Addition of water, H - OH + H2O major product 2-methyl-2-butene minor product

Mechanism of hydration step 1 H+ + H2O catalyst nuclophile  e- electrophile add H+ H+

Mechanism of hydration step 2 .. + H O electrophile nucleophile step 3 oxonium ion + H+ alcohol

Addition of Br2 .. .. .. bromination Br C Br-Br C Br C C step 1 Br + C C Br .. step 1 Br .. + + bromonium ion - - .. Br

Addition of Br2 .. .. .. “anti” addition stereospecific trans isomer - + step 2 “anti” addition stereospecific trans isomer

Addition of H2 hydrogenation C H H-H alkenes  alkanes + alkenes  alkanes heterogeneous catalyst Pt C H “syn” addition cis isomer H - H stereospecific

. . . . Polymerization monomer polymer small molecule large molecule built of monomers catalyst . CH2 – CH2 . ( )– n CH2 – CH2 . . CH2=CH2 polyethylene ethylene H H –(CH2 – CH – CH2 – CH)– n C6H5 C H5C6 H styrene polystyrene

Review - Alkenes addition reactions Y - Z H - X hydrohalogenation + Y - Z H - X hydrohalogenation Markovnikov no catalyst H - OH hydration Markovnikov H+ catalyst homogeneous

Review - Alkenes addition reactions Y - Z H - H hydrogenation + Y - Z H - H hydrogenation “syn” addition heterogeneous catalyst cis- isomer Br - Br bromination “anti” addition trans- isomer polymerization free radical mechanism

Alkynes sp hybridized carbons s p C H eth yne = acetylene addition reactions 2 equivalents Markovnikov

Aromatics C6H6 benzene sp2 hybridized carbons resonance structure 6  electrons delocalized very stable unreactive no addition reactions