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Gas phase basicity of biguanides – Comparison of the equilibrium and the kinetic methods


Glasovac, Zoran; Eckert-Maksić, Mirjana; Kaljurand, Ivari; Saame, Jaan; Leito, Ivo
Gas phase basicity of biguanides – Comparison of the equilibrium and the kinetic methods // International journal of mass spectrometry, 435 (2019), 61-68 doi:10.1016/j.ijms.2018.10.010 (međunarodna recenzija, članak, znanstveni)


Naslov
Gas phase basicity of biguanides – Comparison of the equilibrium and the kinetic methods

Autori
Glasovac, Zoran ; Eckert-Maksić, Mirjana ; Kaljurand, Ivari ; Saame, Jaan ; Leito, Ivo

Izvornik
International journal of mass spectrometry (1387-3806) 435 (2019); 61-68

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Gas-phase basicity ; Biguanide ; Density functional theory ; Intramolecular hydrogen bond ; Mass spectrometry

Sažetak
The gas-phase basicities (GB) of 7 biguanides were measured by the equilibrium and the entropy corrected kinetic methods. The experimental data were compared with the GB values calculated at B3LYP/6-311+G(2df, p)//B3LYP/6-31G(d) level of theory. Calculated GB values for biguanides correlate well with the experimental data and lie on the same regression line as guanidine derivatives. All biguanides belong to the class of superbases having GB above 1000 kJ mol−1 and being comparable or more basic than the most basic guanidines known. The highest GB of 1103 kJ mol−1 was determined for the bis-dimethylaminomethylene-2, 3-bis-(3-dimethylaminopropyl)guanidine (biguanide 4) in which two intramolecular hydrogen bonds (IMHB) can be formed in the protonated form. For selected biguanides and guanidines, contribution of IMHB to the GB was calculated for two conformations with different hydrogen bonding motifs (6- and 8- membered pseudocyclic substructure). In conjugated acids of biguanides having two 3-dimethylaminopropyl or 3-methoxypropyl substituents, conformational preference is determined by maximizing number of possible IMHBs. Hydrogen bond stabilization enthalpies were also calculated using aforementioned B3LYP as well as M06-2X/6-311++G(3df, 2p)//B3LYP/6-31G(d) model and compared to the values obtained for guanidine derivatives. Slightly weaker hydrogen bonds in biguanides with respect to guanidines were ascribed to larger steric congestion while the impact of more extensive delocalization area was found negligible.

Izvorni jezik
Engleski

Znanstvena područja
Kemija



POVEZANOST RADA


Projekt / tema
098-0982933-2920 - Organski i bioorganski procesi u osnovnom i elektronski pobuđenim stanjima (Mirjana Maksić, )

Ustanove
Institut "Ruđer Bošković", Zagreb

Časopis indeksira:


  • Current Contents Connect (CCC)
  • Web of Science Core Collection (WoSCC)
    • Science Citation Index Expanded (SCI-EXP)
    • SCI-EXP, SSCI i/ili A&HCI
  • Scopus


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