Haloalkanes…workbook pgs 131 - 132…
Haloalkanes Compound where a halogen (Group 17)
replaces one of the hydrogens on a carbon Prepared by substitution reaction of an
alkane with a halogen, or by addition reaction of an alkene with HX
General Formula: R- X CnH2n+1X
`Example: CH3CH(Br)CH2CH2CH3
2-bromopentane
Haloalkane Nomenclature If a Hydrogen is replaced by a halogen,
this information is added in the prefix Flourine = “Fluoro-” Chlorine = “chloro-” Bromine = “bromo-” Iodine = “Iodo-”
Like alkenes and alkynes, the longest continuous chain must contain the halide. Also, count the carbons so that the halide has
the lowest number possible
Types of Haloalkanes Just like with alcohols: 3 Types
Primary Haloalkane Haloalkane with only 1 “R” group….
Secondary Haloalkane Haloalkanel with 2 “R” groups…
Tertiary Haloalkane Haloalkane with 3“R” groups…
Types of Haloalkanes
Types of Haloalkanes
Properties of Haloalkanes Halide group (except for fluorine) are slightly
polar and allows for slightly polar molecules IMF due to temporary dipoles and permanent dipole
interactions Haloalkanes have high melting and boiling points
than corresponding alkanes Melting and boiling points increase as mass increases
Chloromethane, bromomethane, and chloroethane are gases; most other haloalkanes up to 6 carbons are liquids; larger ones are solids
Haloalkanes are slightly soluble in water b/c hydrogen bonding can’t occur
Reactions of Haloalkanes Substitution Reactions
Nucleophilic substitution – when a nucleophile (negative ion, like OH-, or group with a lone pair of electrons) is attracted to the partially positive carbon atom nearest the halogen atom
With Ammonia (NH3) Will form amines
Reactions of Haloalkanes Substitution Reactions
Reaction with aqueous hydroxide ion Forms alcohols
Reaction of Haloalkanes Elimination Reaction of Haloalkanes
A molecule of HX is removed and an alkene is formed Under non-aqueous strongly basic conditions
Opposite of Markovnikov’s rule – H comes off the carbon with the fewest number of H’s attached
Primary Haloalkanes very difficult to undergo elimination. Secondary Haloalkanes react faster, Tiertiary the fastest
Top Related