scholarly journals Спектральная диагностика динамики образования гомосопряженного комплекса [HCN.H.NCH]-=SUP=-+-=/SUP=-

2020 ◽  
Vol 128 (4) ◽  
pp. 480
Author(s):  
Г.С. Денисов ◽  
С.М. Меликова ◽  
К.С. Рутковский ◽  
К.Г. Тохадзе
Keyword(s):  
Proton Transfer ◽  
Transfer Reaction ◽  
Reaction Path ◽  
Longitudinal Vibration ◽  
Proton Transfer Reaction ◽  
Mechanical Analysis ◽  
Frequency Change ◽  
Normal Vibrations ◽  
Frequencies Of Normal Vibrations ◽  
Reaction Profile

A quantum-mechanical analysis of the manifestations of the NHN hydrogen bond in the vibrational spectra of the [HCN.H.NCH] + linear complex along the proton transfer reaction profile is given, and the laws governing the diagnostic parameters — potential descriptors of the dynamics of this process — are established. The surface of the potential energy and harmonic frequencies of normal vibrations along the profile of the proton transfer reaction path in the system studied are calculated. It has been shown that when the [HCNH] + and NCH fragments come closer together, a noticeable distortion of the forms of their skeletal vibrations occurs, up to complete mixing into the symmetric and antisymmetric forms. The frequency of the longitudinal vibration of the central proton ν (NH) varies along the reaction path from ~ 3600 to ~ 500 cm-1. In the region of intersection of the terms ν (NH) and ν (CN) an abrupt nature of frequency change is detected.

Solvent effects on the rates and equilibria of the proton transfer reaction of 4-nitrophenylphenylcyanomethane to tetramethylguanidine

1986 ◽  
Vol 64 (12) ◽  
pp. 2365-2367 ◽  
Author(s):  
Mahmood Hojatti ◽  
Kenneth T. Leffek
Keyword(s):  
Dielectric Constant ◽  
Proton Transfer ◽  
Solvent Effects ◽  
Rate Constants ◽  
Transfer Reaction ◽  
Reaction Path ◽  
General Trend ◽  
Equilibrium Constants ◽  
Proton Transfer Reaction ◽  
Constant Function

The equilibrium constants and second-order rate constants, both at 25 °C, have been determined for the proton transfer reaction from 4-nitrophenylphenylcyanomethane to tetramethylguanidine in a number of different solvents. While the equilibrium constants show a good correlation with the dielectric constant function D − 1/2D + 1, the rate constants are randomly scattered with respect to this parameter and also the solvent parameter ET. The rate constants do show a general trend in relation to the solvent parameters AN and DN. These results are interpreted as support for the hypothesis that the transition state of the proton transfer occurs early along the reaction path.

scholarly journals Identifying volatile in vitro biomarkers for oral bacteria with proton-transfer-reaction mass spectrometry and gas chromatography–mass spectrometry

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kajsa Roslund ◽  
Markku Lehto ◽  
Pirkko Pussinen ◽  
Kari Hartonen ◽  
Per-Henrik Groop ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Proton Transfer ◽  
Transfer Reaction ◽  
Proton Transfer Reaction ◽  
Oral Bacteria ◽  
Gas Chromatography Mass Spectrometry ◽  
Volatile Analysis ◽  
Bacterial Volatiles

AbstractWe have measured the volatile fingerprints of four pathogenic oral bacteria connected to periodontal disease and dental abscess: Porphyromonas gingivalis (three separate strains), Prevotella intermedia, Prevotella nigrescens and Tannerella forsythia. Volatile fingerprints were measured in vitro from the headspace gas of the bacteria cultured on agar. Concrete identification of new and previously reported bacterial volatiles were performed by a combination of solid phase microextraction (SPME) and offline gas chromatography–mass spectrometry (GC–MS). We also studied the effect of the reduced electric field strength (E/N) on the fragmentation patterns of bacterial volatiles in online proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS). We aimed to discover possible new biomarkers for the studied oral bacteria, as well as to validate the combination of GC–MS and PTR-MS for volatile analysis. Some of the most promising compounds produced include: 1-Methyl-1,2,3,4-tetrahydroisoquinoline (1MeTIQ), indole, and a cascade of sulphur compounds, such as methanethiol, dimethyl disulphide (DMDS) and dimethyl trisulphide (DMTS). We also found that several compounds, especially alcohols, aldehydes and esters, fragment significantly with the PTR-MS method, when high E/N values are used. We conclude that the studied oral bacteria can be separated by their volatile fingerprints in vitro, which could have importance in clinical and laboratory environments. In addition, using softer ionization conditions can improve the performance of the PTR-MS method in the volatile analysis of certain compounds.

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