Chapter 21 : Organic Chemistry
Organic chemistry:
The study of the compounds of carbon.
C
• 85% of all known compounds
are organic.
• Carbohydrates, lipids,
proteins, enzymes, nucleic
acids, hormones, vitamins, and
almost all other chemicals in
living systems are organic
compounds.
< Abundance of the elements
in the Earth’s crust.
Chapter 21 : Organic Chemistry
Why is organic chemistry a separate discipline within chemistry?
Vitalism: a “vital force”
present in living
organisms was
believed to be
necessary to produce
an organic compound.
Organic
The experiment of
Wöhler in 1828 was the
first in a series of
experiments that led to
the demise of the vital
force theory. See
reaction below:
NH4 Cl + AgNCO
A mmonium Silver
ch loride
cyan ate
heat
Inorganic
O
H2 N-C-NH2 + AgCl
U rea
Silver
chloride
Chapter 21 : Organic Chemistry
Structural formula: Shows the atoms present in a molecule as well as the
bonds that connect them.
VSEPR model: The most common bond angles are 109.5°, 120°, and 180°.
180°
120°
109.5°
H
B
C
N
O
F
Chapter 21 : Organic Chemistry
Hydrocarbon: A compound composed only of carbon and
hydrogen.
Hydrocarbons
Alkanes
Alkanes
(Ch
apter 11)
Alkenes
Alkenes
(Ch
apter 12)
Alkynes
Alkynes12)
(Chapter
Arenes
Arenes
(Chap
ter 13)
(Aromatics)
Only carb on carb on single
bonds
HH
H-C-C-H
HH
Ethan e
One or more
carb on -carbon
double b on ds
One or more
carbon-carbon
trip le bonds
One or more
ben zene-like
rings
H
H
C C
H
H
Eth ene
(Ethylene)
H-C C-H
Ethyne
(A cetylene)
Benzen e
Chapter 21 : Organic Chemistry
Alkanes: Hydrocarbons that contain only
carbon-carbon single bonds.
The first 10 alkanes with unbranched chains:
Name
Conden sed
Molecu lar Stru ctural
Formula Formula
Name
Conden sed
Molecu lar Stru ctural
Formula Formula
CH4
CH3 CH3
hexane C6 H1 4
CH3 ( CH2 ) 4 CH3
heptane C7 H1 6
CH3 ( CH2 ) 5 CH3
CH3 CH2 CH3
octan e
C8 H1 8
CH3 ( CH2 ) 6 CH3
C4 H1 0
CH3 ( CH2 ) 2 CH3
non ane C9 H2 0
CH3 ( CH2 ) 7 CH3
pentane C5 H1 2
CH3 ( CH2 ) 3 CH3
decane
methan e CH4
eth ane
C2 H6
propan e C3 H8
butane
C1 0 H2 2
CH3 ( CH2 ) 8 CH3
Chapter 21 : Organic Chemistry
Line-angle formula:
1. A line represents a single bond.
2. A vertex and a line terminus represent a carbon atom.
3. Hydrogen atoms are not shown in line-angle formulas.
Ball-andstick model
Line-an gle
formula
Conden sed
structu ral
formula
CH3 CH2 CH3
Propan e
CH3 CH2 CH2 CH3
Butane
CH3 CH2 CH2 CH2 CH3
Pen tane
Chapter 21 : Organic Chemistry
Alkyl group: A substituent group derived from an alkane by removal
of a hydrogen atom.
•Commonly represented by the symbol R-.
•Named by dropping the -ane from the name of the parent alkane
and adding the suffix -yl.
N ame
methyl
Con dens ed
Structu ral Formula
-CH3
ethyl
-CH2 CH3
propyl
-CH2 CH2 CH 3
isopropyl -CHCH3
CH 3
bu tyl
-CH2 CH2 CH 2 CH3
N ame
isobu tyl
sec-butyl
Con dens ed
Structu ral Formula
-CH2 CHCH3
CH3
-CHCH2 CH3
CH3
CH 3
t ert-bu tyl -CCH3
CH 3
Chapter 21 : Organic Chemistry
IUPAC, How to name alkanes:
1. The name for an alkane with an unbranched chain of
carbon atoms consists of a prefix showing the number of
carbon atoms and the ending -ane.
