Transcript chapter20(10-27-14)

Section 20.1
Saturated Hydrocarbons
Steven S. Zumdahl
Susan A. Zumdahl
Donald J. DeCoste
Chapter 20
Organic Chemistry
Gretchen M. Adams • University of Illinois at Urbana-Champaign
Section 20.1
Saturated Hydrocarbons
Objectives
1. To understand the types of bonds formed by the carbon
atom
2. To learn about the alkanes
3. To learn about structural isomers
4. To learn to draw structural formulas
5. To learn to name alkanes and substituted alkanes
6. To learn about the composition and uses of petroleum
7. To learn about the chemical reactions of alkanes
Section 20.1
Saturated Hydrocarbons
Carbon Chemistry
• Carbon is unusual.
 Bonds strongly to itself
 Forms long chains or rings
• Biomolecule – molecule that functions in maintaining and
reproducing life
• Organic compounds – vast majority of carbon compounds
 Exceptions – oxides and carbonates
Section 20.1
Saturated Hydrocarbons
A. Carbon Bonding
• When carbon has 4 atoms bound to it, these atoms have
a tetrahedral shape.
Section 20.1
Saturated Hydrocarbons
A. Carbon Bonding
Double bond
• Sharing of 2 pairs of electrons
Triple bond
• Sharing of 3 pairs of electrons
Section 20.1
Saturated Hydrocarbons
B. Alkanes
• Hydrocarbons – compounds composed of carbon and
hydrogen
 Saturated – all carbon-carbon bonds are single bonds
 Unsaturated – containing carbon-carbon multiple bonds
Section 20.1
Saturated Hydrocarbons
B. Alkanes
• Alkanes – saturated hydrocarbons
Section 20.1
Saturated Hydrocarbons
B. Alkanes
• Normal, straight-chain or unbranched hydrocarbons
• Contain strings or chains of carbon atoms
 Representations
Section 20.1
Saturated Hydrocarbons
B. Alkanes
Section 20.1
Saturated Hydrocarbons
C. Structural Formulas and Isomerism
• Structural isomerism – occurs when 2 molecules have the
same atoms but different bonds
Section 20.1
Saturated Hydrocarbons
D. Naming Alkanes
Basic principles
• The name for an alkane is based on Greek root with the
suffix –ane.
Section 20.1
Saturated Hydrocarbons
D. Naming Alkanes
Basic principles
• For branched hydrocarbons use the longest continuous
chain for the root name.
Section 20.1
Saturated Hydrocarbons
D. Naming Alkanes
Basic principles
• Alkanes missing one H atom can have another
hydrocarbon attached at the missing H point.
Section 20.1
Saturated Hydrocarbons
D. Naming Alkanes
Basic principles
• Specify the names of substituents by numbering the C
atoms starting at the end closest to the branching.
Section 20.1
Saturated Hydrocarbons
D. Naming Alkanes
Basic principles
Section 20.1
Saturated Hydrocarbons
D. Naming Alkanes
Basic principles
• If a substituent occurs more than once, use a prefix to
show this.
2,3-dimethylpentane
Section 20.1
Saturated Hydrocarbons
D. Naming Alkanes
Section 20.1
Saturated Hydrocarbons
Exercise
Name each of the following:
CH3
a)
H3C C
CH3
CH2 CH
CH3
CH
CH3
CH3
2,2,4,5-tetramethylhexane
b) H C
3
CH2 CH3
CH2 CH3
C
CH
CH2 CH2
CH2 CH3
3,6-diethyl-3-methyloctane
CH2 CH3
Section 20.1
Saturated Hydrocarbons
E. Petroleum
• Hydrocarbons are an energy resource.
