Chapter 16 ALDEHYDES & KETONES
Chapter 16 ALDEHYDES & KETONES
Functional Group
Aldehydes Ketones
Carbonyl (-C=O) Carbonyl (-C=O)
Contains a polar bond Contains a polar bond
RCHO RCOR
Aliphatic chains Aliphatic chains
NOT as part of ... Aliphatic rings
Aliphatic rings or NOT as part of Aromatic rings
Aromatic rings
Nomenclature
Aldehydes Ketones
IUPAC
Alkanal Alkanone
Carbonyl C = #1 Carbonyl C = lowest # possible
Propanone = acetone
Common
Prefixaldehyde Alkyl alkyl ketone
Multi-functional Group Compounds
To determine which suffix to use, follow this priority list (high to low):
Substituent name
ª Aldehyde
ª Ketone oxo-
ª Alcohol hydroxy-
ª Alkene en- (before suffix)
ª Alkyne yn- (before suffix)
ª Alkoxy alkoxy-
ª Alkyl alkyl-
ª Halogen halo-
Isomerism
Aldehydes Ketones
Constitutional
Skeletal Skeletal
Positional
Common & Naturally Occurring Aldehydes & Ketones
Aldehydes Ketones
Formaldehyde Acetone
Acetaldehyde
Odors/Flavors
Odors/Flavors Cloves (2-heptanone)
Vanillin Butter (butanedione)
Benzaldehyde Fresh-mown hay (coumarin)
Cinnamaldehyde
Steroid Hormones
Testosterone
Progesterone
Cortisone
Physical Properties
Aldehydes Ketones
Boiling Point
Alkanes<Aldehydes<Alcohols Same as for Aldehydes
Bonding/polarity
Water Solubility
ª Water can H-bond with aldehydes Same as for Aldehydes
ª Mass relationship Acetone is infinitely soluble*
Odors
Low MW = unpleasant Pleasant
High MW = fragrant Perfumes & air fresheners
Preparation Reactions
Aldehydes Ketones
Oxidation
1˚ alcohol --> aldehyde 2˚ alcohol --> ketone
Chemical Reactions - Oxidation
Aldehydes Ketones
Aldehyde --> Carboxylic acid Ketone --> NR
Chemical Reactions - Tollen’s Reagent
Aldehydes Ketones
RCHO + Ag+ -->RCOOH + Ag(s) RCOR + Ag+ --> NR
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 the Hydrolysis of acetal produces the
aldehyde + 2 alcohol molecules ketone + 2 alcohol molecules
CH2(OCH3)2 --> HCHO + 2CH3OH
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?
ª Structural characteristics (know the functional group)
ª Aldehydes
ª Ketones
ª Acetals
ª Isomers
ª Nomenclature (the rules for naming the molecules)
ª Common & IUPAC
ª Physical properties (basic/simple)
ª BP; Solubility; Flammability
ª Occurrence and uses (common)
ª Natural (ex.: nuts & spices,melted butter odor, melanin )
ª Synthetic (ex.: formalin, Bakelite)
ª Preparation (what basic reactions produce the molecules)
ª Aldehydes - oxidation of 1˚ alcohols
ª Ketones - oxidation of 2˚ alcohols
ª Characteristic reactions of the molecules
ª Oxidation-reduction
ª Fehling’s & Tollens’ reactions
ª rxn w/ alcohols