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  • 52 Reads
The Influence of Methyl Group Position on the Chemical Shifts Values of all Protons in the 1H NMR Spectra of Trimethylalkane Molecules
In our previous researches (see ECSOC-16, 2012 and ECSOC-17, 2013) we found the interesting dependencies of the protons chemical shift values in unsubstituted, mono- and dimethylsubstituted linear alkanes NMR 1H spectra upon the position of methyl group. In continuation of this topic we begin the investigation of the similar dependencies in trimethylsubstituted linear alkanes. In this paper we describe only four simplest families of trimethylalkanes. The position of the each methyl group in the alkyl chain of trimethylalkanes denoted by the symbol «N1, N2 and N3», indicating the number from the beginning of the chain of carbon atoms to which three "methyl substituents" are attached. For this purpose we have studied and analyzed the literature data of proton chemical shifts in the 1H NMR spectra of four "trimethylalkane families": 2,2,5- (N1 = 2; N2 = 2; N3 = 5); 2,2,4-; 2,2,3- and 2,3,4-trimetyllalkanes. We compared the protons chemical shift values (base spectral parameters) of the same type of protons. For example, for triprotonic signal of terminal methyl groups in the studied trimethylalkane on the one hand, with the studied earlier the same parameters of terminal methyl groups in a) unsubstituted linear alkane, b) monomethylalkane and c) dimethylalrane on the other hand. We fixed the differences between the compared chemical shifts (ie, differential spectral parameters) only for the cases when this difference is equal or exceeds a value equal to 0.02 ppm. These values of the differential spectral parameters we have identified as "significant" (ie, to be discussed). When researching all four families of N1,N2,N3-trimethylalkanes we reveal that only in the case of 2,2,5-trimethylalkane family the chemical shifts of all protons in molecule we can considered as the sum of two previously studied parameters of nonoverlapping pentacarbonic [С1Н12-С2(СН3)(СН3)–С 3Н 32-] and tetracarbonic [–С4H42-C5H5(C5'H5'3)-С6H62-] fragments. In the other two cases of 2,2,N3- trimethylalkanes, when both of these fragments overlap, depending on the relative position of the third methyl group in the molecule must be considered the "octacarbonic" fragment [С1Н13-С2(С2'Н2'3)(С2''Н2''3)–С3Н32-С4Н4(С4'Н4'3)–С5Н52-] as the whole moiety in 2,2,4-trimethylalkanes and "heptacarbonic" fragment [С1Н13-С2(С2'Н2'3)(С2''Н2''3)–С3Н3(С3'Н3'3)-С4Н42–] in 2,2,3-trimethylalkanes. Similarly in the case of last forth family of 2,3,4-trimethylalkanes we consider as the whole moiety another "octacarbonic" fragment [С1Н13-С2H(С2'Н2'3)–С3Н3(С3''Н3''3)-С4Н4(С4'Н4'3)–С5Н52-].We calculate and discuss the mean base and differential spectral parameter values for each protons type in these "polycarbonic fragments" in each of the studied trimethylalkane families.
  • Open access
  • 205 Reads
An Efficient Procedure for Development of Levofloxain Hemihydrates Synthesis and Purification
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Levofloxacin is a broad spectrum synthetic fluoroquinolone antibiotic and is used to treat infections including: respiratory tract infections, cellulites urinary tract infections, prostatis, endocarditis, meningitis, pelvic inflammatory disease, traveler's diarrhea, tuberculosis and plague. Levofloxacin is the S-enantiomer of a racemate, named ofloxacin.Many synthetic routes for preparing levofloxacin have been reported. Most of them involved using non-feasible reagents, high temperature during synthesis, non-recyclable, costly and poisonous solvents. Therefore, the selection of an inexpensive, recoverable and non-toxic medium for synthesis with high yield and also having minimum negative effect on the environment is of prime importance in industrial scale. Levofloxacin is produced by the reaction of (S)-(-)-9, 10-difluoro-3-methyl-7oxo-2, 3-dihydro7H-pyrido [1, 2, 3-de] [1, 4] benzoxazine-6-carboxylic acid with N-methyl piperazine in a polar solvent, preferably at a technically acceptable temperature to form levofloxacin in an industrially feasible yield. The pure levofloxacin is used as hemihydrates, which has the empirical formula of C18H20FN3O4 ½ H2O.Herein, we wish to investigate the effect of various solvent systems on the yield of reaction. Depends on the solvent to be used, different temperature and reaction time for synthesis is considered. The best solvent will be selected based on the comparison of the measured yields and also the ability of recovering it in order to use for next batches. Another aspect of the present research is to develop an efficient method for purification of crude levofloxacin and convert it to hemihydrates form, which is stable and can be used as an API (Active Pharmaceutical Ingredient). The selection of solvent and also the amount of water to be used in purification step in order to change crystalline structure is very important, which will be investigated in this section. The results show that using DMSO for synthesis and Ethanol/Water for purification step are the best choices.
