Aldehydes: Structure and Nomenclature. General formula: RCHO or RCH=OThe aldehyde group is always at the end of a chainIUPAC system: Select the longest continuous carbon chain that contains the C=O group and replace the ending by the suffix al.The CHO group is assigned the number 1 position and takes precedence over other functional groups that may the present such as
1. Aldehydes and Ketones By:
Dr. Siham Lahsasni
Aromatic aldehydes are usually designated as derivatives of the simplest aromatic aldehyde, Benzaldehyde.
Benzaldehyde p-Nitrobenzaldehyde o-Hydroxybenzaldehyde p-Methoxtbenzaldehyde
4. Ketones: Structure and Nomenclature General formula: RCOR’ (R and R’=alkyl or aryl)
Common name: listing the alkyl substitutents attached to the carbonyl group, followed by the word ketone.
IUPAC system: relpace the ending –e by the suffix –one. The chain is numbred in such a way as give the lowest number to the C=O group.
Common Dimethyl ketone Methyl phenyl ketone Methyl vinyl ketone Diphenyl ketone
Acetone Acetophenone Benzophenone
IUPAC Propanone Phenyl ethanone 3-Buten-2-one Diphenylmethanone
6. PHYSICAL PROPERTIES OF KETONES AND ALDEHYDE
Because the polarity of the carbonyl group, aldehydes and ketones are polar compounds.
Dipole-dipole attractions, although important, are not as strong as intractions due to hydrogen bonding. As a result, the boiling points of aldehydes and ketones are higher than those of nonpolar alkanes, but lower than those of alcohols.
The lower aldehydes and ketones are soluble.
7. Preparation of aldehydes and ketones 1- Oxidation of alcohols
2- Reduction of acid chloride
8. 3- Ozonolysis of alkenes
4- Hydration of alkynes
12. REACTIONS OF ALDEHYDES AND KETONES
13. 1- reduction of carbonyl group
a- Addition of metal hydride
14. b- Addition of Grignard Reagents: Formation of alcohols
15. c- Clemmenson reduction
d- The Wolf-kishner reduction
16. e- Wittig reaction
17. 2- Oxidation reaction
b- Tollenis test
c- Iodoform reaction
18. 3- Addition of Hydrogen Cyanide: Formation of cynohydrins
4- Addition of acetylide ions:
19. 5- Addition of alcohols:
20. 6- Addition of Ammonia and Ammonia Derivatives
21. 7- Aldol condensation
The reaction occurs in any aldehyde or ketone containing a hydrogen:
22. 8- Cannizzaro reaction
Aldehyde which does not contain a hydrogen undergoes Cannizzaro reaction.