Ch. 15 Alkene Bromination and Dehydrohalogenation (U1 Exam)

LUMO

lowest unoccupied molecular orbital

HOMO

highest occupied molecular orbital

Why is elemental bromine a strong oxidant

due to its tendency to acquire additional electrons from elsewhere

what was the intermediate of the brommination reaction

brommonium ion

stereospecificity in the bromination reaction

substituents that are trans in the alkene will be trans in the brommonium ion

stereospecificity of addition of bromine ion to brommonium ion (ring-opening)

anti-addition

which carbon of an alkene is generally attacked by a nucleophile

steps involved in electrophilic addition reaction of an alkene

• heat components in reaction flask for about 5 minutes (trans-stilbene, acetic acid, pyridine hydrobromine perbromine)

• cool reaction mixture

• recover product via vacuum filtration

• obtain melting point and compare to literature values for meso and chiral stereoisomers

meso compound

generally contains two or more identical stereocenters; has an internal plane of symmetry that divides the compound in half

steps involved in double dehydrohalogenation

• place stilbene dibromide in a vial

• add potassium hydroxide

• add trimethylene glycol

• heat for 10 minutes

• recover product via vacuum filtration

• recrystallize with ethanol

• recover recrystallization product

E2 reactions require

C-H bond and C-leaving group to be anti-periplanar to each other