What are the stereochemical implications of bimolecular and unimolecular nucleophilic substitution?

If a chiral molecules undergoes nucleophilic substitution what happens to its stereochemistry?

SN1: These reactions occur with the production of a cationic intermediate. These contain an sphybrdised carbon atom with vacant p orbitals (hence the positive charge). The nucleophile can attack from above or below the plane of the molecule therefore producing a racemic mixture of product. If a single enantiomer is reacted with a nucleophile and the reaction proceeds via unimolecular nucleophilic substitution then equal amounts of both possible enantiomer will be formed (providing the carbon atom remains a chiral centre).

SN2: These reactions proceed via a transition state (anionic if the nucleophile is anionic) where the nucleophile attacks from one side and the leaving group leaves from the other. This results in something that resembles an umbrella turning inside out as the three unaffected groups switch sides. This means that if one enantiomer is reacted with a nucleophile then only a single enantiomer will be present in the products, although it's absolute configuration may have changed.

HS
Answered by Henry S. Chemistry tutor

5605 Views

See similar Chemistry A Level tutors

Related Chemistry A Level answers

All answers ▸

Describe the 3 types of isomers?


The recommended daily allowance of methionine for an adult is 15 mg per kg of body mass. Tuna contains 755 mg of methionine per 100 g portion. Calculate the mass, in grams, of tuna that would provide the RDA of methionine for a 60 kg adult.


Given the reaction: H2SO4 + NaOH --> ? + H2O. (a). Work out the salt produced (?) and (b). calculate the pH of the remaining solution when 1.2 g of NaOH and 4.41 g of H2SO4 were added in a 500 ml solution. Of the unreacted H2SO4 95% dissociated.


Describe the trend in the reactivity of group 2 elements with chlorine as you descend down the group.


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences