fundamentals of reactivity

Question 1

what are the 4 factors that influence whether a reaction proceeds via SN1 or SN2 pathway

Answer 1

• steric effects
• the nature of the nucleophile
• the nature of the leaving group
• the nature of the solvent

Question 2

what is the order of carbocation stability

Answer 2

primary < secondary < tertiary

Question 2

why is tertiary carbocation more stable

Answer 2

due to hyperconjugation which is the donation of electron density through the sigma bond framework into a partially filled d orbital

Question 3

why are SN1 reactions more likely to occur for substrates that form tertiary carbocation

Answer 3

since they form carbocation intermediates. the other groups can help stabalise carbocations and help enhance SN1 reactions

Question 4

what are steric effects ?

Answer 4

non bonding interactions that influence the shape and reactivity of ions and molecules

Question 5

describe the steric effects for SN2 reactions

Answer 5

approach of nucleophile and formation of the transition state is sterically hindered of the central carbon carries bulky substituents

Question 6

how does the nucleophile influence whether a reaction proceeds via SN1 or SN2 pathway

Answer 6

rate of SN2 reactions show a first order dependence on the nucleophile
- negative charges make good nucleophiles
stronger the nucleophile the more the reaction will be promoted

Question 7

how does the solvent influence whether a reaction proceeds via SN1 or SN2 pathway

Answer 7

for SN1 reactions polar solvents will favour formation of the carbocation e.g protic like water or aprotic like acetone