ORGANIC REACTIONS OF ALKENES

alkenes

• unsaturated hydrocarbons

• also called olefins

• double bonds

unsaturated hydrocarbons

fewer hydrogens per carbon than alkanes

ethylene

ripening of fruits

α-pinene

major component of turpentine (found in pine tree)

β-carotene

• orange pigment

• source of vitamin A

C_nH_2n

alkenes general formula

trans alkenes

are more stable than their cis isomers because of steric (spatial) interference between the large substituents on the same side of the double bond.

alkyl halide, RX

alkene + HX → _

hydrohalogenation

addition of HX to alkenes

pi bond

bonds that are susceptible to break

Markovnikov’s rule

in the addition to an alkene, the H attaches to the carbon with fewer alkyl substituents, and the X (halogen) attaches to the carbon with more alkyl substituents (more branched)

Hydrogen

attaches the to the carbon with fewer alkyl substituents

X (halogen)

attaches to the carbon with more alkyl substituents (more branched)

Regiospecific

when only one (product) of the two possible orientations of addition occurs

hydration

addition of H₂O to Alkenes

alcohols, ROH

Alkene + water → _

oxymercuration-demercuration

• mercury (II) acetate in aqueous THF (tetrahydrofuran)

• sodium borohydride

• Markovnikov addition

hydroboration

• borane

• basic hydrogen peroxide

• (only applicable in hydration reaction)

• Non-Markovnikov addition

enzymatic hydration

• hydration reaction by using an enzyme

halogenation

addition of X₂ to Alkenes

addition of Br₂

test for unsaturation → _

disappearance of reddish color

positive result of addition of Br₂

hydrogenation

• addition of H₂ to alkenes

• double bond is reduced

palladium metal or platinum

used as a catalyst in hydrogenation

reduction

addition of H, removal of O

alkane

alkenes + H₂ → _

hydroxylation

• oxidation of alkenes

• addition of -OH

• an example of oxidation

diol (glycol)

what is the product of alkene + KMnO₄ in basic solution

cleavage

• oxidation of alkenes

• splitting of molecule

C=O (carbonyl) containing product

what is the product of alkene + KMnO₄ in acidic solution

polymers reaction

addition of radicals to alkenes

polymer

a large (sometimes very large) molecule built up by repetitive bonding together of many smaller molecules, called monomers

polymerization reaction

process of initiation, propagation, and termination

Polyethylene

monomer name: ethylene

formula: H₂C=CH₂

uses: packaging, bottles, cable insulation, films and sheets

Polypropylene

monomer name: propene

formula: H₂C=CHCH₃

uses: automotive moldings, rope, carpet fibers

Poly(vinyl chloride), Tedlar

monomer name: Chloroethylene

formula: H₂C=CHCl

uses: insulation, films, pipes

Polystyrene, Styron

monomer name: Styrene

formula: H₂C=CHC₆H₅

uses: foam and molded articles

Teflon

monomer: tetrafluoroethylene

formula: F₂C=CF₂

uses: valves and gaskets, coatings

Orlon, Acrilan

monomer name: acrylonitrile

formula: H₂C=CHCN

uses: fibers

Plexiglas, Lucite

monomer name: methyl methacrylate

formula: H₂C=C(^CH₃)CO₂CH₃

uses: molded articles, paints

Poly(vinyl acetate)

monomer name: vinyl acetate

formula: H₂C=CHOCOCH₃

uses: paints, adhesive

conjugated dienes

multiple bonds that alternate with single bonds