Dr. Oscar Jaime Restrepo Baena
Department of Materials and Minerals, School of Mines, Universidad Nacional de Colombia, Colombia.

ISBN 978-93-90768-24-0 (Print)
ISBN 978-93-90768-25-7 (eBook)
DOI: 10.9734/bpi/cpcs/v8

This book covers key areas of chemical science research. The contributions by the authors include N-acetylated gemini surfactants, antifungal activity, leather preservatives, soyphospholipid, esterification, antioxidant activity, Alzheimer's disease, X-ray diffraction, preclinical studies, heat-recovery steam generator, protective film, thermal-shock, equivalent operating hours, metal conductivity, multilayer protective films, thermal resistance, hydro-absorption capacity, dynamic laser speckle,  Peleg´s equation, natural zeolite, water mobile phase, chromatographic separations, thermogravimetric analysis, chitosan, scanning electron microscopy,  microwave afterglows, atom density. This book contains various materials suitable for students, researchers and academicians in the field of chemical sciences.


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Design and Synthesis of N-acetylated Gemini Surfactants for Use as Leather Preservatives during the Chrome-tanning Process

Laura Marcela Machuca, María Florencia Acuña Ojeda, Carolina Guadalupe Gutierrez, Marcelo César Murguía

Current Perspectives on Chemical Sciences Vol. 8, 22 February 2021, Page 1-12

A series of N-acetylated non-ionic and cationic gemini surfactants (3a-f) were synthesized and their antifungal potency and surface properties further determined. Critical micelle concentration (CMC), effectiveness of surface tension reduction (gCMC), surface excess concentration (G), and area per molecule at the interface (A) were also determined and the resulting values indicate that the cationic series is characterized by good surface-active and self-aggregation properties. The aim of this work was to compare two novel antifungal agents with 2-(thiocyanomethylthio)-benzothiazole (TCMTB). For this study, two gemini surfactants (3b and 3e) were efficiently prepared and formulated. The antifungal potency of these compounds was tested and their effectiveness as leather preservatives during the chrome-tanning process was assessed using the environmental chamber test (ASTM D 3273-00 Standard) and wet-blue hides on a plate with culture medium (ASTM D 4576-08 Standard). Two strains were used to perform the study: Aspergillus niger ATCC 6275 and Penicillium citrinum ATCC 9849. 3b and 3e showed the ability to preserve hides because of their antifungal activity present in chromium tanning specimens. Compound 3e was found to be a more potent antifungal than compound 3b, but not as potent as TCMTB. This cationic gemini compound (3e) was less toxic than TCMTB for Daphnia magna as a biological model. This work is the result of a patent of invention registered in the patent offices from Argentina.

The fatty acid composition (FAC) of both soyphospholipid (SPL) and coconut oil (CO) was modified by enzymatic interesterification simultaneously. Significant modifications were observed in FAC where in modified soyphospholipid (MSPL), the extent of incorporation of caprylic, capric and lauric acids were 5.735 ± 0.31%, 14.39 ± 0.15% and 7.945 ± 0.13% respectively and in modified coconut oil (MCO) the extent of incorporation of linoleic and linolenic acids were 6.625 ± 0.3% and 1.58 ± 0.35%. Other properties in terms of antioxidant activity of the modified products were determined and significant changes were detected compared to the original SPL and CO. The surface active property such as surface tension was measured in case of modified soyphospholipid (MSPL) product that got reduced by about 4 units. This lowering of surface tension for MSPL can be useful as an emulsifier effective for food use.

Alzheimer's disease, a chronic neurodegenerative disease which usually starts slowly and worsens over time. Alzheimer's disease individuals exhibit retrogression in mental health functions rendering them incapacitated and unable to perform normal daily activities. Elderly persons are the ones commonly afflicted with this disease. However, evidence shows that it can also afflict even individuals as young as 40 years of age. It is a kind of dementia has no cure and in time leads to death. Donepezil is a well-known drug used to treat Alzheimer's disease. Donepezil hydrochloride is the second drug approved by the United States food and drug administration (FDA) for the treatment of mild to moderate alzheimer's diseases (AD). It is a new class of acetyl cholinesterase (AChE) inhibitor having an N-benzylpiperidine and an indanone moiety that shows longer and more selective action. Donepezil HCl, a piperidine derivative, is a highly selective inhibitor of the enzyme AChE that is chemically unique from other AChE inhibitors. In vitro and preclinical studies have demonstrated that Donepezil is much more selective for AChE in the brain than for butyrylcholinesterase (BuChE) in the periphery. Various methods for the synthesis of donepezil and an improved, industrially scalable total synthesis are presented in this chapter. Physical properties and pharmacology are also included.

