Reactions of Alkenes/Alkynes

• Two-Step Reaction

• Markovnikov’s Rule

• Carbocation Rearrangements Possible

Addition of Hydrogen Halide (HX) to an Alkene

• Two-Step Reaction

• Acid-Catalyzed

• Proton Transfers

• Markovnikov’s Rule

• Carbocation Rearrangements Possible

Addition of Water (H2O) to an Alkene (Hydration)

• Two-Step Reaction

• Acid-Catalyzed

• Proton Transfers

• Markovnikov’s Rule

• Carbocation Rearrangements Possible

Addition of Alcohol (R’OH) to an Alkene

• Two-Step Addition

• Concerted Addition, Followed by Oxidation

• Anti-Markovnikov

• Syn Addition

Hydroboration (BH3) of an Alkene

Anti-Markovnikov

Electrophile moves to the more hindered carbon (less substituted)

Anti Addition

Two substituent groups added to opposite faces of the double bond (wedge/dash, dash/wedge)

Syn Addition

Substituent groups added to same faces of double bond (wedge/wedge, dash/dash)

• Only Br2/Cl2

• Makes Halonium Ion as Intermediate

• Anti Addition

Addition of Halogen (X2) to Alkene

• Only Br2/Cl2

• Makes Halonium Ion as Intermediate

• Anti Addition

• Markovnikov’s

• OH Group Attack More Substituted Side

Halohydrin (X2, OH) Formation

• Makes Epoxide

• Concerted Mechanism

• Syn Addition

Addition of Peroxyacid (mCPBA) to Alkene

• Pd/C Catalyst

• Syn Addition

• Reduction Reaction

Hydrogenation (H2) of Alkene

Ozonolysis (O3) of Alkene

• Double Bond “Cleaved”

• Can make Aldehydes and Ketones

• Each Side of Cleaved Double Bond has a new double bonded oxygen

Regioselective

Two constitutional isomers could be made, one is made preferentially

Stereoselective

Favors some stereoisomers from all possible stereoisomer products

Stereospecific

Produces Only One Stereoisomer

Racemic

Makes equal amount of both enantiomers

Vinylic Carbocation

Carbocation formed on alkenes after the reaction of an alkyne; More unstable than monosubstituted

• Markovnikov’s Rule

• 1 Equivalent makes an alkene, excess makes a dihalide

Addition of Hydrogen Halide (HX) to Alkyne

• Only Cl2/Br2

• Anti Addition

• 1 equivalent makes a trans alkene, excess makes a tetrahalide

Addition of Halogen (X2) to Alkyne

• Only one unit of H2O added across triple bond

• HgSO4 necessary for terminal alkenes

• Tautomerizes to make a ketone

Addition of Water to Alkyne

• Only 2 Borons

• Similar to Alkene Hydroboration (Less Substituted)

• Tautomerizes to make an aldehyde

Hydroboration (BR2H/9-BBN, THF) of Alkyne

• Both pi bonds removed (forms alkane

Hydrogenation (H2) of Alkyne

• “Cis” hydrogenation (Z)

• Only one pi bond removed

Lindlar’s Catalyst of Alkyne

• “Trans” hydrogenation

• Only one pi bond removed

Adding Na/Li + NH3 to Alkyne