Transcript Introduction to Organic

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
Ketone
Amide
O
O
NH2
Haloalkane
Aldehyde
Amino acid
O
O
Cl
Br
H2N
H
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
CH3
C5H12
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
Alkyl substituents
Methane
Ethane
Propane
Butane
5
Pentane
6
Hexane
7
Heptane
8
Octane
9
Nonane
10
Decane
-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)
4-ethyl
Octane
2
8
6
7
1.
5
4
3
4-ethyl-3,5-dimethyloctane
1
3-methyl and 5-methyl = 3,5-dimethyl
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)
•
4.
List substituents alphabetically before root name
•
5.
Two or more identical substituents: use prefixes (di-, tri-, tetra-, etc.)
Do not alphabetize prefixes
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:
Formulas
Pentane C5H12
Hexane C6H14
Heptane C7H16
# isomers
3
5
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