-Production of carbonyl compounds
-Oxidation and Reduction reactions
-Further oxidation reactions.
Formation of carbonyl compounds
• Starting with an alcohol, react with an
oxidising agent (such as acidified potassium
• Propan-1-ol + [O] Propanal +water
The carbonyl functional group
The bond is polar due to the difference in electronegativity.
Aldehydes vs. Ketones
• Aldehydes have the carbonyl group at the end
of a carbon chain (joined to only one carbon)
• Ketones have the carbonyl group bonded to
Aldehydes C2H5CHO propanal
Ketones CH3COCH3 propanone
Identification of carbonyls
• IR spectroscopy shows a strong peak around
Oxidation of carbonyl
• Reacting an aldehyde with an oxidising agent
(acidified dichromate ions) produces a
• Propanal + [O] Propanoic acid +water
Reduction of carbonyls
• Carbonyl groups can also be reduced.
• Reduction agent used is Sodium
tetrahydroborate(III) (also called Sodium
• This is classed as a weak reducing agent.
Reduction of carbonyls
• Propanal is reduced to a primary alcohol by
• Propanal + 2[H] Propan-1-ol
• NaBH4 reacts with ketones also.
• Propanone + 2[H] propan-2-ol
• The BH4 ion is acting as a source of hydride
» Hydride ions being a negatively charged hydrogen ion
containing a lone pair of electrons
• The mechanism is an example of nucleophilic
– H- ion is attracted to the δ+C of the carbonyl,
forming a new C-H bond
– The resulting O- ion forms a dative covalent bond
using the H+ from a water molecule
Reduction reaction mechanism
• Propanal + 2[H] propan-1-ol
• Write equations + mechanisms for the
• Define the term nucleophile
• Show the mechanism for the reaction
between butanone and NaBH4
Carbonyl chemistry 2
chemical tests on carbonyls
-How to detect a carbonyl group
-Aldehyde or ketone?
ILPAC experiment 8.4
• Using the instruction sheets, follow the
method for experiment 8.4 A and 8.4 B
• DO NOT DO EXPERIMENT C
• Make full and detailed notes on what you
observe during the reactions.
• We can detect the presence of a carbonyl
group using 2,4-dinitrophenylhydrazine
(abbreviated to 2,4-DNP or 2,4-DNPH).
• 2,4-DNPH is also
called Brady’s reagent when
prepared with methanol and
• When Brady’s reagent is added to an aldehyde
or ketone, a yellow or orange precipitate is
• The precipitate, called a 2,4-
dinitrophenylhydrazone derivative confirms
the presence of a carbonyl functional group.
Aldehyde or ketone
• Aldehydes and ketones can be distinguished
from each other by using Tollen’s reagent
Ammoniacal silver nitrate
• Tollen’s reagent is a weak oxidising agent, the
carbonyl group is oxidised to form a carboxylic
• Silver ions are reduced to silver metal
• Ag+(aq) + e- Ag(s)
• Aldehyde + [O] Carboxylic acid
Carbonyl questions 2
• The carbonyl compounds CH3COCH3 and
CH3CH2CHO are structural isomers.
– Name these compounds
– State the reagents used and observations made to
prove the presence of a carbonyl group in these
– State the reagents and observations made to
distinguish between the two chemicals.
Carbonyl chemistry 3
Identifying a carbonyl compound
-Determining experimentally an
unknown carbonyl compound
• Using the instruction sheets given last lesson,
carry out experiment 8.5, parts A and B
• Complete a detailed method for identifying a
– Purifying by recrystallisation -> melting point
determination -> compare melting point to known
Carbonyl questions 3
• Explain how you would use the solid obtained
from the reaction of an aldehyde with 2,4-
DNPH to prove the original aldehyde was
• The reaction of 2,4-DNPH with ethanal gives
water as a product. Suggest the type of
reaction taking place.