BÀI GIẢNG ORGANIC CHEMISTRY chapter5

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 Chapter 5: ALKENES An sp2 hybridized carbon NOMENCLATURE OF ALKENES The IUPAC name of an alkene is obtained by replacing the “ane” ending of the corresponding alkane with “ene” • 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 Determine the parent hydrocarbon – the longest continuous carbon chain containing the C=C Note: Alkenes can have geometric isomers PREPARATION OF ALKENES Dehydrations of alcohols Acid isomerization isomerization Eliminations of alkyl halides Base Alkyne hydrogenations Pd/CaCO3 + Pb(OAc)2 / quinoline REACTIONS OF ALKENES Additions of hydrogen halides (AE) More stable Markovnikov’s rule 10 Additions of hydrogen – hydrogenation 28 Reaction mechanism: Syn addition 29 Stereochemistry 30 31 Alkene epoxidations – Anti hydroxylations 32 Stereochemistry 33 Reactions of epoxides 34 35 Stereochemistry Anti additions 36 Syn hydroxylations of alkenes 37 Reaction mechanism: Syn additions 38 Permanganate cleavage of alkenes 39 Ozonolysis of alkenes 40 In the presence of an oxidizing agent, the products will be ketones / carboxylic acids 41 Polymerizations 42 ... mechanism: 17 Additions of halogens 18 Major addition product – NOT a dihalide 19 Stereochemistry 20 21 Stereochemistry asymmetric carbons are created Trans-2-butene Æ meso compound 22 Additions... More stable Markovnikov’s rule 10 Carbocation rearrangement More stable 11 More stable 12 Stereochemistry Racemic mixture 13 Already has asymmetric carbon 14 asymmetric carbons are created 15... Anti-Markovnikov 27 Additions of hydrogen – hydrogenation 28 Reaction mechanism: Syn addition 29 Stereochemistry 30 31