3 3-1 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Introduction to Organic Chemistry 2 ed William H.
Brown
Slide 2
3 3-2 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Chapter 3 Alkanes and and Cycloalkanes Cycloalkanes
Slide 3
3 3-3 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Structure Hydrocarbon Hydrocarbon: a compound composed
only of carbon and hydrogen Saturated hydrocarbon Saturated
hydrocarbon: a hydrocarbon containing only single bonds Alkane
Alkane: a satuated hydrocarbon whose carbons are arranged in a
chain Aliphatic hydrocarbon Aliphatic hydrocarbon: another name for
an alkane
Slide 4
3 3-4 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Structure Shape tetrahedral about carbon all bond angles
are approximately 109.5
Slide 5
3 3-5 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Constitutional Isomerism Constitutional isomers
Constitutional isomers: compounds with the same molecular formula
but a different connectivity (order of attachment of their atoms)
example: C 4 H 10
Slide 6
3 3-6 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Constitutional Isomerism World population is about
6,000,000,000
Slide 7
3 3-7 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Nomenclature Alkanes have the general formula C n H
2n+2
Slide 8
3 3-8 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Nomenclature
Slide 9
3 3-9 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Nomenclature International Union of Pure and Applied
Chemistry (IUPAC) Prefix tells the number of carbon atoms ane
Suffix -ane specifies an alkane
Slide 10
3 3-10 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Nomenclature IUPAC system
Slide 11
3 3-11 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Nomenclature Alkyl groups
Slide 12
3 3-12 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Nomenclature Alkyl groups
Slide 13
3 3-13 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Nomenclature 1. The general name of an open-chain
saturated hydrocarbon is alkane 2.. For a branched-chain
hydrocarbon, the alkane corresponding to the longest chain is taken
as the parent chain and its name is the root name 3. Groups
attached to the parent chain are called substituents each is given
a name and a number
Slide 14
3 3-14 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Nomenclature 4. If there is one substituent, number from
the end of the chain that gives it the lower number
Slide 15
3 3-15 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Nomenclature 5. If the same substituent occurs more than
once, the number of each carbon of the parent chain on which it
occurs is given and the number of times it occurs is shown by di-,
tri-, tetra-, etc. 6. If there are two identical substituents,
number the chain to give the lower number to the substituent
encountered first
Slide 16
3 3-16 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Nomenclature 7. If there are two or more different
substituents, list them in alphabetical order, and number from the
end of the chain that gives the substituent encountered first the
lower number
Slide 17
3 3-17 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Nomenclature 8. The prefixes di-, tri-, tetra- etc. are
not included in alphabetization 9. Neither are hyphenated prefixes
such as sec- and tert-. The prefix iso- is not hyphenated, and is
included in alphabetization.
Slide 18
3 3-18 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Classification of C & H Primary (1) C Primary (1) C:
a carbon bonded to one other carbon 1 H: a hydrogen bonded to a 1
carbon Secondary (2) C Secondary (2) C: a carbon bonded to two
other carbons 2 H: a hydrogen bonded to a 2 carbon Tertiary (3) C
Tertiary (3) C: a carbon bonded to three other carbons 3 H: a
hydrogen bonded to a 3 carbon Quaternary (4) C Quaternary (4) C: a
carbon bonded to four other carbons
Slide 19
3 3-19 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Cycloalkanes General formula C n H 2n Ring sizes from 3
to 30 and more are known five- and six-membered rings are the most
common
Slide 20
3 3-20 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Cycloalkanes Line-angle drawings each line represents a
C-C bond each angle represents a C
Slide 21
3 3-21 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. IUPAC - General prefix-infix-suffix prefix prefix shows
the number of carbon atoms in the parent infix infix shows the
nature of the carbon-carbon bonds in the parent
Slide 22
3 3-22 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. IUPAC - General suffix suffix shows the class of
compound
Slide 23
3 3-23 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. IUPAC - General prop-en-e = propene eth-an-ol = ethanol
but-an-one = butanone but-an-al = butanal pent-an-oic acid =
pentanoic acid cyclohex-an-ol = cyclohexanol eth-yn-e = ethyne
Slide 24
3 3-24 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Conformations Conformation Conformation: any
three-dimensional arrangement of atoms in a molecule that results
from rotation about a single bond staggered conformation staggered
conformation: a conformation about a carbon-carbon single bond
where the atoms on one carbon are as far apart as possible from
atoms on the adjacent carbon
Slide 25
3 3-25 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Conformations eclipsed conformation: a conformation about
a carbon- carbon single bond where atoms on one carbon are as close
as possible to the atoms on the adjacent carbon
Slide 26
3 3-26 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Intramolecular Strain Intramolecular strain
Intramolecular strain: strain present in a molecule because of
nonbonded interaction strain and angle strain nonbonded interaction
strain nonbonded interaction strain: arises when atoms not bonded
to each other are forced abnormally close to each other; e.g.,
eclipsed hydrogens in ethane angle strain angle strain: arises from
creation of abnormal bond angles
Slide 27
3 3-27 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Conformations We see nonbonded interaction strain in the
eclipsed conformation of ethane at room temperature, approximately
99% of ethane molecules are in the lower-energy staggered
conformation and 1% or less are in the higher- energy eclipsed
conformation
Slide 28
3 3-28 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Cyclopentane bond angles in planar cyclopentane are 108,
which differs only slightly from 109.5. But there are 10 sets of
eclipsed hydrogens the ring puckers to an envelope conformation,
with average C-C-C bond angles of 105. Puckering increases angle
strain, but reduces the nonbonded interaction strain of eclipsed
hydrogens.
