Transcript Aldehydes & Ketones

Aldehydes &
Ketones
Dr. Michael P. Gillespie
Introduction
• The aldehydes and ketones are characterized by
the presence of the carbonyl group.
• The carbonyl group is a functional group made up
of a carbon atom bonded to an oxygen atom by a
double bond.
• Carbonyl compounds are those that contain a
carbonyl group.
• Aldehydes, ketones, carboxylic acids, and amides
all are carbonyl compounds.
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Carbonyl Group
• The carbonyl group is a
functional group made
up of a carbon atom
bonded to an oxygen
atom by a double
bond.
• Carbonyl groups are
polar.
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Structure and Physical
Properties Aldehydes
• In aldehydes the carbonyl group is attached to
at least one hydrogen; the second group may
be attached to another hydrogen or a carbon
atom.
• Aldehydes are polar due to the polar nature of
the carbonyl group.
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Structure and Physical
Properties Aldehydes
• Aldehydes have higher boiling points than
comparable hydrocarbons, but lower boiling
points than comparable alcohols.
• Small aldehydes are reasonably soluble in
water.
• Large aldehydes are less polar and dissolve
more readily in nonpolar organic solvents.
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Aldehydes
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Structure and Physical
Properties Ketones
• In ketones, the carbonyl group is attached to
two carbon containing groups.
• Ketones are polar due to the polar nature of
the carbonyl group.
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Structure and Physical
Properties Ketones
• Ketones have higher boiling points than
comparable hydrocarbons, but lower boiling
points than comparable alcohols.
• Small ketones are reasonably soluble in water.
• Large ketones are less polar and dissolve more
readily in nonpolar organic solvents.
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Ketones
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Important Aldehydes &
Ketones
• Many members of the aldehyde and ketone family
are important as food and fragrance chemicals,
medicinals, and agriculture chemicals.
• Methanal (formaldehyde) is used to preserve
tissue.
• Ethanal causes the symptoms of hangover.
• Ethanal is oxidized to produce acetic acid.
• Propanone is a useful organic solvent.
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Preparation of Aldehydes &
Ketones
• Aldehydes and ketones are prepared by the
oxidation of alcohols.
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Oxidation Reactions
• Oxidation of a primary alcohol yields an
aldehyde.
• Oxidation of a secondary alcohol yields a
ketone.
• Tertiary alcohols do not react under these
conditions.
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Oxidation Reactions
• Aldehydes can be further oxidized to
carboxylic acids. Ketones do not undergo
further oxidation.
• Tollen’s test and Benedict’s test utilize this
principle to distinguish between the two.
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Reduction Reactions
• Aldehydes and Ketones are readily reduced to
alcohols by hydrogenation.
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Addition Reactions
• The most common reaction is addition across
the double bond of the carbonyl group.
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Aldol Condensation
• Aldol condensation is a reaction in which
aldehydes and ketones form larger molecules.
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Alcohol Abuse
• According to the Centers for Disease Control and
Prevention, more than 75,000 Americans die each
year from alcohol abuse.
• 35,000 die of cirrhosis of the liver.
• Nearly 41,000 die of alcohol related automobile
accidents.
• An estimated 1400 college-age students die each
year of alcohol related causes.
• Alcohol abuse is the third leading cause of
preventable death in the United States.
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Antabuse
• The drug tetraethylthiuram disulfide
(disulfiram) is used to treat alcohol abuse. It is
otherwise known as antabuse.
• People who take Antabuse become violently ill
after consuming any alcoholic beverage.
• The compound inhibits one of the enzymes in
the pathway to oxidize alcohols.
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Antabuse
• The inhibition occurs within 1-2 hours after
consuming the drug and lasts up to 14 days.
• When a person who has taken Antabuse drinks
an alcoholic beverage, the levels of
acetylaldehyde reach levels that are 5 – 10
times higher than would normally occur after a
drink.
• Symptoms of a severe hangover occur within
minutes and may last for hours.
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