Transcript ALDEHYDES & KETONES - Rogue Community College

ALDEHYDES & KETONES
Melanin - a
polymeric
substance
involving many
interconnected
cyclic ketone
units that
colors human
hair & skin
Functional Group
 Aldehydes
 Carbonyl (-C=O) at end of
chain
 Contains a polar bond
 RCHO
 Aliphatic chains
 NOT as part of ...
 Aliphatic rings or
Aromatic rings
 Ketones
 Carbonyl (-C=O) in
middle of chain
 Contains a polar bond
 RCOR
 Aliphatic chains
 Aliphatic rings
 NOT as part of Aromatic
rings
Aldehydes and
ketones are
related to alcohols
in a similar manner
as alkenes are
related to alkanes.
Nomenclature
 Aldehydes
 IUPAC
 Alkanal
 Carbonyl C = #1
 Ketones
 IUPAC
 Alkanone
 Propanone = acetone
 Carbonyl C = lowest
 Common
 Prefixaldehyde
# possible
 Common
 Alkyl alkyl ketone
Multi-functional Group Compounds
 What name do you use when there is more
than one functional group?
 To determine which suffix to use, follow this
priority list (high to low):
Substituent name
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Aldehyde
Ketone
Alcohol
Alkene
Alkyne
Alkoxy (ether)
Alkyl
Halogen
oxohydroxyen- (before suffix)
yn- (before suffix)
alkoxyalkylhalo-
Isomerism
 Aldehydes
 Ketones
 Constitutional
 Skeletal
 Constitutional
 Skeletal
 Positional
 Functional group
 Functional group
(this
is the second time we encounter
this type of isomerism)
Common & Naturally Occurring
Aldehydes & Ketones
 Aldehydes
 Formaldehyde
 methanal
 Acetaldehyde
 ethanal
 Odors/Flavors
 Vanillin
 Benzaldehyde -->
 Cinnamaldehyde
 Lots of nuts & spices
 Ketones
 Acetone
 propanone
 Odors/Flavors
 Cloves (2-heptanone)
 Lots of nuts & spices
 Butter (butanedione)
 Fresh-mown hay (coumarin)
 Steroid Hormones
 Testosterone
 Progesterone
 Cortisone
Physical Properties
 Aldehydes
 Boiling Point
 Alkanes<Aldehydes<Alcohols
 Bonding/polarity
 Water Solubility
 Water can H-bond with aldehydes
 Mass relationship
 Odors
 Low MW = unpleasant
 High MW = fragrant
 Ketones
 Boiling Point
 Same as for Aldehydes
 Water Solubility
 Same as for Aldehydes
 Acetone is infinitely soluble*
 Odors
 Pleasant
 Perfumes & air fresheners
Preparation Reactions
 Aldehydes
 Ketones
 Oxidation
 Oxidation
 1˚ alcohol --> aldehyde
 2˚ alcohol --> ketone
Chemical Reactions - Oxidation
 Aldehydes
 Aldehyde --> Carboxylic acid
 Ketones
 Ketone --> NR
Chemical Reactions - Tollen’s Reagent
 Aldehydes
 Ketones
 RCHO + Ag+ -->RCOOH + Ag(s)
 RCOR + Ag+ --> NR
(a) An aqueous solution of
ethanal is added to a
solution of silver nitrate.
(b) The solution darkens as
ethanal is oxidized to
ethanoic acid.
(c) The inside of the
beaker becomes coated
with metallic silver.
Chemical Reactions - Fehling’s or
Benedict’s Reagent
 Aldehydes
 Ketones
 RCHO + Cu2+ --> RCOOH + Cu2O
 RCOR + Cu2+ --> NR
 Diabetes test
Chemical Reactions - Reduction
(Opposite of Oxidation)
 Aldehydes
 Ketones
 RCHO --> 1˚ alcohol
 RCOR --> 2˚ alcohol
Chemical Reactions - Reaction with Alcohol
 Aldehydes
 Ketones
 RCHO + ROH --> Hemiacetal
 RCOR + ROH --> Hemiacetal
(unstable, unless cyclic)
 Hemiacetal + ROH --> Acetal
 Hemiacetal + ROH --> Acetal
 Hydrolysis of acetal produces
 Hydrolysis of acetal produces
the aldehyde + 2 alcohol
molecules
 CH2(OCH3)2 + H2O --> HCHO + 2CH3OH
the ketone + 2 alcohol
molecules
Phenol + Formaldehyde
 Phenols and formaldehyde
react via substitution
reactions and polymerize via
dehydration reactions.
 Plastics and adhesives (for
plywood)
DMSO (dimethyl sulfoxide)
 Sulfur analog of
Acetone
 Penetrates skin very
quickly.
 Anti-inflammatory rub
 Reduces to dimethyl
sulfide in the body.
 Garlic-like odor
What do you need to know?
 Structural characteristics (know the functional group)
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Aldehydes
Ketones
Acetals
Isomers
 Nomenclature (the rules for naming the molecules)
 Common & IUPAC
 Physical properties (basic/simple)
 BP; Solubility; Flammability
 Occurrence and uses (common)
 Natural (ex.: nuts & spices,melted butter odor, melanin )
 Synthetic (ex.: formalin, Bakelite)
 Preparation (what basic reactions produce the molecules)
 Aldehydes - oxidation of 1˚ alcohols
 Ketones - oxidation of 2˚ alcohols
 Characteristic reactions of the molecules
 Oxidation-reduction
 Fehling’s & Tollens’ reactions
 rxn w/ alcohols