Chapter 15:
Carboxylic Acids and Esters
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CARBOXYLIC ACIDS
• The functional group of carboxylic acids is the carboxyl
group.
• Many carboxylic acids have common names.
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CARBOXYLIC ACIDS IUPAC NOMENCLATURE
• Find the longest carbon chain that contains the –COOH
group.
• Drop the –e from the end of the hydrocarbon name and
substitute –oic acid.
• Number the longest chain. Carbon number 1 is the
carboxyl carbon.
• Name and number other substituents.
Examples:
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• Aromatic acid names are derived from the parent
compound, benzoic acid.
Example:
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PHYSICAL PROPERTIES OF CARBOXYLIC ACIDS
• Low molecular weight carboxylic acids are liquids at room
temperature and have characteristically sharp or
unpleasant odors.
• The –COOH group is very polar. Hydrogen bonding
between –COOH groups creates dimers (two identical
molecules bonded together).
• This gives carboxylic acids high boiling points (greater
than alcohols).
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PHYSICAL PROPERTIES, cont.
• –COOH groups can hydrogen bond with water. If the
hydrophobic –R group is not too large, carboxylic acids are
very water soluble.
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ACIDITY OF CARBOXYLIC ACIDS
• Carboxylic acids behave as weak acids (low dissociation),
forming carboxylate ions in water.
Example:
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SALTS OF CARBOXYLIC ACIDS
• Carboxylic acids react readily with strong bases (NaOH,
KOH) to form salts.
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Examples:
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SALTS, cont.
• To name a carboxylic acid salt, name the metal ion first
and change the –ic ending of the acid name to –ate.
Example:
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USEFUL CARBOXYLIC ACID SALTS
• Na+ and K+ salts of long-chain acids are used as soaps
(sodium stearate).
• Calcium and sodium propanoate are used as
preservatives in bakery products.
• Sodium benzoate is a food preservative used in ketchup
and soda pop.
• Zinc 10-undecylenate is used to treat athlete’s foot.
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CARBOXYLIC ESTERS
• The ester functional group with the ester linkage between
the carbonyl carbon and the oxygen atom:
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ESTERS, cont.
• Esterification is the process of forming an ester linkage
between a carboxylic acid and an alcohol.
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Examples:
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ESTERS, cont.
• Because of the reversible nature of the esterification
reaction, carboxylic acid chlorides and carboxylic acid
anhydrides are used instead of the carboxylic acid to
obtain higher product (ester) yields.
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ESTERS, cont.
Examples:
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ESTERS, cont.
Specific Examples:
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NAMING ESTERS
• The first word of the name of an ester is the name of the
alkyl or aromatic group (R') contributed by the alcohol.
• The second word is the carboxylic acid name, with the –ic
acid ending changed to –ate.
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NAMING ESTERS, cont.
Examples:
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ESTER REACTIONS
• Ester hydrolysis – the reverse of esterification
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Specific Examples:
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ESTER REACTIONS, cont.
• Saponification – similar to hydrolysis, but carried out with a
strong base to produce a carboxylic acid salt
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Examples:
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Esters of Inorganic Acids
• Esters can be formed by reacting alcohols with inorganic
acids such as sulfuric, nitric, or phosphoric acids
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INORGANIC ACID ESTERS, cont.
• Because phosphoric acid has three –OH groups, it can
form mono-, di-, and triesters.
• Mono- and diesters are very important biologically.
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PHOSPHORIC ANHYDRIDES
• Phosphate esters that have two or three phosphate groups
linked together:
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• Adenosine diphosphate (ADP) and adenosine triphosphate
(ATP) are two phosphoric anhydrides of great biological
importance. In each case, the R group is adenosine.
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