Organic Halides
Functional Group
A structural unit in a molecule responsible for its
characteristic behavior under a particular set of
reaction conditions
Families of organic compounds
and their functional groups
Alcohol
ROH
Alkyl halide
RX (X = F, Cl, Br, I)
Amine
primary amine: RNH2
secondary amine: R2NH
tertiary amine: R3N
IUPAC Nomenclature
of Alkyl Halides
IUPAC Nomenclature
There are several kinds of IUPAC nomenclature.
The two that are most widely used are:
functional class nomenclature
substitutive nomenclature
Both types can be applied to alcohols and
alkyl halides.
Functional Class Nomenclature of Alkyl Halides
Name the alkyl group and the halogen as
separate words (alkyl + halide)
CH3F
CH3CH2CHCH2CH2CH3
Br
CH3CH2CH2CH2CH2Cl
H
I
Functional Class Nomenclature of Alkyl Halides
Name the alkyl group and the halogen as
separate words (alkyl + halide)
CH3F
CH3CH2CH2CH2CH2Cl
Methyl fluoride
Pentyl chloride
CH3CH2CHCH2CH2CH3
Br
1-Ethylbutyl bromide
H
I
Cyclohexyl iodide
Substitutive Nomenclature of Alkyl Halides
Name as halo-substituted alkanes.
Number the longest chain containing the
halogen in the direction that gives the lowest
number to the substituted carbon.
CH3CH2CH2CH2CH2F
CH3CHCH2CH2CH3
Br
CH3CH2CHCH2CH3
I
Substitutive Nomenclature of Alkyl Halides
Name as halo-substituted alkanes.
Number the longest chain containing the
halogen in the direction that gives the lowest
number to the substituted carbon.
CH3CH2CH2CH2CH2F
1-Fluoropentane
CH3CH2CHCH2CH3
I
3-Iodopentane
CH3CHCH2CH2CH3
Br
2-Bromopentane
Substitutive Nomenclature of Alkyl Halides
Cl
CH3
CH3
Cl
Halogen and alkyl groups
are of equal rank when
it comes to numbering
the chain.
Number the chain in the
direction that gives the
lowest number to the
group (halogen or alkyl)
that appears first.
Substitutive Nomenclature of Alkyl Halides
Cl
5-Chloro-2-methylheptane
CH3
CH3
2-Chloro-5-methylheptane
Cl
Nomenclature of Alkyl Halides
CH3CH2F
CH3Cl
chloromethane
fluoroethane
CH3CHI
CH3CH2CHBr
CH3
CH3
2-iodopropane
2-bromobutane
In the IUPAC system, alkyl halides are named as substituted
alkanes
CH3
CH3
CH3CH2CHCH2CH2CH2CH3
CH3CH2CHCH2CH2CH2Cl
Br
CH3
1-chloro-5,5-dimethylhexane
2-bromo-5-methylheptane
Br
I
CH2CH3
Cl
1-ethyl-2-iodocyclopentane
CH3
4-bromo-2-chloro-1-methylcyclohexane
Classification
H
CH3CH2CH2CH2CH2F
OH
primary alkyl halide
secondary alcohol
CH3
CH3CHCH2CH2CH3
Br
secondary alkyl halide
CH3CCH2CH2CH3
OH
tertiary alcohol
Different Kinds of Alkyl Halides
Aryl Halides
Aryl halides are halides in which the halogen is
attached directly to an aromatic ring.
Carbon-halogen bonds in aryl halides are
shorter and stronger than carbon-halogen
bonds in alkyl halides.
Aryl Halides
Aryl halides are halides in which the halogen is
attached directly to an aromatic ring.
Carbon-halogen bonds in aryl halides are
shorter and stronger than carbon-halogen
bonds in alkyl halides.
Because the carbon-halogen bond is stronger,
aryl halides react more slowly than alkyl halides
when carbon-halogen bond breaking is rate
determining.
Boiling point increases with increasing
number of halogens
Compound
CH3Cl
CH2Cl2
CHCl3
CCl4
Boiling Point
-24°C
40°C
61°C
77°C
Even though CCl4 is the only compound in this list without a
dipole moment, it has the highest boiling point.
Induced dipole-induced dipole forces are greatest in
CCl4 because it has the greatest number of Cl atoms.
Cl is more polarizable than H.
Physical Properties of Aryl Halides
resemble alkyl halides
all are essentially insoluble in water
less polar than alkyl halides
Cl
 2.2 D
Cl
 1.7 D
Reaction of Alcohols with Hydrogen Halides
ROH +
HX  RX + HOH
Hydrogen halide reactivity
HF
least reactive
HCl
HBr
HI
most reactive
An SN2 reaction proceeds in the direction that allows
the strongest base to displace the weaker base
Example
Cl
1. NaOH, H2O
370°C
OH
2. H+
(97%)
But...
nitro-substituted aryl halides do undergo
nucleophilic aromatic substitution readily
Cl
OCH3
+ NaOCH3
NO2
CH3OH
+ NaCl
85°C
NO2
(92%)
Reaction
F
OCH3
+ NaOCH3
NO2
CH3OH
+ NaF
85°C
NO2
(93%)
Aryl Halides Undergo Substitution When
Treated With Very Strong Bases
Cl
KNH2, NH3
NH2
–33°C
(52%)
Hydrolysis of Chlorobenzene
*
14C
labeling
indicates that
the hightemperature
reaction of
chlorobenzene
with NaOH
goes via
benzyne.
NaOH, H2O
Cl
395°C
OH
*
(43%)
+
*
(54%)
OH