1. Original slide prepared for the Free Radical Substitution AQA organic reaction mechanisms Click a box below to go to the mechanism Electrophilic Addition Nucleophilic Substitution Elimination of HX from haloalkanes Elimination of water from alcohols Electrophilic Substitution Nucleophilic Addition Nucleophilic Addition Elimination Friedel-Crafts AlkylationAcylation (nitrile hydrolysis reaction) Click here for advice AS A2

2. Original slide prepared for the CH 4 + Cl 2 CH 3 Cl + HCl Overall reaction equation Conditions ultra violet light excess methane i.e. homolytic breaking of covalent bonds to reduce further substitution Free radical substitution chlorination of methane

3. Original slide prepared for the CH 4 + ClCH 3 + HCl Cl 2 Cl + Cl CH 3 + Cl 2 CH 3 Cl + Cl CH 3 ClCH 3 + Cl initiation step two propagation steps termination step ultra-violet CH 3 CH 3 + CH 3 minor termination step Free radical substitution mechanism

4. Original slide prepared for the CH 3 Cl + Cl 2 CH 2 Cl 2 + HCl Overall reaction equations Conditionsultra-violet light CH 2 Cl 2 + Cl 2 CHCl 3 + HCl CHCl 3 + Cl 2 CCl 4 + HCl excess chlorine Further free radical substitutions

5. Original slide prepared for the Electrophilic addition CH 3 CH=CH 2 + Br 2 CH 3 CHBrCH 2 Br bromine with propene hydrogen bromide with but-2-ene CH 3 CH=CHCH 3 + HBrCH 3 CH 2 CHBrCH 3 2-bromobutane 1,2-dibromopropane concentrated sulphuric acid with but-2-ene CH 3 CH=CHCH 3 + HOSO 3 HCH 3 CH 2 CH(OSO 3 H)CH 3 2-butylhydrogensulphate mechanism mech

6. Original slide prepared for the Br Electrophilic addition mechanism CH 3 H H H C C ++ -- H H H C C Br + - carbocation CH 3 H H H C C Br 1,2-dibromopropane bromine with propene reaction equation

7. Original slide prepared for the Electrophilic addition mechanism CH 3 H H C C H H C C H + carbocation CH 3 H H C C BrH 2-bromobutane hydrogen bromide with trans but-2-ene -- ++ Br H reaction equation Br -

8. Original slide prepared for the CH 3 H H C C OSO 3 H H ++ -- - carbocation 2-butylhydrogensulphate CH 3 H H C C H + H H C C H OSO 3 H CH 3 Electrophilic addition mechanism concentrated H 2 SO 4 with cis but-2-ene reaction equation

9. Original slide prepared for the hydroxide ion with bromoethane ethanol CH 3 CH 2 Br+ OH - CH 3 CH 2 OH + Br - ( aqueous ) Nucleophilic substitution propanenitrile CH 3 CH 2 I (ethanol)+ CN - (aq)CH 3 CH 2 CN + I - cyanide ion with iodoethane ammonia with bromoethane aminoethane CH 3 CH 2 Br + NH 3 CH 3 CH 2 NH 2 2+ NH 4 + Br - mechanism

10. Original slide prepared for the ++ -- CH 3 H Br C H - OH CH 3 H OH C H Br - hydroxide ion with bromoethane Nucleophilic substitution mechanism ethanol reaction equation

11. Original slide prepared for the ++ -- CH 3 H Br C H CN - CH 3 H CN C H Br - cyanide ion with iodoethane Nucleophilic substitution mechanism propanenitrile reaction equation

12. Original slide prepared for the ammonia with bromoethane Nucleophilic substitution mechanism aminoethane ++ -- CH 3 H Br C H - H CH 3 H NH 2 C H + CH 3 H NH 2 C H NH 3 H NH 3 + Br - reaction equation NH 3

13. Original slide prepared for the Acid hydrolysis of nitriles: propanoic acid CH 3 CH 2 CN+ H 2 O + H + CH 3 CH 2 COOH+ NH 4 + Reflux with strong acideg HCl (aq) Nitrile hydrolysis 2

