Download Condensation is a chemical reaction in which one molecule is

Condensation is a chemical reaction in which one molecule is formed
and one small molecule (often water) is lost.
LEARNING OBJECTIVES [ edit ]
Recognize the chemical principles of condensation reactions as they relate to polymerization.
Recall the basics of a condensation reaction.
KEY POINTS [ edit ]
During condensation reaction, two molecules combine to form a single molecule with the loss of a
small molecule; in dehydration reaction, this lost molecule is water.
Intermolecular condensation occurs between two separate molecules,
while intramolecular condensation is the union between atoms or groups of the same molecule,
often leading to ring formation.
Condensation reactions are used in condensation polymerization, when a series of condensation
steps form long chains; this reaction may be either a homopolymerization of a single monomer or
a copolymerization of two co-monomers; many biological transformations are condensation
reactions.
TERMS [ edit ]
condensation reaction
any reaction in which two molecules react with the resulting loss of a water molecule (or other
small molecule); the formal reverse of hydrolysis
condensation polymerization
a polymerization mechanism in which monomers react to form dimers first, then trimers, longer
oligomers, and eventually long chain polymers
dehydration reaction
an elimination (condensation) reaction in which the small molecule that is removed is water
Give us feedback on this content: FULL TEXT [edit ]
In acondensation reaction,
twomolecules or parts thereof combine,
releasing a small molecule. When this
small molecule is water, it is known as
a dehydration reaction. Other possible lost
molecules include hydrogen chloride,
methanol, and acetic acid.
When two separate molecules react, their
condensation is termed intermolecular. A
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simple example is the condensation of
two amino acids to form a peptide. This reaction example is the reverse of hydrolysis, which
splits a chemical entity into two parts through action from the polar water molecule, which
itself splits into hydroxide and hydrogen ions.
Peptide bond formed during condensation reaction
The condensation (dehydration) of two amino acids to form a peptide bond (red) with expulsion of water
(blue).
When a condensation is performed between different parts of the same molecule, the reaction
is termed intramolecularcondensation; in many cases, this leads to ring formation. An
example is the Dieckmann condensation, in which the two estergroups of a single diester
molecule react with each other to lose a small alcohol molecule and form a βketoester product.
Many condensation reactions follow a nucleophilic acylsubstitution or an aldol
condensation reaction mechanism (see previous concept for more information). Other
condensations, such as the acyloin condensation, are triggered by radicalconditions.
Condensation Polymerization Reactions
In one type of polymerization reaction, a series of condensation steps takes place whereby
monomers or monomer chains add to each other to form longer chains. This is termed
"condensation polymerization," or "step-growth polymerization," and occurs in such
processes as the synthesis of polyesters or nylons. Nylon is a silky material used to make
clothes made of repeating units linked by amide bonds, and is frequently referred to as
polyamide. This reaction may be either a homopolymerization of a single monomer A-B with
two different end groups that condense, or a copolymerization of two co-monomers A-A and
B-B. Small molecules are usually liberated in these condensation steps, unlike polyaddition
reactions.
O
O
+ n H2N R' NH2
n
C R C
HO
OH
O
O
C R C N R' N
H
H
+ 2 H 2O
n
Condensation of diacid and diamine
The condensation of a diacid and diamine is an example of A­B polymerization.
Condensation polymers often require heat, form slower than do addition polymers, and are
lower in molecular weight. This type of reaction is used as a basis for making many important
polymers, such as nylon, polyester, and various epoxies. It is also the basis for the laboratory
formation of silicates and polyphosphates. Many biological transformations, such as
polypeptide synthesis, polyketide synthesis, terpene syntheses, phosphorylation, and
glycosylations are condensations.
Nylon molecular structure
Nylon is a synthetic polymer produced by condensation polymerization.