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1

Adenine adsorption in different pH acetate buffer

Gugała-Fekner Dorota

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 2

art. no. 144446

EN

The research results facilitate the description of adenine adsorption on the mercury electrode with reference to the pH of the supporting electrolyte which was the acetate buffer with pH of 3, 4, 5 and 6. The thermodynamic analysis indicates that the curves of the differential capacity of the studied systems with adenine do not overlap with the curves for the supporting electrolyte – the acetate buffer. This indicates the occurrence of adsorption of the studied compound on the mercury electrode within the whole range of applied concentrations in the case of every tested pH value of the acetate buffer. Adsorption energy and interaction constants were determined using the Frumkin isotherm and the viral isotherm. It was demonstrated that a adenine molecule is adsorbed on the mercury electrode in a buffer with pH 4, 5 and 6 through the negative pole, whereas in a buffer with pH 3 through the positive pole. Physical adsorption was observed in the studied systems. This is indicated by the occurrence of a typical maximum on the curve of the relation the relative surface excess amounts and the potential of the electrode; crossed curves of the following relation surface charge of the electrode from its potential (surface charge of the electrode from its potential σ = f(E)) at one point and, thus, the possibility of determining electrical parameters characterizing maximum adsorption as well as the absence of linearity of the function free energy of adsorption as a function of electrode potential ∆G0 = f(E).

2

Wybrane zasady purynowe jako inhibitory korozji stali węglowej

Trela J., Scendo M.

Ochrona przed Korozją

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2012

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nr 5

220-223

PL

Zbadano wpływ stężenia puryny (PU) i adeniny (AD) na proces korozji stali węglowej, St3S (SW) w kwaśnych roztworach chlorków. Stwierdzono, że wydajność inhibitowania korozji badanej stali wzrasta wraz ze wzrostem stężenia inhibitorów w roztworze. Wartości standardowej energii swobodnej adsorpcji świadczą, że zarówno PU jak i AD ulegają adsorpcji chemicznej zgodnie z izotermą Langmuira. Przedyskutowano mechanizm powstawania warstwy ochronnej na powierzchni stali węglowej.

EN

The influence of concentration of purine (PU) and adenine (AD) on the corrosion of St3S (SW) carbon steel in acid chloride solution was studied. The inhibition efficiency increases with increase of concentration of both inhibitors. The values of standard free energies of adsorption prove the chemical adsorption of PU and AD according to Langmuir isotherm. The mechanism of formation the protective layer on the surface of the carbon steel was discussed.

3

Naturalne inhibitory korozji miedzi i mosiądzu w miękkich wodach zawierających chlorki

Drela I., Falewicz P., Stokłosa J.

Ochrona przed Korozją

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2012

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nr 4

156-159

PL

Przedstawiono wyniki badań korozyjnych, prowadzonych metodą potencjodynamiczną, dla miedzi i mosiądzu w wodzie zawierającej 5 g//dm3 NaCl oraz wybrane naturalne związki organiczne. Jako potencjalne inhibitory korozji dla miedzi i mosiądzu badano adeninę, teofilinę i inozynę. Stwierdzono, że skuteczność ochrony miedzi przed korozją może osiągać wartość 70%, przy stężeniu adeniny w wodzie na poziomie 100-150 mg/dm3. Dobrą ochronę przed korozją mosiądzu zapewnia teofilina (skuteczność ochronna ponad 70% przy stężeniu w wodzie 50 mg/dm3) oraz adenina (skuteczność ochronna ok. 70% przy stężeniu 100 mg/dm3). Wszystkie trzy badane związki wykazują inhibitowanie głównie katodowych procesów korozyjnych miedzi i mosiądzu.

