Syn vs Anti Carboxylic Acids in Hybrid Peptides: Experimental and Theoretical Charge Density and Chemical Bonding Analysis

Pal, Rumpa; Reddy, M. B. Madhusudana; Dinesh, B.; Venkatesha, Manjunath A.; Grabowsky, Simon; Jelsch, Christian; Guru Row, Tayur N. (2018). Syn vs Anti Carboxylic Acids in Hybrid Peptides: Experimental and Theoretical Charge Density and Chemical Bonding Analysis. Journal of physical chemistry. A, 122(14), pp. 3665-3679. American Chemical Society 10.1021/acs.jpca.7b10939

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A comparative study of syn vs anti carboxylic acids in hybrid peptides based on experimental electron density studies and theoretical calculations shows that, in the anti form, all three bond angles surrounding Ccarboxyl of the -COOH group are close to ∼120°, as expected for a C-sp2 atom, whereas in the syn form, the ∠Cα-C(O)-Ohydroxyl angle is significantly smaller by 5-10°. The oxygen atom in the carboxyl group is more electronegative in the anti form, so the polarity of the acidic O-H bond is higher in the anti form compared to the syn form, as observed within the limitations of H atom treatment in X-ray diffraction. Consequently, the investigated anti carboxylic acid forms the strongest O-H···O hydrogen bond among all model compounds. Furthermore, according to natural bond orbital analysis, the oxygen lone pairs are clearly nonequivalent, as opposed to the general notion of hybridization of equivalent sp2 and sp3 lone pairs on carbonyl or hydroxyl oxygen atoms. The hybridization of the lone pairs is directly related to the directionality and strength of hydrogen bonds.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Departement of Chemistry and Biochemistry

UniBE Contributor:

Grabowsky, Simon

Subjects:

500 Science > 570 Life sciences; biology
500 Science > 540 Chemistry

ISSN:

1089-5639

Publisher:

American Chemical Society

Language:

English

Submitter:

Simon Grabowsky

Date Deposited:

06 Feb 2020 11:26

Last Modified:

06 Feb 2020 11:26

Publisher DOI:

10.1021/acs.jpca.7b10939

BORIS DOI:

10.7892/boris.138412

URI:

https://boris.unibe.ch/id/eprint/138412

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