated
structural isomers
geometric isomers
3. Alkynes:
C
C
4. Aromatic hydrocarbons
Reactivity of hydrocarbons
•  addition reactions
•  combustion reactions
Mary J. Bojan
Chem 110
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HYDROCARBONS are the simplest organic
compounds: containing only C and H
Alkanes
Alkenes
Alkynes
Aromatic
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saturated
have the maximum number of H
attached to the C skeleton.
unsaturated
have double or
triple bonds
Chem 110
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ALKENES
Contain one or more double bonds
H
H
CnH2n
C
C
C
C
H
H
ethene
Bond angle
H
H
C
C
H
CH 3
propene
Rotation about double bond is restricted
Mary J. Bojan
Chem 110
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Butene: There are several possible structures for a
chain of 4 carbons with one double bond.
C 4H 8
C backbone
condensed molecular
formula
1-butene
2-butene
2-methylpropene
Mary J. Bojan
Chem 110
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Butene: Expand the condensed molecular formula
into a structural formula, focusing on the double bond.
C 4H 8
1-butene
CH2=CHCH2CH3
2-methylpropene
(CH3)2C=CH2
2-butene
CH3CH=CHCH3
Mary J. Bojan
Chem 110
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There are different classes of isomers:
Structural vs. Geometric
Structural isomers:
same molecular formula: different structure
1-butene
2-methylpropene
2-butene
Geometric isomers
same molecular formula: different geometry
cis-2-butene
trans-2-butene
cis-isomer:
trans-isomer:
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same side
opposite side (across)
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ALKYNES are hydrocarbons that
contain one or more triple bonds
ethyne
(acetylene)
H
H
H
C
C
H
H
propyne
H
C
C
H
H
C
H
C
C
H
C
H
H
2-butyne
1-butyne
structural isomers
CnH2n–2 no geometric isomers are possible
Mary J. Bojan
Chem 110
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Aromatic Hydrocarbons
Contain alternating single and double C-C Bonds
Benzene is the prototypical molecule
H
H
H
C
C
C
C
H
C
C
H
H
H
H
H
C
C
C
C
C
C
H
H
H
Usually written:
Aromatic hydrocarbons are less reactive than alkenes:
We can draw resonance structures:
resonance implies added stability
Mary J. Bojan
Chem 110
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Reactivity of Hydrocarbons
Same reaction:
hydrocarbon +
Br2
ALKANE
Heptane + Br2
Colorless
red
ALKENE (and ALKYNES)
2-pentene + Br2
Colorless
red
AROMATIC
toluene + Br2
Colorless
red
CH3
Mary J. Bojan
Chem 110
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Aromatic hydrocarbons have RESONANCE:
resonance adds extra stability.
Alkene + Br2
Aromatic + Br2:
reacts readily
no reaction
•  alkenes are very reactive toward addition.
(alkynes even more so.)
•  Benzene is NOT reactive
Mary J. Bojan
Chem 110
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Functional Group classes: groups of molecules that contain
a representative group of elements in a fixed pattern
Molecules in the class have similarities in structure and
function (reactivity).
Seemingly small changes in structure can have big affect on
molecular properties
Example: adding
an oxygen
changes a
hydrocarbon
into an alcohol
or an ether…
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Functional Group Type
hydrocarbon
CH3!CH2!H
ethane
gas
bp –89°C
Chem 110
alcohol
ether
CH3!CH2!OH CH3!O!CH3
ethanol
di-methyl ether
liquid
gas
bp 78°C
bp –24 °C
water soluble
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Functional group classes contain a representative group of elements in a
fixed pattern:
Each class has similarities in structure and function (reactivity).
Functional Group Classes
Alcohols
R−OH
R≠H
Groups which have
a carbonyl
R = alkyl group
Ethers R−O−R
R,R ≠ H
Aldehydes
Amines
H N H
H N R'
R N R'
R
R
R"
C
Ketones
O
O
C
C
H
R
R
Carboxylic
Acid
(R,R ≠ H)
R'
Ester
Amide
O
O
O
C
C
C
R
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O
Chem 110
OH
R
OR'
R
NHR'
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Focus on the atoms bonded to O and N
atoms in these Functional Groups.
Alcohols
R−OH
hydroxyl group
hydrocarbon (alkyl) group
Ether
R−O−R
Amines
H N H
H N R'
R N R'
R
R
R"
Mary J. Bojan
Chem 110
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For these Functional Groups, notice the atoms
bonded to the C in the carbonyl group.
C O
O
Aldehyde
C
R
H
O
Ketone
C
R
R'
O
Carboxylic Acids
−COOH
C
R
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Chem 110
OH
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Amines and carboxylic acids are organic
Acids and Bases
AMINES
weak bases, organic bases (like NH3)
CARBOXYLIC ACIDS
weak acids, organic acids
Mary J. Bojan
Chem 110
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Questions
Which of the following hydrocarbon classes does NOT have a
double or triple bond?
1
2
3
4
alkane
alkene
alkyne
aromatic
Which one of the following functional group
classes does not have a double bond?
1
2 
3 
3 
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aldehyde
Ketone
amine
ester
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The presence and properties of functional groups are
responsible for the action of drugs.
What functional groups are present in these molecules?
O
C
H
OH
O
C
HO
C
CH 3
O
CH3
O
Acetaminophen
Acetyl salicylic acid
H3C
Ibuprofen
N
O
CH3
OH
CH3
Mary J. Bojan
Chem 110
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What s Next?
•  Formulas tell us how atoms are connected to
each other
•  Lewis structures tell us where the electrons
are.
QUESTIONS
•  What are the shapes of these molecules?
•  Can we use information about bonding,
connectivity of atoms, molecular formulas, etc.
to predict the shapes (and properties) of
molecules?
Mary J. Bojan
Chem 110
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