EN

The results of corrosion tests conducted by the potentiodynamic method for copper and brass in water containing 5 g/dm3 NaCl and selected natural organic compounds are presented. As potential corrosion inhibitors for copper and brass adenine, theophylline and inosine were tested. It was found that the effectiveness of corrosion protection of copper can achieve a value of 70%, at a concentration of adenine in water at the level 100-150 mg/dm3. Good protection against corrosion for brass provides theophylline (inhibition effi ciency more than 70% at a concentration in water 50 mg/dm3) and adenine (inhibition effi ciency about 70% at a concentration of 100 mg/dm3). All three tested compounds exhibit primarily inhibition of cathodic corrosion processes for copper and brass.

4

Wybrane zasady purynowe jako ekologiczne inhibitory korozji miedzi

Scendo M.

Ochrona przed Korozją

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2011

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nr 12

659-663

PL

Badano wpływ stężenia puryny (PU) i jej pochodnej adeniny (AD) na proces korozji miedzi w 0,5 M roztworze NaNO3 (pH 6). Wykazano, że wydajność inhibitowania wzrasta ze wzrostem stężenia PU lub AD. Wartości standardowej entalpii swobodnej adsorpcji świadczą, że PU i AD ulegają chemisorpcji na powierzchni elektrody. Warstwa utworzona przez inhibitory jest szczelna i zapewnia dobrą ochronę miedzi przed korozją.

EN

The influence of the concentration of purine (PU) and its derivative adenine (AD) on the corrosion of copper in a 0.5 M NaNO3 solution (pH 6) was studied. It was shown that the inhibition efficiency increases with the increase in the concentration of PU and AD. The values of the standard free energies of adsorption prove that PU and AD undergo chemical adsorption on the electrode's surface. The adherent layers of both the inhibitors were postulated to account for the protective effect.

5

Adenine and Some of Its Analogues in DMSO-d6 Solution: an NMR and GIAO-DFT Study

Dybiec K., Molchanov S., Gryff-Keller A.

Polish Journal of Chemistry

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2009

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Vol. 83, nr 5

857-868

EN

The results of GIAO-DFT calculations [at B3LYP/6-311++G(2d,p) PCM and PBE1PBE/6-311+G(2fd,p) PCM levels] of 13C NMR and 15N NMR parameters have been employed to reinvestigate tautomerism of adenine in DMSO solution. The separate 13C NMR sig nals of N7-H and N9-H adenine tautomers have been observed for the first time. The ex erimental 13C chemical shifts, 3J(C,H) coupling constants and 15N chemical shifts of adenine and three of its methyl derivatives (9MeA, 7MeA and 3MeA) have been quantitatively analyzed using the calculated parameter values. This procedure has provided the solution populations of the predominant adenine tautomers being in agreement with the available literature data. The apparent dependence between the amino group geometry and the chemical shift of the adjacent carbon in 2-aminopyridine system has also been discussed.

6

Accurate Gas Phase Basicities of Hydroxyl Radical Modified Purines Estimated by Advanced Quantum Chemistry Methods

Cysewski P., Kozłowska K.

Polish Journal of Chemistry

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2008

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Vol. 82, nr 12

2255-2268

EN

The gas phase basicities (GPB) of purines and their hydroxyl radical modified analogs were characterized by different methods and diverse basis sets. The macroscopic and microscopic protolytic properties of six derivatives were analyzed in details. Most of studied model purine analogs, namely 8-oxo-adenosine (AB), 8-oxo-guanosine (GA), xanthosine (GB) and fapy-guanosine (GC) have reduced basicities from 2.0 kcal/mol (AB) to 6.4 kcal/mol (GA) compared to non-modified model purine nucleosides. The fapy-adenosine (AC) and 2-OH-adenosine (AA) are characterized by higher basic character compared to non-modified adenosine. Besides, it is presented the detailed analysis of GPB in accuracies estimated by means of HF, MP2, B3LYP, G3MP2 and G3MP2B3 methods. The B3LYP/aug-cc-pvdz approach seems to be the most accurate among studied methods and precise enough for estimation of GPB. However, the microscopic protonation features are much more sensitive to applied method since the difference in energies between some tautomers are often less than 1 kcal/mol with method dependent succession. The correct sequence of neutral and cationic forms may be however obtained using one of the model composite chemistry approaches, e.g. G3MP2B3. In the cases where B3LYP/aug-cc-pvdz and G3MP2B3 methods lead to contradictory predictions of order of neutral or protonated tautomers the latter is suggested to be used in the interpretation of microscopic protonation properties. Nevertheless, if only macroscopic property is necessary the B3LYP/aug-cc-pvdz level is sufficient since it provides GPB values with 1.0 kcal/mol accuracy.

