An Introduction to Organic
Compounds:
Chapter 3
Nomenclature, Physical Properties, and
Representation of Structure
Chapter 3
1
Contents of Chapter 2

Nomenclature

Structures of Alkyl Halides, Alcohols,
Ethers, and Amines

Physical Properties

Conformations of Alkanes

Cycloalkanes
Chapter 3
2
Counting to Ten in Organic










01 = meth
02 = eth
03 = prop
04 = but
05 = pent
06 = hex
07 = hept
08 = oct
09 = non
10 = dec
Mother
Enjoys
Peanut
BUTter
PENTagon
HEXagon or HEX nut
HEPTember (Roman sept is Greek hept)
OCTober
NONember (Roman nov is Greek non)
DECember
Chapter 3
3
Alkanes
Chapter 3
4
Primary, Secondary, Tertiary





A primary carbon has one other C directly bonded to it.
A secondary carbon is directly bonded to two other C’s.
A tertiary carbon is directly bonded to three other C’s.
Multivalent atoms are 1º, 2º, or 3º by bonding to C’s.
Univalent atom or group not really 1º, 2º, or 3º on its
own - ID depends on type of carbon it is bonded to.
Chapter 3
5
Nomenclature of Alkyl
Substituents

There are four alkyl groups that contain
four carbons
Chapter 3
6
Nomenclature of Alkyl
Substituents

The prefix sec- occurs only in sec-butyl
Chapter 3
7
Nomenclature of Alkyl
Substituents

The prefix tert- can be used with butyl or
pentyl (also known as amyl) but not with
hexyl
Chapter 3
8
IUPAC Systematic
Nomenclature - Alkanes
•
•
Determine longest continuous chain (i.e. parent
hydrocarbon)
Cite the name of substituent before the name of
the parent hydrocarbon along with the number
of the carbon to which it is attached
Chapter 3
9
IUPAC Systematic
Nomenclature - Alkanes
•
Number in the direction that gives the
lower number for the lowest-numbered
substituent. Substituents are listed in
alphabetical order – neglecting
prefixes such as di- tri- tert- etc.
Chapter 3
10
IUPAC Systematic
Nomenclature - Alkanes
•
When both directions
yield the same lower
number for the
lowest numbered
substituent, select
the direction that
yields the lower
number for the next
lowest numbered
substituent
Chapter 3
11
IUPAC Systematic
Nomenclature - Alkanes
•
If same substituent numbers are
obtained in either direction, number in
direction giving lowest number to the
first named substituent
Chapter 3
12
IUPAC Systematic
Nomenclature - Alkanes
•
If compound has two or more chains of
the same length, parent hydrocarbon is
chain with greatest number of
substituents
Chapter 3
13
IUPAC Systematic
Nomenclature - Alkanes
•
•
•
Names such as sec-butyl and tert-butyl are
acceptable, but systematic substituent names are
preferable
Numbering of the substituent begins with the carbon
attached to the parent hydrocarbon
This number together with the substituent name is
placed inside parentheses
Chapter 3
14
Nomenclature of Cycloalkanes

Cycloalkanes generally are shown as skeletal
structures
Chapter 3
15
Nomenclature of Cycloalkanes
•
•
Ring is the parent hydrocarbon unless the
alkyl substituent has more carbons; in that
case the substituent becomes the parent
hydrocarbon
If only one substituent, no need to give it a
number
Chapter 3
16
Nomenclature of Cycloalkanes
•
If the ring has 2 substituents, list in
alphabetical order and give number 1 to
first named group
Chapter 3
17
Nomenclature of Cycloalkanes
•
If there is more than one substituent, list in
alphabetical order; one substituent is given
the position number 1; number either
clockwise or counterclockwise - lowest
numbers
Chapter 3
18
Nomenclature of Alkyl Halides

Common name - Name the alkyl group
first, followed by the name of the
halogen expressed as an -ide name
Chapter 3
19
Nomenclature of Alkyl Halides

IUPAC name - The halogen is treated
as a substituent
Chapter 3
20
Nomenclature of Ethers

Common name Name(s) of alkyl
group(s) listed
first followed by
the word “ether”
Chapter 3
21
Nomenclature of Ethers

IUPAC name - The smaller alkyl group
is converted to an “alkoxy” name and
used as a substituent
Chapter 3
22
Nomenclature of Alcohols

Common name Name of the Alkyl
group followed by
the word “alcohol”
Chapter 3
23
Nomenclature of Alcohols


