Brown, LeMay Ch 25
AP Chemistry
Monta Vista High School
Problem Set: #5, 7, 9, 10, 11, 15, 20, 23 (not c), 41(not c), 44;
Recommended: #2, 16, 17, 43, 69
25.1: Organic Chemistry
 The study of carbon compounds, but not limited to
living systems
 Biochemistry: study of the chemistry of living things
Hydrocarbons are Compounds composed of only C and H

Combust to form CO2 and H2O
 Hydrocarbons have a
-parent carbon chain: It is the longest continuous
carbon chain (does not have to be straight)
- and a side substituent: Ex: alkyl groups
2
25.2: Intro to Hydrocarbons
Types:
1. Alkanes: contain only single C-C bonds. General
formula Cn H2n+2, ending -ane


Also called saturated (contain the maximum # of H’s)
Ex. Methane, Ethane etc.
Unsaturated: contain < maximum # of H’s
2. Alkenes: contain at least one C=C bond. General
Formula CnH2n, ending - ene
3. Alkynes: contain at least one C≡C bond. General
Formula CnH2n-2, ending - yne
4. Aromatics: C’s connected in a planar ring (contain s
and p bonds) and have delocalization. Contain
benzene ring, ex: benzene, chlorobenzene
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Organic Nomenclature
prefix
base
suffix
What substituents?
What “family”?
How many carbons in longest chain?

Originally formulated by IUPAC in 1892
(http://www.acdlabs.com/iupac/nomenclature/)
1. Find the longest continuous chain of C atoms; use
the name of this chain as the base of the
compound’s name. This is called the parent
carbon chain.
1 = meth= hex-
2 = eth3 = prop- 4 = but- 5 = pent-6
7 = hept- 8 = oct- 9 = non- 10 = dec4
2. Number the C atoms in the longest chain, beginning
with the end nearest to a substituent. If different
substituents are present, give the lowest number to
the substituent with highest priority (see list on the
website). The idea is to number the parent carbon
chain to give the side substituents the lowest
numbering.
Priority List: carboxylic acid> aldehyde>
ketone>alcohol> double or triple bond> alkyl
group
http://www.chem.ucalgary.ca/courses/351/orgnom/functional/func.html
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3. Name and give the location (carbon #) of each
substituent as prefixes or suffixes. (It varies.)
4. When 2 or more substituents are present, name
them in alphabetical order as prefixes
When 2 or more of the same substituents are present, use a Greek prefix
(di-, tri-, tetra-, penta-, hexa-, …)
Examples:
Saturated hydrocarbons
 Alkanes: CnH2n+2; suffix is -ane
 Cycloalkanes: CnH2n (n>2); prefix is cyclo C’s bonded in a ring; not planar like an aromatic compound
(except cyclopropane)
Ex: Draw Lewis structures of the first 4 cycloalkanes and
name them.
cyclopropane
cyclobutane
cyclohexane
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Ways to represent Organic Compounds
Molecular Formula
Ex: C4H10
condensed formula Ex:
H3C–CH2–CH2–CH3 or CH3CH2CH2CH3
CH3CH2CH2CH3
Structural formula Ex:
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Understanding Check
 Draw condensed formula and structural formula for
the following: C3H8
Ex: Name all the molecules.
methane
CH4
C2H6
ethane
C3H8
propane
C4H10
butane
C5H12
2-methylpropane
pentane
2,2-dimethylpropane
2-methylbutane
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Write the name of the following:
______________________
______________________
______________________
______________________
______________________
_______________________
______________________
______________________
Draw condensed structural formulas for the
following hydrocarbons:
•2,3-dimethylpentane
•2,4-dimethylhexane
•Cyclohexane
•2,2-dimethylpropane
•2,4-dimethyl-1-hexene
•2,4,6-trinitromethylbenzene
•cis-2,3-dichloro-2-butene
•1,1,2-trichloroethane
•1,2-methylcyclohexane
•1,4-dichlorobenzene
•1-chloro-2-butyne
•1,3-cyclohexadiene
25.4 – 25.5: Functional Groups
Notation:
 “R” stands for:

