Topic 10: Carbonyls: Structure, Bonding and Preparation

Question 1

Which bond is the HOMO and LUMO in in carbonyl compounds

Answer 1

pi - HOMO (Cp-Op)
pi star - LUMO (Cp-Op)

Question 2

Why does the C=O bond give intense IR stretches?

Answer 2

Strong permanent dipole moment

Question 3

Differences between C=C and C=O

Answer 3

C=O is a stronger, shorter bond, thermodynamically more stable
Often the formation can be the driving force of a reaction

Question 4

Why is chromium useful for the oxidation of alcohols?
Examples of chromium based oxidants + conditions

Answer 4

Various oxidation states
Pyridinium dichromate (PDC), mild, neutral conditions, stops at aldehyde
Jones oxidant (CrO3, H2SO4), strongly acidic, H2O, goes all way to carboxylic acid

Question 5

NMO is

Answer 5

A cheap and readily available N-oxide and reoxidises the ruthenium (catalyst) to regenerate the active oxidant

Question 6

Swern Oxidation, also called … is a mild reaction that works on … . It is highly … so no … is ever seen

Answer 6

activated DMSO oxidation
most alcohols
chemoselective
over-oxidation

Question 7

Pinnick oxidation allows oxidation of … to … . The oxidant has the formula … and is formed in situ and the addition of … is vital as it scavenges the … side product as it would readily react with the products

Answer 7

aldehydes
carboxylic acids
OClOH
2,3-dimethylbut-2-ene
HOCl

Question 8

Carbonyl species are … species and readily react with …

Answer 8

electrophilic
nucleophiles

Question 9

Carbonyl groups

Answer 9

aldehyde
ketone
carboxylic acid
ester
amide
acid chloride
acid anhydride