Slide 29
3 3-29 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Cyclohexane Chair conformation Chair conformation: the
most stable puckered conformation of a cyclohexane ring all bond
angles are approx. 109.5 all bonds on adjacent carbons are
staggered
Slide 30
3 3-30 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Cyclohexane - chair Six H are equatorial and six are
axial
Slide 31
3 3-31 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Cyclohexane Boat conformation Boat conformation: a
puckered conformation of a cyclohexane ring in which carbons 1 and
4 are bent toward each other less stable than the chair
conformation by +7 kcal/mol
Slide 32
3 3-32 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Cyclohexane There are two equivalent chair conformations
all C-H bonds equatorial in one chair are axial in the other, and
vice versa
Slide 33
3 3-33 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Methylcyclohexane Equatorial and axial methyl
conformations
Slide 34
3 3-34 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Example 3.8 Label all axial-axial interactions in this
chair conformation
Slide 35
3 3-35 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Tetrodotoxin Produced in the liver and ovaries of the
puffer fish
Slide 36
3 3-36 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Cis-Trans Isomerism Cis-trans isomers have the same
molecular formula the same connectivity an arrangement of atoms in
space that cannot be interconverted by rotation about single bonds
under ordinary conditions
Slide 37
3 3-37 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Cis-trans Isomerism 1,2-dimethylcyclopentane
Slide 38
3 3-38 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Cis-trans Isomerism 1,4-Dimethylcyclohexane planar
hexagon representations
Slide 39
3 3-39 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Cis-trans Isomerism trans-1,4-dimethylcyclohexane
Slide 40
3 3-40 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Cis-trans Isomerism cis-1,4-dimethylcyclohexane
Slide 41
3 3-41 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Physical Properties Low-molecular-weight alkanes
(methane....butane) are gases at room temperature Higher-molecular
weight alkanes (pentane, decane, gasoline, kerosene) are liquids at
room temperature High-molecular weight alkanes (paraffin wax) are
semisolids or solids at room temperature
Slide 42
3 3-42 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Physical properties Constitutional isomers have different
physical properties
Slide 43
3 3-43 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Oxidation of alkanes Oxidation - the basis for their use
as energy sources for heat: natural gas, liquefied natural gas
(LPG), fuel oil power: gasoline, diesel, and aviation fuel
Slide 44
3 3-44 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Sources of alkanes Natural gas 90-95% methane Petroleum
gases gasoline, kerosene fuel oil lubricating oils asphalt
Coal
Slide 45
3 3-45 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Gasoline Octane rating Octane rating: the percent
2,2,4-trimethylpentane (isooctane) in a mixture of isooctane and
heptane that has equivalent antiknock properties
Slide 46
3 3-46 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Synthesis gas A mixture of carbon monoxide and hydrogen
in varying proportions depending on the means by which it is
manufactured
Slide 47
3 3-47 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. Synthesis Gas Synthesis gas is a feedstock for the
industrial production of methanol and acetic acid it is likely that
industrial routes to other organic chemicals from coal via methanol
will also be developed
Slide 48
3 3-48 Copyright 2000 by John Wiley & Sons, Inc. All rights
reserved. AlkanesandCycloalkanes End Chapter 3