Section 20.1
Saturated Hydrocarbons
E. Petroleum
• Petroleum – thick, dark liquid composed mostly of
hydrocarbon compounds
• Natural gas – consists mostly of methane, usually
associated with petroleum deposits
Section 20.1
Saturated Hydrocarbons
F. Reactions of Alkanes
• Combustion – reaction with oxygen
• Substitution – one or more H atoms are replaced with
different atoms
Section 20.1
Saturated Hydrocarbons
F. Reactions of Alkanes
• Dehydrogenation – one or more H atoms are removed
and the product is an unsaturated hydrocarbon
Section 20.2
Unsaturated Hydrocarbons
Objectives
1. To learn to name hydrocarbons with double and triple
bonds
2. To understand addition reactions
3. To learn about the aromatic hydrocarbons
4. To learn to name aromatic compounds
Section 20.2
Unsaturated Hydrocarbons
A. Alkenes and Alkynes
• Alkenes – hydrocarbon containing carbon-carbon double
bonds
 General formula CnH2n
• Alkynes – hydrocarbons containing carbon-carbon triple
bonds
 General formula CnH2n – 2
Section 20.2
Unsaturated Hydrocarbons
A. Alkenes and Alkynes
Section 20.2
Unsaturated Hydrocarbons
Exercise
Name each of the following:
a)
CH3
CH3
H3C CH CH2 C
C
CH3
CH3
2,3,5-trimethyl-2-hexene
b)
CH2 CH3
H3C C
CH
CH2 CH3
CH2
CH
6-ethyl-3-methyl-3-octene
CH2
CH3
Section 20.2
Unsaturated Hydrocarbons
A. Alkenes and Alkynes
Reactions of Alkenes
• Addition reactions – new atoms form single bonds to the
carbons formerly involved in a double or triple bond
 Hydrogenation – use H2 as the reactant to be added
 Halogenation – addition of halogen atoms
• Polymerization – joining of many small molecules to form
a large molecule
Section 20.2
Unsaturated Hydrocarbons
B. Aromatic Hydrocarbons
• Aromatic hydrocarbons – cyclic unsaturated
hydrocarbons with strong aromas
Section 20.2
Unsaturated Hydrocarbons
B. Aromatic Hydrocarbons
• Benzene – simplest aromatic hydrocarbon
Section 20.2
Unsaturated Hydrocarbons
C. Naming Aromatic Compounds
• Monosubstituted benzenes –
use the substituent name as
a prefix of benzene
Section 20.2
Unsaturated Hydrocarbons
C. Naming Aromatic Compounds
• Disubstituted
benzenes
 Use numbers to
indicate the
position of
substituents and
the substituent
name as a prefix
of benzene.
Section 20.2
Unsaturated Hydrocarbons
C. Naming Aromatic Compounds
• Complex aromatic molecules
Section 20.2
Unsaturated Hydrocarbons
Benzene as a side group is called phenyl
• Phenyl (phenyl group): A portion of a molecular
structure which is equivalent to benzene minus one
hydrogen atom: -C6H5
Chlorobenzene or Phenyl chloride
Section 20.3
Introduction to Functional Groups and Alcohols
Objectives
1. To learn the common functional groups in organic
molecules
2. To learn about simple alcohols and how to name them
3. To learn about how some alcohols are made and used
4. To learn about simple ethers and how to name them
Section 20.3
Introduction to Functional Groups and Alcohols
A. Functional Groups
• Functional group – additional atom or groups of atoms
(containing elements in addition to H and C) found on a
mostly hydrocarbon molecule
Section 20.3
Introduction to Functional Groups and Alcohols
B. Alcohols
• All alcohols contain the –OH group.
Section 20.3
Introduction to Functional Groups and Alcohols
B. Alcohols
Section 20.3
Introduction to Functional Groups and Alcohols
The different kinds of alcohols
• Alcohols fall into different classes depending on where
the –OH is positioned on the chain of carbon atoms.
• There are some chemical differences between the
various types.
• Primary, Secondary, and Tertiary alcohols will be
discussed on the next several slides.
• Common alcohols:
– Methanol-wood alcohol
– Ethanol-as an antiseptic and in alcoholic beverages
– Isopropanol-in rubbing alcohol
Section 20.3
Introduction to Functional Groups and Alcohols
Primary Alcohols
• In a primary (1o) alcohol, the carbon which carries the –
OH group is only attached to one alkyl group.
• Examples of primary alcohols:
Ethanol
1-propanol
2-methyl-1-propanol
Section 20.3
Introduction to Functional Groups and Alcohols
Secondary Alcohols
• In a secondary (2o) alcohol, the carbon with the –OH
group attached is joined directly to two alkyl groups,
which may be the same or different.
• Examples
2-propanol
2-butanol
3-pentanol
Section 20.3
Introduction to Functional Groups and Alcohols
Tertiary Alcohols
• In a tertiary (3o) alcohol, the carbon with the –OH group
attached is joined directly to three alkyl groups, which
may be the same or different.
• Examples
2-methyl-2-propanol
2-methyl-2-butanol
Section 20.3
Introduction to Functional Groups and Alcohols
C. Properties and Uses of Alcohols
• Methanol
 starting material for making acetic acid and many
adhesives, fibers and plastics
 motor fuel
• Ethanol
 Fermentation product
 Fuel additive used to make gasohol
Section 20.3
Introduction to Functional Groups and Alcohols
C. Properties and Uses of Alcohols
• Other alcohols
 Ethylene glycol (ethane-1,2-diol) – automotive antifreeze
 Phenol (benzenol) – production of adhesives and
plastics
Section 20.3
Introduction to Functional Groups and Alcohols
C. Ethers
• An ether is a hydrocarbon with an oxygen sandwiched
between the carbons.
