Alkenes PPT 23-24 PDF

3.3.4 Alkenes Starter 1. Name CH3CH=CH3CHBrCH3 2. Draw 2-chlorobut-2-ene 3. Draw a functional group isomer of but-1-ene 4. Draw the product when ethene reacts with bromine (Br2) Alkenes 3.3.4  But-2-ene CH3CH=CHCH3 Draw all C-H bonds...

3.3.4 Alkenes Starter 1. Name CH3CH=CH3CHBrCH3 2. Draw 2-chlorobut-2-ene 3. Draw a functional group isomer of but-1-ene 4. Draw the product when ethene reacts with bromine (Br2) Alkenes 3.3.4  But-2-ene CH3CH=CHCH3 Draw all C-H bonds CH3C(CH3)=CHCH2CH3  H CH3 H H C C C C H CH2CH3 H CH2CH2CH3 2-methylbut-1-ene pent-1-ene cyclopentane We studied structural isomerism in 3.3.1 Introduction to Organic Chemistry  Geometrical (E-Z Isomerism) Molecules with the same structural formula, but the bonds are arranged differently in space.  QUICK CHECK - E/Z or neither? E Z Z Neither E-1-bromo-2-chloroethene Z-1-bromo-2-chloroethene restricted rotation around the C=C bond 2 different atoms/groups attached to each C of the C=C double bond  CH3 CH2Cl Z Z-1-chloro-2-ethylbut-2-ene Quick check – on whiteboards H 3C CH2CH3 CH2F Br Cl Z E-2-iodopent-2-ene Z-1-bromo-1-chloro-2-methylbut-1-ene  E Z (1Z,3E)-1-bromopenta-1,3-diene Halogenoalkane - e.g. 1,2-dichlorobutane or 2-bromo-1-chlorobutane Other possible products E-1-chlorobut-1-ene Z-1-chlorobut-2-ene E-1-chlorobut-2-ene Electron pair acceptor  A general equation for electrophilic addition reactions in alkenes: electrophile Alkene Saturated product - Unsaturated H H H H H H C C H C C H H C C H + H H X X :Y- X Y Y H H H H H H C C H C C H H C C H + H H H H :Br - H Br Br H H CH3 H CH3 CH3 C C H C C H H C C H + H H H Cl H :Cl - H Cl Br2 is non-polar. How can it act as a nucleophile? H H H H H H C C H C C H H C C H + H H Br Br :Br - Br Br Br H H H H H H C C H C C H H C C H + H H H H - H OSO3H :OSO3H OSO3H  Electrophilic Addition H H H H H H H H C C H C C H H C C H H C C H + H H H H + H H–O–H OH : H+ H–O–H H+  Bromoethane Ethene 1,2-dibromoethane Ethylhydrogensulfate Ethanol CH3CH=CHCH3 + Br2 → CH3CHBrCHBrCH3 CH3CH=CHCH3 + HCl → CH3CHClCH2CH3 CH3CH=CHCH3 + H2SO4 → CH3CH(OSO2OH)CH2CH3 CH3CH=CHCH3 + H2O → CH3CH(OH)CH2CH3 CH3 CH3 CH3 CH3 CH3 CH3 C C H C C H H C C H + H H Br Br Br Br - :Br Br CH3 CH3 CH3 CH3 CH3 CH3 C C H C C H H C C H + H H H H - H Cl :Cl Cl CH3 CH3 CH3 CH3 CH3 CH3 C C H C C H H C C H + H H H H - H OSO2OH :OSO2OH OSO2OH H3 C CH3 H3C CH3 H3C CH3 H3C CH3 C C H C C H H C C H H C C H + H H H H + H H–O–H OH : H+ H–O–H H+ High challenge, low stress: H H CH3 H CH3 CH3 C C H C C H H C C H + H H H H - H OSO2OH :OSO2OH OSO2OH H H CH2CH3 H CH2CH3 CH2CH3 C C H C C H H C C H + H H H H H Br - Br :Br  1-bromopropane or 2-bromopropane Cyclohexene 2,3-dibromobutane 3-amino-3-methyl pentane or 2-amino-3-methyl pentane 1-bromo-1-methylcyclohexane Or 1-bromo-2-methylcyclohexane Recap – Review pages 1-9 and answer the following questions on your whiteboards Retrieval Practice 1. What is an electrophile? 2. What is the name of the mechanism alkenes undergo? 3. Outline the mechanism for ethene with hydrogen bromide 4. Stretch Q - Outline the mechanism for the following reaction: Recap – Review pages 1-9 and answer the following questions on your whiteboards 1. What is an electrophile? Electron pair acceptor 2. What is the name of the mechanism alkenes undergo? Electrophilic addition 3. Outline the mechanism for ethene with hydrogen bromide H H H H H H C C H C C H H C C H + H H H H :Br - H Br Br Recap – Review pages 1-9 and answer the following questions on your whiteboards Retrieval Practice Stretch Q - Outline the mechanism for the following reaction: H H +O –– H + –– H H+ : H–O–H  Lesson Outcomes Review electrophilic addition Evaluate what happens when unsymmetrical alkenes undergo electrophilic addition Explain why major and minor products are formed Learn what addition polymers are and explain why they are non-biodegradable  forms from the most stable carbocation H 1○ H 2○ C 3○ C–C+ C–C–C C–C–C + + H Least stable Most stable  H 1○ H 2○ C 3○ C–C+ C–C–C C–C–C + + H Quick check – on whiteboards Classify this carbocation. Which is more stable? Why?  