Download Name as Substituent

Name as Substituent
• On a molecule with a higher priority
functional group, C=O is oxo- and -CHO
is formyl.
• Aldehyde priority is higher than ketone.
COOH
CH3
O
CH3
O
C
CH CH2
C H
3-methyl-4-oxopentanal
CHO
3-formylbenzoic acid
=>
4.5 Isomerism in aldehydes and
ketones
• Aldehydes and ketones are constitutional
isomers
• Aldehydes and ketones can have skeletal
and positional isomers if there are enough
carbons.
• Stereoisomers are also possible if there is
a ring or C=C in the molecule
4.6 Selected Common aldehydes
and ketones
•
•
•
•
•
•
Formaldehyde
Acetone
Vanillin
Benzaldehyde
Cinnamaldehyde
Butanedione
Formaldehyde
• Gas at room temperature.
• Formalin is a 40% aqueous solution.
H
H
H
O
C
H
C
O
O
C H
O
H
trioxane, m.p. 62C
heat
H C H
H2O
formaldehyde,
b.p. -21C
HO
OH
H C
H
formalin
=>
Industrial Importance
• Acetone and methyl ethyl ketone are
important solvents.
• Formaldehyde used in polymers like
Bakelite.
• Flavorings and additives like vanilla,
cinnamon, artificial butter.
=>
•
•
•
•
•
•
Formaldehyde -formalin
Acetone – solvent and metabolic product
Vanillin - vanilla flavoring
Benzaldehyde - almond flavor
Cinnamaldehyde - cinnamon
Butanedione - butter
4.7 Physical properties
• Boiling points – page 121
• Solubility – water solubility page 123
Boiling Points
• More polar, so higher boiling point than
comparable alkane or ether.
• Cannot H-bond to each other, so lower
boiling point than comparable alcohol.
=>
Solubility
• Good solvent for alcohols.
• Lone pair of electrons on oxygen of
carbonyl can accept a hydrogen bond from
O-H or N-H.
• Acetone and acetaldehyde are miscible in
water.
=>
4.8 Preparation of Aldehydes and
Ketones
• Oxidation
– 2 alcohol + Na2Cr2O7  ketone
– 1 alcohol  aldehyde