• They tend to by very good solvents, much like water, and
have relatively low reactivity.
Section 20.3
Introduction to Functional Groups and Alcohols
Rules for Naming Ethers (common method)
• There are two predominate methods of naming ethers.
The first is the common method and is most useful with
simple ethers.
(The second method is preferred; next slide)
• For the first method, if the carbon chains one side of the
oxygen are considered alkyl groups you simply name the
groups then write ether.
CH CH O CH
3 2
3
Ethyl methyl ether
Section 20.3
Introduction to Functional Groups and Alcohols
Rules for Naming Ethers (Preferred method)
• The other method follows the official IUPAC rules:
• Determine the longest alkyl chain for the root name.
• Treat the oxygen and the remaining carbons as aside
chain.
• The prefix includes the alkyl chain with a suffix of oxy for
the oxygen.
CH CH O CH
3 2
3
methoxyethane
Section 20.3
Introduction to Functional Groups and Alcohols
Practice Naming Ethers (answers next slide!)
Section 20.3
Introduction to Functional Groups and Alcohols
Answers to Last Slide
(a) Diisopropyl ether
(a) Cyclopentyl propyl ether
(a) 4-Bromo-1-methoxybenzene
(d) 1-Methoxycyclohexene
(d) Ethyl isobutyl ether
Section 20.3
Introduction to Functional Groups and Alcohols
Preparation of Ethers
• Dehydration of two alcohols:
• Alkyl halide and alkoxide:
Section 20.4
Additional Organic Compounds
Objectives
1. To learn about aldehydes and ketones
2. To learn to name aldehydes and ketones
3. To learn about some common carboxylic acids and
esters
4. To learn about amines.
5. To learn how to name amines.
6. To learn about some common polymers
Section 20.4
Additional Organic Compounds
A. Aldehydes and Ketones
• Carbonyl group – carbon oxygen group found in both
aldehydes and ketones
 Ketone – carbonyl group is bonded to two carbon
atoms
Section 20.4
Additional Organic Compounds
A. Aldehydes and Ketones
 Aldehyde – carbonyl group always appears on the end
of the hydrocarbon chain and has at least one H atom
bonded to the carbonyl group
Section 20.4
Additional Organic Compounds
A. Aldehydes and Ketones
Section 20.4
Additional Organic Compounds
B. Naming Aldehydes and Ketones
• Aldehydes
 Use the parent alkane name.
• Remove the e and replace it with al.
Section 20.4
Additional Organic Compounds
B. Naming Aldehydes and Ketones
• Ketones
 Use the parent alkane name.
• Remove the e and replace it with one.
• Use a number to indicate the position of the
carbonyl group in the hydrocarbon chain.
 Select the number so that the carbonyl has the lowest
possible number.
Propanone (acetone)
2-butanone (methyl-ethyl-ketone MEK)
Section 20.4
Additional Organic Compounds
C. Carboxylic Acids and Esters
• Carboxylic acids – contains the carboxyl group
 COOH
• General formula RCOOH
• Weak acids in solution
Section 20.4
Additional Organic Compounds
C. Carboxylic Acids and Esters
• To name carboxylic acids
 Use the parent alkane name.
• Remove the e and replace it with oic.
Section 20.4
Additional Organic Compounds
C. Carboxylic Acids and Esters
Section 20.4
Additional Organic Compounds
C. Carboxylic Acids and Esters
• Esters – a carboxylic acid reacts with an alcohol to form
an ester and a water molecule
 General formula
Section 20.4
Additional Organic Compounds
C. Carboxylic Acids and Esters
• To name esters
 Use the alkyl name from the alcohol followed by the
acid name, where the –ic ending is replaced by –ate.
isopropylethanoate
Section 20.4
Additional Organic Compounds
Amines
• What are amines?
• The easiest way to think of amines is as near relatives of
ammonia, NH3.
• In amines, the hydrogen atoms in the ammonia have
been replaced one at a time by hydrocarbon groups.
On this page, we are only looking at cases where the
hydrocarbon groups are simple alkyl groups.
Section 20.4
Additional Organic Compounds
The different kinds of amines
• Amines fall into different classes depending on how
many of the hydrogen atoms are replaced.
Primary
Secondary
Tertiary
In a primary (1°) amine, one carbon group is bonded
to the nitrogen atom.
A secondary (2°) amine has two carbon groups.
A tertiary (3°) amine has three carbon groups.
Section 20.4
Additional Organic Compounds
Common Names of Amines
• Simple amines are named as alkylamines.
• The alkyl groups bonded to the N atom are listed in
alphabetical order in front of amine.
