Carboxylic Acids and
Esters
S
Carboxylic acid IUPAC naming
S 1) Find the longest carbon chain with the carboxyl group in it –COOH.
S 2) Name it with the hydrocarbon parent name, dropping the –e and
adding –oic acid
S Examples:
methanoic acid
ethanoic acid
propanoic acid
butanoic acid
Common Names
S Unfortunately, the IUPAC naming system is NOT the most
widely used system for naming carboxylic acids.
S The common name usually refers to the natural source of
the acid.
S Examples: formic acid (named for formica Latin word
meaning ant), acetic acid (named for the Latin word for
vinegar), propionic acid, butyric acid (comes from the Latin
term for butter, since it is found in butterfat.)
Another twist in naming
S Another common practice is to use Greek letters to refer to the
carbons attached to the carboxyl group to determine where branches
are attached.
S Examples:
S ⍺ hydroxybutryic acid
β chloropropionic acid
Practice
S 1) 3-chloropenanoic acid
5)
S 2) Ɣ hydroxybutyric acid
S 3) phenylacetic acid
S 4)
6)
Physical Properties of
Carboxylic Acids
S Those with 1-4 carbons in their chain are soluble in water. From 5-8
carbons, they are partially soluble, and above 8 carbons, they are
INSOUBLE in water.
S They have relatively high boiling points due to the COOH group, especially
compared with nonpolar substances.
S Under 10 carbons are liquids at room temp. Above 10 carbons, the acids are
wax-like solids.
S These substances ionize in water (which is why they are acids). The H
(from the OH group) detaches.
S They are ALL weak acids, so they do not ionize completely in water.
Physical Properties of
Carboxylic Acids
S They are especially important in biochemistry. If the liver releases
too many carboxylic acids (which ionize in the blood stream), then
the pH of the blood lowers and ketosis begins. This is the
mechanism that is prevalent when diabetes is uncontrolled.
S Another example is Dopa, a drug used to alleviate Parkinson’s
symptoms. Dopamine is positively charged, so it doesn’t cross the
blood-brain barrier. However, when Dopa was created, dopamine
was combined with a carboxylic acid (which forms an anion). The
charges balance and a neutral molecule is created, which will cross
the blood-brain barrier. Once there, it is converted back into
dopamine and it alleviates the symptoms.
Unsaturated Carboxylic Acids
S Acrylic acid (IUPAC propanoic acid) is used to manufacture
polymers with the acrylate monomer. They are widely used
in textiles, paints and lacquers. Sodium polyacrylate is also
used in diapers to absorb an immense amount of liquid.
S Even 1 double bond can have a tremendous effect on the
properties of carboxylic acids.
S Steric acid- CH3(CH2)12COOH is a solid with a m.p. of
70℃
S Oleic acid-CH3(CH2)7CH=CH(CH2)7COOH is a liquid with
a b.p. of 16 ℃
Dicarboxylic Acids
S Several common ones, like maleic acid, which was previously only
found in apples and fruit juice. When heated it can release CO2,
and form acetic acid. Precursor to barbituates.
S Oxalic acid is another common dicarboxylic acid, found in
spinach, cabbage and rhubarb. Poisonous, but not in small
quantities… forms kidney stones in humans.
S Succinic, fumaric and citric acids are also dicarboxylic acids that
are useful and commonly found.
Adipic Acid
S Most important commercially produced dicarboxylic acid.
S Used to produce nylon, polyurethane foams and lubricants
Hydroxy Acids
S
Examples: Lactic acid, Tartaric
acid, Salicylic acid and Malic
acid
S
Salicylates are part of a class of
drugs called analgesics- (pain
relievers) and antipyretics (fever
reducers)
Amino Acids
S
General formula for amino acids,
amine group in alpha position:
Carboxylate group= acidic
Amino group= basic
There are 20 amino acids that are
responsible for making proteins in our
bodies.
Preparing Carboxylic acids
S
1) Oxidation of primary alcohols and aldehydes
Preparing Carboxylic acids
S
2) Oxidation of alkyl groups attached to aromatic rings
S
If a basic solution is involved, then the salt will be made instead of
the acid.
Preparing Carboxylic acids
S
3) Hydrolysis of nitriles
S
Nitriles are C triple bonded to N, the H+ is acid
Chemical Reactions with
Carboxylic Acids
S
1) Substitution reactions
The OH group is replaced by several
other groups while the C=O group
remains intact.
Acid Chloride Formation
S
Carboxylic acids react with thionyl chloride to form acid chlorides.
S
Acid chlorides are REALLY reactive, will hydrolyze back to COOH in
presence of H2O.
S
Acid chlorides can be used to make esters and amides also.
Acid Anhydride formation
S Water is eliminated from the reaction of 2 molecules of carboxylic
acids, or acid chloride.
S The reaction to make acetic anhydride is one of the most
common.
Esterification
S
Making esters from carboxylic
acids and alcohols is called
esterification.
Amide formation
S
Making amides from carboxylic acids and ammonia or other amines.
Chemical Reactions with
Carboxylic Acids
S
2) Acid-Base reactions
S
Many act as acids in solution, especially
those with small carbon chains
S
When carboxylic acids react with
bases, the H+ reacts with the OH in
the base to form water.
