Reaction Mechanisms

Question 1

What is the rate-determining step

Answer 1

The slowest step so the one with the highest activation energy

Question 2

What is a SN2 reaction

Answer 2

A nucleophilic substitution reaction with a mechanism that involves two molecules in the rate-determining step, bond making and breaking happen simultaneously so intermediate formed with weak bonds to nucleophile and leaving group

Question 3

Describe the mechanism for hydrolysis of 1-bromobutane

Answer 3

C-Br bond breaks at the same time as the nucleophile OH- forms C-OH bond, transition state in which carbon forms five bonds and have partial delta charges in transition state

Question 4

What is an SN1 reaction

Answer 4

Nucleophilic substitution reaction with a mechanism that involves only one molecule in the rate-determining step

Question 5

What overall order is hydrolysis of a primary halogenoalkanes

Answer 5

Overall second order, eg rate=k[halogenoalkane][OH-]

Question 6

What is the overall order of hydrolysis of tertiary halogenoalkanes

Answer 6

Overall first order, eg rate=k[halogenoalkane]

Question 7

Describe mechanism of hydrolysis of tertiary halogenoalkane

Answer 7

C-Br bond breaks first in slow step to form an ionic intermediate (tertiary carbocation) which is the rate-determining step, then nucleophile rapidly forms new bond with C+ ion, concen of OH- does not affect rate of reaction as not involved in rate-determining step

Question 8

What is a transition state

Answer 8

The state of reacting atoms when they are at the top of the activation energy barrier for a reaction step, is at higher energy than reactants

Question 9

Can the presence of a catalyst change the mechanism of a reaction

Answer 9

Yes, true of both homogenous and heterogenous catalysts