Organic Compounds that Contain
Oxygen or Sulfur
Three families of compounds that contain a C atom
singly bonded to O or S are:
1. Alcohols, which contain an OH (hydroxyl) group
2. Ethers, which have two alkyl groups bonded to
an O atom
1
Organic Compounds that Contain
Oxygen, Halogen, or Sulfur
3. Alkyl halides, which contain a halogen atom,
(X= F, Cl, Br, or I) bonded to a tetrahedral carbon.
4. Thiols, which contain a SH (sulfhydryl) group.
2
Organic Compounds that Contain
Oxygen, Alkyl Halides, or Sulfur
Two families of compounds that contain a carbonyl
group C=O:
1. Aldehydes, which have at least one H atom
bonded to the carbonyl carbon.
2. Ketones, which have two alkyl groups bonded to
the carbonyl carbon.
3
Structure and Properties of Alcohols
• Alcohols contain a hydroxyl (OH) group.
• Alcohols are classified by the number of C atoms
bonded to the C with the OH group.
A primary (1o) alcohol has
an OH group on a C bonded
only to 1 C atom.
1o
4
Structure and Properties of Alcohols
A secondary (2o) alcohol has
an OH group on a C bonded
only to 2 C atoms.
2o
3o
A tertiary (3o) alcohol has
an OH group on a C bonded
only to 3 C atoms.
5
Structure and Properties of Alcohols
• An alcohol (ROH) contains an O atom with a bent
shape like H2O and a bond angle similar to a
tetrahedral.
• Alcohols have an H atom bonded to an O atom,
making them capable of intermolecular hydrogen
bonding.
• This gives alcohols much stronger
intermolecular forces than hydrocarbons.
6
Structure and Properties of Alcohols
• As a result, alcohols have higher boiling and melting
points than hydrocarbons of comparable molecular
weight and shape.
melting point: -138 ºC
boiling point: -0.5 ºC
melting point: -127 ºC
boiling point: 97 ºC
stronger intermolecular forces
higher boiling and melting point
7
Structure and Properties of Alcohols
• Alcohols are soluble in organic solvents.
• Low molecular weight alcohols (6 Cs or less)
are soluble in water.
• Higher molecular weight alcohols (6 Cs or more)
are not soluble in water.
2 Cs in chain
water soluble
8 Cs in chain
water insoluble
8
Nomenclature of Alcohols
In the IUPAC system, alcohols are identified
by the suffix -ol.
To name an alcohol:
• Find the longest carbon chain containing the
carbon bonded to the OH group.
• Number the carbon chain to give the OH group
the lower number, and apply all other rules of
nomenclature.
9
Nomenclature of Alcohols
Sample Problem 12.2
Give the IUPAC name of the following alcohol.
Step [1]
Find the longest carbon chain containing the
C bonded to the OH group.
5 Cs in longest chain
pentane ----> pentanol
• Change the –e ending of
the parent alkane to the
suffix –ol.
10
Nomenclature of Alcohols
Step [2]
Number the carbon chain to give the OH group
the lower number, and apply all other rules
of nomenclature.
1-pentanol
Answer
3,3-dimethyl-1-pentanol
11
Nomenclature of Alcohols
• When an OH group is bonded to a ring, the OH
is automatically on C1.
• The “1” is usually omitted from the name.
• The ring is then numbered to give the next
substituent the lower number.
12
Structure and Properties of Ethers
• Ethers (ROR) have two alkyl groups bonded to
an O atom.
• The O atom of an ether has a bent shape like
H2O and a bond angle similar to a tetrahedral.
13
Naming Ethers
Simple ethers are usually assigned common names:
• Name both alkyl groups bonded to the O atom.
• Arrange these names alphabetically.
• Finally, add the word “ether” to the end.
• For identical alkyl groups, add the prefix di-.
CH3 O
methyl
CH2CH3
ethyl
ethyl methyl ether
CH3CH2 O
ethyl
CH2CH3
ethyl
diethyl ether
14
Structure and Properties of Ethers
Physical Properties
• Ether has two polar C—O bonds with a bent
shape, therefore it has a net dipole.
• Ether does not contain an H atom bonded to an
O atom, so ether cannot form intermolecular
hydrogen bonds.
15
Structure and Properties of Ethers
Physical Properties
These facts give ethers:
• stronger intermolecular forces than alkanes.
