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

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Discussion Overview

The discussion revolves around the chemical structure of polyglycolic acid (PGA) and its classification as a polyester, specifically focusing on the relationship between its monomer and polymer forms. Participants explore the definitions and characteristics of esters and glycosidic bonds, as well as the implications of these structures in understanding PGA.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants assert that esters have the general form R-CO-OR', while questioning how PGA fits this definition.
  • One participant states that PGA has a specific form, [-O-CH3-CO-], and expresses confusion about its classification as an ester.
  • Another participant challenges the initial claim about PGA's structure, suggesting that the correct representation is [-CH2-COO-], which they argue is equivalent to [-OCH2-CO-].
  • There is a discussion about the presence of glycosidic bonds in PGA, with one participant proposing that these bonds may be related to the ester classification.
  • Some participants express uncertainty about whether an ester always contains a glucosidic bond.
  • A later reply indicates that the monomer of PGA is singular, leading to the conclusion that it is the monomer that contributes to the polymer's classification as an ester.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the structural representation of PGA or its classification as an ester. There are competing views on the correct formula and the relationship between the monomer and polymer.

Contextual Notes

There are unresolved questions regarding the definitions of esters and glycosidic bonds, as well as the implications of these definitions for understanding the structure of PGA. Some assumptions about chemical structures and classifications remain unexamined.

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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