جستجوی مقالات مرتبط با کلیدواژه « alcohols » در نشریات گروه « شیمی »

‎Let G be a connected graph and S be a k element subset of the vertex set V(G)‎. ‎The Steiner-k distance d_{G}(S) between vertices of S is the minimum size among all connected subgraphs whose vertex set contains S‎. ‎In this paper‎, ‎we have defined the Steiner k-eccentric connectivity index and derived a closed formula for the same in case of some standard graphs‎. ‎Also‎, ‎we have used Steiner 3-eccentric connectivity index to predict values of boiling point of some primary and secondary amines‎, ‎cross sectional area and molar refraction of alcohols‎. ‎For each‎, ‎regression model is developed and statistical analysis is conducted and these have ensured at least 97\% accuracy‎.

This article investigates an efficient and eco-friendly protocol for protecting amines and alcohols as important molecules in organic chemistry, using Fe3O4@MCM-41/Zr@Piperazine as a newly reported magnetic mesoporous nanostructured catalyst. Firstly, the protection of alcohols was developed through their transformation to trimethylsilyl ethers. Then this reagent was applied for the acceleration of the acetylation of amines and alcohols with acetic anhydride and acetyl chloride, respectively. Finally, the influence of this highly active nanocatalyst on the formyl protection of amines was studied. The outgoings of these works illustrated the superiorities of this functionalized mesoporous mixed metal nanocatalyst in terms of accomplishing the reactions in high yields during proper reaction times and its superparamagnetic nature leading to easy separation, and several times, reusability. Highlights  1. Investigating the catalytic effect of Fe3O4@MCM-41@NH-SO3H,on some protection reactions of amino and alcoholic groups.2.  Use of a newly reported magnetic mesoporous silica nanostructured catalyst in organic reactions.3. The successful synthesis of formamides, trimethylsilyl ethers, acetamides and acetate derivatives via a green, easy and simple experimental procedure.4. Accomplishing the reactions in high yields during proper reaction times.5. Easy separation and reusability of the catalyst due to its superparamagnetic nature.

Recently, the pseudo lattice theory has been used to derive a simple linear correlation for the prediction of the surface tension of pure ionic liquids and their mixtures. That linear equation includes the parameters of coulomb interactions and the short-range interaction between the ions. In this work, a new correlation was derived for the solutions of ionic liquids in molecular solvents. The obtained correlation, predicts that the difference between the experimental surface tension and an approximated surface tension without including ion-solvent interaction, ( ) is a function of -5/3 order of molar volume.  can be calculated by using thermophysical experimental data. The linearity of the plots of  versus V-5/3 for mixtures of ionic liquids and solvents (alcohols and water) confirms the applicability of the pseudo lattice theory for these systems. The slope of the obtained lines, Bmix, is a measure of ion-solvent interaction and is independent of the temperature and mole fraction. Finally, an empirical linear relationship between Bmix and pure ionic liquid properties was extracted for each solvent. The equation of the last linear correlation is valuable for approximating and consequently, the surface tension of solutions at a varied range of temperatures and mole fractions.

Dehydration of alcohols has attracted a great deal of attention owing to its wide application in ‎several medical, pharmaceutical and chemical industries. High separation efficiency, low energy ‎consumption, simplicity and minimum contamination are the main characteristics which make ‎pervaporation (PV) a promising method in the area of alcohol dehydration to provide extremely ‎pure alcohols. Due to their permselectivity and high processability, polymers are the main ‎materials for PV membranes. For this purpose, poly(vinyl alcohol) (PVA) is the most commonly ‎used polymer because of its desired hydrophilicity, flexibility, good film-forming ability and low ‎cost. However, excessive swelling is the main challenge in fabrication of PVA membranes for ‎dehydration application; to overcome this disadvantage, various attempts have been made to ‎modify PVA membranes for separation of water and alcohols. In this paper, various ‎modifications and developments that have been made to improve the PV performance of PVA-‎based membranes for separation of water and alcohols have been reviewed.‎

Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, photochemical reactions, and redox reactions. In organic synthesis, organic reactions are used in the construction of new organic molecules. The production of many man-made chemicals such as the production of pharmaceuticals drugs, plastics, food additives, fabrics depends on organic reactions. Factors governing organic reactions are essentially the same as that of any chemical reaction. Factors specific to organic reactions are those that determine the stability of reactants and products such as conjugation, hyperconjugation, and aromaticity and the presence and stability of reactive intermediates such as free radicals, carbocations, and carbanions. An organic compound may consist of many isomers. Selectivity in terms of regioselectivity, diastereoselectivity, and enantioselectivity is, therefore, an important criterion for many organic reactions. There is no limit to the number of possible organic reactions and mechanisms. However, certain general patterns are observed that can be used to describe many common or useful reactions. Each reaction has a stepwise reaction mechanism that explains how it happens, although this detailed description of steps is not always clear from a list of reactants alone. Organic reactions can be organized into several basic types. Some reactions fit into more than one category. For example, some substitution reactions follow an addition-elimination pathway. This overview isn't intended to include every single organic reaction. Rather, it is intended to cover the basic reactions.