• weaker intermolecular forces than alcohols.
As a result, ethers of comparable size and shape
tend to have:
• higher melting and boiling points than hydrocarbons.
• lower melting and boiling points than alcohols.
16
Structure and Properties of Ethers
Physical Properties
17
Structure and Properties of Ethers
Physical Properties
• Ethers are soluble in organic solvents.
• Low molecular weight ethers (5 Cs or less) are
soluble in water, as water can hydrogen bond to
the ether’s O atom.
• Higher molecular weight ethers (6 Cs or more)
are not soluble in water.
18
Focus on Health & Medicine
Ethers as Anesthetics
• A general anesthetic is a drug that interferes with
nerve transmission in the brain, resulting in a loss
of consciousness and the sensation of pain.
• Diethyl ether was first demonstrated as an
anesthetic in the nineteenth century.
• Modern variations include the three ethers below:
19
Reactions of Alcohols
Dehydration
• Dehydration is the loss of H2O from a starting
material.
• It occurs when an alcohol is treated with a strong
acid like H2SO4, and forms an alkene product.
• Dehydration is an example of an elimination
reaction, in which parts of the starting material are
“lost” and a multiple bond is formed.
20
Reactions of Alcohols
Dehydration
• Examples:
21
Reactions of Alcohols
Oxidation
Oxidation results in a(n):
• increase in the number of C—O bonds.
• decrease in the number of C—H bonds.
The symbol [O] indicates an oxidation reaction.
22
Reactions of Alcohols
Oxidation
• Oxidation occurs by replacing the C—H bonds
on the carbon bearing the OH group by C—O
bonds.
• All oxidation products from alcohol starting
materials contain a C=O, a carbonyl group.
23
Reactions of Alcohols
Oxidation
• Primary (1o) alcohols first oxidize to aldehydes
(RCHO), replacing 1 C—H with 1 C—O.
• Aldehydes are further oxidized to carboxylic
acids (RCOOH), replacing 1 C—H with 1 C—O.
1o alcohol
(ROH)
aldehyde
(RCHO)
carboxylic acid
(RCOOH)
24
Reactions of Alcohols
Oxidation
• Secondary (2o) alcohols are oxidized to ketones
(R2CO) replacing 1 C—H with 1 C—O.
25
Reactions of Alcohols
Oxidation
• Tertiary (3o) alcohols have no H atoms on the C
with the OH group, so they are not oxidized.
26
Focus on The Human Body
Oxidation and Blood Alcohol Screening
• The oxidation of ethanol with K2Cr2O7 was the
first available method for the routine testing of
alcohol concentration in exhaled air.
• Oxidation with K2Cr2O7 is characterized by a color
change, as the red-orange reagent is reduced to a
green Cr3+ product.
27
Focus on Health & Medicine
The Metabolism of Ethanol
• When ethanol is consumed it is quickly absorbed
in the stomach and small intestines.
• In the liver, the enzymes alcohol and aldehyde
dehydrogenase act as oxidizing reagents.
CH3CH—OH
[O]
O
C
CH3
ethanol
[O]
H
acetaldehyde
O
C
CH3
OH
acetic acid
• Consuming more ethanol than can be metabolized
leads to a buildup of acetaldehyde, which is toxic.
28
Organic Compounds that Contain
Alkyl Halides
• Alkyl Halides contain a halogen atom
(X= F, Cl, Br, or I) bonded to a tetrahedral carbon.
• Alkyl halides are classified by the number of C
atoms bonded to the C with the halogen.
29
Structure and Properties of Alkyl Halides
• Alkyl halides contains a polar C–X bond, but are
incapable of hydrogen bonding.
For an alkyl halide, the…
• boiling point and melting point increase with the
size of the alkyl group due to increased surface area.
• boiling point and melting point increase with the
size of the halogen.
30
Structure and Properties of Alkyl Halides
31
Nomenclature of Alkyl Halides
HOW TO Name an Alkyl Halide
Example
Give the IUPAC name of the following
alkyl halide:
Step [1]
Find the longest chain containing the
halogen.
32
Nomenclature of Alkenes and Alkynes
HOW TO Name an Alkene or Alkyne
Step [2] Apply all other rules of nomenclature.