  • Open access
  • 64 Reads
Preparation, Characterization and Microwave Absorption Performance of Ba(Ni0.5Mn0.5ZrO)Fe10O19/ Polybutadiene Nanocomposite
The magnetic materials, especially ferrites, are an important class of electromagnetic waves absorbers especially, at the range of gigahertz (GHz) frequency. Conventional absorptive materials such as metal powders and ferrites are high in density and have poor environmental stability, which restricts their usefulness in applications requiring light- weight mass . One way to overcome these problems is to use a suspending agent, which could enwrap magnetic nanocparticles and the PBD provides both electrostatic and steric repulsion against particle aggregation. Also fabrication of flexible and transparent shielding structures could widen the range of application.In this paper, Ba(Ni.5Mn0.5ZrO)Fe10O19/ Polybutadiene magnetic nanocomposite was fabricated successfully via sol-gel method and masking method. The samples were characterized using SEM, UV-visible, EDX, ATR, XRD and VSM analyses. Finally vector network analyzer was employed to determine the ability of composites in microwave absorption at the range of 8-12 GHz (X-band). The results demonstrated the transparent shielding products have considerable capability in attenuation of electromagnetic wave and a minimum reflection loss of 9.1 db was obtained at 10.4 GHz for ferrite/PBD 10wt%.
  • Open access
  • 61 Reads
Triplet-Singlet Intersection at Hydrogen Transfer Stage in Reactions of Organic Sulfides Photooxidation
Methanethiol and hydrogen sulphide photooxidation reaction pathways contain stages of hydrogen transfer, after which intersection crossing supposed to be to achieve singlet products of the reaction. While studying this stages no minimum was found at the point near reactants in the singlet state. At the same time there is a minimum in the triplet state. Moreover energy of reactants in the singlet state exceeds energy in the triplet state. That observation allows us to suppose intersection between the singlet and the triplet potencial energy surfaces at the hydrogen transfer stage. It may increase chance of the triplet-singlet transition. Calculation of the potencial energy surface profiles, sliced along with the hydrogen transfer path for both the singlet and the triplet states, performed with UB3LYP 6-311G++(d) method of the density functional theory have showed both existence and reaction coordinate of intersection.
  • Open access
  • 147 Reads
Citric Acid as an Organic Complexing/Fuel Agent for the Synthesis of Ce Doped Co–Zn Ferrite Nanoparticles
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Complexant organic agents can effectively chelate metal ions with varying ionic sizes. They also serve as reductant being oxidized by nitrate ions, thus working as fuel in a synthetic method named auto combustion sol-gel. However, citric acid (C6H8O7) is most frequently used in producing in large variety of ferrites. It is inexpensive and is a more effective complexing agent than other complexant producing fine ferrite powder with smaller particle size. The spinel ferrites are unique materials exhibiting ferrimagnetic and semiconductor properties and can be considered as magnetic semiconductors. Among different ferrite materials, Co0.5Zn0.5Fe2O4 with a spinel structure are attractive for the biomedical application as a result of suitable Curie temperature, magneto crystalline anisotropy, moderate saturation magnetization and super paramagnetic behavior at room temperature. The interactions between the ions, when they are substituted with various metal cations allows some tunable changes in the electrical and magnetic properties of nanoferrites. In current work, citric acid as a complexant/fuel agent was used for the synthesis of Co0.5Zn0.5Ce0.05Fe1.95O4 ferrite sample based on the sol–gel auto combustion method. It is important to select appropriate complexant additives for phase formation by the auto-combustion method. The elemental analysis of the sample was carried out by using energy dispersive X-ray spectrometer (EDAX).The XRD and FT-IR studies show the formation of one spinel phase, the SEM showed the spherical nanoparticles. The magnetic properties have been measured at room temperature by a Vibrating Sample Magnetometer (VSM).
  • Open access
  • 277 Reads
Synthesis and Properties of a New Ionic Liquid Which Jellyfies at Room Conditions
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In this communication the synthesis and physical properties of the new ionic liquid 1-ethyl-3-methyl imidazolium decyl sulfate, are shown. The interest of this new salt lies in its tendency to jellify when it is exposed to the atmosphere by absorbing water from moisture up to about a 10% of its own mass; then it keeps the mass ±2% stable depending on the atmospheric humidity grade. The rigid-gel state appears from 15 ºC to 60 ºC. Below 15 ºC it crystallizes and above 60 ºC it liquefies. According to TGA measurements the compound is stable up to 300ºC. 1-ethyl-3-methyl imidazolium decyl sulfate was prepared in two steps. First the alkylation of 1-methylimidazole with diethyl sulfate afforded 1-ethyl-3-methylimidazolium ethyl sulfate. Then a later trans-esterification reaction allowed obtaining the desired 1-ethyl-3-methyl imidazolium decyl sulfate with high yield and purity. Its structure was confirmed by 1H, 13C NMR and IR spectroscopy as well as Mass Spectrometry. The FTIR spectrum of this new compound, and the temperature behavior of some physical properties such as electrical conductivity, viscosity, density and refractive index, will be presented.
