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CHEM 266L (6)

Reaction review sheet.pdf

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Steve Forsey

Chemical Reactions Review 1 Chemical Reactions Review This is not a comprehensive list of reactions but is an excellent start. Not all reactions are balanced and mechanisms are incomplete or shortened. Question Things to think about Answer Pr Pr Me CH 2H C2 3 OR RO Me S N Et Et H C ROH S R 3 Cl weak base + (racemic mixture) H3CH 2 H 3 CH CH CH H3CH 2 2 2 3 3o E (+ Z) E (+ Z) E2 H H Me Me Et CH CH Cl Z 2 3 RONa H H 3 Cl Me H H CH C strong base 3 2 o Me Et 3 E Cl H H H Et Et Cl Nu CH CH good nucleophiles H major 2 3 Nu CH 2CH 3product that are not strong bases H3C H Cl weak base: I , CH COO 2 carbon - aprotic solvent H3C 3 inversion at stereocenter 2o good nucleophile,CN, HS does not favour ionization aprotic solvent S N - favoured E2 - minor products CH 2H 3 all strong bases are good RONa nucleophiles major product H o Cl Strong base but 2 carbon - steric interaction H 3 2o minor products E2 - favoured 1 carbon major product CH CH CH CH Br Strong base or CH 3H C2 CH2Nu 2 3 2 2 2 Good nucleophile little steric interaction 1o minor products SN 2 - favoured 1 carbon Et - + but the strong base is bulky Et C O Na Et lots of steric interaction major product CH 3H C2 CH2Br 2 o SN2 - unlikely to occur 1 E2 - favoured Chem 266 S.P.Forsey Chemical Reactions Review 2 CH Br Strong base or noβ carbons - no E2 CH Nu 3 Good nucleophile 3 H 3C H vinyl halide CC Strong base or sp short stong no reaction r H B good nucleophile bond aryl halide Br Strong base or 2 good nucleophile sp short stong no reaction bond H3C H fast N 1 and N 2 S 1 - resonance stabilized carbocation intermediate CC why? N H Br SN2 - stabilized transition state through hyperconjugation Br fast S 1 and S 2 SN1 - resonance stabilized carbocation intermediate N N S 2 - stabilized transition state through hyperconjugation why? N 1) resonance stability of What is the order for decreasing stability benzylic and allylic benzylic > allylic > of a carbocation, why? 2) hyperconjugation of 3 > 2 > 1 > methyl alkanes What is the order for decreasing (CH 3 2=C(CH 3 2 hyperconjugation CH 3CH=CHCH >3 stability of alkenes, why? CH 3H=CH >2H =CH2 2 What is the order of decreasing reactivity 1) hyperconjugation of T.S. benzylic > allylic > benzylic and allylic o o o in aNS 2 reaction, why? 2) steric interaction methyl >1 >2 >3 Stabiltity of intermediate What is the order of decreasing reactivity 1) Resonance stabilization benzylic > allylic > in a S 1 reaction, why? o o o N benzylic and allylic 3 > 2 > 1 > methyl 2) hyperconjugation H H 3 D H3C D H 3 CH H 3 H C H H D CH 3H 2Na Br D 3 H Br CH CH OH 3 2 H H CH 3 CH 3 CH 3 H 3 H H 3C H Br E2 favoured CH3 base - alkene, acid2HSO4 OH but some H 2O /4 2 alkenes CH 3 CH CH 2 o O CH 25 C likely 3 major product Br H 2 is a good leaving group acid is a good nucleophile 1) CH 3OH N HBr major product CH 3 CHC 3 o O - H H 25 C Br H H Br