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Article ; Online: A UNIFIED FORMULA FOR HYDROCARBONS WITH APPLICATIONS TO FUNCTIONAL GROUPS

Higo B. Nogueira / Norberto de Kássio V. Monteiro / Pedro de Lima-Neto

Química Nova, Vol 43, Iss 7, Pp 974-

2020 Volume 976

Abstract: Was supposed a numerical relationship between atoms of Hydrogen and Carbon in a hydrocarbon, assumption valid for all types of chains. In the proposed equation, variables such as number and types of carbon bonds are present, as well as the possible ... ...

Abstract	Was supposed a numerical relationship between atoms of Hydrogen and Carbon in a hydrocarbon, assumption valid for all types of chains. In the proposed equation, variables such as number and types of carbon bonds are present, as well as the possible cycles. It was shown that the equation reduces to the known “general formulas” when applied to the type of chain in question. There is also a generalization of the equation to include elements of the group 16 (6A) of the Periodic Table, expanding its application to the molecules containing functional groups of this elements (we used functional groups containing oxygen as examples). This application generates an equation for each functional group, in an effort to study them algebraically; this effort points to the objective of the article, which is to provide algebraic foundations for the countable properties in chemical bonding. Finally, possible generalizations of the equation were mentioned, pointing out ways to be followed by those who are interested in this new subject. Even though it was done as a pure science research, it is easy to ignore non-interesting variables and introduce new interesting ones.
Keywords	hydrocarbon ; functional group ; chalcogens ; unified formula ; Chemistry ; QD1-999
Subject code	540
Language	English
Publishing date	2020-08-01T00:00:00Z
Publisher	Sociedade Brasileira de Química
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Quantum computational investigations and molecular docking studies on amentoflavone

Márcia M. Marinho / Francisco Wagner Q. Almeida-Neto / Emanuelle M. Marinho / Leonardo P. da Silva / Ramon R.P.P.B. Menezes / Ricardo P. dos Santos / Emmanuel S. Marinho / Pedro de Lima-Neto / Alice M.C. Martins

Heliyon, Vol 7, Iss 1, Pp e06079- (2021)

2021

Abstract: Chagas disease is a neglected tropical disease caused by the protozoan parasite Trypanosoma cruzi, with approximately 6–7 million people infected worldwide, becoming a public health problem in tropical countries, thus generating an increasing demand for ... ...

Abstract	Chagas disease is a neglected tropical disease caused by the protozoan parasite Trypanosoma cruzi, with approximately 6–7 million people infected worldwide, becoming a public health problem in tropical countries, thus generating an increasing demand for the development of more effective drugs, due to the low efficiency of the existing drugs. Aiming at the development of a new antichagasic pharmacological tool, the density functional theory was used to calculate the reactivity descriptors of amentoflavone, a biflavonoid with proven anti-trypanosomal activity in vitro, as well as to perform a study of interactions with the enzyme cruzain, an enzyme key in the evolutionary process of T-cruzi. Structural properties (in solvents with different values of dielectric constant), the infrared spectrum, the frontier orbitals, Fukui analysis, thermodynamic properties were the parameters calculated from DFT method with the monomeric structure of the apigenin used for comparison. Furthermore, molecular docking studies were performed to assess the potential use of this biflavonoid as a pharmacological antichagasic tool. The frontier orbitals (HOMO-LUMO) study to find the band gap of compound has been extended to calculate electron affinity, ionization energy, electronegativity electrophilicity index, chemical potential, global chemical hardness and global chemical softness to study the chemical behaviour of compound. The optimized structure was subjected to molecular Docking to characterize the interaction between amentoflavone and cruzain enzyme, a classic pharmacological target for substances with anti-gas activity, where significant interactions were observed with amino acid residues from each one's catalytic sites enzyme. These results suggest that amentoflavone has the potential to interfere with the enzymatic activity of cruzain, thus being an indicative of being a promising antichagasic agent.
Keywords	Antichagasic agent ; Biflavonoid ; DFT ; Fukui analysis ; NLO ; Science (General) ; Q1-390 ; Social sciences (General) ; H1-99
Subject code	540
Language	English
Publishing date	2021-01-01T00:00:00Z
Publisher	Elsevier
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article: Square Wave Adsorptive Stripping Voltammetry Determination of Chlorpyriphos in Irrigation Agricultural Water

