266 Reactions Review

266 Reactions Review - Chemical Reactions Review 1 Chemical...

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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 CH 2 CH 2 CH 3 H 3 C H 3 CH 2 C Cl ROH weak base 3 o S N 1 H 3 CH 2 C H 3 C CH 2 CH 2 CH 3 + Pr OR Et Me Pr RO Et Me S R (racemic mixture) E (+ Z ) E (+ Z ) CH 2 CH 3 H 3 C H 3 CH 2 C Cl RONa strong base 3 o Cl H Me H Et Me Cl Me H H Et Me E2 Cl H H H Et Et Z E CH 2 CH 3 H H 3 C Cl 2 o Nu weak base: I - , CH 3 COO - good nucleophile, - CN, HS - aprotic solvent good nucleophiles that are not strong bases 2 o carbon - aprotic solvent does not favour ionization S N 2 - favoured Nu H H 3 C CH 2 CH 3 inversion at stereocenter major product E2 - minor products CH 2 CH 3 H H 3 C Cl 2 o RONa Strong base all strong bases are good nucleophiles but 2 o carbon - steric interaction E2 - favoured minor products major product CH 3 CH 2 CH 2 CH 2 Br 1 o Strong base or Good nucleophile 1 carbon little steric interaction S N 2 - favoured o CH 3 CH 2 CH 2 CH 2 Nu major product minor products CH 3 CH 2 CH 2 CH 2 Br C Et Et Et O - Na + 1 o but the strong base is bulky lots of steric interaction S N 2 - unlikely to occur E2 - favoured o major product Chem 266 S.P.Forsey
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Chemical Reactions Review 2 CH 3 Br Strong base or Good nucleophile no β carbons - no E2 CH 3 Nu CC H 3 C HB r H Strong base or good nucleophile vinyl halide sp 2 short stong bond no reaction Br Strong base or good nucleophile aryl halide sp 2 short stong bond no reaction H 3 C H H Br fast S N 1 and S N 2 why? S N 1 - resonance stabilized carbocation intermediate S N 2 - stabilized transition state through hyperconjugation Br fast S N 1 and S N 2 why? S N 1 - resonance stabilized carbocation intermediate S N 2 - stabilized transition state through hyperconjugation What is the order for decreasing stability of a carbocation, why? 1) resonance stability of benzylic and allylic 2) hyperconjugation of alkanes benzylic > allylic > 3 o > 2 o > 1 o > methyl What is the order for decreasing stability of alkenes, why? hyperconjugation (CH 3 ) 2 C=C(CH 3 ) 2 > CH 3 CH=CHCH 3 > 3 CH=CH 2 >CH 2 =CH 2 What is the order of decreasing reactivity in a S N 2 reaction, why? 1) hyperconjugation of T.S. benzylic and allylic 2) steric interaction benzylic > allylic > methyl >1 o >2 o >3 o What is the order of decreasing reactivity N 1 reaction, why?
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This note was uploaded on 10/31/2011 for the course CHEM 266 taught by Professor Pols during the Fall '07 term at Waterloo.

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266 Reactions Review - Chemical Reactions Review 1 Chemical...

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