KEMORG1 Chapter 8 - Elimination

(8.1-8.3) What is true regarding the bonds in an elimination reaction

• 2 pi bonds are formed

• 1 pi bond is formed

• 1 pi bond is broken

• 2 sigma bonds are broken

• 2 sigma bonds are formed

(8.1 - 8.3) What is involved in an elimination reaction?

• Alkyl Halide

• Nucleophile

• Base

• Acid

Answer explanation

RX + B --> Alkene + H-B + X-

Base bonds with protons, C-H electrons form the pi bond, LG takes electrons to become halide anion

(8.1 - 8.3) the alpha carbon is connected to _____ while the beta carbon is connected to _____

• Hydrogen, Halogen

• Hydrogen, Hydrogen

• Halogen, Halogen

• Halogen, Hydrogen

Answer explanation

beta elimination: both LG are on diff carbons

alpha elimination: both LG are on same carbon

(8.1 - 8.3) Dehydrohalogenation (elimination of Alkyl Halide) is NOT commonly induced by

• -OH

• RO-

• -OCH2CH3

• HCl

Answer explanation

common bases used: negatively charged oxygen compounds

(8.1- 8.3) Hybridization in alkenes

• sp

• sp2

• sp3

• sp3d

Answer explanation

3 e- groups, trigonal planar geometry, bond angle 120. Double bond is made of 1 sigma and 1 pi

(8.1 - 8.3) The pi bond in an alkene is caused by

• overlap of sp2 orbitals

• overlap of s orbitals

• overlap of p orbitals

• overlap of sp3 orbitals

Answer explanation

sigma bond is from overlap of sp2 orbitals

(8.1 - 8.3) Which configuration of alkenes would be more stable

• cis

• trans

Answer explanation

due to less steric strain

(8.1 - 8.3) What would increase the stability of an alkene

• s character

• p character

• e- dontaing groups

• e- withdrawing groups

Answer explanation

s character: e- bound closer to nucleus = stronger bonds

e- donating groups: sp2 C wants to accept e-, e.g. from alkyl groups (R groups)

(8.4 - 8.5) ___ is unimolecular, ___ is bimolecular

• E2, E1

• E1, E2

• E2, E2

• E1, E1

Answer explanation

analogous to Sn1 and Sn2, differ in timing of bond cleavage and bond formation

(8.4 - 8.5) What is the rate equation in an E2 mechanism

• rate = k[Base][RX]

• rate = k[Base]^2

• rate = k[RX]^2

• rate = k[RX][Nu]

Answer explanation

second order, concerted reaction

E2 is more common than E1