14. Original slide prepared for the Elimination of HBr from 2-bromopropane CH 3 H H H C C OH - CH 3 H H H C C BrH propene H OH Br - CH 3 CHBrCH 3 + OH - CH 3 CH=CH 2 + H 2 O + Br - (in ethanol) acting as a base Elimination of HX from haloalkanes

15. Original slide prepared for the elimination + OH - RCH=CH 2 + H 2 O + X - (ethanol) nucleophilic substitution alcohol + OH - RCH 3 CH 2 OH + Br - (aqueous) RCH 2 CH 2 X alkene hydroxide acts as a base hydroxide acts as a nucleophile Haloalkanes and hydroxide ions

16. Original slide prepared for the Elimination of H 2 O from propan-1-ol CH 3 CH 2 CH 2 OHCH 3 CH=CH 2 + H 2 O Elimination of water from alcohols Heat with concentrated H 2 SO 4

17. Original slide prepared for the CH 3 H H H C C propene H OH H + CH 3 H H OH C C HH CH 3 H H OH C C H H H + CH 3 H H C C HH + H OH H + protonated alcohol carbocation Elimination mechanism – water from propan-1-ol reaction equation

18. Original slide prepared for the Electrophilic Substitution Nitration of benzene C6H6C6H6 + HNO 3 C 6 H 5 NO 2 + H 2 O Conditions / Reagents concentrated HNO 3 and concentrated H 2 SO 4 50 o C mechanism

19. Original slide prepared for the electrophilic substitution mechanism (nitration) 2. Electrophilic attack on benzene NO 2 + 3. Forming the product + NO 2 H the nitronium ion HNO 3 + 2H 2 SO 4 + 2HSO 4 - + H 3 O + 1. Formation of NO 2 + NO 2 + reaction equation and re-forming the catalyst H O SO 3 H O SO 3 H -

20. Original slide prepared for the Friedel-Crafts alkylation Alkylation of benzene C6H6C6H6 + RCl C6H5RC6H5R+ HCl Conditions / Reagents RCl (haloakane)and anhydrous AlCl 3 0 - 25 o C Where an H atom attached to an aromatic ring is replaced by a C atom electrophilic substitution to prevent further substitution R = alkyl group

21. Original slide prepared for the Alkylation example Three steps in electrophilic substitution mechanism 1. Formation of the electrophile (a carbocation) AlCl 3 - Cl AlCl 3 CH 3 CH 2 + With chloroethaneoverall reaction equation C 6 H 6 + CH 3 CH 2 ClC 6 H 5 CH 2 CH 3 + HCl CH 3 CH 2 Cl

22. Original slide prepared for the CH 3 CH 2 + Alkylation electrophilic substitution mechanism 2 2. Electrophilic attack on benzene + H CH 3 CH 2 ethylbenzene 3. Forming the product AlCl 3 - Cl AlCl 3 H Cl and re-forming the catalyst

23. Original slide prepared for the Friedel-Crafts acylation Acylation of benzene C6H6C6H6 + RCOCl C 6 H 5 COR+ HCl Conditions / Reagents RCOCl (acyl chloride)and anhydrous AlCl 3 50 o C An H atom attached to an aromatic ring is replaced by a C atom where C is part of C=O electrophilic substitution

24. Original slide prepared for the CH 3 C Cl O Acylation example Three steps in electrophilic substitution mechanism 1. Formation of the electrophile (an acylium ion) AlCl 3 - Cl AlCl 3 With ethanoyl chlorideoverall reaction equation C 6 H 6 + CH 3 COClC 6 H 5 COCH 3 + HCl + CH 3 CO

25. Original slide prepared for the + H CH 3 C O Acylation electrophilic substitution mechanism 2 2. Electrophilic attack on benzene phenylethanone - Cl AlCl 3 AlCl 3 H Cl 3. Forming the product and re-forming the catalyst + CH 3 CO O