Melo, Luisa C / Adriana N. Correia / Djenaine De Souza / Maria A. L. Milhome / Murilo S. S. Julião / Pedro de Lima-Neto / Ronaldo F. do Nascimento

Journal of analytical chemistry. 2018 July, v. 73, no. 7

2018

Abstract: This work describes the electroanalytical determination of Chlorpyriphos pesticide in natural waters using hanging mercury drop electrode allied to square wave adsorptive cathodic stripping voltammetry. The best responses were obtained in Britton‒ ... ...

Abstract	This work describes the electroanalytical determination of Chlorpyriphos pesticide in natural waters using hanging mercury drop electrode allied to square wave adsorptive cathodic stripping voltammetry. The best responses were obtained in Britton‒Robinson buffer solutions at pH 2.0, using a frequency of 100 s–1, a scan increment of 5 mV, a square wave amplitude of 25 mV and an accumulation potential of–0.4 V during 60 s. Therefore, voltammetric responses showed the presence of one well-defined and irreversible reduction peak, at–1.08 V vs. Ag/AgCl/KCl 1.0 M, which involves two electrons in the reduction of carbon‒nitrogen bond in the N-heterocyclic system with the participation of protonation equilibrium preceding the electron transfer reaction. Analytical curves were constructed and compared to similar curves performed by gas chromatograph coupled to a selective nitrogen‒phosphorus detector, which demonstrates that the proposed methodology is suitable for determining contamination by Chlorpyriphos in complex samples.
Keywords	chlorpyrifos ; electrodes ; electron transfer ; electrons ; gas chromatography ; heterocyclic nitrogen compounds ; mercury ; pH ; potassium chloride ; silver ; silver chloride
Language	English
Dates of publication	2018-07
Size	p. 695-704.
Publishing place	Pleiades Publishing
Document type	Article
ZDB-ID	2057336-4
ISSN	1608-3199 ; 1061-9348
ISSN (online)	1608-3199
ISSN	1061-9348
DOI	10.1134/S1061934818070109
Database	NAL-Catalogue (AGRICOLA)

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Article: Chitosan-magnetite nanocomposite as a sensing platform to bendiocarb determination

de Oliveira, Raissa C / Adriana N. Correia / Camila P. Sousa / Helena Becker / Juliano C. Denardin / Pedro de Lima-Neto / Pierre B. A. Fechine / Rafael M. Freire / Simone Morais / Tiago M. Freire

Analytical and bioanalytical chemistry. 2018 Nov., v. 410, no. 27

2018

Abstract: A novel platform for carbamate-based pesticide quantification using a chitosan/magnetic iron oxide (Chit-Fe3O4) nanocomposite as a glassy carbon electrode (GCE) modifier is shown for an analytical methodology for determination of bendiocarb (BND). The ... ...

Abstract	A novel platform for carbamate-based pesticide quantification using a chitosan/magnetic iron oxide (Chit-Fe3O4) nanocomposite as a glassy carbon electrode (GCE) modifier is shown for an analytical methodology for determination of bendiocarb (BND). The BND oxidation signal using GCE/Chit-Fe3O4 compared with bare GCE was catalyzed, showing a 37.5% of current increase with the peak potential towards less positive values, showing method’s increased sensitivity and selectivity. Using square-wave voltammetry (SWV), calibration curves for BND determination were obtained (n = 3), and calculated detection and quantification limits values were 2.09 × 10−6 mol L−1 (466.99 ppb) and 6.97 × 10−6 mol L−1 (1555.91 ppb), respectively. The proposed electroanalytical methodology was successfully applied for BND quantification in natural raw waters without any sample pretreatment, proving that the GCE/Chit-Fe3O4 modified electrode showed great potential for BND determination in complex samples. ᅟ Graphical abstract
Keywords	bendiocarb ; calibration ; chitosan ; glassy carbon electrode ; iron oxides ; magnetism ; nanocomposites ; oxidation
Language	English
Dates of publication	2018-11
Size	p. 7229-7238.
Publishing place	Springer Berlin Heidelberg
Document type	Article
ISSN	1618-2642
DOI	10.1007/s00216-018-1330-1
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Structural, Vibrational and Electrochemical Analysis and Antibacterial Potential of Isomeric Chalcones Derived from Natural Acetophenone

