Spencer L. Seager
Michael R. Slabaugh
www.cengage.com/chemistry/seager
Chapter 15
Carboxylic Acids and Esters
Jennifer P. Harris
CARBOXYLIC ACIDS
• The functional group of carboxylic acids is the carboxyl
group.
• Many carboxylic acids have common names.
CARBOXYLIC ACID EXAMPLES
CARBOXYLIC ACID EXAMPLES (continued)
FATTY ACIDS
• Fatty acids are carboxylic acids with long hydrocarbon
chains, generally 12 to 20 carbon atoms.
• They were first isolated from natural fats.
• These fats are known almost exclusively by their common
names.
lauric acid
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:
CARBOXYLIC ACIDS
IUPAC NOMENCLATURE (continued)
• Aromatic acid names are derived from the parent compound,
benzoic acid.
• Example:
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).
PHYSICAL PROPERTIES OF
CARBOXYLIC ACIDS (continued)
PHYSICAL PROPERTIES OF
CARBOXYLIC ACIDS (continued)
PHYSICAL PROPERTIES OF
CARBOXYLIC ACIDS (continued)
• –COOH groups can hydrogen bond with water. If the
hydrophobic –R group is not too large, carboxylic acids are
very water soluble.
PHYSICAL PROPERTIES OF
CARBOXYLIC ACIDS (continued)
ACIDITY OF CARBOXYLIC ACIDS
• Carboxylic acids behave as weak acids (low dissociation),
forming carboxylate ions in water.
• Example:
SALTS OF CARBOXYLIC ACIDS
• Carboxylic acids react readily with strong bases (NaOH,
KOH) to form salts.
SALTS OF CARBOXYLIC ACIDS (continued)
• Examples:
SALTS OF CARBOXYLIC ACIDS (continued)
• To name a carboxylic acid salt, name the metal ion first and
change the –ic ending of the acid name to –ate.
• Example:
SALTS OF CARBOXYLIC ACIDS (continued)
• The physical properties of carboxylic acid salts:
• Solids at room temperature
• Usually soluble in water because they are ionic
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.
USEFUL CARBOXYLIC ACID SALTS
(continued)
• A mixture of sodium citrate and citric acid is widely used as a
buffer to control pH.
• The buffer can be found in:
• Jelly
• Ice cream
• Candy
• Whipped cream
• Medicines
• Human blood for transfusions (also an anticoagulant)
CARBOXYLIC ESTERS
• The ester functional group with the ester linkage between
the carbonyl carbon and the oxygen atom:
CARBOXYLIC ESTERS (continued)
• The ester functional group is a key structural feature in fats,
oils, and other lipids.
• The ester functional group is also found in fruits and flowers.
• Many esters are fragrant and represent some of nature’s
most pleasant odors.
• Esters are commonly used as flavoring agents in foods and
scents in personal products.
CARBOXYLIC ESTERS (continued)
• Esterification is the process of forming an ester linkage
between a carboxylic acid and an alcohol.
CARBOXYLIC ESTERS (continued)
• Examples:
CARBOXYLIC ESTERS (continued)
• 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.
CARBOXYLIC ESTERS (continued)
• General reactions:
CARBOXYLIC ESTERS (continued)
• Specific Examples:
CARBOXYLIC ESTERS (continued)
• Polyesters are polymers made by the esterification process.
• Polyesters formation is an example of a condensation
polymerization, in which monomers form a polymer and a
small molecule is also formed.
n(monomers) → (polymer)n + nH2O
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.
NAMING ESTERS (continued)
• Examples:
ESTER REACTIONS
• Ester hydrolysis is the reverse of esterification.
• Enzyme-catalyzed hydrolysis of the esters in animal fats and
vegetable oils is an important process that takes place when
the fats and oils are digested by the human body and other
biological organisms.
ESTER REACTIONS (continued)
• Specific Examples:
ESTER REACTIONS (continued)
• Saponification is similar to hydrolysis, but is carried out with
a strong base to produce a carboxylic acid salt.
ESTER REACTIONS (continued)
• Example:
ESTER SAPONIFICATION
• Carbonyl carbon attracts hydroxide, double bond breaks
• Double bond reforms, ester linkage breaks
• Carboxylic acid forms, but donates it proton to the strongly
basic anion to form alcohol
REACTION MAP FOR CARBOXYLIC ACIDS
ESTERS OF INORGANIC ACIDS
• Esters can be formed by reacting alcohols with inorganic
acids such as sulfuric, nitric, or phosphoric acids.
ESTERS OF INORGANIC ACIDS (continued)
• Because phosphoric acid has three –OH groups, it can form
mono-, di-, and triesters.
ESTERS OF INORGANIC ACIDS (continued)
• Mono- and diesters are very important biologically.
• At body pH, the two –OH groups of the phosphoric acid are
ionized, and the phosphate group has a charge of 2-.
PHOSPHORIC ANHYDRIDES
• Phosphoric anhydrides are phosphate esters that have
two or three phosphate groups linked together.
PHOSPHORIC ANHYDRIDES (continued)
• Adenosine diphosphate (ADP)
and adenosine triphosphate
(ATP) are two phosphoric
anhydrides of great biological
importance. In each case, the
R group is adenosine.
• At the pH of body fluids,
the –OH groups
attached to the
phosphorus
lose H+ and acquire
negative charges.
• At the pH of body fluids, the
charge on ADP is 3-.
PHOSPHORIC ANHYDRIDES (continued)
• At the pH of body fluids, the
–OH groups
attached to the phosphorus
lose H+ and acquire negative charges.
• At the pH of body fluids, the charge on
ATP is 4-.