Paul TC-2007 Free radical substitution Eletrophilic addition Nucleophilic substitution Elimination Addition – Elimination Electrophilic substitution Esterification Alkaline hydrolysis Nucleophilic addition ORGANIC REACTION MECHANISMS ASA2 Dehydration Friedel-Crafts Bromination Nitration Acylation Addition polymerisation Bond fission Hydration of alkene Formation of polypeptides Formation of polyamides Formation of polyesters Bromination of alkene

Paul TC-2007 BOND FISSION Br x Homolytic fission Heterolytic fission Free radicals (= an unpaired electron) ElectrophileNucleophile (= electron pair acceptor)(= electron pair donor) (Breaking of the bond) Reaction of ALKANES = Free radical substitution Reaction of ALKENES = Electrophilic addition Br 2 Br +. + Br - Br 2 2 Br. HOMOLYTIC FISSION HETEROLYTIC FISSION Curly arrow One electron moving A pair of electrons moving

Paul TC-2007 Initiation Propagation Termination FREE RADICAL SUBSTITUTION MECHANISM Least favourable Possible Major organic product Br 2 Br C H HH H Br C H H H C H H H C H H H H H H C H H H C H H H C H H H C H H HH Br  Br 2 CH 3 + Br 2  CH 3 Br + Br CH 4 + Br  CH 3 + HBr Br 2  2 Br C H H H C H H C H H H H H + 2 CH 3  H 3 C-CH 3 C H H H C H H H Br C H H H C H H H C H H H + Most favourable H 3 C + Br  CH 3 Br Initiation Propagation Termination

Paul TC methylpropene C C H3CH3C H3CH3C H H Br -+-+ C + C Carbocation (Electrophile) : Br - Nucleophile H3CH3C H3CH3C H H C C Br BROMINATION OF ALKENE H3CH3C H3CH3C H H 1,2-dibromo-2-methylpropane

Paul TC-2007 HYDRATION OF ALKENE MECHANISM C C H3CH3C H3CH3C H H 2-methylpropene H+H+ C + C H H3CH3C H3CH3C H H O H H C C H O+O+ H3CH3C H3CH3C H H H H 2-methylpropan-1-ol C C H O H3CH3C H3CH3C H H H H+H+

Paul TC-2007 H Cl H C = C H Cl H C = C H Cl H CC H Trigonal planar Cl H C = C H + Cl H CC H Cl H CC H Cl H C = C H + Repeat unit = Any 2 consecutive C along the C chain Cl H CC H n or Chloroethene Polychloroethene 120 o Trimer Monomer Dimer ADDITION POLYMERISATION MECHANISM

Paul TC-2007 NUCLEOPHILIC SUBSTITUTION MECHANISM ELECTRON CLOUD from the nucleophile SHIFTS toward  + C atom, and a DATIVE COVALENT BOND starts to form. As this happens, the C – X bond is WEAKENS and eventually BREAKS HETEROLITICALLY. R - X + :Nu - R - Nu + :X - OH - Cl - δ+ δ- H C H Cl H H C H HO H δ + δ - + +

Paul TC-2007 H Cl H C H C H H OH - Cl - Cl H C H C H H - H C H C H H ELIMINATION MECHANISM H2OH2O + +

Paul TC-2007 H+H+ H O H C H C H H H H O H C H C H H H H + H H C C H H O H H + DEHYDRATION +H+H+

Paul TC-2007 C O HO R + H OR + H + C O R H + C O R + H OR H H H C O R O R + R C O R O + H + H C O R O R H2OH2O + ESTERIFICATION MECHANISM Protonation Nucleophilic attack Proton transfer Water elimination Proton elimination

Paul TC-2007 ADDITION-ELIMINATION MECHANISM (NUCLEOPHILIC SUBSTITUTION) Cl - δ+ δ- HO C H O δ+ δ- Cl C H O OH - δ + δ - C O-O- OH H Cl Nucleophilic addition Elimination Nucleophilic substitution δ+δ-δ+δ- + +