33
Organic Compounds that Contain Sulfur
• Thiols contain a sulfhydryl group (SH) bonded to
a tetrahedral carbon.
• Because S is just below O on the periodic table,
thiols are similar to alcohols.
• Thiols have a bent shape around the S atom.
34
Organic Compounds that Contain Sulfur
• However, thiols contain no O—H bonds, so they
are incapable of intermolecular hydrogen bonding.
• This gives thiols lower boiling and melting points
than similar alcohols.
CH3CH2—OH
ethanol
CH3CH2—SH
ethanethiol
bp 78 oC
bp 35 oC
35
Organic Compounds that Contain Sulfur
• Thiols have a characteristic foul odor (skunk,
onions, etc.)
• They can be oxidized to disulfides.
36
Organic Compounds that Contain Sulfur
• The disulfides can be converted back to thiols
with a reducing agent.
• The symbol for a general reducing agent is [H],
since hydrogen atoms are often added during
reduction.
37
Organic Compounds that Contain Sulfur
• To make straight hair curly, the disulfide bonds
holding the hair proteins together are reduced.
• The hair is then turned around curlers, and an
oxidizing agent is applied.
• This re-forms the disulfide bonds in the hair, now
giving it a curly appearance.
38
Aldehydes and Ketones
Structure and Properties of Aldehydes and
Ketones
Two families of compounds contain a carbonyl group:
Aldehydes (RCHO)
Ketones (RCOR or R2CO)
39
Aldehydes and Ketones
Structure and Properties of Aldehydes
and Ketones
• The carbonyl carbon atom is trigonal planar, with
bond angles of 120o.
• O is more electronegative than C, so the carbonyl
group is polar.
• The carbonyl C is e− rich (δ−) and the carbonyl
O is e− poor (δ+).
40
Nomenclature
Naming Aldehydes
To name an aldehyde using the IUPAC system:
• Find the longest chain containing the CHO group.
• Change the “-e” ending of the parent alkane to “-al.”
• Number the chain to put the CHO group at C1, but
omit “1” from the name.
• Apply all other nomenclature rules.
CH3
CH3CHCH C
3 2
CH3
butane  butanal
O
1
H
Answer:
2,3-dimethylbutanal
41
Nomenclature
Naming Aldehydes
Common names are used for simple aldehydes;
the names contain the suffix “-aldehyde.”
formaldehyde
acetaldehyde
benzaldehyde
42
Nomenclature
Naming Ketones
To name a ketone using the IUPAC system:
• Find the longest chain containing the carbonyl
group.
• Change the “-e” ending of the parent alkane to
“-one.”
• Number the chain to give the carbonyl carbon the
lower number.
• Apply all other nomenclature rules.
O
CH3 C
1
2
pentane  pentanone
CHCH2CH3
CH3
3
Answer:
3-methl-2-pentanone
43
Nomenclature
Naming Ketones
• With cyclic ketones, numbering begins at the
carbonyl carbon, “1” is omitted from the name.
• The ring is then numbered clockwise or
counterclockwise to give the first substituent the
lower number.
Sample Problem 12.7
Step [1]
Name the ring.
cyclohexane  cyclohexanone
44
Nomenclature
Naming Ketones
Sample Problem 12.7
Step [2]
Number and name the substituents,
making the C=O C1.
1
3
Answer:
3-ethyl-4-methylcyclohexanone
4
45
Physical Properties
Aldehydes and ketones have higher boiling points
than similar hydrocarbons because:
• They are polar molecules.
• They have stronger intermolecular forces than
alkanes and alkenes.
CH3CH2CH2CH2CH3
pentane
bp 36 oC
CH3CH2CH2CHO
butanal
bp 76 oC
Increasing boiling point
46
Physical Properties
Aldehydes and ketones have lower boiling points
than similar alcohols because:
• They do not have an O—H bond.
• Therefore, they cannot have intermolecular
hydrogen bonding.
• Thus, they have weaker intermolecular forces
than alcohols.
CH3CH2COCH3
2-butanone
bp 80 oC
CH3CH2CH2CH2OH
1-butanol
bp 118 oC
Increasing boiling point
47
Physical Properties
• Aldehydes and ketones are soluble in organic
solvents.
• Those molecules with less than 6 Cs are soluble
in both organic solvents and water.
• Those molecules with 6 Cs or more are soluble
in organic solvents, but insoluble in water.