Reduction of aldehydes and ketones to the corresponding alcohols in the presence of sodium cyanoborohdride as reductive agent and Tonsil clay as catalyst under solvent free conditions was investigated. Tonsil (catalyst) decreased the reduction time of each aldehyde and ketone to proportional alcohols in comparison with their reduction in the absence of catalyst with high degree purity of alcohols. Reduction reactions were carried out in solvent free condition in less than 15 minutes at room temperature. All obtained alcohols from reduction of related carbonyl compounds were detected by FT-IR and 1H/13C NMR spectra.

The hazardous and toxic nature of many solvents, in particular organic solvents that are extensively used in large scale for organic reactions have transformed a serious threat to the environment. Therefore, the design of solvent-free catalytic reaction has received considerable attention during recent times in the field of green synthesis. A solvent-free or solid state reaction may be accomplished using the reactants single or merge them in clays, zeolites, silica, alumina or other substrates. Esters, thioesters and amides are important and valuable compounds in the area of industry, medicine, pharmaceutical and heterocyclic chemistry. In this paper, various solvent-free systems to synthesize esters, thioesters and amides via the acylation of alcohols, phenols, thiols and amines are described. In this review we summarized the activities presented mainly the recent years.

Efficient and selective oxidation of alcohols with NaIO4 catalyzed by an organic-inorganic hybrid material in which manganese(III)5,10,15,20-tetrakis(4-aminophenyl)porphyrin chloride, MnIII(TAPP)Cl, is covalently linked to a Lindqvist structure of polyoxometalate, Mo6O192-, at room temperature is reported. The effect of various parameters such as catalyst amount, solvent and oxidant were studied. The catalyst, MnP-POM, showed high activity not only in the oxidation of benzylic and linear alcohols but also in the oxidation of secondary alcohols and their corresponding ketones were obtained in good yields. A good selectivity observed in the case of cinnamyl alcohol and the only alcoholic group is oxidized and no epoxide was obtained. The MnP-POM catalyst is stable under the reaction conditions and While, the homogeneous MnIII(TAPP)Cl cannot recover even one time, the hybrid catalyst can be filtered and reused several times without significant loss of its initial activity. Covalent linkage of the MnIII(TAPP)Cl to the POM provide way of stabilizing the metalloporphyrin against deactivation during the catalytic cycles

By exposing to NaClO aqueous solution (commercial bleach), NiBr2 is transformed quantitatively into an insoluble nickel oxide hydroxide species. This compound contains large surface area and is a beneficial heterogeneous catalyst for oxidizing numerous organic materials. The oxidation of aldehydes and primary alcohols to carboxylic acids and secondary alcohols to ketones is showed with 1 mol % of NiBr2 catalyst and NaClO as the terminal oxidant. It is demonstrated that the controlled and selective oxidizing of numerous organic compounds with this system resulting in 55-95 % separation yields and 87-95 % purity. In most cases, the oxidations can be carried out with no organic solvent, causing this method attractive as a “greener” substitute to traditional oxidations.

In the present study, AgNO3 is employed as an effective catalyst for transesterification of β-keto esters with various alcohols under conventional and non-conventional conditions. The alcohols are easily converted into corresponding acetates in very good yields and less reaction times. However, a decrease in reaction times as well as moderate yields were observed when performed under non-conventional conditions such as Sonication and Microwave irradiation. Contrary to many other silver salts catalysts, AgNO3 has shown remarkable levels of activity and stability towards transesterification reaction. The tendency in reaction rates was found to be MWAS (3-6 min) <<< Sonication (30-45 min) <<< Conventional (8-12 hrs).

During this study, we report the green synthesis of magnetic copper ferrite nanoparticles using tragacanth gum as a reducing and stabilizing agent by the sol-gel method. The green synthesized CuFe2O4 MNPs are characterized by powder X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), vibrating sample magnetometer (VSM) and scanning electron microscopy (SEM). The X-ray powder diffraction (XRD) analysis revealed the formation of Cubic phase ferrite MNPs with average crystallite size of 14 nm. This study has demonstrated that CuFe2O4 nanoparticles can act as an efficient catalyst for selective oxidations of alcohols applying oxone (potassium hydrogen monopersulfate) as oxidant in the presence of acetonitrile as solvent at 40 ºC. Primary and secondary alcohols gave the corresponding products in good yields. Furthermore, the catalyst can be simply recovered and reused several times with almost no loss in activity.