IUPAC name - The OH group is a site of
reactivity (a functional group)
Functional group is denoted by the suffix, “ol”
CH3OH
CH3CH2OH
methanol
ethanol
Chapter 3
24
IUPAC Nomenclature of
Alcohols
•
•
•
Parent Hydrocarbon is the longest
continuous chain that contains the OH
Number the chain in direction that gives
functional group the lowest number
If both a substituent and a functional
group are present, the functional group
gets the lower number
Chapter 3
25
IUPAC Nomenclature of
Alcohols
•
•
If the functional group gets the same
number when counted from both
directions, use direction which gives the
substituent the lower number
If there is more than one substituent, cite
substituents in alphabetical order
Chapter 3
26
IUPAC Nomenclature of
Alcohols

System is summarized as [Substituent]
[Parent Hydrocarbon] [Functional Group]
Chapter 3
27
Nomenclature of Amines


Common name - Name of the Alkyl group(s)
(in alphabetical order) followed by the
syllable “amine”
The whole name is a single word
methylamine
methylpropylamine
Chapter 3
28
Nomenclature of Amines



IUPAC name - The NH2 group is a site of
reactivity (a functional group)
Functional group is denoted by the suffix,
“amine”
Final “e” of longest alkane group replaced by
suffix “amine” (don’t run vowels together)
CH3CH2CH2CH2NH2
1-butanamine
butan-1-amine
Chapter 3
29
IUPAC Nomenclature of
Amines
• Find the longest chain bonded to the
nitrogen
• Final “e” is replaced with “amine”
• Number the carbon to which nitrogen is
bonded
• Number any substituents on the alkyl
chain
• Use italicized N- for each additional
substituent(s) on the nitrogen
Chapter 3
30
Properties of Alkyl Halides,
Alcohols, Ethers, & Amines


For alkanes, there are only induced
dipole-induced dipole interactions (also
known as van der Waals forces or
London forces)
van der Waals forces are a function of
surface area
Chapter 3
31
Induced Dipole-Induced
Dipole Interactions
Chapter 3
32
Hydrogen Bonding: Strong
Dipole-Dipole Interactions
Chapter 3
33
Dipole-dipole Interactions


Particularly important for alcohols and amines
Ethers and alkyl halides have dipole moments,
but their intermolecular attractions are not as
strong as hydrogen bonds
Chapter 3
34
Comparative Boiling Points
Chapter 3
35
Solubility

The more carbons that are present, the
less soluble an organic compound is in
water
Chapter 3
36
Conformations of Alkanes:
Rotation About C-C Single Bonds
Chapter 3
37
Drawing Cyclohexane in the
Chair Conformation
Chapter 3
38
Interconversion of Cyclohexane
Conformations


As a result of simultaneous rotation about
all C-C bonds, a chair conformation of
cyclohexane can interconvert to another
chair conformation by a ring-flip
In the process, equatorial bonds become
axial and vice versa
Chapter 3
39
Monosubstituted
Cyclohexanes

When there is one substituent on the
cyclohexane ring, the two chair
conformations are no longer equivalent
Chapter 3
40
Conformations of 1,4Disubstituted Cyclohexanes
two methyl groups
on same side of ring
two methyl groups on
opposite sides of ring
H
CH3
H
cis-1,4-dimethylcyclohexane
CH3
H3C
CH3
H
H
trans-1,4-dimethylcyclohexane
Chapter 3
41
Conformations of 1,4Disubstituted Cyclohexanes
The cis isomer must have one
substituent in an axial position and one
in an equatorial position

H
H
ring-flip
CH3
H
CH3
H3C
equatorial
axial
H
CH3
axial
cis-1,4-dimethylcyclohexane
Chapter 3
42
Conformations of 1,4Disubstituted Cyclohexanes

The trans isomer has both substituents
in either the equatorial or in the axial
positions
axial
CH3
H
ring-flip
H
CH3
H3C
H
equatorial
equatorial
CH3
H
much more stable
much less stable
trans-1,4-dimethylcyclohexane
Chapter 3
axial
43
Conformations of cis-1,3Disubstituted Cyclohexanes

A cis-1,3-disubstituted cyclohexane can
exist in one of two conformations
H
ring-flip
H
H
CH3
H3C
C
H3C
CH3
CH3
H
C
CH3
CH3
CH3
much more stable
much less stable
cis-1-tert-butyl-3-methylcyclohexane
Chapter 3
44
Conformations of trans-1,3Disubstituted Cyclohexanes

Both conformers of trans-1-tert-butyl-3methylcyclohexane have one substituent
in an axial position and one in an
equatorial position
Chapter 3
45