TUTORIAL 3 –
NOMENCLATURE AND
PHYSICAL PROP.
Marc MacKinnon
Classification of Amines
NH 3
ammonia
R NH 2
primary amine
R
R NH
R
R N R
secondary amine tertiary amine
•  Amines are functional groups and therefore denoted as
suffixes
•  The “e” at the end gets replaced with amine
N
NH 2
3-hexanamine
HN
N-methyl-4-octanamine
N,N-dimethylcyclohexanamine
Nomenclature of amines
•  Positions of normal substituents on the chain are
indicated by number
•  Positions of substituents on nitrogen are indicated by N
F
Br
N
HN
2-ethyl-N,N-dimethyl-1-cyclobutanamine
• 
Cl
5-bromo-4-chloro-3-fluoro-N-methyl-2-nonanamine
Boiling Point
•  The stronger the attractive forces between two identical
molecules the higher the boiling point
•  Three main type of forces:
•  Van der Waals forces
•  Dipole-dipole interactions
•  Hydrogen bonding
• 
Van der Waals forces
• 
• 
• 
• 
Weakest type of interaction
The higher the molecular weight the more van der Waals interactions
Therefore, higher BP
Think about separating sheets of paper versus separating bed sheets
Van der Waals force
•  The molecular weight trend breaks down when branching
is introduced
•  Picking up one sheet of paper from a ream versus picking
a crumpled piece of paper
•  Isomers of hexane
n-hexane 68oC
iso-hexane 60oC
2,3-dimethylbutane 56oC
3-methylpentane 63oC
2,2-dimethylbutane 50oC
Dipole-dipole interactions
•  Stronger then van der Waals forces
•  Attraction between polar bonds
O
O
cyclohexane 80oC
tetrahydropyran 88oC
O
1,4-dioxane 101 oC
Hydrogen Bonding
•  Strongest of the intermolecular forces
•  Interaction between hydrogen bond donor (H bonded to
an electronegative F, O, N) and hydrogen bond acceptor
(electronegative F, O, N)
ethanol 78oC
water 100oC
acetic acid 118oC
Hydrogen Bonding in DNA
•  H-bonding is responsible for the double helix structure of
DNA
•  Its why there or DNA base pairs
O
N
R
N
N H
H
H N
O
N H
N
N
N
N H
H
N
R
R
N
N
O
H N
N
O
N
R
H
guanadine
cytosine
adenine
thymine
Solubility
•  Golden rule of solubility: Like dissolves like
Polar dissolves polar
(water and salt)
Nonpolar dissolves nonpolar
(baby oil and ear wax)
•  Oil and water don’t mix appreciably, oil slicks form the
shinny film on top (Free Willy 2)
•  You need detergent to wash dishes to help dissolve the
oily residue into water
σ-bonds
•  Single bonds have freedom to rotate about the axis of the
bond
•  There are an infinitely large number of conformations
(positions of each H in relation to the others)
•  They aren’t all (energetically) equal
Rotational Conformations (rotamers)
•  Staggered (favoured) and eclipsed (disfavoured) and
everything in between
Cyclohexane
•  We often draw cyclohexane as a planar hexagon rings
•  This structure implies bond angles of 120°, but these
aren’t ideal sp3 orbitals
H
H
H
H
H
H
H
H
H H
H
H
•  Red are the equatorial positions
•  Green are the axial positions
Cyclohexane
•  Energetics of the conformations
Equatorial versus Axial
•  Equatorial is more stable then axial
•  Equatorial groups point into empty space
•  Axial groups “bump” into other axial groups 3 C’s away
(C3 and C5)
•  We say it is sterically hindered