[wm334]

Dear all,

If I make a polyester using various diols and dicarboxylic acids,

what determines the final product?

rate constant, concentrations?
pka of acids?

something else?

[wildfyr]

The answer is all of thr above. Could you be more specific? Those factors affect virtually all reactions. Do you mean the molecular weight of the final product?

If that is the case, the answer is the most important factors are the ratio of monomers and your ability to remove water from the system

[wm334]

If I am making a polyesters and I use varying acids e.g. Teraphthalic acid succinc acid and varying alcohols ethylene glycol butyl glycol.
How do I begin to see the mechanism I may draw is correct and predict the structure of the polymer

[wildfyr]

It's Fischer esterification. That's the organic chemistry that is happening.

[wm334]

but how may I theroetically guess/calculate what the main ester is? what the polymer chain is eg ABC ABAB etc?

I have seen Hammet plot for Benzoic acid

not sure where to keep looking

[wildfyr]

A diol+diester is AABB. Each alcohol reacts with the corresponding carboxylic acid twice.  Are you asking what happens if you have a mix with several diacids and diols?

If that is so, you get a basically statistical mixture at high conversion. it's actually a good assumption in this polymerization that any given alcohol or carboxylic acid has the same reactivity as any other in solution. At low conversion (less than 95%) then you may see a preference for more nucleophilic alcohols to react faster. However primary alkyl alcohols are all essentially the same.

[wm334]

great thanks