I believe that in a polymer system involving carboxylic acid and urethane, 3 types of H-bondings are possible (please correct me if there are more than 3), (1) between -COOH and -COOH (double H bond), (2) between urethane groups, (3) between -COOH and -NHCOO.
Among these -COOH-COOH H-bonding should be the strongest since it is a dimer, but which one comes second and why?
Is it possible to find the exact bond energy? At the very least I am looking forward to a theoretical explanation.
Thank you in advance for your valuable responses.
Dear Anjali Preman, as a whole H-bond strength energies depend on the electronegativity of the element to which H- is attached and the on the counter part on the size of the element supplying the free doublet e-, without neglecting the influence of substituent groups and the surrounding environment. Please have a look at the following documents. My Regards
https://doi.org/10.1021/jp103470e
https://doi.org/10.1021/ja408762r
https://doi.org/10.1080/00387017208064689
How to Model Inter- and Intramolecular Hydrogen Bond Strengths with Quantum Chemistry
- Christoph A. Bauer*
Cite this: J. Chem. Inf. Model. 2019, 59, 9, 3735–3743
Publication Date:August 14, 2019
https://doi.org/10.1021/acs.jcim.9b00132
Copyright © 2019 American Chemical Society
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SUBJECTS:
- Free energy,
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Journal of Chemical Information and Modeling
Abstract
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This article presents the computation of both inter- and intramolecular hydrogen bond strengths from first-principles. Quantum chemical calculations conducted at the dispersion-corrected density functional theory level including free energy and solvation contributions are conducted for (i) one-to-one hydrogen-bonded complexes of alcohols to N-methyl pyrrolidinone measured by an infrared spectroscopy method and (ii) a set of experimental intramolecular hydrogen bond-forming phenol and pyrrole compounds, with intramolecular hydrogen bond strengths derived from a nuclear magnetic resonance method. The computed complexation free energies in solution show a correlation to experiment of R2 = 0.74 with a root mean square error of 4.85 kJ mol–1. The intramolecular hydrogen bonding free energies in solution show a correlation of R2 = 0.79 with a root mean square error of 5.51 kJ mol–1. The results of this study can be used as a guide on how to build reliable quantum chemical databases for computed hydrogen bonding strengths.
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