Find your answer in my article:

"New macrocyclic complexes containing amide, imine and secondary amine

functions".

Fathi. M. A. M. Aqra. Transition Metal Chemistry, 24, 337 (1999).

IR spectroscopy can help. You can see amide CO peak at around 1720cm-1.

13C and IR can explain well in moderate to simple molecules. Deuterium exchange in proton NMR can help

IR should be efficient in the case of polymers

Maybe try less hi-tech approach and more old school like ninhydrin color reaction. Or conductometric/potentiometric titration using some strong non-oxidizing acid. Of course, the polymer has to be dissolved.

Of course IR will be the perfect technique to use and the carbonyl stretch absorbs in the region ~1690-1640 cm-1. Also C-13 NMR will help, the amide carbon resonates at ~ 150-180 ppm.

Good luck

Thanks for all the precious answers... the easiest then is IR.. will the IR signal will be clear knowing that I have free carboxylic groups, free amines also?...

And Dr. Kamiński : Ninhydrin will detect the amine groups also, I will use it already to assess how much free -NH2 groups I have. My polymer is hyalorunic acid and PEG... so it's water soluble...

Hi! You can use elemental analysis to complement the NMR (H and C) and IR analysis, it can give you one idea to quantify each element .

Ftir

The carboxylic acids O–H stretch appears as a very broad band in the region 3300-2500 cm-1 while the N–H stretches of primary amines are two bands from 3400-3300 and 3330-3250 cm-1 plus N–H bend (primary amines only) from 1650-1580 cm-1. please, see the attached figures to help.

Good luck

Here is the primary amine model

In peptide synthesis, we use the ninhydrin test. Amides have no reaction and the solution will stay yellow. Free amines will react and turn the solution purple. You can use this for fast visually inspection, or use with UV-Vis to quantify a reaction.

I Agree with Dr. Amer and others that suggested simple spectroscopic analysis. You can also follow the international standard ISO-9702 protocol, that allows you to determine the number of primary, secondary, and tertiary amine groups in a resin, just performing some simple titrations. Using the protocol you can check the degree of amidation in your polymer before and after your derivatization and measure the efficiency of your reaction.

i agree with dr Amer, Ir ithink will be satiscfactory for solving the problem

IR combined with 13C NMR is going to be a sufficient and I think reliable for qualitative purpose.

Thanks for all the valuable information, Especially Dr. Amer... As I understood I will see two peaks very close to each other, one for the carboxylic C=O, and one the amide C=O. (or a big peak in between)

Attached is a (claimed) spectrum of a triblock copolymer (Hyalorunic Acid- PEG-PLGA) from literature (PLGA: polylactic co glycolic Acid).

They mention: (C = O stretch absorption at

1610.96 per cm a nd N– H bending at 3405.48 per cm)

Dr. Capobianco's suggetion looks very interesting also, is it using ninhydrin?... I already ordered the reagent but I didn't consider it an enough proof of the amidation... I will use it for quantifying the degree of amidation, as you are suggesting Dr. I will have to check how to get the ISO protocol also... because it looks like we have to buy it from the company. Thanks again

Dear Almoustafa, I cannot pass you the cited ISO method because it is copyright protected. However how it works is easily understandable:

1) you measure the total amine content by performing a potentiometric titration with hydrobromic or perchloric acid of your polymer dissolved in glacial acetic acid.

2) you convert your primary and secondary amine into amides, reacting a portion of your polymer with an excess of acetic anhydride in acetic acid (30 min rT) then you perform again the above titration to measure the tertiary amine content.

3) you react the primary amines of your polymer with an excess of 2,4-pentanedione in DMF, in a stoppered flask, 30 min at 40 °C (to form imines), then you measure the consumed 2,4-pentanedione (i.e. your primary amines) by potentiometric titration with a KOH solution.

4) you calculate the secondary amine content of your polymer subtracting the primary (point 3) and tertiary (point 2) amines from the total amine content (point 1).

The Official ISO normative give you the details.

IR or Raman spectra will give you good result.

You can confirm it by TLC spot test with ninhydrin spray. Fastest and cheapest way to detect.

Find your answer in my article:

"New macrocyclic complexes containing amide, imine and secondary amine

functions".

Fathi. M. A. M. Aqra. Transition Metal Chemistry, 24, 337 (1999).