Alkylated phenols and their derivatives are important materials in both organic synthesis and chemical manufacturing. Mono-alkylphenols and di-alkylphenols are used as raw materials for the manufacture of a wide variety of products such as resins, wire enamels, varnishes, printing inks, antioxidants, flame retardants, ultraviolet absorbers, fungicide, petroleum additives and rubber chemicals [1-17]. Friedel–Crafts alkylation of phenol with tert-butyl alcohol (TBA) produces 2-tert-butylphenol (2-TBP), 4-tert-butylphenol (4-TBP), 2,4-di-tert-butylphenol (2,4-DTBP), 2,6-di-tert-butylphenol (2,6-DTBP) and tert-butylphenol ether (TBPE), depending on both the catalyst and the reaction conditions. Based on previous researches, it is well known that moderate acid catalysts or high reaction temperature led to carbon alkylated products and TBPE is produced in the presence of weak acidic catalysts as a major product. 2-TBP is the jarless product of alkylation of phenol with TBA owing to the presence of phenolic (–OH) group on the aromatic ring that kinetically favours o-alkylation. However, due to steric hindrance, thermodynamically unfavoured o-isomer (2-TBP) is readily isomerized into less hindered p-isomer (4-TBP), especially in moderate acidic media. If strong acid catalysts are used in the alkylation reaction, 2,4-DTBP is a dominant product [17,18]. 2,4-DTBP is used in the manufacture of its triphosphite and benzotriazole, which are employed as a co-stabilizer for PVC or UV absorbers in polyolefins [12,13]. 2-TBP is an intermediate for pesticides, fragrances and antioxidants [14]. High selectivity toward 4-TBP is favored since this product imparts enhanced properties to the class of metallic detergents (phenates) used in lubricating oil... ... middle of paper ... ...rt-butylation of phenol and few studies on the solvent free alkylation of phenol with TBA have been published [9,51,52]. Therefore, in continuation of our researches to introduce the efficient and green catalysts [53-58], we investigated alkylation of phenol and some substituted phenols with TBA over ZP nanoparticles under solvent free conditions. The reaction conditions such as amount of the catalyst, reaction time, temperature and mole ratio were investigated in details. Also, we have investigated this alkylation over P2O5/Al2O3, P2O5/SiO2 and α-ZrP (prepared in the absence of the polymers) and the results were compared with those were obtained from ZPA and ZPP. In comparison with the other reported methods, the following advantages are achieved: (1) higher conversion of phenol, (2) better selectivity toward 4-BTP and (3) easy recovery of the product and catalyst.
Beryllium is a highly toxic metal and if exposed to it, at or above the threshold values, it can lead to a chronic beryllium disease (CBD) (i.e. berylliosis) or an acute beryllium disease. Toxic exposure to beryllium is most often thru an inhalation pathway. Beryllium has a variety of effects. Some beryllium combines with a protein and is deposited in the liver, spleen and kidneys, but the beryllium when bound with a biological protein, a hapten, can result in the chronic form of the disease which is believed to be a delayed hypersensitivity immune response. The major toxicological effects of beryllium are on the respiratory tract,specifically the lungs and their alveoli.
Earlier in history, from about the time zinc was discovered, or, from the 12th century, zinc was used in many ways. Starting in that same time period, zinc was brought into the industry and was used to improve peoples lives. In 1374 in India, when it was officially recognized as the eighth metal known to man, it was being used for medicinal purposes, such as a cure for sore eyes and healing wounds on the body.
The spots moved 3.8cm, 2.3cm, 2.1cm, 1.8cm, and 2.5 cm, for the methyl benzoate, crude product, mother liquor, recrystallized product, and isomeric mixture, respectively. The Rf values were determined to be.475,.2875,.2625,.225, and.3125, for the methyl benzoate, crude product, mother liquor, recrystallized product, and isomeric mixture, respectively. Electron releasing groups (ERG) activate electrophilic substitution, and make the ortho and para positions negative, and are called ortho para directors. In these reactions, the ortho and para products will be created in a much greater abundance. Electron Withdrawing groups (EWG) make the ortho and para positions positive.
As a final point, the unknown secondary alcohol α-methyl-2-naphthalenemethanol had the R-configuration since it reacted the fastest with S-HBTM and much slower with R-HBTM. TLC was a qualitative method and ImageJ served as a quantitative method for determining which reaction was the faster esterification. Finally, 1H NMR assisted in identifying the unknown from a finite list of possible alcohols by labeling the hydrogens to the corresponding peaks.
