In the previous list “n” stands for normal. In this
case the bond is from the first carbon of the longest
chain. Three other prefixes that occur commonly
are:
sec- short for secondary
tert- short for tertiary
iso (no hyphen is used)
Examples:
H H H H
H C C C C H
H H
H
sec-butyl
2161
In the previous list “n” stands for normal. In this
case the bond is from the first carbon of the longest
chain. Three other prefixes that occur commonly
are:
sec- short for secondary
tert- short for tertiary
iso (no hyphen is used)
Examples:
H
H C H
H
H
H H H H
H C C C H
H C C C C H
H
H
H H
H
sec-butyl
tert-butyl
2162
In the previous list “n” stands for normal. In this
case the bond is from the first carbon of the longest
chain. Three other prefixes that occur commonly
are:
sec- short for secondary
tert- short for tertiary
iso (no hyphen is used)
Examples:
H
H
H C H
H C H
H
H
H
H
H H H H
H C C C H H C C C
H C C C C H
H
H
H H H
H H
H
sec-butyl
tert-butyl
isobutyl
2163
The term isoalkane is used to denote a branched
chain alkane with a methyl group attached to the
penultimate carbon atom of the main chain.
2164
The term isoalkane is used to denote a branched
chain alkane with a methyl group attached to the
penultimate carbon atom of the main chain.
As the number of carbon atoms increase, the
prefixes become less useful, because an increasingly
large number of prefixes would be needed. In this
case, the standard numbering scheme (described
about nine slides later) is used.
2165
Structures of some alkanes
2166
Structures of some alkanes
H
H C H
H
2167
Structures of some alkanes
H
H C H
H
H H
H C C H
H H
2168
Structures of some alkanes
H
H C
H
H
H C
H
H
H H
H C C H
H H
H H
C C H
H H
2169
Structures of some alkanes
H
H C
H
H
H C
H
H
H
C
H
H H
H C C H
H H
H
H H H H
H C C C C H
C H
H
H H H H
2170
Structures of some alkanes
H
H C
H
H
H C
H
H
H
C
H
H H
H C C H
H H
H
H H H H
H C C C C H
C H
H
H H H H
These are straight chain examples.
2171
Structures of some alkanes
H
H C
H
H
H C
H
H
H
C
H
H H
H C C H
H H
H
H H H H
H C C C C H
C H
H
H H H H
These are straight chain examples. Note that the
alkanes have only single bonds.
2172
Branched alkanes
2173
Branched alkanes
H H H H
H C C C C H
H H CH3 H
2174
Branched alkanes
H H H H
H C C C C H
H H CH3 H
4
3
2
1
2175
Branched alkanes
H H H H
H C C C C H
H H CH3 H
4
3
2
1
2-methylbutane
(the 2 is a bit redundant)
2176
Branched alkanes
H H H H
H C C C C H
H H CH3 H
4
3
2
1
2-methylbutane
(the 2 is a bit redundant)
Number the longest chain so as to give the
lowest number to the substituent (in this case a
methyl group) off the main chain.
2177
H H H H H
H C C C C C H
H H CH3CH3H
2178
H H H H H
H C C C C C H
H H CH3CH3H
5
4
3
2
1
2179
H H H H H
H C C C C C H
H H CH3CH3H 2,3-dimethylpentane
5
4
3
2
1
2180
H H H H H
H C C C C C H
H H CH3CH3H 2,3-dimethylpentane
There is more than one form of the preceding
compound. We will discuss later how to name the
different forms of this compound.
5
4
3
2
1
2181
H H H H H H H H
H C C C C C C C C H
H H CH3CH2H H H H
CH3
2182
H H H H H H H H
H C C C C C C C C H
H H CH3CH2H H H H
CH3
Note: there is a methyl and an ethyl group off
the main chain.
2183
H H H H H H H H
H C C C C C C C C H
H H CH3CH2H H H H
CH3
1
2
3
4
5
6
7
8
Note: there is a methyl and an ethyl group off
the main chain.
2184
H H H H H H H H
H C C C C C C C C H
H H CH3CH2H H H H
CH3
8
7
6
5
4
3
2
1
5 and 6 bigger than
3 and 4 – so this is
wrong numbering
Note: there is a methyl and an ethyl group off the
main chain.
2185
H H H H H H H H
H C C C C C C C C H
H H CH3CH2H H H H
CH3
1
2
3
4
5
6
7
8
Note: there is a methyl and an ethyl group off
the main chain.
2186
3-methyl-4-ethyloctane (complexity order)
H H H H H H H H
H C C C C C C C C H
H H CH3CH2H H H H
CH3
1
2
3
4
5
6
7
8
Note: there is a methyl and an ethyl group off
the main chain.
2187
3-methyl-4-ethyloctane (complexity order)
4-ethyl-3-methyloctane (alphabetical order)
H H H H H H H H
H C C C C C C C C H
H H CH3CH2H H H H
CH3
1
2
3
4
5
6
7
8
Note: there is a methyl and an ethyl group off
the main chain.
2188
Summary of the simple rules to name an alkane.
Prefix + root + suffix
2189
Ways of depicting an alkane
2190
The impact of free rotation about carbon
– carbon single bonds.
2191
When assigning groups in alphabetical order, the
prefixes are not considered. For example, for an
alkane with an ethyl and two methyl groups as
substituents, the ethyl substituent group is named
first, followed by the dimethyl.
