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Chapter 23: Organic Chemistry
Key topics:
Nomenclature
Functional groups
Drawing skeletal structures
Organic Chemistry
o study of carbon-containing compounds
o originally: compounds produced by living organisms
o now: includes man-made compounds such as plastics
Why Carbon is Different
electron configuration: [He]2s22p2
o effectively prohibits ion formation
(energetically VERY unfavorable to gain/lose 4 e–)
o fills octet by sharing e–
Small atomic radius, n = 2 valence shell (no 2d orbitals)
o short, strong bonds
o good p orbital overlap to give π bonds
o no 2d orbitals imparts stability (Si more reactive)
o catenation to form chains and rings containing single,
double and triple bonds
ethane: stable in water and air
disilane: breaks down in water and spontaneously combusts in air
Classes of Organic Compounds
Variety comes from
o carbon forming chains by bonding to itself
o presence of elements other than C and H
o Functional groups – a group of atoms that determines
many of a molecule’s properties
o multiple bonds
Alkanes:
• contain C atoms connected by single bonds, and
H atoms connected to C with single bonds
Low density; totally insoluble in water
• Naming:
1. Identify the longest continuous C chain to get the
parent name (root + “ane”)
2. Number the C’s in the continuous chain, beginning at
the end closest to the substituent (branch point)
3. Identify the substituent and use a number and a prefix
to specify location and identity, respectively
# of Carbons
1
2
3
4
5
6
7
8
9
10
Root name
Meth–
Eth–
Prop–
But–
Pent–
Hex–
Hept–
Oct–
Non–
Dec–
• alkyl group: alkane minus one H
-- substituent
Name:
H
H
H C H
H H
H H H
H C H
H H
H H H
H C C C C C C H
H C C C C C C H
H H
H H H
H C H
H H
H H H
H C H
H
H
3,3-dimethylhexane
---------------------------------------------
---------------------------------------------
---------------------------------------------
Other Functional Groups:
• functional groups determine chemistry that compound will
undergo (electrostatic maps shown below)
Alcohols:
• contains –OH group (hydroxyl group)
Methanol, ethanol, and propyl alcohol are miscible with water
• naming:
1. Identify the longest chain that includes the –OH group
2. Change the –e ending to -ol
3. Number to give the –OH the lowest number
4. When the chain also contains an alkyl substituent, give
the –OH the lowest number
---------------------------------------------
--------------------------------------------Carboxylic Acids:
• contains –COOH (carboxy) group
polar; form strong hydrogen bonds with each other and water
• naming:
1. Identify the longest chain that includes the carboxyl
group
2. Change the –e ending to –oic acid
3. Number starting with the carbonyl (C=O) carbon
4. Use numbers and prefixes to indicate the position and
identity of any substituents
Esters:
• contain –COO– group (between two other non-H groups)
polar but cannot form strong hydrogen bonds
• naming:
-- Name as derivative of carboxylic acid by replacing the
–ic acid ending with –ate
st
-- 1 part of name specifies the substituent that replaces
the ionizable hydrogen of the corresponding acid
Aldehydes:
• contains –COH (carbonyl group) – at end of chain
polar but cannot form strong hydrogen bonds with each other;
however can form strong hydrogen bonds with water.
• naming:
1. Identify the longest chain that includes the carbonyl
group
2. Change the –e ending to -al
3. Number starting with the carbonyl (C=O) carbon
4. Use numbers and prefixes to indicate the position and
identity of any substituents
Ketones:
• contains –CO– (carbonyl group) -- between two other groups
polar but cannot form strong hydrogen bonds with each other;
however can form strong hydrogen bonds with water.
• naming:
1. Identify the longest chain that includes the carbonyl
group
2. Change the –e ending to -one
3. Number to give the carbonyl group the lowest possible
number
4. Use numbers and prefixes to indicate the position and
identity of any substituents
--------------------------------------------CH3
O
CH3
CH
CH2
C
OH
--------------------------------------------O
CH3
CH2
CH2
C
CH3
---------------------------------------------
Primary Amines:
• contains –NH2 group
moderately polar; can form strong hydrogen bonds to each
other and to water
• naming:
1. Identify the longest chain that includes the –NH2 group
2. Change the –e ending to -amine
3. Number starting with the carbon to which the –NH2
group is bonded
4. Use numbers and prefixes to indicate the position and
identity of any substituents
Primary Amides:
• contains –CONH2 group (e.g. peptides)
can form strong hydrogen bonds to each other; therefore
amides have high melting and boiling points
• naming:
1. Can be named as derivatives of carboxylic acids
-- Or, by replacing the –e ending with –amide
Compounds with More than One Substituent:
• Prefixes of di, tri, tetra, penta and so forth are used to
denote the number of substituents
• Substituent names are alphabetized
• Numbers are used to indicate position of the alphabetized
substituents
• Prefixes are not counted when alphabetizing
Representing Organic Molecules:
• large numbers of ways to organize atoms in an organic
molecules: e.g. C5OHx
• Condensed structural formula (Condensed Structure):
shows the same information as a structural formula
but in condensed form
octane: C8H18
molecular formula
CH3(CH2)6CH3
condensed structural formula
-- branches indicated using parentheses
2-methylheptane
C8H18
Molecular formula
CH3CH(CH3)(CH2)4CH3
condensed structural formula
• Kekulé structures: similar to Lewis structure but without
showing lone pairs
• Skeletal Structures: Consist of straight lines that represent
carbon-carbon bonds.
-- Heteroatoms (atoms other than C or H) shown explicitly