IR SPECTROSCOPY OF GLUE BASED ON OXALIC ACID, FORMALDEHYDE, AND PHTHALIMIDE
Creators: name: Ganiev B.Sh
name: Nazarov S.I
name: Amrieva S.K
Publisher: name: Zenodo
Year: 2025

description: Oxalic acid, formaldehyde, and phthalimide represent three such compounds that offer promising characteristics for adhesive applications. Oxalic acid, a dicarboxylic acid derived from natural sources, possesses carboxyl groups that can participate in crosslinking reactions. Formaldehyde is a widely used crosslinking agent due to its ability to form strong bonds with various functional groups. Phthalimide, a cyclic imide compound, offers potential as a modifying agent in adhesive formulations.


In this study, we present a spectroscopic analysis of the chemical composition of oxalic acid, formaldehyde, and phthalimide adhesives. We use infrared (IR) spectroscopy and density functional theory (DFT) to analyze the data.


IR spectroscopic analysis of the synthesized adhesive revealed characteristic absorption bands corresponding to functional groups present in oxalic acid, formaldehyde, and phthalimide. The presence of specific peaks confirmed the successful incorporation of these compounds into the adhesive matrix and provided insights into the chemical structure of the adhesive.


The structure of the synthesized material was investigated using IR spectroscopy. The results obtained were then compared with those of quantum chemical calculations based on the IR spectra. Based on the DFT calculations for phthalimide in the synthesis of oligomers with adhesive properties, we compared the infrared (IR) spectra obtained from the calculations with the experimental IR spectra. The analysis of functional groups was performed using the following frequency ranges:


N-H imine functional group vibrations


Heteroaromatic compounds containing an NH group exhibit an N-H stretching absorption band in the region between 3500 and 3200 cm⁻¹. The nitrogen and hydrogen bonds present in phthalimide give rise to N-H stretching, in-plane, and out-of-plane bending vibrations. In this study, we designated the FT-IR band at 3182,55 cm⁻¹ as the N-H stretching vibration. We assigned the bands at 1386,82 and 974,05 cm⁻¹ to in-plane and out-of-plane bending modes of NH. In the IR spectrum obtained from the DFT calculations of phthalimide, valence vibrations (NH) are observed at a frequency of 3654.09 cm⁻¹ and deformational vibrations are observed at 1346.29 cm⁻¹.


O-H vibrations in aromatic rings and the methylene functional group 


2-((1,3-dioxoisoindolin-2-yl)methoxy)-2-oxoacetic acid acid molecule has 3775.57 cm-1 unique symmetric valence vibrations.


 





	
		
			
			

			
			
			

			
			
			

			
		
		
			
			
Fig. 1. Comparison of the observed and calculated infrared spectra of (1) phthalimide; (2) 2-(hydroxymethyl)isoindoline-1,3-dione and (3) 2-((1,3-dioxoisoindolin-2-yl)methoxy)-2-oxoacetic acid: (a) observed in the solid phase; (b) calculated using the B3LYP/6-31G(d,p) method.
			
		
	




C-N vibrations


The appearance of medium to strong absorption bands in the range of 1138-1158 cm-1 is due to the stretching vibration of the C-N bond in the newly formed phthalymide derivates. Based on DFT calculations, the vibration of the C-N bond in the 2-(hydroxymethyl)isoindoline-1,3-dione molecule is in the region of 1147.77 cm-1 and 2-((1,3-dioxoisoindolin-2-yl)methoxy)-2-oxoacetic acid observed in the region of 1139.45 cm-1 in the molecule.


C-H vibrations in aromatic rings and the methylene functional group 


C-H group-specific vibrations in the IR spectra of phthalimide, 2-(hydroxymethyl)isoindoline-1,3-dione, and 2-((1,3-dioxoisoindolin-2-yl)methoxy)-2-oxoacetic acid, obtained spectral absorption lines based on DFT calculations observed in the following areas:


Absorption lines specific to C-H bonds in the aromatic ring in the phthalimide molecule are νas(C-H) 3191.81; 3204.72 and 3216.47 cm-1 and νs (C-H) were observed at 3219.85 cm-1.


In 2-(hydroxymethyl)isoindoline-1,3-dione molecule, the absorption lines characteristic of the C-H bonds of the methylene (-CH2-) group in the ring are νas(C-H) 3150.46 and νs (C-H) 3037.93 cm-1 in the sphere, in the aromatic ring Absorption lines specific to C-H bonds are nas (C-H) 3192.14; 3204.95 and 3216.40 cm-1 and ns (C-H) were observed at 3219.85 cm-1.


Absorption lines typical of C-H bonds of the methylene (-CH2-) group in the ring of 2-((1,3-dioxoisoindolin-2-yl)methoxy)-2-oxoacetic acid molecule are νas (C-H) 3171.38 and νs (C-H) 3095.37 cm-1 area, and the absorption lines characteristic of C-H bonds in the aromatic ring are νas(C-H) 3194.53; 3207.07 and 3218.34 cm-1 and νs (C-H) were observed at 3221.68 cm-1.


Based on the obtained results, the structure of the substance with adhesive properties was determined and was fully concluded with other additional physical and chemical studies.