aldehydes & ketones dr. michael p. gillespie. introduction the aldehydes and ketones are...
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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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