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 αhydroxybutryic acid
βchloropropionic acid
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 Unsaturated refers to the presence of double bonds in the
chain.
S Acrylic acid (IUPAC propenoic 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.
Aromatic Carboxylic Acids
S The carboxylic acid is directly attached to an aromatic ring (benzene
ring). The parent compound of this series is benzoic acid.
S Then you name the branches attached, ending the name in benzoic acid.
S Example: 2-hydroxybenzoic acid (aka salicylic acid) This is the pre-
cursor to aspirin.
Hydroxyacids
S These are hydroxyacids that are pre-cursors to aspirin and
other analgesics (pain relievers) and antipyretics (fever
reducers).
Dicarboxylic acids
S If you have more than 1 carboxylic acid in a structure, they must be at
both ends of an aliphatic carbon chain.
S The name them using IUPAC rules, you must change the hydrocarbon
chain name by dropping –e suffix and adding –dioic acid.
S Oxalic acid is the common name of the simplest dicarboxylic acid. Can
you give the IUPAC name?
Important Acids with Multiple
Carboxylic Groups
Preparing Carboxylic Acids
S 1) Oxidation of an aldehyde or primary alcohol
-
The use of an oxidation agent, like K2Cr2O7 and sulfuric acid are
required.
S 2) Oxidation of Alkyl groups attached to aromatic rings
-
The use of a basic permanganate solution or acidic potassium
dichromate solution is required to achieve this reaction.
-
The result is the carbon attached to the ring will form a carboxyl
group, regardless of the chain length. The now detached chain
forms either CO2 or the salt of a carboxylic acid.
Preparing Carboxylic Acids