What is the relationship between the monomer and polymer in PGA?

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SUMMARY

The discussion clarifies the relationship between the monomer and polymer in polyglycolic acid (PGA), establishing that PGA is indeed a polyester due to its structure, which includes ester linkages. The monomer of PGA is identified as glycolic acid, represented by the formula [-OCH2-CO-]. Participants confirmed that PGA consists of repeating units of this monomer, which contributes to its classification as an ester. The confusion arose from misinterpretations of the ester structure and the polymer's representation.

PREREQUISITES
  • Understanding of ester chemistry, specifically the structure R-CO-OR'
  • Familiarity with polyglycolic acid (PGA) and its chemical composition
  • Knowledge of glycosidic bonds and their role in polymer chemistry
  • Basic grasp of polymerization processes and monomer definitions
NEXT STEPS
  • Research the chemical properties and applications of polyglycolic acid (PGA)
  • Study the mechanisms of ester formation and polymerization
  • Explore the significance of glycosidic bonds in polysaccharides and polyesters
  • Learn about the structural variations of esters and their implications in polymer chemistry
USEFUL FOR

Chemistry students, polymer scientists, and professionals in materials science who are interested in the structural properties and applications of polyglycolic acid and related polymers.

soopo
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Esters have the form R-CO-OR'.

PGA has the form [-O-CH3-CO-].
It is a polyester that means an ester according to Wikipedia.
I cannot see why it is an ester.
It does not have two oxygens bind to one carbon.

Why is PGA an ester?
 
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soopo said:
Esters have the form R-CO-OR'.

PGA has the form [-O-CH3-CO-].

No it doesn't. Review that part again.
 
chemisttree said:
No it doesn't. Review that part again.

The form of the ester is right: http://en.wikipedia.org/wiki/Ester

One part of PGA has the above form.
I had only the given part of PGA in the exam. It was my first time to see PGA.

I am trying to deduce somehow that PGA has an ester -part.
PGA is poly glycosidic acid.
This means that there is a glycosidic bond in the polymer, probably many.
Glycosidic bond is within an ester: http://en.wikipedia.org/wiki/Glycosidic_bond

Does an ester have always a glucosidic bond?

It seems that the key to solve the problem was to think about the abbreviations of PGA, not the single unit of the polymer.
 
5 bonds to carbon. It's wrong.

You gave a general formula for an ester as R-CO-OR' but you chose to show it in a different way for the polymer. Does this help?

PGA (polyglycolic acid) = [-CH2-COO-]
which is equivalent to [-OCH2-CO-]
 
chemisttree said:
5 bonds to carbon. It's wrong.

You gave a general formula for an ester as R-CO-OR' but you chose to show it in a different way for the polymer. Does this help?

PGA (polyglycolic acid) = [-CH2-COO-]
which is equivalent to [-OCH2-CO-]

WOOT!
Thank you!
I did not get it that it is the monomer of the PGA.
It seems that PGA does not have different monomers: only the one.

I now see that the monomer really make the polymer an ester.
 

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