1. Carbonyl chemistry -Production of carbonyl compounds
-Oxidation and Reduction reactions
-Further oxidation reactions.

2. Formation of carbonyl compounds
Starting with an alcohol, react with an oxidising agent (such as acidified potassium dichromate)
Propan-1-ol + [O]  Propanal +water

3. The carbonyl functional group
PLANAR WITH BOND ANGLES OF 120°
ORBITAL OVERLAP
NEW ORBITAL
The bond is polar due to the difference in electronegativity.

4. 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 two carbons.
C = O H
C = O H
CH3
C = O
CH3
C = O
C2H5
CH3

5. Naming aldehydes/ketones
Aldehydes C2H5CHO propanal
Ketones CH3COCH3 propanone
CH3CH2COCH3 butanone
CH3COCH2CH2CH3 pentan-2-one
CH3CH2COCH2CH3 pentan-3-one
C6H5COCH3 phenylethanone

6. Identification of carbonyls
IR spectroscopy shows a strong peak around cm-1

7. Oxidation of carbonyl
Reacting an aldehyde with an oxidising agent (acidified dichromate ions) produces a carboxylic acid.
Propanal + [O]  Propanoic acid +water

8. Reduction of carbonyls
Carbonyl groups can also be reduced.
Reduction agent used is Sodium tetrahydroborate(III) (also called Sodium Borohydride)
This is classed as a weak reducing agent.

9. Reduction of carbonyls
Propanal is reduced to a primary alcohol by sodium borohydride.
Propanal + 2[H]  Propan-1-ol

10. Reduction continued NaBH4 reacts with ketones also.
Propanone + 2[H]  propan-2-ol

11. Reduction explained
The BH4 ion is acting as a source of hydride ions (:H-)
Hydride ions being a negatively charged hydrogen ion containing a lone pair of electrons
The mechanism is an example of nucleophilic addition.
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

12. Reduction reaction mechanism
Propanal + 2[H]  propan-1-ol

13. Carbonyl questions Write equations + mechanisms for the reduction of:
Butanal
2-methylhexan-3-one
Define the term nucleophile
Show the mechanism for the reaction between butanone and NaBH4

14. Carbonyl chemistry 2 chemical tests on carbonyls
-How to detect a carbonyl group
-Aldehyde or ketone?

15. 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.

16. Condensation 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
sulfuric acid.

17. Using 2,4-DNPH
When Brady’s reagent is added to an aldehyde or ketone, a yellow or orange precipitate is formed.
The precipitate, called a 2,4-dinitrophenylhydrazone derivative confirms the presence of a carbonyl functional group.

18. Aldehyde or ketone
Aldehydes and ketones can be distinguished from each other by using Tollen’s reagent
Tollen’s reagent is a weak oxidising agent, the carbonyl group is oxidised to form a carboxylic acid.
Ammoniacal silver nitrate

19. Tollen’s reagent. Silver ions are reduced to silver metal
Ag+(aq) + e-  Ag(s)
Aldehyde + [O]  Carboxylic acid

20. 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 compounds
State the reagents and observations made to distinguish between the two chemicals.

21. Carbonyl chemistry 3 Identifying a carbonyl compound
-Determining experimentally an unknown carbonyl compound

22. ILPAC 8.5
Using the instruction sheets given last lesson, carry out experiment 8.5, parts A and B
Complete a detailed method for identifying a carbonyl compound
Purifying by recrystallisation -> melting point determination -> compare melting point to known values.

23. 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 butanal.
The reaction of 2,4-DNPH with ethanal gives water as a product. Suggest the type of reaction taking place.