Chapter 5 2016

Slide 1 1 ORGANIC CHEMISTRY Dr Nam T S Phan Faculty of Chemical Engineering HCMC University of Technology Office room 211, B2 Building Phone 38647256 ext 5681 Email ptsnam@hcmut edu vn 2 Chapter 5 ALK[.]

NOMENCLATURE OF ALKENES

• Ethylene is an acceptable synonym for ethene in the IUPAC

system

• Propylene, isobutylene and other common names ending in

“ylene” are NOT acceptable IUPAC names

The IUPAC name of an alkene is obtained by replacing

the “ane” ending of the corresponding alkane with “ene”

Note: Alkenes can have geometric isomers

isomerization

Eliminations of alkyl halides

Base

Alkyne hydrogenations

Pd/CaCO 3 + Pb(OAc) 2 / quinoline

Witttig reaction

Using less

sterically

hindered alkyl halide

Stereoselectivity of Witttig reaction Æ depends

on the ylide structure

Carbocation rearrangement

More stable

More stable

Stereochemistry

Racemic mixture

Already has 1 asymmetric carbon

2 asymmetric carbons are created

Additions of hydrogen bromide (A R )

Radical addition (A R ) – only for HBr

Electrophilic addition (A E)

Reaction

mechanism:

Additions of halogens

Major

addition product – NOT a

dihalide

Stereochemistry

24

2 asymmetric carbons are created

Trans-2-butene Æ meso compound

Additions of water – hydration reactions

Water is too weakly acidic to allow the hydrogen to act

as an electrophile

H 2 SO 4 , H 3 PO 4 …

Markovnikov’s rule

Additions of borane: hydroboration-oxidation

Regioselectivity:

Anti-Markovnikov

Additions of hydrogen – hydrogenation

Reaction mechanism:

Syn addition

Stereochemistry

34

Alkene epoxidations – Anti hydroxylations

Stereochemistry

Reactions of epoxides

38

Stereochemistry Anti additions

Syn hydroxylations of alkenes

Reaction mechanism: Syn additions

Permanganate cleavage of alkenes

Ozonolysis of alkenes

In the presence of an oxidizing agent, the products

will be ketones / carboxylic acids

Polymerizations