Chem357_SN1_E1__FINAL_Student_ - 1 Substitution...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 1 Substitution & Elimination Substitution & Elimination Unit 3 - S Unit 3 - S N 1 & E1 1 & E1 Paula Y. Paula Y. Bruice Bruice , , Chapter 8 & 9 Chapter 8 & 9 2 Solvolysis Solvolysis Reactions - S Reactions - S N 1 & E1 1 & E1 Let us consider the following empirical result: How can this happen? C Br CH 3 CH 3 CH 3 HO CH 3 CH 3 CH 3 H-Br + H 2 O (solvent) N O T E t h a t H 2 O i s t h e s o l v e n t h e r e . H 2 C H 3 C CH 3 3 2.0 x 10-3 3.0 x 10-3 2.0 x 10-3 1.0 x 10-3 1.0 x 10-3 1.0 x 10-3 Rate of S N 1 (M/s-1 ) 5.0 x 10-4 0.40 M 0.40 M 7.5 x 10-4 0.60 M 0.20 M 5.0 x 10-4 0.40 M 0.20 M 2.5 x 10-4 0.20 M 0.60 M 2.5 x 10-4 0.20 M 0.40 M 2.5 x 10-4 0.20 M 0.20 M Rate E1 (M/s-1 ) [ alkyl Br ] (M) [ H 2 O ] (M) + H 2 O (solvent) H 2 C H 3 C CH 3 C Br CH 3 CH 3 CH 3 + HO CH 3 CH 3 CH 3 H-Br + H 2 O nucleophile electrophile ! " ! + RATE = k [alkylBr] [H 2 O] x y Solvolysis Solvolysis Reactions - S Reactions - S N 1 & E1 1 & E1 4 + H 2 O (solvent) H 2 C H 3 C CH 3 C Br CH 3 CH 3 CH 3 + HO CH 3 CH 3 CH 3 H-Br + H 2 O nucleophile electrophile ! " ! + RATE = k [alkylBr] BOTH SN1 and E1 reactions are 1 s t o r d e r with respect to alkylBr and I N D E P E N D E N T o f [ H 2 O ] . The reactions are 1 s t o r d e r O V E R A L L . So what does this mean? Solvolysis Solvolysis Reactions - S Reactions - S N 1 & E1 1 & E1 5 C Br H 3 C H 3 C CH 3 ! " ! + C CH 3 H 3 C CH 3 Br pure p orbital SLOW r.d.s S N 1 & E1 Mechanisms 1 & E1 Mechanisms 6 C Br H 3 C H 3 C CH 3 O CH 3 CH 3 CH 3 ! " ! + H 2 O C CH 3 H 3 C CH 3 Br O H 3 C H 3 C H 3 C pure p orbital H H H H H 2 O H 2 O OH H 3 C H 3 C H 3 C HO CH 3 CH 3 CH 3 MECHANISM: P L A N A R C A R B O C A T I O N R E S U L T S SLOW r.d.s FAST S N 1 & E1 Mechanisms 1 & E1 Mechanisms 7 S.M. Products ! G Reaction Coordinate T.S. 1 S N 1 T.S. 2 C Br H 3 C H 3 C CH 3 C CH 3 H 3 C CH 3 O H 3 C H 3 C CH 3 H H OH H 3 C CH 3 H 3 C T.S. 3 O H H OH H 3 C CH 3 H 3 C Energetics Energetics for S for S N 1 Reaction 1 Reaction 8 C Br H 3 C H 3 C CH 3 ! " ! + H 2 O C CH 3 H 3 C C Br OH H 3 C H 3 C H 3 C MECHANISM: SLOW r.d.s FAST H H H H 2 O FAST H 3 C H 3 C CH 2 S N 1 E1 O H 3 C H 3 C CH 3 H H S N 1 & E1 Mechanisms 1 & E1 Mechanisms 9 S.M. ! G Reaction Coordinate T.S. 1 S N 1 and E1 T.S. 2 C Br H 3 C H 3 C CH 3 C CH 3 H 3 C CH 3 O H 3 C H 3 C CH 3 H H OH H 3 C CH 3 H 3 C T.S. 3 O H H (CH 3 ) 3 C OH T.S. 2 (CH 3 ) 2 C=CH 2 H 3 C H 3 C CH 2 S N 1 E1 S N 1 versus E1 1 versus E1 Energetics Energetics 10 S N 1 unimolecular (ie. 1st order) substitution reaction nucleophilic N O T E : The "1" D O E S N O T mean that it is "one step"!!...
View Full Document

Page1 / 19

Chem357_SN1_E1__FINAL_Student_ - 1 Substitution...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online