Alkenes Flashcards
Carbons of double bonds have what kind of hybridizaton?
sp2
How are the bond angles for sp2 carbons?
120º
Terminal alkenes boil at
Lower temperatures
Trans-alkenes are less polar and have
Higher mps / lower bps than cis-alkenes
Alkenes are most commonly synthesized via
Elimination of alcohols or alkyl halides via ∆
E1 is
Unimolecular elimination
E1 has two steps and is capable of producing
Carbocations
Which solvents are ideal for E1?
Polar protic
What does E1 prefer?
Highly branched molecules
E1 prefers
Good leaving groups
What kind of temperatures are ideal for E1 reactions?
Higher temperatures
E2 is
Bimolecular elimination
Heat and acidic conditions allow for
E1
Heat and basic conditions allow for
E2
How does the halide have to be for E2 reactions?
Anti to proteins
E2 molecules like
Highly substituted molecules
Which bases allow for E2 reactions?
Strong, bulky ones
H2 / metal reduce alkenes to alkanes, producing
Syn addition of Hydrogens
Addition of HX to an alkene aims to create a
More stable carbocation, via Mark-add addition
Addition of X2 to an alkene aims to add
Anti halides
The reverse reaction of acid-catalyzed hydration is
Acid-catalyzed dehydration
Free radical addition of Br2 to alkenes results in a
Anti-Mark addition
Hydroboration creates a product via
Anti-mark but syn addition
What allow for the Oxidation of alkenes?
- KMnO4
- Ozonolysis (O3)
- mCPBA
KMnO4 produces
1,2 diols with syn orientation
What does KMnO4 do under acidic conditions?
It cleaves double bond
KMnO4 can cleave nonterminal alkenes to form
2 equivalents of -COOH
KMnO4 can cleave terminal alkenes to form
A -COOH + CO2
What happens if KMnO4 cleaves a disubstituted nonterminal alkene?
Ketones are formed
Ozonolysis with O3 is the
Cleavage of a double bond, forming either 2 aldehydes or ketones
mCPBA or CH3CO3H allow for the formation of
Oxiranes