Zinc is known to prevent and treat the intoxication of lead which often proves more effective along with the combination of methionine or thiamine (Flora et al., 1989; 1991). Supplementation of zinc simultaneously with methionine or thiamine helps effectively reduce urinary excretion of ALA and the lead induced ALAD activity in the blood. It is suggested from such studies that the combination therapy including the essential nutrient elements and vitamins concurrently with exposure to lead could be more effective than treating the lead toxicity after exposure. This helps to reduce the absorption of lead in the gastrointestinal tract. Thus it can be attributed that zinc help to reduce the lead absorption
The most common form of polyethylene is petroleum based or olefins based; as before mentioned polyethylene compounds have a wide commercial applicability and are made from non-renewable resources (Harding, Dennis, von Blottnitz, Harrison, & S.T.L., 2007). Its manufacturing processes are regarded as energy intensive and release significant amount of CO2 and heat into the atmosphere (Broderick, 2008). Next a little more detailed description of polyethylene’s production processes will be presented, with a focus on the way the material inputs are extracted and synthesized.
Phys. Chem. C 2013, 117, 6651−6657). One mL of platinum seed solution just prepared was mixed with a 29 mL nanopure water and was stirred continuously in a water bath by placing the water bath on a hotplate with an electromagnetic device. 45 µL of 0.1 M H2PtCl4.6H2O was injected into stirred solution. 500 µL of solution containing 34 mM trisodium citrate and 71 mM L-ascorbic acid was added into the stirred solution. After fitting with reflex condenser to a RB flask, temperature of the heating bath was raised to 1200C gradually starting from room temperature at 50C/min. rate. Within 25-40 minutes, faint yellowish color changed to black revealing the formation of bigger platinum nanoparticles. Boiling was continued for 1 h to complete reaction. The particles size were characterized by Nanosight instrument (Nanosight500, Malvern,
In 1817, an aging Swedish chemist was pouring over his work on a late afternoon in Stockholm, Sweden. He was analyzing a strange ore named Petalite that had been procured from an island off the coast of Sweden called Utö. The ore Petalite (which is now recognized to be LiAl(Si2O5)2) had been discovered by a Brazilian scientist, José Bonifácio de Andrada e Silva towards the end of the 18th century on a visit to Sweden. This Swedish scientist, Johann August Arfvedson, detected traces of an unknown substance in his sample of Petalite. This was the first discovery of Lithium.
In this experiment, Borneol was oxidized to Camphor and later reduced to two possible diastereomers, in which isoborneol was favored, with the use of sodium hypochlorite and sodium borohydride. Hypochlorous acid served as the oxidizing agent and was vital in the formation of the ketone making up the bicyclic compound Camphor. Second most important, sodium borohydride provided the reducing agent, hydride, which added in on the endo side of the second carbon (C2) to make the exo alcohol isoborneol. The mechanisms of oxidation and reduction mirrored similar reactions such as esterification, β-elimination, and nucleophilic attack. The chirality and stereochemistry was observed in each step and played a role in forming the exo product isoborneol
Uranium was discovered by Martin Heinrich Klaproth, a German chemist, in the mineral pitchblende (primarily a mix of uranium oxides) in 1789.Klaproth, as well as the rest of the scientific community, believed that the substance he extracted from pitchblende was pure uranium, it was actually uranium dioxide (UO2). After noticing that 'pure' uranium reacted oddly with uranium tetrachloride (UCl4), Radioactivity was first discovered in 1896 when Antoine Henri Becquerel, a French physicist, detected it from a sample of uranium. Today, uranium is obtained from uranium ores such as pitchblende, uraninite , carnotite and autunite as well as from phosphate rock , lignite (brown coal) and monazite sand . Since there is little demand for uranium metal, uranium is usually sold in the form of sodium diuranate , also known as yellow cake, or triuranium octoxide).
Base catalysts are highly sensitive to water content due to soap formation which makes separation difficult. Acid catalyst are used when the acid values of the non-edible oils are higher than the performance range of base catalysts. The acid value represents the number of acidic functional groups and is measured in terms of the quantity of potassium hydroxide required to neutralize the acidic characteristics of the sample. The protonation of the carbonyl group of the ester promotes the formation of a carbocation, which after nucleophilic attack of the alcohol produces a tetrahedral intermediate. This intermediate will eliminate glycerol to form a new ester and to reform the catalyst. Acid-catalyzed transesterification are carried out in the absence of water. The problems with the use of these catalysts are: the requirement for more alcohol; slower reaction rates; higher reaction temperatures and pressures; reactor corrosion and environmental issues. Both homogeneous and heterogonous acid catalysts can be used for transesterification. The acid catalysts more commonly used include, sulfuric acid, hydrochloric acid, phosphoric acid, and sulfonated organic acids. Due to the fact that the FFA content of neat edible oils is normally low but these oils are costly and conversion of too much edible oil into biodiesel may cause food crises, use