Paul TC-2007 ALKALINE HYDROLYSIS MECHANISM OH - R CO R O Nucleophilic attack C O-O- R HO Na + OR O-O- R Break down of the tetrahedral intermediate CO R O H OHR CO R O-O- Na + Proton transfer

Paul TC-2007 NO H H NITRATION H+H+ + Formation of the electrophile: NO 2 + nitronium ion HNO 3 + H 2 SO 4 H 2 NO HSO 4 - H 2 NO 3 + H 2 O + NO 2 + H + + HSO 4 - H 2 SO 4 Regeneration of the catalyst: Electrophilic substitution: HSO 4 - HNO 3 + H 2 SO 4 H 2 O + NO HSO 4 - C 6 H 6 + HNO 3 C 6 H 5 NO 2 + H 2 O Overall equation: H 2 SO 4 cat. 50 o C

Paul TC-2007 Br + + H H BROMINATION H+H+ + Formation of the electrophile: Br + Br 2 + FeBr 3 Br + + FeBr 4 - H + + FeBr 4 - FeBr 3 +HBr Regeneration of the catalyst: Electrophilic substitution: FeBr 4 - C 6 H 6 + Br 2 C 6 H 5 Br + HBr Overall equation: FeCl 3 cat.

Paul TC-2007 CH H H FRIEDEL-CRAFT MECHANISM H+H+ + Formation of the electrophile: CH 3 + CH 3 Cl + FeCl 3 CH FeCl 4 - H + + FeCl 4 - FeCl 3 + HClRegeneration of the catalyst: Electrophilic substitution: FeCl 4 - C 6 H 6 + CH 3 ClC 6 H 5 CH 3 + HCl Overall equation: FeCl 3 cat.

Paul TC-2007 COCH H H ACYLATION MECHANISM H+H+ + Formation of the electrophile: CH 3 CO + CH 3 COCl + FeCl 3 CH 3 CO + + FeCl 4 - H + + FeCl 4 - FeCl 3 + HClRegeneration of the catalyst: Electrophilic substitution: FeCl 4 - C 6 H 6 + CH 3 COClC 6 H 5 COCH 3 + HCl Overall equation: FeCl 3 cat.

Paul TC-2007 NΞC -NΞC - C H O H H C H NΞCNΞC O - HCΞNCΞN δ + δ - H C H NΞCNΞCOH - CΞN NUCLEOPHILIC ADDITION MECHANISM oxoanion Dative covalent bond formation  bond weakens and breaks heterolytically This reaction is useful because the chain is extended by 1 carbon. 2-hydroxynitrile Dative covalent bond formation  bond weakens and breaks heterolytically δ + δ - + +

Paul TC-2007 C H R N O OH C H H + + C H R N O C H H OH ` C H R N O OH C H H C H R N O C H C H R N O C H H C H R N O C H Peptide link (amide) FORMATION OF POLYPEPTIDES Repeat unit (aminoacid residue) Peptide link (amide) + 2 H 2 O C H R N O C H n Monomer 2-amino acid Trimer

Paul TC-2007 Peptide link (amide) Peptide link (amide) (CH 2 ) n N H H N H H O OH C O C (CH 2 ) n N H H N H H O OH C O C (CH 2 ) n N H N H H N H N H O C O C O C O OH C O C +++ Peptide link (amide) Repeat unit 2 monomers +3 H 2 O DIBASIC ACID and DIAMINE to form POLYAMIDES (CH 2 ) n O C O C Repeat unit (CH 2 ) n N H N H

Paul TC-2007 Ester link ++ Ester link Ester link + 3 H 2 O OH O CHO O C (CH 2 )n OH O CHO O C (CH 2 )n OHO H O CHO O C (CH 2 )n O C O C H OO Repeat unit (2 monomers) (CH 2 ) n OHO H + OO H REACTION OF DIBASIC ACID and DIOL to form POLYESTERS O C O C (CH 2 )n H OO Repeat unit (2 monomers)