carbocations

Question 1

Mechanism for Friedel-Craft acylation

Answer 1

Notes

Question 2

Name of the ion intermediate during Friedel Crafts acylation

Answer 2

acylium ion

Question 3

Conditions for carbocations

Answer 3

Must be planar with an empty p orbital

Question 4

Resonance definition

Answer 4

Conjugation of charge with p orbital or a lone pair of electrons

Question 5

Examples of stabilised carbocation intermediates

Answer 5

oxonium and iminium ions

Question 6

What factors stabilise carbocations

Answer 6

Resonance, adjacent lone pairs, adjacent electron donating groups

Question 7

Common reaction pathways of carbocations

Answer 7

Reaction with nucleophile, loss of proton to form a pi bond, rearrangements

Question 8

Conditions for alkyl or hydride shifts

Answer 8

The substituent must be anti-peri-planar to the vacant p orbital

Question 9

Wagner-Meerwein rearrangement

Answer 9

a 1,2-alkyl rearrangement to generate a more stable carbocation

Question 10

Draw a pinacol

Answer 10

See notes

Question 11

What is a pincol rearrangement

Answer 11

Subjection of a pinacol to acidic conditions to give a heavily substituted ketone (pinacalone)

Question 13

Reaction between a pinacol and sulphuric acid

Answer 13

See notes

Question 14

Semi pinacol products and conditions

Answer 14

Formed when the less hindered hydroxyl group is lost, through the addition of a tosylate. Occurs under basic (Py) or neutral conditions

Question 15

Tiffeneau-Demjanov rearrangement outline and mechanism

Answer 15

The expansion of an n-cyclic hydroxyl alkyl amine to an n+1-cyclic ketone. NaNO2 and HCl See notes.

Question 16

Reagents of the Tiffeneau-Demjanov rearrangement

Answer 16

NaNO2 and HCl

Question 17

Intermediate of the Tiffaneau-Demjanov rearrangement

Answer 17

Diazonium salt intermediate

Question 18

Stereochemical conditions of the Tiffeneau-Demjanov rearrangement

Answer 18

The sigma orbital of the migrating group must be anti-periplanar to the sigma* orbital of the leaving group