Porphyrins are natural occurring compounds consisting of tetrapyrrolic macrocycle as shown in Figure 1.1 (A). Porphyrins are essential for living organism as they involve in various biological processes such as oxygen binding, electron transfer, biocatalysis and photochemical routes (Cragg, 2005). Metals in biological system are often bound to porphyrin forming metalloporphyrins. For example, magnesium binds to porphyrin to form chlorophyll (Figure 1.1 (B)) that plays the role as a light harvesting agent in the photosynthesis process. While iron binds to porphyrin to form haemoglobin (Figure 1.1 (C)) which is responsible for sophisticated oxygen transport in mammals (Donald, 2001).
Figure 1.1 Molecular structure of (A): porphyrin, (B): chlrophyll and (C): haemoglobin
The abundance and importance of porphyrin in nature make it interesting scaffold for technological and scientific studies. The π electrons rich macrocycle of porphyrin makes its structure rigid and stable. In addition, the four nitrogen atoms in the macrocycle readily coordinate to wide variety transition metals. Besides, the large macrocycle in porphyrin provides spaces for further functionalization. Its properties can be fine-tuned by introducing substituents or changing the central metal ion. This ability enables porphyrin to be modulated to fit different applications by
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In homogeneous catalysis, oxidation of alcohols to corresponding aldehyde and ketone requires a stoichiometric amount of oxidant such as chromium(VI), permanganate, DMSO and DDQ (Cardona and Permeggiani, 2015). Consequently, all of these oxidants suffer drawbacks of generating high amounts of organic and inorganic toxic side products after the reaction. Furthermore, these methods are usually carried
The purpose of this experiment is to determine the absolute configuration of an unknown chiral secondary alcohol using the competing enantioselective conversion (CEC) method. This method uses both R- and S- enantiomers of a chiral acyl-transfer catalyst called homobenzotetramisole (HBTM), in separate parallel reactions, and thin layer chromatography to identify the stereochemistry of the secondary alcohol, whether it be an R- or S- enantiomer. Quantitative analysis was performed using a program called ImageJ after the appropriate picture was taken of the stained TLC plate. The molecular structure of the unknown alcohol was identified using 1H NMR spectroscopy by matching the hydrogens to the corresponding peak.
The goal of this two week lab was to examine the stereochemistry of the oxidation-reduction interconversion of 4-tert-butylcyclohexanol and 4-tert-butylcyclohexanone. The purpose of first week was to explore the oxidation of an alcohol to a ketone and see how the reduction of the ketone will affect the stereoselectivity. The purpose of first week is to oxidize the alcohol, 4-tert-butylcyclohexanol, to ketone just so that it can be reduced back into the alcohol to see how OH will react. The purpose of second week was to reduce 4-tert-butylcyclohexanol from first week and determine the effect of the product's diastereoselectivity by performing reduction procedures using sodium borohydride The chemicals for this lab are sodium hypochlorite, 4-tert-butylcyclohexanone
Wittig reactions allow the generation of an alkene from the reaction between an aldehyde/ketone and an alkyl halide (derived from phosphonium salt).The mechanism for the synthesis of trans-9-(2-phenylethenyl) anthracene first requires the formation of the phosphonium salt by the addition of triphenylphosphine and alkyl halide. The phosphonium halide is produced through the nucleophilic substitution of 1° and 2° alkyl halides and triphenylphosphine (the nucleophile and weak base). An example is benzyltriphenylphosphonium chloride, which was used in this experiment. The second step in the formation of the of the Wittig reagent, which is primarily called a ylide and derived from a phosphonium halide. In the formation of the ylide, the phosphonium ion in benzyltriphenylphosphonium chloride is deprotonated by the base, sodium hydroxide to produce the ylide as shown in equation 1.