Priscila Teixeira da Silva / Thiago Sampaio de Freitas / Diniz Maciel Sena Jr. / Paulo Nogueira Bandeira / Murilo Ségio da Silva Julião / Emmanuel Silva Marinho / Ana Aline Coêlho Alcanfor / Emanuelle Machado Marinho / Pedro de Lima-Neto / Carlos Emídio Sampaio Nogueira / Henrique Douglas Melo Coutinho / Antonio Linkoln Alves Borges Leal / Humberto Medeiros Barreto / Natália Martins / Alexandre Magno Rodrigues Teixeira / Hélcio Silva dos Santos

Applied Sciences, Vol 10, Iss 4713, p

2020 Volume 4713

Abstract: Background: Chalcones are part of a family of small phenolic compounds that are being extensively studied for presenting a diversity of molecular structures and biological activities. In this paper, two chalcones, ( E )-1-(2-hydroxy-3,4,6- ... ...

Abstract	Background: Chalcones are part of a family of small phenolic compounds that are being extensively studied for presenting a diversity of molecular structures and biological activities. In this paper, two chalcones, ( E )-1-(2-hydroxy-3,4,6-trimethoxyphenyl)-3-(3-nitrophenyl)prop-2-en-1-one (1), ( E )-1-(2-hydroxy-3,4,6-trimethoxyphenyl)-3-(4-nitrophenyl)prop-2-en-1-one (2), were synthesized by Claisen–Schmidt condensation. Methods: The molecular structures of these chalcones were determined by Nuclear Magnetic Resonance and characterized by infrared, Raman spectroscopy, and electrochemical analysis at room temperature. Vibrational wavenumbers were predicted using Functional Density Theory (DFT) calculations, and their normal modes were analyzed in terms of potential energy distribution (PED). Besides this, DFT calculations were performed to obtain the molecular orbitals and their quantum descriptors. The UV-Vis absorption spectrum of the synthesized chalcones was measured and compared with each other. In addition, analyses of antimicrobial activity and modulation of antibiotic resistance were carried out to assess the antibacterial potential of these chalcones. Results : The vibrational spectra of polycrystalline chalcones obtained by ATR-FTIR , FT-Raman and DFT calculations allowed a complete assignment of the vibrational modes, and revealed the quantum chemical parameters. Both chalcones did not show good responses when associated with the antibiotics Ciprofloxacin and Cephalexin against S. aureus 10 and E. coli 06 strains. However, a significant potentiating of the Gentamicin activity against S. aureus 10 and E. col 06 strains was observed for chalcone 2. On the other hand, when associated with Norfloxacin, an antagonistic effect was observed. The results found for EtBr suggest that, although the tested chalcones behave as efflux pump inhibitors, probably inhibiting other efflux pumps, they were not able to inhibit NorA. Thus, these synthetic chalcones are not recommended for use in association with ...
Keywords	chalcones ; NMR ; UV-VIS ; FT-Raman ; ATR-FTIR ; electrochemical ; Technology ; T ; Engineering (General). Civil engineering (General) ; TA1-2040 ; Biology (General) ; QH301-705.5 ; Physics ; QC1-999 ; Chemistry ; QD1-999
Subject code	540
Language	English
Publishing date	2020-07-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Utilização de eletrodos sólidos de amálgama para a determinação analítica de compostos orgânicos e inorgânicos

Djenaine de Souza / Luisa Célia Melo / Adriana Nunes Correia / Pedro de Lima-Neto / Orlando Fatibello-Filho / Lucia Helena Mascaro

Química Nova, Vol 34, Iss 3, Pp 487-

2011 Volume 496

Abstract: This review reports the use of solid amalgam electrodes in the electroanalytical determination of organic and inorganic compounds. The different types of amalgam electrodes are presented, and attention is paid to solid amalgam electrode, and here is ... ...

