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Hydration energies of protonated and sodiated thiouracils.

Wincel H - J. Am. Soc. Mass Spectrom. (2014)

Bottom Line: The water binding energies of protonated thiouracils, [2SU]H(+) and [6Me2SU]H(+), were found to be of the order of 51 kJ/mol for the first, and 46 kJ/mol for the second water molecule.For [4SU]H(+), these values are 3-4 kJ/mol lower.The structural aspects of the precursors for hydrated complexes are discussed in conjunction with available literature data.

View Article: PubMed Central - PubMed

Affiliation: Institute of Physical Chemistry, Polish Academy of Sciences, 01-224, Warsaw, Poland, wincel@ichf.edu.pl.

ABSTRACT
Hydration reactions of protonated and sodiated thiouracils (2-thiouracil, 6-methyl-2-thiouracil, and 4-thiouracil) generated by electrospray ionization have been studied in a gas phase at 10 mbar using a pulsed ion-beam high-pressure mass spectrometer. The thermochemical data, ΔH(o)n, ΔS(o)n, and ΔG(o)n, for the hydrated systems were obtained by equilibrium measurements. The water binding energies of protonated thiouracils, [2SU]H(+) and [6Me2SU]H(+), were found to be of the order of 51 kJ/mol for the first, and 46 kJ/mol for the second water molecule. For [4SU]H(+), these values are 3-4 kJ/mol lower. For sodiated complexes, these energies are similar for all studied systems, and varied between 62 and 68 kJ/mol for the first and between 48 and 51 kJ/mol for the second water molecule. The structural aspects of the precursors for hydrated complexes are discussed in conjunction with available literature data.

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Arrival time distributions of the reactant, [6Me2SU]Na+, and product, [6Me2SU]Na+ ٠(H2O), ions. The inset shows the ratio of ion intensities, [6Me2SU]Na+(H2O)/[6Me2SU]Na+ as a function of ion residence time
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Fig1: Arrival time distributions of the reactant, [6Me2SU]Na+, and product, [6Me2SU]Na+ ٠(H2O), ions. The inset shows the ratio of ion intensities, [6Me2SU]Na+(H2O)/[6Me2SU]Na+ as a function of ion residence time

Mentions: Mass spectra were registered with continuous ion sampling, while for equilibrium determination the ion beam was injected into the RC in a pulsed mode by applying short pulses (+52 V, 90–200 μs) to the deflection electrode. Typically, several thousand injection pulses were sufficient to accumulate a reasonable signal of the ion arrival time distribution (ATD) for each mass on the multichannel scaler (Fig. 1).Figure 1


Hydration energies of protonated and sodiated thiouracils.

Wincel H - J. Am. Soc. Mass Spectrom. (2014)

Arrival time distributions of the reactant, [6Me2SU]Na+, and product, [6Me2SU]Na+ ٠(H2O), ions. The inset shows the ratio of ion intensities, [6Me2SU]Na+(H2O)/[6Me2SU]Na+ as a function of ion residence time
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4221615&req=5

Fig1: Arrival time distributions of the reactant, [6Me2SU]Na+, and product, [6Me2SU]Na+ ٠(H2O), ions. The inset shows the ratio of ion intensities, [6Me2SU]Na+(H2O)/[6Me2SU]Na+ as a function of ion residence time
Mentions: Mass spectra were registered with continuous ion sampling, while for equilibrium determination the ion beam was injected into the RC in a pulsed mode by applying short pulses (+52 V, 90–200 μs) to the deflection electrode. Typically, several thousand injection pulses were sufficient to accumulate a reasonable signal of the ion arrival time distribution (ATD) for each mass on the multichannel scaler (Fig. 1).Figure 1

Bottom Line: The water binding energies of protonated thiouracils, [2SU]H(+) and [6Me2SU]H(+), were found to be of the order of 51 kJ/mol for the first, and 46 kJ/mol for the second water molecule.For [4SU]H(+), these values are 3-4 kJ/mol lower.The structural aspects of the precursors for hydrated complexes are discussed in conjunction with available literature data.

View Article: PubMed Central - PubMed

Affiliation: Institute of Physical Chemistry, Polish Academy of Sciences, 01-224, Warsaw, Poland, wincel@ichf.edu.pl.

ABSTRACT
Hydration reactions of protonated and sodiated thiouracils (2-thiouracil, 6-methyl-2-thiouracil, and 4-thiouracil) generated by electrospray ionization have been studied in a gas phase at 10 mbar using a pulsed ion-beam high-pressure mass spectrometer. The thermochemical data, ΔH(o)n, ΔS(o)n, and ΔG(o)n, for the hydrated systems were obtained by equilibrium measurements. The water binding energies of protonated thiouracils, [2SU]H(+) and [6Me2SU]H(+), were found to be of the order of 51 kJ/mol for the first, and 46 kJ/mol for the second water molecule. For [4SU]H(+), these values are 3-4 kJ/mol lower. For sodiated complexes, these energies are similar for all studied systems, and varied between 62 and 68 kJ/mol for the first and between 48 and 51 kJ/mol for the second water molecule. The structural aspects of the precursors for hydrated complexes are discussed in conjunction with available literature data.

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