Section 20.4
Additional Organic Compounds
IUPAC Names of Amines
• In the IUPAC system, amines are named as
alkanamines.
• The –e in the alkane name of the longest chain is
changed to –amine.
• The chain is numbered to locate the amine group
and substituents.
Section 20.4
Additional Organic Compounds
Primary amines
• In primary amines, only one of the hydrogen atoms in the
ammonia molecule has been replaced.
That means that the formula of the primary amine
will be R-NH2 where "R" is an alkyl group.
• Examples include:
Methanamine
Ethanamine
Propanamine
Isopropanamine
Section 20.4
Additional Organic Compounds
• The common name at this level is methylamine and,
similarly, the second compound drawn above is usually
called ethylamine.
• Where there might be confusion about where the -NH2
group is attached to a chain, the simplest way of naming
the compound is to use the "amino" form.
Section 20.4
Additional Organic Compounds
Secondary amines
• In a secondary amine, two of the hydrogens in an
ammonia molecule have been replaced by hydrocarbon
groups. At this level, you are only likely to come across
simple ones where both of the hydrocarbon groups are
alkyl groups and both are the same.
• Dimethanamine
diethanamine
Section 20.4
Additional Organic Compounds
Tertiary amines
• In a tertiary amine, all of the hydrogens in an ammonia
molecule have been replaced by hydrocarbon groups.
Again, you are only likely to come across simple ones
where all three of the hydrocarbon groups are alkyl
groups and all three are the same.
• The naming is similar to secondary amines. For
example:
Section 20.4
Additional Organic Compounds
Physical Properties of Amines
We will look at the boiling point difference on
the next several slides.
Section 20.4
Additional Organic Compounds
Primary amines
• It is useful to compare the boiling point of methylamine,
CH3NH2, with that of ethane, CH3CH3.
• Both molecules contain the same number of electrons
and have, as near as makes no difference, the same
shape. However, the boiling point of methylamine is 6.3°C, whereas ethane's boiling point is much lower at 88.6°C.
• The reason for the higher boiling points of the primary
amines is that they can form hydrogen bonds with each
other as well as van der Waals dispersion forces and
dipole-dipole interactions.
Section 20.4
Additional Organic Compounds
Secondary amines
• For a fair comparison you would have to compare the boiling
point of dimethylamine with that of ethylamine. They are
isomers of each other - each contains exactly the same
number of the same atoms.
• The boiling point of the secondary amine is a little lower than
the corresponding primary amine with the same number of
carbon atoms.
• Secondary amines still form hydrogen bonds, but having the
nitrogen atom in the middle of the chain rather than at the end
makes the permanent dipole on the molecule slightly less.
• The lower boiling point is due to the lower dipole-dipole
attractions in the dimethylamine compared with ethylamine.
Section 20.4
Additional Organic Compounds
Tertiary amines
• This time to make a fair comparison you would have to
compare trimethylamine with its isomer 1-aminopropane.
• If you look back at the table on slide 18, you will see that
the trimethylamine has a much lower boiling point
(3.5°C) than 1-aminopropane (48.6°C).
• In a tertiary amine there aren't any hydrogen atoms
attached directly to the nitrogen. That means that
hydrogen bonding between tertiary amine molecules is
impossible. That's why the boiling point is much lower.
Section 20.4
Additional Organic Compounds
Solubility in water
•The small amines of all types are very soluble in water. In
fact, the ones that would normally be found as gases at room
temperature are normally sold as solutions in water - in much
the same way that ammonia is usually supplied as ammonia
solution.
Smell
•The very small amines like methylamine and ethylamine
smell very similar to ammonia - although if you compared
them side by side, the amine smells are slightly more
complex.
•As the amines get bigger, they tend to smell more "fishy", or
they smell of decay.
Section 20.4
Additional Organic Compounds
D. Polymers
• Polymers – large chainlike molecules made from many
small molecules called monomers
 Simplest polymer – polyethylene
 Polyethylene results from addition polymerization.
Section 20.4
Additional Organic Compounds
D. Polymers
• Condensation polymerization – a small molecule (often
water) is released for each addition of a monomer to the
polymer chain
 Nylon (co-polymer)
• Copolymer – 2 different types of monomers combine to
form the chain
Section 20.4
Additional Organic Compounds
Sodium Silicate polymer
• When sodium silicate and ethyl alcohol are put together,
the silicate particles begin to link up with each other to
form long chains as the ethyl groups (sometimes shown
as "R") replace oxygen atoms in the silicate ion. (Some
become cross-linked between chains.)
Water molecules are by-products of the formation of the
polymerization bond.
• The large molecule is a solid. It is a type of silicone
polymer.