In a separate beaker, acetone (0.587 mL, 8 mmol) and benzaldehyde (1.63 mL, 16 mmol) were charged with a stir bar and stirred on a magnetic stirrer. The beaker mixture was slowly added to the Erlenmeyer flask and stirred at room temperature for 30 minutes. Every 10 minutes, a small amount of the reaction mixture was spotted on a TLC plate, with an eluent mixture of ethyl acetate (2 mL) and hexanes (8 mL), to monitor the decrease in benzaldehyde via a UV light. When the reaction was complete, it was chilled in an ice bath until the product precipitated, which was then vacuum filtrated. The filter cake was washed with ice-cold 95% ethanol (2 x 10 mL) and 4% acetic acid in 95% ethanol (10 mL). The solid was fluffed and vacuum filtrated for about 15 minutes. The 0.688 g (2.9 mmol, 36.8%, 111.3-112.8 °C) product was analyzed via FTIR and 1H NMR spectroscopies, and the melting point was obtained via
The purpose of the experiment was to study the kinetics of the hydrolysis of ester, p-nitrophenyl acetate (NPA) that is catalyzed by the buffer imidazole (Im). In terms of kinetics, specifically speaking, the rate of reaction as determined by the concentration, reaction orders, and rate constant with each species in a chemical reaction. By using the concentration of the catalyst and the temperature, the overall reaction rate was determined. The rate constants of K0, Kobs, and Kcat can be derived via the plotting of the absorbtion at 400nm of p-nitrophenol vs. the concentration of the catalyst imidazole. Lastly, the free energy of activation, ΔGǂ, that is necessary to force the reactant’s transformation of the reactants to the transition state structure will be determined by using the equation ΔGǂ = ΔHǂ – TΔSǂ derived from the Eyring plot.
David and John Free. (26 Nov 2006). MadSci Network: Chemistry. Retrieved on March 6, 2011, from http://www.madsci.org/posts/archives/2007-02/1171045656.Ch.r.html
Purpose/Introduction: In this experiment, four elimination reactions were compared and contrasted under acidic (H2SO4) and basic (KOC(CO3)3) conditions. Acid-catalyzed dehydration was done on 2-butanol and 1-butanol; a 2o and 1o alcohol, respectively. The base-induced dehydrobromination was performed on 2-bromobutane and 1-bromobutane isomeric halides. The stereochemistry and regiochemistry of the four reactions were analyzed by gas chromatography (GC) to determine product distribution (assuming that the amount of each product in the gas mixture is proportional to the area under its complementary GC peak).
“Fierce pain, paralysis and sickness took over my body, for week’s doctors seemed to think I was either making it up, mad or anorexic. Eventually they discovered it was porphyria, and it was inherited from my father… We learned that antibiotics prescribed for a minor infection, had probably triggered it in my case, but after that, I generally suffered attacks in my pre-menstrual period. These attacks varied in severity, but the pain and vomiting were omnipresent… My weight gradually dropped, as I was unable to regain it in the short periods of time between attacks, which led me to an attack which left me almost completely paralyzed.” (Elizabeth, 2011)
The heme prosthetic group, a protoporphrin IX ring structure with an iron atom ion the ferrous (Fe2+) oxidation state exist in both in myoglobin and he...
Predictions may be made about the suitability of possible catalysts by assuming that the mechanism of catalysis consists of two stages, either of which can be first:
Thickett, Geoffrey. Chemistry 2: HSC course. N/A ed. Vol. 1. Milton: John Wiley & Sons Australia, 2006. 94-108. 1 vols. Print.
The solution for the resistance to oxidation of p-toluic acid was solved by the discovery of bromide-controlled air oxidation in 1955 that was led to the implementation of AMOCO process [28-31]. In AMOCO process, the oxidation of para-xylene was conducted using a combination of three ions as a homogeneous catalyst which is cobalt, manganese and bromide ions. Acetic acid and oxygen/air were used as solvent and oxidant, respectively [32]. The common bromide ion sources are hydrobromic acid (HBr) and sodium bromide (NaBr). The oxidation operated at 175-225°C and 15-30 bar of oxygen. The terephthalic acid formed mostly in the form of solid due to the low solubility of terephthalic acid in the acetic acid. AMOCO process successfully gives a promising reaction yield, since more than 98% of para-xylene reacted, while terephthalic acid selectivity yield was about 95% in the reaction time of 8-24 hours (Scheme 3).
23. S. Alwarappan, S. Boyapalle, A. Kumar, C.-Z. Li and S. Mohapatra, J. Phys. Chem. C, 2012, 116, 6556–6559
Plontke, R. (2003, March 13). Chemnitz UT. TU Chemnitz: - Technische Universität Chemnitz. Retrieved April 1, 2014, from http://www.tu-chemnitz.de/en/
Photosynthesis is a key contributor to all living things; photosynthesis provides the oxygen, food, and nutrients that help all living things stay healthy and alive. Photosynthesis converts solar energy into the chemical energy of a carbohydrate. Photosynthetic organisms, including land plants, algae, and cyanobacteria, which are called autotroph...