Quiz | Further Reactions of Haloalkanes
Which statement is correct about a SN1 reaction?
The reaction is stereospecific
The bond-breaking step is the fastest step of the reaction
SN1 reactions proceed through an intermediate carbocation
The kinetic rate involves the nucleophile
SN1 reactions are nucleophilic substitutions which proceed through an intermediate carbocation ⇒ SN1 reactions are unimolecular with a bond-breaking step following by a bond-making step. The bond-breaking step is slower and therefore determines the rate: it is the rate-determining step
Which of the following statements regarding the E2 mechanism is incorrect?
E2 mechanism is always bimolecular
E2 mechanism is second order
E2 mechanism occurs in one step
E2 mechanism occurs with a syn periplanar geometry
E2 reactions are nucleophilic eliminations which do not proceed via an intermediate ⇒ E2 reactions are bimolecular with simultaneous bond-making and bond-breaking steps. E2 reactions always occur with an anti periplanar geometry (preferred over syn periplanar geometry)
Which statement is incorrect about an E1 reaction between (CH3)3CBr and NaOH?
It competes with an SN1 reaction
An alkene is formed
The reaction occurs with an anti periplanar geometry
The kinetic rate only involves (CH3)3CBr
Due to planar carbocation, E1 reactions do not always occur with an anti periplanar geometry
SN1 and E1 reactions always compete
Which of the following starting materials most likely reacts via an E1 mechanism?
CH3CH2I
CH3CH2Br
(CH3)2CHBr
(CH3)3CBr
The more stable the carbocation intermediate, the faster the E1 reaction. A tertiary carbocation is more stable than a secondary or a primary (hyperconjugation) ⇒ (CH3)3CBr will react via an E1 mechanism
What is the major product of an elimination reaction between 3-chloro-2,3-dimethylpentane and NaOH?
2,3-dimethylpent-2-ene
3,4-dimethylpent-2-ene
2-methyl-3-methylenepentane
No selectivity observed
In elimination reactions, the major product is the most substituted alkene. This is the Zaitsev's rule
Which conditions favor an E1 reaction?
strong sterically hindered base / primary alkyl halide
strong sterically hindered base / tertiary alkyl halide
good nucleophile / primary alkyl halide
good nucleophile / tertiary alkyl halide