Unsubstituted phthalocyanines of Co, Fe and Mn supported on zinc oxide nanoparticles were prepared and were well characterized with X-ray diffraction and scanning electron microscopy. The oxidation of alcohols with tert-butylhydroperoxide, in the presence of metallophthalocyanines supported on zinc oxide nanoparticles was investigated. These MPc/ZnO nanocomposites were effective catalysts for the oxidation of alcohols such as cyclohexanol (83.4% conversion; 100% selectivity), benzyl alcohol (70.5% conversion; 100% selectivity) and hexanol (62.3% conversion; 100% selectivity). The influences of reaction time, various metals and type of substrates and oxidants on the oxidation of alcohols were also studied, and optimized conditions were investigated. Under these reaction conditions, the activity of the catalysts decreases in the following order: CoPc/nano-ZnO > FePc/nano-ZnO > MnPc/nano-ZnO. It shows that TBHP is more efficient oxidant due to weaker O-O bond with respect to H2O2 and the following order has been observed for the percentage of conversions of alcohols: 2º > benzylic > 1º.

Densities and viscosities of binary mixtures of methyl tert-butyl ether (MTBE) with 1-alkanols include 1-butanol, or pentanol, or hexanol, or heptanol were measured as a function of composition from 293.15 to 308.15 K at atmospheric pressure. The temperatures studied were 293.15, 298.15, 303.15 and 308.15 K. The experimental results have been used to calculate the viscosity deviation Dh and volumetric properties such as , and . Both and Dh values were negative over the entire range of mole fraction for all temperatures and systems studied. The results for all volumetric and viscometric properties are discussed on the basis of molecular interactions between the components of the mixtures.

Triethylammonium halochromates are easily synthesized by addition of triethylamine to aqueous solutions of CrO3 and HX (X= F, Cl), and show ability in the oxidation of alcohols to their corresponding aldehydes and ketones under microwave irradiation.

Nanomagnetic NiFe2O4 was used as the efficient, stable, reusable catalyst for selective oxidation of alcohols to their corresponding carbonyl compounds using oxone (potassium hydrogen monopersulfate) as oxidant in the presence of water as solvent at room temperature. The oxidation of various primary and secondary alcohols has been examined and related corresponding products were obtained with good yields. The catalyst was investigated with XRD, SEM, ICP and IR techniques. Furthermore, the catalyst could be easily recovered and reused for several times without loss of activity.

A mild, efficient and fast method for the oxidation of alcohols and trimethylsilyl, tetrahydropyranyl and methoxymethyl ethers to their corresponding carbonyl compounds using CrO3 in the presence of rice husk ash (RHA) is reported. All reactions were performed at room temperature in high to excellent yields. A new, efficient and green catalyst, heterogeneous reaction conditions, easy work-up of the products and high reaction rates are the main advantages of this method.

Zinc ferrite (ZnFe2O4) nanoparticles were synthesized via the auto-combustion assisted sol-gel method of Zn2+ and Fe3+ ions (molar ratio 1:2) in ammonia solution. The prepared nanomagnetic catalyst was characterized by IR, XRD, SEM and ICP. The diameter of the ZnFe2O4 MNPs (63.7 nm) was determined by Debye-Scherre equation via their XRD pattern. Nanomagnetic ZnFe2O4 efficiently catalyzes oxidation of alcohols and gave the corresponding carbonyl-containing products in good yields. The reactions were carried out in an aqueous medium at r.t in the presence of oxone (potassium hydrogen monopersulfate) as an oxidant. In addition, the catalysts could be reused up to 5 runs without significant loss of activities.

A mild, efficient and fast method for the oxidation of alcohols and trimethylsilyl and tetrahydropyranyl ethers to their corresponding carbonyl compounds using CrO3 in the presence of sulfonic acid functionalized ordered nanoporous Na+-montmorillonite (SANM) and under solvent-free conditions is reported. All reactions were performed at room temperature in high to excellent yields. Ease of the preparation and handling of the catalyst, heterogeneous conditions, easy work-up of the products and high reaction rates are the main advantages of this method.

In this research, different alcohols and phenols are subjected to the reaction with HMDS in the presence of ionic liquid and silica-supported catalysts. Silylation was accomplished under mild reaction conditions at room temperature in short reaction times and good to excellent yields.