Alkyl group, such as

H
-CH3
-C2H5
-C3H7, etc.
Carbonyls: contain a C=O
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Name of Formula
group of group
Carboxylic
acid
Suffix
Name
O
||
R-C-OH
Example
structure
Example
chemical
name
methanoic acid
-oic acid
or
“R-COOH”
O
||
R-C-O-R
Ester
or
“R-COOR”
ethyl
propanoate
-yl
___oate
propyl
ethanoate
Aldehyde
O
||
R-C-H
or
“R-CHO”
Ketone
O
||
R-C-R
-one
R-O-H
-ol (suffix
if highest
priority)
Alcohol
or
“R-OH”
-al
2-methylbutanal
2-butanone
hydroxyl(prefix if
lower
priority)
2,3-pentadiol
diethyl ether
Ether
R-C-O-C-R
___ ether
NH2
Amine
R-NH2
-amine
NH2
2,2-pentadiamine
\
Alkene
/
C=C
/
\
Alkyne R-C≡C-R
Halide
R-X
-ene
-yne
halo(bromo-,
chloro-,
fluoro-,
iodo-)
1-propene
2-butyne
2-bromopropane
Cycloalkene
C ring
with
cyclodouble ___-ene
bond(s)
Cycloalkane
cyclo___-ane
C ring
1-cyclopentene
cycloheptane
-yl
Alkane
(as
-(CH2)nfunctional
CH3
group) or
-ane
2,3-dimethylbutane
Isomers:
 Compounds with same molecular formula but different
structures (different bonding arrangements)
 There are two main types of isomers:
1. Structural Isomers: Same formula but differ in the
arrangement of atoms around the carbon chain. Structural
isomers can be:
a. branched chain (depending on C chain)
b. positional (position of a side group)
c. functional group isomers (position of a functional group).
2. Stereoisomers: Same formula but different 3-D orientation.
They can be of two types:
a. Geometric Isomers ( cis, trans, double bonded C atoms
only)
b. Optical Isomers (3D- orientation different- chirality)
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Ex: Draw all the structural isomers for...
CH4
C2H6
C3H8
C4H10
C5H12
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25.4: Geometric Isomers (cis-trans)
 Alkenes: CnH2n; prefix is bond #; suffix is –ene
(more than one double bond: –diene, -triene)
 Geometrical isomers: same formula & same groups, but
different structures.
cisgroups with highest priority on same side of
bond axis (high priority = high atomic mass)
transgroups with highest priority diagonal/across the
double bond
Ex: Draw and name all the isomers of C4H8.
y
y
x
x
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The essential requirement for this stereoisomerism is that each
carbon of the double bond must have two different substituent
groups (one may be hydrogen). This is illustrated by the following general
formulas. In the first example, the left-hand double bond carbon has two
identical substituents (A) so stereoisomerism about the double bond is not
possible (reversing substituents on the right-hand carbon gives the same
configuration). In the next two examples, each double bond carbon atom
has two different substituent groups and stereoisomerism exists,
regardless of whether the two substituents on one carbon are the same as
those on the other.
Credits:
http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/sterisom.htm
Optical Isomers
Two molecules are optical isomers if
they are non super imposable, mirror
images of each other.
http://www.wellesley.edu/Chemistry/Flick/chem341/opticalisomers.html
Credit: Google Images
*25.7: Chirality
 Chiral: a molecule having a nonsuperimposable
mirror image
(Originally discovered by Louis Pasteur)
 Compounds containing C atoms with four different
substituents are inherently chiral
 Optical isomers or enantiomers: nonsuperimposable
mirror images

Labeled “L” (levo, left-handed) and “D” (dextro, right-handed)
 Racemic: a mixture containing both enantiomers (both
L and D)
http://nobelprize.org/educational_games/chemistry/chiral/
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 Alkynes: CnH2n-2; prefix is bond #; suffix is
–yne
 Reactions: unsaturated molecules are more chemically
reactive than saturated compounds

Addition: H3C-C≡C-CH3 + Br2 → ?
Br―Br

→ H3C-C=C-CH3
| |
Br Br
Hydrogenation:
CH3-CH=CH-CH3 + H2 → ?
H―H
→ H3C-CH―CH-CH3
|
|
H H
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 Aromatics: named like alkanes, but primarily based
on benzene
 Prefix describes relative positions of substituents:
ortho2 substituents next to each other
meta2 substituents separated by one C
para2 substituents separated by two C’s
ortho-
meta-
para-
 Naphthalene: “mothballs”
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