minor product Chem 266 S.P.Forsey Chemical Reactions Review 3 base - OH H O is a good leaving group 2 Conjugate base - poor nucleophile CH 3H 85% H SO There is no appreciable amounts major product CH 3 CHC 3 2 4 of H Opresent(E1) 80 C 2 H H H3C H C H H H H minor product Br o MgBr Mg Grignard Reagent A δ- δO 1) HCOH δ+ CH 2H A δ- MgBr δ+C 2)H 3 + H H δO 1) H3COH δ- δ+ δ- OH CH 3H M2Br + CH3CH 2gBr δ+C 2)H3O H CH 3 CH 3H 2HCH 3 δ- δ- δ+ δ- O OH RMgX 1) 3CCOCH 3 RMgBr δ+C R C CH 2) H O+ CH 3 3 H 3 3 CH 3 δ- reacts OH 1) 3 CCOOCH 3 δ- δ+ - O 2 times RMgX + RMgBr δ+C R C CH 3 2) 3 O H3C OCH 3 R δ- δ+ δ- δO 1) CO2 RMgBr δ+ RMgX + C RCOOH 2) H3O O δ- 3 an sp carbon with a negative charge is a RCH CCH RCH M2Br A RCH 2CMgBr + RCH 3 2 stronger base than a sp carbon δ- 1) H CCOCH -δ+ O OH A 3 3 RCH CCMgBr δ- δ+ C RCH 2 C C CH 2) H3O+ 2 H C CH 3 3 3 CH 3 a carbon with a negative charge is a stronger base - + R1MgX + R2OH than on oxygen with a R2O MgX + R H1 negative charge What is the difference between LiAlH will reduce carboxylic acids, esters, ketones and aldehydes 4 LiAlH4and NaBH 4 NaBH 4ill only reduce ketones and aldehydes O 1) LiAl4 /E2 O R CH OH + R OH R1 C OR 2 2) H O reduction 1 2 2 2 O NaBH 4 reduction RCH 2H RC H H O 2 Chem 266 S.P.Forsey Chemical Reactions Review 4 O OH R C R NaBH 4 reduction 1 2 H 2 R1CHR 2 H2CrO 4 RCH 2H oxidation RCOOH (or Na2C2 O7/2 SO4) PCC partial O RCH 2H oxidation RCH OH R CR H2CrO 4 1 2 O H or oxidation R1 C R 2 KMnO 4 NaOH RCH 2H KMnO 4 NaOH oxidation RCOOH OH KMnO RCR 2 4 3 alcohol No Reaction NaOH R3 + O H O O conc H2O 4 R1CH 2H R 2CH2C OH R1CH 2H + R2CH 2 OH R1CH 2CCH R2 2 Cl O + O CH 3SO2Cl + -H - RCH 2H or CH C H SO Cl A RCH 2H O S O RCH 2S O RCH 2S CH 3 + Cl 3 6 4 2 O CH3 H CH 3 O O Nu RCH 2S CH3 RCH Nu + O S CH 3 react A with 2 S N Nu O O What is the order for decreasing same as carbocations benzylic > allylic > allylic, benzylic - resonance o o o stability of free radicals, why? alkyl groups - hyperconjugation 3 > 2 > 1 > methyl Bromine is less reactive thus is more selective What is the selectivity differencean chlorine. Bromination will predominately go between Cl and Br radicals? through the most stable intermediate where as chlorination will give mixtures CH 3 CH3 CH3 think about the Br CH free radical intermediate 3 B2 stability CH approx. 100% CH 3 CH 3 o 3 hυ/120 Br CH 3 CH3 CH3 H CH 3 CH2Br H H minor product Chem 266 S.P.Forsey Chemical Reactions Review 5 CH 3 H CH3 CH3 CH3 Cl CH 3 C2 Cl CH2 CH 3 approx. 2 CH 3 CH 3 o hυ/25 H CH3 H think about the reactivity CH3 CH 2l of the halogen radical H : 3 CH 2l CH3 CH3 CH 3 CH 3 CH3 H Br H Br H Br H Br Cl Br Br Cl CH3 H Br Cl H H Cl H H Cl H H H H H H 2 o H H hυ/25 CH 3 CH3 CH3 CH 2l CH 3 CH3 racemic. CH3 This arises by abstraction of H at C-2 giving a planar radical H H RC C R 2 NaNH 2 RCCR 2 double E2 Br Br H H 3 NaNH2 double E2 R1 C C H A also acidic R 1 CC Na + proton Br Br react A withR2CH 2r S 2 R C CCH R N 1 2 2 base - alkene Br
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