2. For branched-chain alkanes, the longest chain of carbon
CH3
atoms is the parent chain and its name is the root name.
2
3
1
CH
CHCH
3
3
3. Name and number each substituent on the parent chain
and use a hyphen to connect the number to the name.
2-Methylprop ane
4.Number the parent chain from the end that gives the
lower number to the substituent encountered first.
5.Indicate the number of times the substituent occurs by a
CH3 CH2 CH3
prefix di-, tri-, tetra-, penta-, hexa-, and so forth.
6
4
2
1
5
CH3 CCH2 CHCH2 CH3
3
6.Use a comma to separate position numbers.
7. Alphabetize the names of substituents first, and then CH3 4-Eth yl-2,2-d imethylhexan e
(n ot 2,2-d imethyl-4-ethylhexane)
insert these prefixes
8.Do not include the prefixes di-, tri-, tetra- in alphabetizing.
IUPAC = International Union of Pure and Applied Chemistry
Chapter 21 : Organic Chemistry
Cyclic hydrocarbon: A hydrocarbon that contains carbon atoms
joined to form a ring.
Cycloalkane: A cyclic hydrocarbon in which all carbons of the ring are
saturated (has only carbon-carbon single bonds).
Cycloalkanes with ring sizes of from 3 to over 30 carbon atoms are
found in nature.
Five-membered (cyclopentane) and six-membered (cyclohexane)
rings are especially abundant in nature.
Cyclopentan e
Cycloh exane
1
Is opropylcyclopentane
4
1-tert- Butyl-4-methylcyclohexane
Physical properties:
1. Non-polar (they dissolve in other non-polar solvents!)
2. Melting/Boiling points and Density:
Name
methan e
eth ane
propan e
Conden sed
Stru ctrual
Formula
Mol w t
(amu)
CH4
CH3 CH3
CH3 CH2 CH3
CH3 ( CH2 ) 2 CH3
16.0
30.1
44.1
mp
(°C)
-182
-183
D ensity
of Liquid
bp
(°C) (g/mL at 0° C)*
(a gas)
-164
-88
(a gas)
58.1
-190
-138
-42
0
(a gas)
(a gas)
CH3 ( CH2 ) 3 CH3
72.2
-130
36
0.626
hexane
CH3 ( CH2 ) 4 CH3
-95
69
0.659
heptane
octan e
non ane
CH3 ( CH2 ) 5 CH3
CH3 ( CH2 ) 6 CH3
CH3 ( CH2 ) 7 CH3
CH3 ( CH2 ) 8 CH3
86.2
100.2
-90
98
0.684
114.2
128.3
142.3
-57
-51
-30
126
151
174
0.703
0.718
0.730
butane
pentane
decane
*For comp aris on , th e dens ity of H2 O is 1 g/mL at 4°C.
Chapter 21 : Organic Chemistry
Natural gas
• 90 to 95 percent methane.
• 5 to 10 percent ethane, and
• A mixture of other relatively
low-boiling alkanes.
Petroleum
• A thick, viscous liquid mixture of
thousands of compounds, most
of them hydrocarbons formed
from the decomposition of
marine plants and animals.
Chapter 21 : Organic Chemistry
O H
Example: C3H8O
An alcohol may be primary (1°), secondary (2°), or tertiary (3°).
CH3 -C-OH
H
CH3 -C-OH
CH3
CH3 -C-OH
H
A 1° alcohol
CH3
A 2° alcohol
CH3
A 3° alcoh ol
H
Chapter 21 : Organic Chemistry
Example: C3H9N
N
Chapter 21 : Organic Chemistry
Example: C4H8O
O
C
Chapter 21 : Organic Chemistry
Example: C3H6O2
O
C O
Chapter 21 : Organic Chemistry
Example: C3H6O2
O
C O H