Potentiometric study of equilibrium acidities of some carbon acids in acetonitrile

2002 ◽  
Vol 80 (9) ◽  
pp. 1259-1264 ◽  
Author(s):  
M Stanczyk-Dunaj ◽  
W Galezowski ◽  
A Jarczewski
Keyword(s):  
Proton Transfer ◽  
Transfer Reaction ◽  
Proton Transfer Reaction ◽  
Glass Electrode ◽  
Buffer Solution ◽  
Tetrabutylammonium Hydroxide ◽  
Potentiometric Study ◽  
Tetrabutylammonium Salt ◽  
Influence Of Water ◽  
Carbon Acids

The pKa values for 30 C-acids of the type CH·R1·R2·R3 — where the R1, R2, and R3 substituents are H, alkyl, and aryl, and the most common electron withdrawing groups used in studies of proton-transfer reaction — are given herein. The pKa values have been measured potentiometrically in acetonitrile, using a glass electrode. These values were determined in a buffer solution consisting of a C-acid and its tetrabutylammonium salt, at constant ionic strength (0.001 M), at 25°C. The measurements were done under nitrogen, to prevent oxidation of the anion. The influence of water within the sample of the tetrabutylammonium hydroxide base was negligible. The lowest pKa value of 19.1 was found for bis(4-nitrophenyl)cyanomethane, while the largest pKas that could be measured were limited by the basicity of the hydroxide ion, and did not exceed 28. A satisfactory agreement between spectrophotometric and potentiometric acidities was achieved. Key words: C-acids, pKa values, acetonitrile, potentiometry, proton transfer.

Equilibrium acidities of some carbon acids in acetonitrile

1997 ◽  
Vol 75 (3) ◽  
pp. 285-288 ◽  
Author(s):  
W. Galezowski ◽  
M. Stanczyk ◽  
A. Jarczewski
Keyword(s):  
Proton Transfer ◽  
Transfer Reaction ◽  
Proton Transfer Reaction ◽  
Buffer Solutions ◽  
Carbon Acids

The pK a values for C-acids (4-nitrophenylnitroalkanes, 4-nitrophenyl-(4-X-phenyl)cyanomethanes, 2,4,6-trinitrotoluene, and 9-cyanofluorene) in acetonitrile have been measured. These values were determined spectrophotometrically in buffer solutions consisting of a strong amine base and its picrate or perchlorate using known potentiometric pKa's of amines, and they range from 19 for bis(4-nitrophenyl)cyanomethane to 25.1 for ethyl bis(4-nitrophenyl)acetate. Keywords: C-acids, pKa values, equilibrium, reactivity, proton transfer reaction.

STUDY OF PROTON TRANSFER BETWEEN CARBON ACIDS AND AMINE BASES USING COMPUTATIONAL METHODS

2006 ◽  
Vol 05 (03) ◽  
pp. 633-645 ◽  
Author(s):  
SEIFOLLAH JALILI ◽  
MINA SOLEIMANI
Keyword(s):  
Hydrogen Bonding ◽  
Proton Transfer ◽  
Computational Methods ◽  
Density Functional ◽  
Transfer Reaction ◽  
Proton Transfer Reaction ◽  
Model Systems ◽  
Comparable Amount ◽  
Aim Theory ◽  
Carbon Acids

In this work, the proton transfer between carbon acids and amine bases was investigated using computational methods. The effect of substitutions on the interaction between 1-nitro-1-(4-nitrophenyl) alkanes (with R = H , CH 3) and 1-5-7-triazabicyclo[4,4,0]dec-5-ene) (TBD) was investigated. The solvent effects on proton transfer reaction between 1-nitro-1-(4-nitrophenyl) alkanes (in which R = H , CH 3) and TBD have been calculated in acetonitrile and water solvents. The products of proton transfer reactions between C -acids and 7-methyl-1-5-7-triazabicyclo[4,4,0]dec-5-ene (MTBD) were dissociated into free ions, while those of the TBD reaction contained a comparable amount of ions and ion pairs. In addition, the free energy of activation for proton transfer reaction between C -acids with R = H , CH 3 and TBD was calculated. The intermolecular hydrogen bonding formation between 4-nitrophenylnitromethane and TBD was investigated using the Hartree–Fock method, density functional theory (DFT), and atoms in molecules (AIM) theory. The effects of hydrogen bonding on structural parameters of model systems were also studied. The results are in agreement with the results of AIM theory.

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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