E.g. 4-ethyl-2,2-dimethylnonane and not
2,2-dimethyl-4-ethylnonane
2192
When you have two (or more) alkyl substituents, number
the longest chain in the direction that gives the smallest
number to the first named substituent.
E.g. 3-ethyl-5-methylheptane and not
3-methyl-5-ethylheptane
(Draw out the structure)
Where there are two or more longest chains of identical
length, select the chain with the greater number of
substituents.
E.g. 3-ethyl-2-methylhexane and not
3-isopropylhexane
(Draw out the structure)
2193
Exercises: Draw the structures of:
(1) 2,2,3-trimethylbutane
(2) 4-ethyl-2-methylnonane
(3) 2,4-dimethyloctane
2194
Exercises: Draw the structures of:
(1) 4-isopropyldecane
(2) 2-methyl-4-(1-methylethyl)heptane
(3) 4-isopropyl-2-methylheptane
(4) 5-tert-butylnonane
2195
Physical properties of the alkanes
The series of straight-chain alkanes shows a very
smooth gradation of physical properties. As the
series is ascended, each additional CH2 group
contributes a fairly constant increment to the
boiling point and to the density – and to a lesser
extent to the melting point.
This makes it possible to estimate the properties of
an unknown member of the series from those of its
neighbors.
2196
Alkenes
2197
Alkenes
These are hydrocarbons with at least one or
more double bonds.
2198
Alkenes
These are hydrocarbons with at least one or
more double bonds.
The parent alkanes are used to name the
alkene family of compounds.
2199
Alkenes
These are hydrocarbons with at least one or
more double bonds.
The parent alkanes are used to name the
alkene family of compounds.
The name ending change is:
ane
ene
2200
alkane
ethane
alkene
ethene
structure
H
H
C C
H
H
2201
alkane
ethane
alkene
ethene
structure
H
H
H
propane
propene
H
C C
C C
H
H
CH3
H
2202
alkane
butane
alkene
butene
structure
2203
alkane
alkene
structure
butane
butene
In this case there are three possible compounds.
2204
alkane
alkene
structure
butane
butene
In this case there are three possible compounds.
H
1-butene
H
C C
H
CH2 CH3
2205
alkane
alkene
structure
butane
butene
In this case there are three possible compounds.
H
1-butene
H
The number 1 indicates on which carbon
C C
the double bond starts.
H
CH2 CH3
2206
alkane
alkene
structure
butane
butene
In this case there are three possible compounds.
H
1-butene
H
The number 1 indicates on which carbon
C C
the double bond starts.
H
CH2 CH3
2- butene
CH3
CH3
C C
H
H
2207
alkane
alkene
structure
butane
butene
In this case there are three possible compounds.
H
1-butene
H
The number 1 indicates on which carbon
C C
the double bond starts.
H
CH2 CH3
2- butene
CH3
CH3
C C
H
H
H
CH3
C C
H
CH3
2208
alkane
alkene
structure
butane
butene
In this case there are three possible compounds.
H
1-butene
H
The number 1 indicates on which carbon
C C
the double bond starts.
H
CH2 CH3
2- butene
cis-2-butene
trans-2-butene
CH3
CH3
C C
H
H
H
CH3
C C
H
CH3
2209
Z and E isomers
Some cases arise in which it is very difficult to name
a compound unambiguously, e.g.
2210
Z and E isomers
Some cases arise in which it is very difficult to name
a compound unambiguously, e.g.
Br
Cl
C C
I
CH3
2211
Z and E isomers
Some cases arise in which it is very difficult to name
a compound unambiguously, e.g.
Br
Cl
Is this a cis or trans compound?
C C
I
CH3
2212
Z and E isomers
Some cases arise in which it is very difficult to name
a compound unambiguously, e.g.
Br
Cl
Is this a cis or trans compound?
C C
I
CH3
A way to sort out this problem is to use the symbols
2213
Z and E isomers
Some cases arise in which it is very difficult to name
a compound unambiguously, e.g.
Br
Cl
Is this a cis or trans compound?
C C
I
CH3
A way to sort out this problem is to use the symbols
Z (zusammen = together)
2214
Z and E isomers
Some cases arise in which it is very difficult to name
a compound unambiguously, e.g.
Br
Cl
Is this a cis or trans compound?
C C
I
CH3
A way to sort out this problem is to use the symbols
Z (zusammen = together)
E(entgegen
= opposite)
2215
Rules
1. Compare the two groups on one carbon atom of
the carbon-carbon double bond.
2216
Rules
1. Compare the two groups on one carbon atom of
the carbon-carbon double bond.
2. Assign the two groups priorities using the CahnIngold-Prelog rules for R and S configurations.
2217
Rules
1. Compare the two groups on one carbon atom of
the carbon-carbon double bond.
2. Assign the two groups priorities using the CahnIngold-Prelog rules for R and S configurations.
3. Repeat steps 1 and 2 for the second carbon of the
carbon-carbon double bond.
2218
Rules
1. Compare the two groups on one carbon atom of
the carbon-carbon double bond.
2. Assign the two groups priorities using the CahnIngold-Prelog rules for R and S configurations.
3. Repeat steps 1 and 2 for the second carbon of the
carbon-carbon double bond.
4. If the two groups of highest priority are on the
same side of the double bond, we have the Z
isomer. If the two groups are on opposite sides we
have the E isomer.
2219
Arrange the atoms in decreasing order of atomic
number, e.g. I, Br, Cl, S, P, F, O, N, C, H
2220