GENERAL PROPERTIES OF CARBONYL COMPOUNDS

Sl. No.	ALDEHYDES ( HCHO, CH3CHO, C6H5CHO )	KETONES ( CH3COCH3, C6H5COCH3, C6H5COC6 H5 )
1	Strong and even mild oxidising agents oxidise them to mono carboxylic acids having the same number of carbon atoms.	Strong oxidising agents only oxidise them to mono carboxylic acids having lesser number of carbon atoms.
2	Restores the original colour of the Schiff’s reagent.	Does not restore the colour of Schiff‘s reagent.
3	Reduces Tollen’s reagent to metallic silver (i.e Gives Silver Mirror)	Does not reduce.
4	Aliphatic aldehydes alone reduce Fehling’s solution to red Cu2O.	Do not reduce.
5	Na / Hg + H2O or LiAlH4 or NaBH4 or H2 / Pt reduce them to 1o alcohols.	Na / Hg + H2O or LiAlH4 or NaBH4 or H2 / Pt reduce them to 2o alcohols.
6	Aldehydes not having α –H atom alone with base undergo Cannizzaro reaction.	Do not undergo
7	Aldehydes having α –H atom alone with base undergo Aldol condensation.	Ketones having α –H atoms alone with base undergo Aldol type condensation.
8	With Grignard reagent HCHO gives 1o alcohol and other aldehydes give 2o alcohols.	Gives 3o alcohols.
9	Forms addition products with NaHSO3	Acetone forms addition products with NaHSO3 while others does not form.
10	HCHO and C6H5CHO forms condensation products with NH3 while CH3CHO forms addition products with NH3	Acetone alone forms condensation products with NH3
11	Aromatic aldehydes alone form Schiff 's base with 1o amines	Do not form Schiff ’s base (or Anils)
12	The aldehydes having CH3CO- group (CH3CHO) undergo Haloform reaction	The Ketones having CH3CO - group (CH3COCH3 and C6 H5COCH3 ) undergo Haloform reaction.
13	Aromatic Aldehydes alone undergo electrophilic substitution reaction at meta-position	Aromatic Ketones alone undergo electrophilic substitution reaction at meta-position
14	Aromatic aldehydes alone undergo Benzoin condensation, Perkin’s reaction, Claisen or Claisen-Schimidt reaction, Knoevenagal reation.	Do not undergo
15	Aliphatic aldehydes alone undergo polymerization	Do not undergo

Aldehydes and Ketones:

1) React with HCN to form cyanohydrin.

2)  Undergo condensation (addition followed by elimination) reaction with ammonia derivatives which contain primary amino group (NH₂OH, NH₂NH₂, NH₂NHC₆H₅, NH₂NHCONH₂) to form compounds containing carbon-nitrogen double bonds.     

                                         OH

                                           |

> C = O +  H₂N - Z ⇆    - C -    → > C = N - Z + H₂O

                                           |

                                          NH-Z
                                        Unstable

Where, Z = -H, Alkyl (-R), Aryl (Ar), -OH, -NH₂, -NH C₆H₅, -NHCONH₂, etc.

3) Clemmenson reduction (or) Wolff-Kishner reduction converts them to hydrocarbons (> C = O group is reduced to – CH₂ – group)

GENERAL METHODS OF PREPARATION OF CARBONYL COMPOUNDS