sn1,2 e1,2

Question 1

SN1 & E1

Answer 1

Question 2

SN1 & E1 rate law

Answer 2

rate determining step=conc of substrate only
Hence, unimolevular reaction.

Question 3

SN2 & E2

Answer 3

Question 4

SN2 & E2 rate law

Answer 4

rate determining step=conc of substrate and base/Nu
Hence, bimolecular reaction

Question 5

Substitution reaction

Answer 5

A substitution reaction occur when the leaving group is replaced with a nucleophile

Question 6

Elimination Reaction

Answer 6

• In elimination reaction a proton from the ß-position is removed together with the leaving group forming a double bond.
• This type of reaction is called ß elimination or 1,2 elimination
• Thus, some types of beta elimination reactions are named on the basis of the leaving group. For example, when the leaving group is specifically a halide, the reaction is also called a dehydrohalogenation; when the leaving group is water, the reaction is also called dehydration

Question 7

The role of the hydroxide ion in a substitution reaction

Answer 7

• OH^- acts as Nu
• For example, one of the lone pairs on the oxygen can attack the slightly positive carbon. This leads on to the loss of the bromine as a bromide ion, and the -OH group becoming attached in its place.

Question 8

The role of the hydroxide ion in an elimination reaction

Answer 8

• OH^- acts as strong base
• the hydroxide ion hits one of the hydrogen atoms in the CH3 group and pulls it off. This leads to a cascade of electron pair movements resulting in the formation of a carbon-carbon double bond, and the loss of the bromine as Br-.

Question 9

Is E2 mechanism step wise or concerted mechanism?

Answer 9

• a concerted process, a base abstracts a proton and the leaving group leaves simultaneously
• no steric hindrace for E2 unlike SN2.
• An E1 reaction is generally accompanied by a competing SN1 reaction, and a mixture of products is generally obtained
• In E2, reagent act as base pluck of the hydrogen, while in SN2 as as nucleophile to attack electrophilic position undergo steric hindrace when tertiary.
• on the other hand, E2, for a tertiary substrate, the transition state exhibits a partial double bond that is more highly substituted, and therefore, the transition state will be lower in energy.

-That doesn’t mean that primary substrates are slow
to react in E2 reactions. In fact, primary substrates readily undergo E2 reactions. Tertiary substrates simply react more rapidly under the same conditions

Question 10

Is E1 mechanism step wise or concerted mechanism?

Answer 10

• a stepwise process, first the leaving group leaves, and then the base abstracts a proton.
• base does not participate in this step, and therefore, the concentration of the base does not affect the rate.
• involves formation of a carbocation intermediate, and the rate of reaction will be dependent on the stability of the carbocation like Sn1
• An E1 reaction is generally accompanied by a competing SN1 reaction, and a mixture of products is generally obtained
• when OH act as nucleophile, attack at carbocation.

Question 11

Is SN2 mechanism step wise or concerted?

Answer 11

• Concerted reaction - bonds are formed and broken at the same time.
• Alkyl halides with bulky substituents react more slowly than less bulky alkyl on the central carbon atom. Thus order of reactivity : primary halide > secondary halide > tertiary halide

Question 12

Is SN1 mechanism step wise or concerted?

Answer 12

• step wise reaction, leaving group leave to form a intermediate carbocation and nucleophile attacks carbocation
• The more stable the carbocation, the faster the SN1 reaction .Tertiary halides will react faster than primary halides (carbocation is more stable)