Transcript Ring Formation

Ring Formation

Also called the intramolecular reaction

A chain containing two mutually reactive groups
can react with it self and a ring structure forms.

Ring formation depends strongly on the number
of atoms linked together in the ring .
Example

Preparation of a polyester.

O
HO-----C-OH
C-O

O
5,6
and to some extent 7 members rings
are stable and have tendency to for ring.
Example
Self
condensation of w-hydroxyl carboxylic acids
HO - (CH2)3 - COOH
CH2-CH2 + H2O


CH2 O

C

O
3, 4, 8, 9, 10 and 11 rings are un stable due to bond angle
strain and steric repulsion’s between atoms. (Rowded
into the center of the ring respectively and usually not
formed).
 12 members and larger rings are more stable and can be
formed.
 Their probability of formation decreases as the ring size
increases. This is because the probability of the two
ends of a single chain meeting decreases as the chain
Non Linear Step Polymerization

The presence of a reactivity monomer with functionality > 2,
causes branching initially and crosslinking structure
ultimately.

This has a great effect on the structure and molar mass of
the polymer.

Normally the resulting polymer are rigid.

The point at which the first net work molecules is formed is
known as the gel-point (gelation) i.e. change of the Reaction
mixture from a viscous liquid to solid gel which shows no
tendency to flow.
Example

The reaction of dicarboylic acid with a triol.

HOOC-R1-COOH + HO-R2-OH

OH

O O
O
O
O
----O-R2-O-C-R1-C-O-R2-O-C-R1-C-O-R2










O
O
O
C=O
R1
C=O
O
O O
-----O-C-R1-C-O-R2
O
C=O
R1-C-O-R2-O----O O
Thank You
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