Abstract	This review reports the use of solid amalgam electrodes in the electroanalytical determination of organic and inorganic compounds. The different types of amalgam electrodes are presented, and attention is paid to solid amalgam electrode, and here is presented details about the pre-treatment for activation and renovation and also possible modifications in its surface. The wide potential range, higher signal-to-noise ratio, mechanical stability enabling their application in flowing systems, and principally their resistance toward passivation, indicate that the solid amalgam electrodes are environmentally friendly alternatives to mercury electrodes, without loss in the sensitivity and reproducibility in voltammetric responses.
Keywords	solid amalgam electrodes ; mercury ; environmentally friendly sensor ; Chemistry ; QD1-999
Language	English
Publishing date	2011-01-01T00:00:00Z
Publisher	Sociedade Brasileira de Química
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article: Evaluation of antioxidant action by electrochemical and accelerated oxidation experiments of phenolic compounds derived from cashew nut shell liquid

Maia, Francisco Jonas Nogueira / Francisco Wirley Paulino Ribeiro / JosÃ© Hilton Gomes Rangel / Diego Lomonaco / Francisco Murilo Tavares Luna / Pedro de Lima-Neto / Adriana Nunes Correia / Selma Elaine Mazzetto

Industrial crops and products. 2015 May, v. 67

2015

Abstract: This paper describes the use of electrochemical methods and accelerated oxidation experiments (EN 14112, Rancimat method) for the determination of antioxidant activity of phenolic compounds (cardanol, cardol and tert-butylated cardanol) derived from ... ...

Abstract	This paper describes the use of electrochemical methods and accelerated oxidation experiments (EN 14112, Rancimat method) for the determination of antioxidant activity of phenolic compounds (cardanol, cardol and tert-butylated cardanol) derived from cashew nut shell liquid (CNSL), a byproduct obtained during the processing of cashew nuts classified as a renewable raw material, natural of low-value. Through the electrochemical study, having as reference the anodic peak potential (Epa) and peak current (Ip), was observed that the cardol had the best performance, followed by tert-butylated cardanol and this by cardanol, showing that the presence of electron-donating groups as tert-butyl and hydroxyl exerts a positive influence on the antioxidant action of these compounds. These analyzes showed also that unsaturated compounds presented current values superior than saturated ones, indicating that the unsaturated molecules participate in greater number of the electro-oxidation process. The accelerated oxidation experiments were performed through analysis of biodiesel samples additivated with CNSL-based antioxidants at 500ppm, and the same sequence of activity presented by the electrochemical study was observed, showing that this class of compounds can be applied effectively to inhibit the oxidative process of biofuel.
Keywords	antioxidant activity ; antioxidants ; biodiesel ; cashew nuts ; electrochemistry ; oxidation ; phenolic compounds ; raw materials
Language	English
Dates of publication	2015-05
Size	p. 281-286.
Publishing place	Elsevier B.V.
Document type	Article
ZDB-ID	1132158-1
ISSN	1872-633X ; 0926-6690
ISSN (online)	1872-633X
ISSN	0926-6690
DOI	10.1016/j.indcrop.2015.01.034
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Eletrodegradação de Ponceau 2R utilizando ânodos dimensionalmente estáveis e Ti/Pt

Francisco Wirley Paulino Ribeiro / Sâmeque do Nascimento Oliveira / Pedro de Lima-Neto / Adriana Nunes Correia / Lúcia Helena Mascaro / Roberto de Matos / Ernesto Chaves Pereira de Souza / Marcos Roberto de Vasconcelos Lanza

Química Nova, Vol 36, Iss 1, Pp 85-

2013 Volume 90

Abstract: This paper reports the electrochemical degradation of the azo dye Ponceau 2R under galvanostatic electrolysis in the 1 to 200 mA cm-2 range at room temperature using dimensionally-stable anodes of oxygen (DSA-O2), chlorine (DSA-Cl2) and a titanium ... ...