One of the main critical elements affecting the resource of combined cycle power plants (CCPP) heat recovery steam generators (HRSG) is the outlet high-pressure superheater header. The protection of headers, heat-exchange pipes, steam pipelines from corrosion is carried out by maintaining the correct water-chemical regime, which causes the formation of thin protective films. The combination of a protective film layer and a layer, for example, of heating steam condensate on the inner surface of pipelines with a heat carrier flowing inside, creates a significant thermal resistance of the multilayer wall and helps to reduce thermal stresses arising in them under variable conditions. These protective films, which protect pipes from corrosion, are formed on the inner surfaces of CCPP heat recovery steam generators pipe systems at temperatures above 230°C and good deaeration.

The paper presents the results of computational analysis of the effect of thin multilayer protective films on the CCPP HRSG headers and steam pipelines thermal stress state under various variable operating conditions, in particular, during start-ups from various thermal states and thermal shocks. Calculations were carried out at different film thicknesses and under the condition that their thermal conductivity is lower than the thermal conductivity of base metal. As a result of the calculations, it was possible to determine the heating modes of headers and steam pipelines, for which the protective films influence is the greatest.

It is shown that multilayer protective films noticeably affect the stresses arising in the pipe and the accumulation of damage, mainly at large temperature disturbances (during thermal shocks).

The effect of protective films on the non-heated pipes thermal stressed state was evaluated in terms of reducing resource consumption and accumulating equivalent operating hours under variable modes. It is shown that the resource of a high-pressure superheater outlet header 426 x 34 mm can be increased by 6 % only due to the presence of a protective film 50 microns thick with a thermal conductivity equal to half the thermal conductivity of the base metal.

Hydro-adsorption and Textural Properties Study of Microporous Zeolites by Dynamic Laser Speckle Technique

Ruth D. Mojica-Sepulveda, Luís J. Mendoza-Herrera, Eduardo Grumel, Delia B. Soria, Carmen I. Cabello, Marcelo Trivi, Myrian Tebaldi

Current Perspectives on Chemical Sciences Vol. 8, 22 February 2021, Page 50-66

Adsorption phenomena have various technological applications such as desiccants, catalysts and gas separation. Its uses depend on the textural properties of the solid adsorbent and the type of liquid or gas adsorbed. Therefore, it is important to find simple tools to measure these properties. The most common measurement methods are physicochemical based on N2 adsorption to determine the specific surface area and pore size distribution. However, these methods have certain limitations for microporous materials.

This chapter shows the use of the Dynamic Laser Speckle (DLS) technique to measure and compare the hydro-adsorption capacity of a microporous natural zeolite and its acidic, basic and calcinated forms. According to the water adsorption process of the samples, the DLS experimental results show the temporal evolution of the speckle patterns. The optical results obtained from the speckle patterns are adjusted using an improved Peleg´s equation. This new approach by the adsorption of water from solids allows a correlation with its specific surface areas where parameters obtained from DLS results are calibrated with those calculated by different conventional isotherms using the N2 adsorption-desorption method.

This paper describes a harmless HPLC technique for detecting imidacloprid (ICP) and its metabolite, 6-chloronicotinic acid (6CA), using an isocratic 100% water mobile phase. Chromatographic separations were performed a Daisopak® SP-200-3-C1-P with water mobile phase and a photodiode-array detector. The total run time was < 6 min. The system suitability was well within the international acceptance criteria. The detection limits were 0.018 ?g/ml for ICP and 0.005 ?g/ml for 6CA, respectively. As the first examination problem in the establishment of an international harmonized method for the residue monitoring of ICP and 6CA, this paper describes an isocratic 100% water mobile phase HPLC conditions to detect ICP and 6CA. A harmless HPLC method for simultaneous detecting ICP and 6CA was developed and may be further applied to the quantification in animal-derived foods.

Research on Sustainable Conversion of Agriculture and Food Waste into Activated Carbons Devoted to Fluoride Removal from Drinking Water in Senegal

Mohamad M. Diémé, Maxime Hervy, Saïdou N. Diop, Claire Gérente, Audrey Villot, Yves Andres, Courfia K. Diawara

Current Perspectives on Chemical Sciences Vol. 8, 22 February 2021, Page 73-87

The objective of this study was to investigate the production of activated carbons (AC) from cashew
shells, and millet stalks and their efficiency in fluoride retention. These agricultural residues are
collected from Senegal. It is known that some regions of Senegal, commonly called the groundnut
basin, are affected by a public health problem caused by an excess of fluoride in drinking water used
by these populations. The activated carbons were produced by a combined pyrolysis and activation
with water steam; no other chemical compounds were added. Then, activated carbonaceous materials
obtained from cashew shells and millet stalks were called CS-H2O and MS-H2O respectively. CS-
H2O and MS-H2O show very good adsorbent features, and present carbon content ranges between
71% and 86%. The BET surface areas are 942 m2:g????1 and 1234 m2:g????1 for CS-H2O and MS-H2O
respectively. A third activated carbon produced from food wastes and coagulation-flocculation sludge
(FW/CFS-H2O) was produced in the same conditions. Carbon and calcium content of FW/CFS-
H2O are 32.6 and 39.3% respectively. The kinetics sorption were performed with all these activated
carbons, then the pseudo-first equation was used to describe the kinetics sorption. Fluoride adsorption
isotherms were performed with synthetic and natural water with the best activated carbon from
kinetics sorption, Langmuir and Freundlich models were used to describe the experimental data.
Regarding equilibrium data, the experimental data are better described by Langmuir model than by
the Freundlich model. The results showed that carbonaceous materials obtained from CS-H2O and
MS-H2O were weakly efficient for fluoride removal. With FW/CFS-H2O, the adsorption capacity is
28:48 m2:g????1 with r2 = 0:99 with synthetic water.

