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CCEA organic reaction mechanisms

CCEA organic reaction mechanisms. Click here for advice. Click a box below to go to the reaction Click ‘M’ to go to its mechanism. AS. M. Free Radical Substitution. PLEASE NOTE This version is the second draft following feedback.

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CCEA organic reaction mechanisms

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  1. CCEA organic reaction mechanisms Click here for advice Click a box below to go to the reactionClick ‘M’ to go to its mechanism AS M Free Radical Substitution PLEASE NOTE This version is the second draft following feedback. Teachers following this specification are welcome to email any requests for changes to:contact@chemit.co.uk Electrophilic Addition M Nucleophilic Substitution M Nucleophilic Addition M A2 Electrophilic Substitution M

  2. Free Radical Substitution chlorination of methane i.e. homolytic breaking of covalent bonds Overall reaction equation CH4 + Cl2 CH3Cl + HCl Conditions ultra violet light excess methane to reduce further substitution

  3. Free Radical Substitution mechanism Cl + Cl CH4 + Cl CH3 + HCl CH3 + Cl2 CH3Cl + Cl CH3 + Cl CH3 + CH3 ultra-violet Cl2 initiation step two propagation steps termination step CH3Cl minor termination step CH3CH3

  4. Further free radical substitutions Overall reaction equations CH3Cl + Cl2 CH2Cl2 + HCl CH2Cl2 + Cl2 CHCl3 + HCl CHCl3 + Cl2 CCl4 + HCl Conditions ultra-violet light excess chlorine

  5. Electrophilic Addition hydrogen bromide with ethene mechanism CH2=CH2 + HBr CH2CH2Br bromoethane

  6. hydrogen bromide with ethene H H C C H H H H H C C H + + H H - Br Br H H - H C C H Br H Electrophilic Addition mechanism reaction equation carbocation bromoethane

  7. Nucleophilic Substitution primary bromoalkane hydroxide ion with bromoethane mechanism CH3CH2Br + OH- (aqueous) CH3CH2OH + Br- ethanol tertiary bromoalkane hydroxide ion with 2-bromo,2-methylpropane mechanism (CH3)3CBr + OH- (aqueous) (CH3)3COH + Br- 2-methylpropan-2-ol

  8. hydroxide ion with bromoethane (SN2) H Br H - + C H C H3C CH3 H H OH OH - Br Br C CH3 - H OH Nucleophilic Substitution mechanism slow ethanol reaction equation SN2 S(substitution) 2(species reacting in the slowest step) N(nucleophilic)

  9. OH- ion with 2-bromo,2-methylpropane (SN1) CH3 CH3 CH3 - + OH + C C CH3 Br C CH3 CH3 CH3 CH3 CH3 - - Br Br - OH Nucleophilic Substitution mechanism slow 2-methylpropan-2-ol SN1 reaction equation S(substitution) 1(species reactingin the slowest step) N(nucleophilic)

  10. Nucleophilic Addition addition of hydrogen cyanide to propanone to form 2-hydroxy-2-methylpropanenitrile CH3C(OH)(CN)CH3 + HCN CH3COCH3 Conditions / Reagents NaCN (aq) to provide the CN- nucleophile andH2SO4 (aq) to provide the H+ heat under reflux

  11. Nucleophilic Addition mechanism C N - O + O O H C CH3 C CN CH3 C CN CH3 CH3 CH3 CH3 CN hydrogen cyanide with propanone + HCN CH3COCH3 CH3C(OH)(CN)CH3 NaCN (aq) is a source of cyanide ions H+ 2-hydroxy-2-methylpropanenitrile

  12. Electrophilic Substitution Nitration of benzene C6H6 + HNO3 C6H5NO2 + H2O Conditions / Reagents concentrated HNO3 and concentrated H2SO4 50oC mechanism

  13. Electrophilic Substitution mechanism (nitration) NO2 + 1. Formation of NO2 H + + NO2 O SO3H- + NO2 NO2 H O SO3H the nitronium ion HNO3 + 2H2SO4 + H3O+ + 2HSO4- 2. Electrophilic attack on benzene 3. Forming the product and re-forming the catalyst reaction equation

  14. 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 (for 2005 exams) by the CCEA 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.

  15. References Steve Lewis for the Royal Society of Chemistry

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