Elimination Rxns

Question 1

Which rxn occurs in a single, concerted step: E1 or E2?

Answer 1

E2

Question 2

what happens in an elimination rxn?

Answer 2

a H gets attacked by a base, and a pi bond is created, resulting in the elimination/kicking off of a leaving group

Question 3

Does E2 rxn favor strong base or weak base?

Answer 3

strong

Question 4

Does the SMALL base in E2 rxn favor primary electrophiles or tertiary?

Answer 4

tertiary

Question 5

Does the LARGE base in E2 rxn favor primary electrophiles or tertiary?

Answer 5

tertiary > secondary > primary

Question 6

Which elimination rxn makes carbocation intermediates?

Answer 6

E1

Question 7

Which rxn occurs in a two steps E1 or E2?

Answer 7

E1

Question 8

Does E1 rxn favor strong base or weak base?

Answer 8

weak

Question 9

How substituted does E1 like its electrophiles to be?

Answer 9

most substituted

Tertiary > secondary&raquo_space; primary

Question 10

Which E1 product is favored: cis or trans?

Answer 10

trans

Question 11

Which elimination rxn requires you to draw/rotate the Newman projection to show that the substrate’s H is 180 degrees from its leaving group?

Answer 11

E2

Question 12

what kinds of molecules play the role of nucleophiles in elimination rxns? Starts with letter b…

Answer 12

bases

Question 13

what are 4 of the small, strong bases that can facilitate E2 elimination rxns?

Answer 13

• OH
• OCH3 (aka -OMe)
• OCH2CH3

Question 14

what are 5 of the LARGE, strong bases that can facilitate elimination rxns?

Answer 14

t-butOK
DMN
DBU

Question 15

do small, strong bases favor the least substituted opportunity for pi bond, or the most substituted one?

Answer 15

most;

favors the option that creates the most substituted pi bond

Question 16

do LARGE, strong bases favor the least substituted opportunity for pi bond, or the most substituted one?

Answer 16

least

favors the option that creates the LEAST substituted pi bond

Question 17

when an E2 rxn occurs on a ring, what must be true of the H and the leaving group?

Answer 17

They must be in the DIFFERENT planes

Question 18

what are the two ways to make OH a good leaving group for elimination rxns?

Answer 18

1. protonation: O in the OH takes an H from an H3O+ (only works if you don’t also have a strong base in the rxn bc the strong base would neutralize your strong acid H3O+)
2. conversion to tosylate: H on OH gets replaced by the Ts from TsCl & pyrdine

Question 19

what does tosylate look like on your molecule?

Answer 19

OTs