Abstract	This paper reports the electrochemical degradation of the azo dye Ponceau 2R under galvanostatic electrolysis in the 1 to 200 mA cm-2 range at room temperature using dimensionally-stable anodes of oxygen (DSA-O2), chlorine (DSA-Cl2) and a titanium electrode of platinum coated with platinum oxide (Ti/Pt). The methodology applied was efficient for removing the color of the Ponceau 2R and the highest percentage removal of total organic carbon was obtained at 200 mA cm-2. Despite not having been observed complete mineralization, approximately80% removal of aromatic rings was estimated, resulting in drastic reduction of toxicity of the sample.
Keywords	Ponceau 2R ; DSA ; Ti/Pt ; Chemistry ; QD1-999
Language	English
Publishing date	2013-01-01T00:00:00Z
Publisher	Sociedade Brasileira de Química
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Eletrodegradação de Ponceau 2R utilizando ânodos dimensionalmente estáveis e Ti/Pt Electrodegradation of Ponceau 2R using dimensionally-stable anodes and Ti/Pt

Química Nova, Vol 36, Iss 1, Pp 85-

2013 Volume 90

Abstract	This paper reports the electrochemical degradation of the azo dye Ponceau 2R under galvanostatic electrolysis in the 1 to 200 mA cm-2 range at room temperature using dimensionally-stable anodes of oxygen (DSA-O2), chlorine (DSA-Cl2) and a titanium electrode of platinum coated with platinum oxide (Ti/Pt). The methodology applied was efficient for removing the color of the Ponceau 2R and the highest percentage removal of total organic carbon was obtained at 200 mA cm-2. Despite not having been observed complete mineralization, approximately80% removal of aromatic rings was estimated, resulting in drastic reduction of toxicity of the sample.
Keywords	Ponceau 2R ; DSA ; Ti/Pt ; Chemistry ; QD1-999
Language	English
Publishing date	2013-01-01T00:00:00Z
Publisher	Sociedade Brasileira de Química
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Optical Absorption of the Antitrypanocidal Drug Benznidazole inWater

Eveline M. Bezerra / João R. Bezerra-Neto / Francisco A. M. Sales / Ricardo P. dos Santos / Alice M. C. Martins / Pedro de Lima-Neto / Ewerton W. S. Caetano / Eudenilson L. Albuquerque / Valder N. Freire

Molecules, Vol 19, Iss 4, Pp 4145-

2014 Volume 4156

Abstract: UV-vis optical absorption spectra of the antitrypanocidal drug benznidazole solvated in water were measured for various concentrations. The spectra show a prominent peak around 3.80 eV, while deconvolution of the UV-vis optical absorption spectra ... ...

Abstract	UV-vis optical absorption spectra of the antitrypanocidal drug benznidazole solvated in water were measured for various concentrations. The spectra show a prominent peak around 3.80 eV, while deconvolution of the UV-vis optical absorption spectra revealed six bands centered at 3.60, 3.83, 4.15, 4.99, 5.60, and 5.76 eV. Benznidazole electronic transitions were obtained after density functional theory (DFT) calculations within the polarized continuum (PCM) model for water solvation. Molecular geometry optimizations were carried out, and the measured absorption peaks were related to specific molecular orbital transitions obtained within the time dependent DFT (TD-DFT) with excellent agreement between theory and experiment.
Keywords	benznidazole ; antitrypanocidal drug ; optical absorption ; TD-DFT calculations ; aqueous environment ; Organic chemistry ; QD241-441
Language	English
Publishing date	2014-04-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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