S
The counter ion in the base attaches
to the O- to form the carboxylate
ion.
S
Those with long carbon chains are not
soluble in water.
S
Acetic acid (vinegar) is a carboxylic
acid.
S
Carboxylic acid react with sodium
hydrogen carbonate to release CO2.
S
The H on the OH group is easily
ionized… however, all carboxylic acids
are weak acids.
S
Phenol will NOT react with
NaHCO3
Synthesis of Aspirin
S
When salicylic acid is added to acetic anhydride, aspirin is formed! It must
be acidified for the reaction to occur!
Synthesis of Aspirin
S
S
There are several ways to test the
purity of your product:
1) Melting points
The melting point of salicylic acid is
158℃ while the melting point of
aspirin is 135 ℃.
If you get a melting point that is
higher than 135, it is likely
contaminated with reactant.
S
2) Reaction with FeCl3
S
The phenol group on salicylic
acid (your reactant)reacts with
FeCl3 to form a color.
S
The product (aspirin) does not
have this group.
S
The less color noticed, the more
pure your product!
Practice
S Propionic acid is a common carboxylic acid. In one
reaction it is reacted with thionyl chloride (SOCl2). In a
second reaction methanol is added. Show both reactions!
Naming Esters
S 1) Identify the part of the molecule that comes from the
acid.
S 2) Change the ending of the acid name to –ate by dropping
the –ic acid. This is the ending of the ester name.
Example: ethanoic acid ethanoate
propionic acid  propionate
Naming Esters
S
3) Next identify the alkyl group
attached to the alcohol part of
the ester (after the O). This will
be the prefix before the acid part.
S
Examples 
Practice
Artificial or Natural Fragrances
and Flavors?
S
Chemically, they are exactly the same. Whether the chemical compound is made in
the lab or extracted from a natural source, the chemical is identical.
Physical Properties
S
Low molar mass esters are
typically nonpolar. They have
much less solubility than either
the acid or alcohol component of
the compound. Therefore, the
boiling points are lower also.
S
High mass esters are typically solids
and are waxy.
S
In fact, many common waxes are high
mass esters, like car wax and carnuba
wax.
S
High mass esters may also be classified
as polyesters, such as Dracon.
S
These are formed by polymerization
reactions between neighboring esters.
Chemical Reactions of Esters
S
1) Acid Hydrolysis
S
S
When acids are added, the ester
reforms the carboxylic acid and
alcohol from which it was made.
2) Alkaline hydrolysis
(saponification)
S
Strong bases (NaOH or KOH)
are used to create the alcohol and
the salt of the carboxylic acid.
This is the process used to make
soap!
S
More on this later!!!
Chemical Reactions of Esters
S
The hydrolysis of esters is one of
the primary reasons polyester can
be used as stitches that dissolve
inside of a patient.
Trigycerols
S
Fats and oils are made of esters
of glycerol… hence why they are
referred to as
triglycerides/triglycerols.
S
Primary difference between fats
and oils is the state of matter at
room temperature.
S
The glycerol part is present in all
fats and oils, so the difference is
the fatty acid chains.
S
Fats have much more caloric
value per mass than carbs and
proteins.
S
It is essential to eat some
unsaturated fatty acids because
they are necessary for certain
functions in the body.
S
Vegetable sources are usually
oils.
S
Animal sources are usually solid
fats.
Hydrogenation of Glycerides
S
Low cost vegetable oils can
undergo hydrogenation reactions
to make solids by saturating the
unsaturated fats.
S
When this is only partially
completed, the fats are known as
partially hydrogenated fats… like
margarine and Crisco.
S
However, in the process, sometimes
the fats contained cis and trans
double bonds.
S
Trans-fats are known to be
increasingly responsible for
atherosclerosis (heart disease).
Hydrogenolysis
S
Process that results in production
of several alcohol molecules, that
are then used in the manufacture
of detergents.
S
Reduces triacylglycerol
molecules with hydrogen, copper
chromite catalyst and heat and
pressure.
Saponification
S
This is the alkaline hydrolysis of
an ester.
S
Synthetic detergents have been
made since the 1930s.
S
When triclyercides are involved,
glycerol is produced along with
the fatty acid salts of the esters.
S
They are different in structure
than soap but not different in
function.
S
The result is soap.
S
Soaps used to be crudely made,
but now are much more
sophisticated.
How Does Soap Work
S
Soap is so effective at cleaning because there are both hydrophobic and
hydrophilic parts in the molecule.
Antibacterial and Synthetic soap
S
Actually, there is little need for
antibacterial agents in soap.
Washing hands for 20-30 seconds
with regular soap removes as
many bacteria as an antibacterial
soap would in the same time.
S
Synthetic detergents are now
much more popular than
“regular” soaps.
S
By changing the structure of the
chain, synthetic detergents were
able to be classified as
biodegradable, which has helped
solve a large environmental
problem.
Phosphate Esters
S
When alcohols are reacted with
phosphoric acid, phosphate esters
are formed.
S
These are important as markers in
biological systems, such as being
able to track glucose use in diabetic
patients.
S
Disubstituted phosphate esters are
also able to be formed, since there
is more than 1 –OH site on
phosphoric acid.
S
The phosphate diesters are
important in our RNA and DNA.