Haloalkanes and Haloarenes

Lesson

Part 1 — organic compounds in which a halogen atom replaces hydrogen: how they are named, made and how they behave physically.

In this lesson you will

Classify halogen compounds and name them by IUPAC rules
Describe the polarity, length and strength of the C–X bond
Write methods of preparing haloalkanes and haloarenes from alcohols, hydrocarbons and by halogen exchange
Explain trends in boiling point, density and solubility

Table of familiar halogen compounds and their uses
Compound	Use
Chloroform	Solvent; once an anaesthetic
Halothane	Inhaled anaesthetic
Chloramphenicol	Antibiotic (contains chlorine)
PVC	Pipes and cable insulation
Freons	Old refrigerants; damage the ozone layer

Concept

Classifying halogen compounds

By the number of halogen atoms (mono-, di-, poly-) and by the type of carbon bearing the halogen.

Table classifying halogen compounds as primary, secondary, tertiary, allylic, benzylic, vinylic and aryl halides with examples
Class	C bearing X	Example
Primary (1°) alkyl halide	sp³ C joined to one other C	$\ce{CH3CH2Br}$
Secondary (2°)	sp³ C joined to two C	$\ce{(CH3)2CHCl}$
Tertiary (3°)	sp³ C joined to three C	$\ce{(CH3)3CBr}$
Allylic halide	sp³ C next to a C=C	$\ce{CH2=CHCH2Cl}$
Benzylic halide	sp³ C next to a benzene ring	$\ce{C6H5CH2Cl}$
Vinylic halide	sp² C of a C=C	$\ce{CH2=CHCl}$
Aryl halide	sp² C of a benzene ring	$\ce{C6H5Cl}$

Concept

Naming halogen compounds

In IUPAC names the halogen is a prefix (fluoro, chloro, bromo, iodo) with a locant on the longest chain. Common names use the alkyl group + halide.

Table of common and IUPAC names of seven halogen compounds
Structure	Common name	IUPAC name
$\ce{CH3CH2Br}$	Ethyl bromide	Bromoethane
$\ce{(CH3)2CHCl}$	Isopropyl chloride	2-Chloropropane
$\ce{(CH3)3CBr}$	tert-Butyl bromide	2-Bromo-2-methylpropane
$\ce{CH2=CHCH2Cl}$	Allyl chloride	3-Chloroprop-1-ene
$\ce{C6H5CH2Cl}$	Benzyl chloride	(Chloromethyl)benzene
$\ce{CH2BrCH2Br}$	Ethylene dibromide (vic)	1,2-Dibromoethane
$\ce{CH3CHCl2}$	Ethylidene chloride (gem)	1,1-Dichloroethane

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