  • Open access
  • 93 Reads
Application of Aminocoumarins for the Role Offluorescent Molecular Probe of Cationic Photopolymerization Process
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Coumarin (benzo-α-pyrone) derivatives are wide and very important group of chemical compounds. Today, they are used in many areas of industry and science. Due to their low toxicity, there is the possibility of use coumarins in biology, medicine, perfumery and cosmetics industry. Coumarin derivatives have interesting ability to emit fluorescence in the visible range upon excitation of the molecule to a higher energy level after exposure of UV radiation. Coumarin substitution of certain functional groups (including the amino group) can affect the fluorescence shift to shorter or longer wavelengths.In this research an attempt has been made to demonstrate the use of the technique of molecular fluorescence probe FPT (Fluorescence Probe Technology) to monitor the cationic photopolymerization process of the triethylene glycol divinyl ether (TEGDVE), using for that purpose ten commercially available coumarin derivatives: Coumarin 1, Coumarin 120, Coumarin 102, Coumarin 153 and Coumarin 6H. Spectroscopic characteristics of all chemical compounds were investigated, which included measurements of absorbance and fluorescence characteristics. Then, in the spectroscopy studies, the changes of the probe fluorescence were collected, monitoring the physicochemical changes occuring in the composition, ie. changes of both microviscosity and polarity of enviroment in which the coumarin probe was located. The utility of the aminocoumarins for the monitoring of progress of photopolymerization reactions was tested using fluorescence intensity ratio R, the probe sensitivity S and the number of progress of the reaction β. Obtained results revealed that the majority of the compounds tested can be successfully qualified for the role of molecular fluorescent probes capable of monitoring the cationic photopolymerization. It has been found that the presence of amino groups in the basic structure of the coumarin derivative is not a factor limiting the usefulness of these compounds as molecular probes of FPT method. Acknowledgment Research financed within the project LIDER(LIDER/014/471/L-4/12/NCBR/2013) by The National Centre for Research andDevelopment (NCBiR)
  • Open access
  • 94 Reads
Theoretical Study of the Solvent Effect on the properties of Indole‑Cation‑Anion Complexes
The properties of ternary indole-cation-anion (IMX) complexes are theoretically studied as simplified models of real systems in which some of the fragments used are parts of bigger and complicated structures, like proteins. The electro-neutrality of real systems and the presence of ions of both charges interacting simultaneously with aromatic residues in the proteins modeled justify the move from cation-π or anion-π (non-bonding interactions analyzed by our group in previous studies) to cation-π-anion complexes. With the intention of approaching more the model to reality, the solvent was also included in the study: aqueous solvent was represented by a combination of PCM + explicit addition of one water molecule to some IMX complexes. As model systems for this study the complexes with indole and the following cations and anions were selected: M = Na+, NH4+; X = HCOO–, NO3– or Cl–. The effect of the solvent was studied not only on the energy but as well on some structural parameters like the proton transfer from the ammonium cation to the basic anion and the cation-anion separation. The results indicate that the PCM method alone properly reproduces the main energetic and geometrical changes, even at quantitative level, but the explicit hydration allows refining the solvent effect and detecting cases that do not follow the general trend.
  • Open access
  • 109 Reads
A Highly Efficient Synthesis of 2,4,5-Trisubstituted Imidazoles Catalyzed by Composite Magnetic Nanoparticle Under Mild Reaction Conditions
Recently, the design and applications of new methods in organic synthesis based on multicomponent reaction (MCRs) is attracted academic and industrial research groups. On the other hand, imidazoles are a very interesting class of heterocyclic compounds, because they have many pharmacological properties such as angiotensin inhibitors, anti-inflammatory, glucagon antagonist, antiviral, antimicrobial, fungicidal and etc. Progress in nanoscience and nanotechnology have attracted researchers toward the synthesis of functional magnetic nanoparticles (MNPs), which is one of the most active research areas in advanced materials. MNPs that have unique magnetic properties and other functionalities have enabled a wide spectrum of applications. Magnetic nanocatalysts can easily be separated and recycled from the products by an external magnet. Moreover, their catalytic performance is improved, for the available surface area of the nonoporous MNPs is external and the internal diffusion is practically avoided.In continuation of our interest in the application of new catalysts in organic synthesis via MCRs, herein, an efficient and highly selective synthesis of substituted imidazoles has been developed by the condensation of benzil or benzoin with various substituted aldehydes and ammonium acetate using urea-functionalized Fe3O4@SiO2 magnetic nanoparticles as a catalyst under mild reaction conditions and excellent yields.