Bio Based Paper Coatings Containing Protein, Polysaccharide and Essential Oil

Urška Vrabic Brodnjak

Current Perspectives on Chemical Sciences Vol. 8, 22 February 2021, Page 88-102

Modifications of the packaging paper surface play an important role in a variety of industries, especially in the food sector. In general, packaging paper can be exposed to many external environmental influences such as humidity, temperature, stress, forces, pressure and chemical impacts, etc. Therefore, modifications of the paper surface play an important role in a variety of industries.  Namely, unmodified paper has poor water and oil resistance due to its porous structure. In the study, packaging paper was successfully coated with six different coating solutions containing combinations of chitosan, zein and rosemary essential oil. The chitosan and zein were actually coated in two layers; the mixed chitosan-rosemary oil and the mixed zein-rosemary oil were each applied as one layer to the paper. The results showed increased oil barrier properties in the papers coated with mixed zein-rosemary oil and reduced water permeability in the papers coated with chitosan-rosemary oil coating solution. The result of this two-layer coating showed excellent water (Cobb60 value of 2.18 g/m2) and oil barrier properties. All coated papers showed high thermal stability, especially those coated with chitosan, zein and rosemary oil as layer-by-layer. Scanning electron microscopy was used to verify the surface differences of the coated papers, such as closed structure, pores and smoother surface, especially in layer-wise coated samples. Due to the good mechanical and chemical properties, coated papers with rosemary oil can be used in many applications, possibly also in the field of repellents. In the future, the effect of the analysed dual coating against insect infestation will be analysed.  

N, H and C-atoms Density in Flowing Afterglows of Microwave R/N2-H2 and R/N2-CH4 Discharges with R=N2, He, Ar and Applications to TiO2 Surface Nitriding

A. Ricard, J. Amorim, M. Abdeladim, J. P. Sarrette, Y. K. Kim

Current Perspectives on Chemical Sciences Vol. 8, 22 February 2021, Page 103-143

Variations of N,H and C-atoms density have been determined along the reduced pressure flowing afterglows of microwave R/N2-H2 and R/N2-CHdischarges with R=N2, He and Ar. Density of H and C-atoms and other nitrogen active species such as  N2(A), N2(X,v>13), N2+,NH, N(2D), CN were obtained from that of  N-atoms calibrated by NO titration , using the method of band intensity ratios in several conditions (between early and  late afterglows). It has been obtained in addition the density of O-atoms and NO molecules coming from air impurity. It has been deduced the wall destruction probability of  H, O and C-atoms on the quartz afterglow tube: ?HR,N2  = (1-3) 10-3 , ?OR,N2  =(0.4-1) 10-3 and ?CN2=(0.7) 10-3. The effects of H and C –atoms on N-atoms inclusion inside TiO2 surfaces are reported.

Experimental and Theoretical Investigations of Some Tridentate Substituted Salicylaldimines

Abidemi Iyewumi Oloyede-Akinsulere, Jelili Olalekan Babajide, Simon Olonkwoh Salihu

Current Perspectives on Chemical Sciences Vol. 8, 22 February 2021, Page 144-158

Five substituted tridentate salicylaldimines, (E)-2-((2-hydroxybenzylidene)amino)phenol, (E)-2-(((2-hydroxyphenyl)imino)methyl)-4-nitrophenol, (E)-4-chloro-2-(((2-hydroxyphenyl)imino)methyl)phenol, (E)-2-(((2-hydroxyphenyl)imino)methyl)-4-methoxyphenol, (E)-4-bromo-2-(((2-hydroxyphenyl)imino) methyl)-6-methoxyphenol were synthesized and characterized by elemental analysis, IR, UV and NMR (1H and 13C). Moreover, theoretical calculations using density functional theory were performed on the optimized structures of the salicylaldimines to augment the experimental data. The antibacterial potentials of the compounds were evaluated by agar-well diffusion method and the total antioxidant capacities determined by phosphomolybdenum assay. The result showed that the methoxy-substituted compound exhibited the highest antibacterial and antioxidant activities while the nitro-substituted compound exhibited the least activities. This implies that the electron donating group on the compound increases its antibacterial and antioxidant activities.