7

Puryna i adenina jako inhibitory korozji miedzi w kwaśnych roztworach chlorków

Scendo M.

Ochrona przed Korozją

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2006

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nr 12

385-390

PL

Badano wpływ stężenia puryny lub adeniny na proces anodowego roztwarzania miedzi w kwaśnych 1,0 M roztworach chlorków (pH 3,0 i 1,0). Do pomiarów prowadzonych metodą woltamperometrii stosowano stacjonarną elektrodę dyskową (SDE). Dysk wykonany był z elektrolitycznie czystej miedzi (99,99% Cu). Wydajność (skuteczność) inhibitowania (IE) korozji miedzi wzrasta ze wzrostem stężenia PU lub AD (pH 3,0). Działanie inhibitorów polega na utworzeniu dobrze przylegającej warstwy ochronnej. Adsorpcję PU i AD opisuje izoterma Langmuira. Puryna i adenina ulegają chemisorpcji na powierzchni miedzi.

EN

The influence of the concentration of purine (PU) or of adenine (AD) on the anodic dissolution of copper in 1.0 M acidic chloride solutions (pH 3.0 and 1.0) has been studied by means of the voltammetry method, for which a stationary disk electrode (SDE) was used. The disk was made of copper (99.99% Cu). The tests showed that the inhibiting effi ciency (IE) of the corrosion of copper increases together with a rise in the concentration of PU or AD (pH 3.0). Inhibitors create a well adhering protective layer which is postulated to account for their protective effect. The adsorption of PU and AD has been found to occur on the surface of copper according to the Langmuir isotherm. Purine and adenine are chemically adsorbed on the copper surface.

8

Complexes of Adenine with Metal Ions: Stability and Excited States

Rubina A., Rubin Y., Sorokin V., Shukla M., Leszczyński J.

Polish Journal of Chemistry

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2005

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Vol. 79 / nr 12

1873-1882

EN

Molecular geometry optimizations and excited state energy calculations were performed for the N9H and N7H tautomers of adenine (Ade) and their complexes with selected transition metal ions (Cu+, Cu2+, Zn2+ and Ag+). The ground state geometry optimizations were carried out at the HF and UHF (for open-shell metal ions) levels, while transition energies were calculated using the configuration interaction involving single excited configurations (CIS method). Single point ground state energy calculations were also performed at the full MP2 (UMP2 for open-shell systems) level. The 6-31+G(d,p) basis set was used for all but Ag+ containing complexes for which the LANL2DZ basis set was used. Experimental UV-spectra of adenine complexes with Cu2+ and Ag+ metal cations in the water solution were also obtained. These spectra show red-shift of approximately 1000 cm-1 in comparison with that of the adenine. The analysis of the first electronic singlet - * transition energies suggests that metal ion binding to the N1 or N7 atomic sites of adenine generally leads to the red-shift, while the binding at the N9 site leads to blue shift of the absorption maximum of complexes. The most probable binding site for the Cu+ and Zn2+ ions is found to be the N7 atomic site of the N9H tautomer of adenine. Divalent copper Cu2+ ion would bind at the N1 site. Co-existence of the two forms of adenine complexes with silver ion ([N9H-Ade-AgN1]+, and [N9H-Ade-AgN7]+) is also revealed.