Reactions of cyclic compounds

Question 1

Reactivity of axial hydroxyl species

Answer 1

The lone pairs on the oxygen are blocked through interactions with adjacent axial substituents. This makes equatorial OH groups much more reactive nucleophiles

Question 2

Nucleophilic substitution of cyclohexane substituents

Answer 2

The 180 degree attack of an SN2 reaction is much more accessible when the substituent is axial. There is a lot of steric hinderance to the line of attack of equatorial substituents

Question 3

Elimination reactions of cyclohexane substituents

Answer 3

There are no anti-periplanar substituents to allow for E2 elimination for equatorial substituents. In this instance, the axial site is preferred.

Question 4

Uses of LiBu3BH

Answer 4

A bulky reducing agent. Reduces carbonyl groups to alcohols but only via the less hindered face

Question 5

Attack of carbonyls on cyclohexane structures

Answer 5

Attacks via the Burgi-Dunitz angle. This angle is less hindered equatorially than it is axially and so is favoured

Question 6

Attack with small reducing agents as supposed to bulky reducing agents

Answer 6

Gives the opposite selectivity, not no selectivity.

Question 7

Product of the addition of Br in cyclohexene structures and opening of epoxides

Answer 7

The diaxial product is favoured. This product goes via a chair like transition state unlike the diequatorial product that goes via a boat like transition state