On your whiteboards, draw the 2 possible products when propene reacts with HBr and name them. Challenge – which is the major product? Why?  2○ Carbocation Major Product More Stable H H H H H H H C C C H H C C C H + H Br H H H H H H :Br - H C C C H H H H H H H H H Br H C C C H + H C C C H H H H H Br :Br - 1○ Carbocation Minor Product Less Stable  2○ Carbocation Major Product H H More Stable H H H H H H H H C C C H C C C H H C C C H H H + H H H H H OSO2OH - OSO2OH :OSO2OH  H H H H H H H C C C H C C C H + H H H H H - :OSO2OH OSO2OH 1○ Carbocation Less Stable H H H H C C C H H H OSO2OH Minor Product H H H H H H C C – CH2CH2CH3 H C C CH2CH2CH3 H C C – CH2CH2CH3 + H H H :Br - H Br Br H CH3 H CH3 H CH3 C C –CH3 H C C CH3 H C C – CH3 + H H H :Br - H Br Br H H H CH2CH2CH3 c. H2SO4 C C + H2 O H C C CH2CH2CH3 H H H OH CH3 H CH3 H c. H2SO4 CH3 – C C – CH3 + H2 O CH3 C C CH3 OH H Here are the mechanisms for the chemical reactions. a) H H H H H H C C – CH2CH2CH3 H C C CH2CH2CH3 + H C C – CH2CH2CH3 H H - H :OSO2OH H OSO2OH OSO2OH b) CH3 H CH3 H CH3 H CH3 – C C – CH3 CH3 – C C CH3 CH3 – C C –CH3 + H OSO2OH H H - :OSO2OH OSO2OH On whiteboards – name the MAJOR product. 2-bromopropane 3-amino-3-methyl pentane 1-bromo-1-methylcyclohexane  Quickcheck Deep processing Q5 in the past paper question booklet Extension – Page 28 in the notes booklet M1, M2 and M4 are awarded for the three curly arrows shown on the mechanism (1 mark for each correct) M3 is for the structure of the carbocation intermediate M1 The major product is formed via a tertiary carbocation intermediate and the minor product is formed via a secondary carbocation intermediate M2 The tertiary carbocation is more stable than the secondary carbocation What was your score out of 7? Student response – what do you think? Question Outline the mechanism for the formation of 2-bromopropane from propene. Explain why more 2-bromoproane is formed than 1-bromopropane. (6 marks) 3/6  Lesson Outcomes Review electrophilic addition Evaluate what happens when unsymmetrical alkenes undergo electrophilic addition Explain why major and minor products are formed Learn what addition polymers are and explain why they are non-biodegradable  C6H5 H C6H5 This is the structure of phenylethene and poly(phenylethene), also called polystyrene. CH3 CH3 CH3 OH C C C C Cl Cl Cl Cl CH3 CH2CH3 Cl F C C C C CH3 H F F CH3 CH3 F CH3 C C C C Cl F CH3 F H CN C C OH H Poly(ethene) Poly(propene)  Problems with plastics How many times have you used single use plastic today? Are there any ways you could reduce this? Why are single use plastics not good? Bigger picture Are clothes made from recycled materials really more sustainable? | Environment | The Guardian  Lesson Outcomes Review electrophilic addition Evaluate what happens when unsymmetrical alkenes undergo electrophilic addition Explain why major and minor products are formed Learn what addition polymers are and explain why they are non-biodegradable  Organic so far… In pairs, complete the following table Name of Reagent Conditions Starting Product mechanism compound Free radical Halogen UV light Alkane Haloalkane substitution Nucleophilic NaOH Warm & Aqueous Haloalkane Alcohol substitution Nucleophilic NH3 Excess Haloalkane Primary Amine substitution Nucleophilic KCN Aqueous & Ethanol Haloalkane Nitrile substitution Elimination NaOH Hot & Ethanol Haloalkane Alkene Electrophilic HBr Alkene Haloalkane addition Electrophilic H2SO4 Alkene Alkylhydrogen addition sulfate Electrophilic H2O(g) Conc H2SO4 Alkene Alcohol addition catalyst  Organic so far… In pairs, complete the following table Name of Reagent Conditions Starting Product mechanism compound Free radical Halogen UV light Alkane Haloalkane substitution Nucleophilic NaOH Warm & Aqueous Haloalkane Alcohol substitution Nucleophilic NH3 Excess Haloalkane Primary Amine substitution Nucleophilic KCN Aqueous & Haloalkane Nitrile substitution Ethanol In pairs, complete the following table Elimination NaOH Hot & Ethanol Haloalkane Alkene Electrophilic HBr Alkene Haloalkane addition Electrophilic H2SO4 Alkene Alkylhydrogen addition sulfate Electrophilic H2O(g) Conc H2SO4 Alkene Alcohol addition catalyst  Quickcheck Deep processing Q3 in the past paper question booklet Extension – Page 30 in the notes booklet Electrophilic addition Nucleophilic substitution Addition polymerisation Polypropene Give your score out of 15 on your whiteboards  Extension For each reaction, give the name of the mechanism, reagents and conditions