26. Original slide prepared for the Nucleophilic Addition Reduction of carbonyls RCHO + 2[H] RCH 2 OH Conditions / Reagents NaBH 4 and H 2 SO 4 (aq) Room temperature and pressure primary alcohol RCOR + 2[H] RCH(OH)R secondary alcohol

27. Original slide prepared for the ++ -- Nucleophilic Addition Mechanism reduction of propanone H+H+ NaBH 4 is a source of hydride ions RCOR + 2[H] RCH(OH)R alcohol CH 3 C O C O H H propan-2-ol H CH 3 C O H H H+H+ from H 2 SO 4 (aq)

28. Original slide prepared for the Nucleophilic Addition RCHO + HCN RCH(OH)CN Conditions / Reagents NaCN (aq)and H 2 SO 4 (aq) Room temperature and pressure RCOR + HCN RC(OH)(CN)R supplies the CN - nucleophile supplies H + addition of hydrogen cyanide to carbonyls to form hydroxynitriles

29. Original slide prepared for the Nucleophilic Addition Mechanism hydrogen cyanide with propanone H+H+ NaCN (aq) is a source of cyanide ions CH 3 COCH 3 + HCN CH 3 C(OH)(CN)CH 3 CH 3 C O C O CN H H+H+ 2-hydroxy-2-methylpropanenitrile from H 2 SO 4 (aq) ++ -- CN CH 3 C O CN

30. Original slide prepared for the Nucleophilic Addition Elimination Acylation of water to give carboxylic acids RCOCl + H 2 O RCOOH Conditions room temperature and pressure carboxylic acid + HCl OH R C O

31. Original slide prepared for the Formation of ethanoic acid + H 2 O CH 3 COOH+ HCl CH 3 COCl ethanoyl chloride ethanoic acid mechanism OH CH 3 C O

32. Original slide prepared for the Nucleophilic Addition Elimination Mechanism CH 3 Cl C O ++ -- OH H CH 3 Cl C O OH H + CH 3 C O OH H + CH 3 C O OH ClH nucleophilic addition elimination reaction equation

33. Original slide prepared for the Acylation of primary amines to N-alkyl amides RCOCl + 2 R’NH 2 RCONHR’ Conditions room temperature and pressure N-alkylamide + R’NH 3 + Cl - NHR’ R C O N-propylethanamide NHCH 2 CH 2 CH 3 CH 3 C O

34. Original slide prepared for the Formation of N-propyl ethanamide from + CH 3 CH 2 CH 2 NH 2 CH 3 CONHCH 2 CH 2 CH 3 + CH 3 CH 2 CH 2 NH 3 + Cl - 2CH 3 COCl ethanoyl chloride 1-aminopropane N-propylethanamide mechanism

35. Original slide prepared for the ++ -- Nucleophilic Addition Elimination Mechanism CH 3 Cl C O NHCH 2 CH 2 CH 3 H CH 3 Cl C O NHCH 2 CH 2 CH 3 H + CH 3 C O NHCH 2 CH 2 CH 3 H + Cl NH 2 CH 2 CH 2 CH 3 CH 3 C O NHCH 2 CH 2 CH 3 H + NH 2 CH 2 CH 2 CH 3 Cl nucleophilic addition elimination reaction equation

36. Original slide prepared for the Advice To get back to the mechanism links page from anywhere in the presentation, click the button at the top right corner of the screen. This version provides the organic mechanisms specified (2002/3) by the AQA exam board. Each stage of a reaction equation, its conditions and mechanism are revealed in turn on a mouse click or keyboard stroke. Note that there is another version available where each reaction and mechanism play automatically after an initiating click or key stroke. The number of ways of navigating through this presentation may depend on the version of PowerPoint being used and how it is configured. Some possible ways of advancing: left mouse click or return key or right arrow key or up arrow key. Some possible ways of reversing: backspace key or left arrow key or down arrow key.

37. Original slide prepared for the Steve Lewis for the Royal Society of Chemistry References