48
Focus on Health & Medicine
Interesting Aldehydes and Ketones
Cinnamaldehyde, the major component of
cinnamon bark:
Vanillin, the primary component of the extract of the
vanilla bean:
49
Oxidation of Aldehydes
Aldehydes contain a hydrogen atom bonded directly
to the carbonyl carbon; they can be oxidized to
carboxylic acids:
50
Reactions of Aldehydes and Ketones
Oxidation of Aldehydes
In oxidation, the aldehyde C—H bond is converted
into a carboxylic acid C—OH bond.
51
Reactions of Aldehydes and Ketones
Oxidation of Aldehydes
Ketones cannot be oxidized because there is no
C—H bond.
52
Reactions of Aldehydes and Ketones
Oxidation of Aldehydes
Aldehydes can be selectively oxidized in the presence
of other functional groups using the Tollens reagent.
53
Looking Glass Chemistry
Molecules and Their Mirror Images
Stereochemistry is the 3-dimensional structure of
compounds.
Stereoisomers differ only in the 3-dimensional
arrangement of atoms.
• The cis and trans examples below are
stereoisomers.
54
Molecules and Their Mirror Images
What It Means to be Chiral or Achiral
• Left hands and right hands are mirror images of
each other.
55
Molecules and Their Mirror Images
What It Means to be Chiral or Achiral
• Left and right hands are not identical
(nonsuperimposable).
• A molecule that is not superimposable on its mirror
image is chiral.
56
Molecules and Their Mirror Images
What It Means to be Chiral or Achiral
• Two socks from a pair are mirror images that are
superimposable.
• A molecule that is superimposable on its mirror
image is achiral.
57
Molecules and Their Mirror Images
The Chirality of Molecules
To determine whether a molecule is chiral or achiral
we must examine what groups are bonded to each
carbon atom:
• A chiral molecule has at least one carbon atoms
bonded to four different groups.
• An achiral molecule does not contain a carbon
atom bonded to four different groups.
To superimpose a molecule and its mirror image
you can perform any rotation but you cannot
break bonds.
58
Molecules and Their Mirror Images
The Chirality of Molecules
• For CH2BrCl:
• Rotate the
molecule to
align bonds:
59
Molecules and Their Mirror Images
The Chirality of Molecules
• For CHBrClF:
60
Molecules and Their Mirror Images
The Chirality of Molecules
• The two mirror images of CHBrClF are enantiomers,
mirror images that are not superimposable.
• A molecule that is not superimposable on its mirror
image is a chiral molecule.
• A carbon atom with four different groups like
CHBrClF is called a chirality center.
61
Chirality Centers
Locating Chirality Centers
• To locate a chirality center, look at each tetrahedral
C atom in a molecule.
• Look at the four groups—not the four atoms—
bonded to it.
62
Chirality Centers
Locating Chirality Centers
• We consider all atoms in a group as a whole unit.
63
Chirality Centers
Locating Chirality Centers
• Chirality centers in the examples below are
labeled in red:
64
Fischer Projections
A Fischer Projection takes a 3-D tetrahedral shape,
and re-draws it.
• A carbon atom is located at the intersection.
• The horizontal bonds come forward, on the
wedges.
• The vertical bonds go back, on the dashed lines.
65
Fischer Projections
• We can draw the cross and Fischer projection
for both enantiomers of 2-butanol:
66
Focus on Health & Medicine
Chiral Drugs
• Many drugs are chiral, and often they must interact
with a chiral receptor to be effective.
• One enantiomer of a drug may be effective in
treating a disease whereas its mirror image may be
ineffective.
• One enantiomer may “fit” the chiral receptor
and evoke a specific response.
• Its mirror image may not fit the same receptor,
making it ineffective.
67
Focus on Health & Medicine
Chiral Drugs
68
Focus on Health & Medicine
Chiral Pain Relievers
• Ibuprofen is an active anti-inflammatory agent
whose enantiomer is inactive, and is sold as a
racemic mixture.
69
Focus on Health & Medicine
Parkinson’s Disease and L-Dopa
• L-Dopa, a dopamine precursor, is used to help treat
the dopamine deficient brains of Parkinson’s
patients.
• Dopamine cannot be directly taken by a patient
because it cannot cross the blood-brain barrier.
70