Synthesis of a Potential Enzyme Inhibitor

Synthesis of a Potential Enzyme InhibitorDelaram Salehi out-of-the-way(prenominal)dAimSynthesis and characterisation of Benzocaine.IntroductionThe Fischer esterification of 4-amino benzoic harsh is catalysed by an window pane is fully reversible.Method3g of 4-aminobenzoic acid was weighed out and placed into a dry 100cm3 round crapper flask (ensuring no residues atomic recite 18 left inside the joint).20 cm3 of methylated spirits was measured out and added to the 4-aminobenzoic acid in the round bottom flask.3 cm3 of concentrated Sulfuric acid was measured out and added to the round bottom flask mixture (ensuring no residues are left on the joint), a condenser was fit onto the round bottom flask and the mixture was gently swirled.Using a heating mantle, the mixture was heated and upon boiling refluxed for 30 minutes.At the end of reflux, the heat source was remote and the mixture was allowed to cool to room temperature.Upon cooling, the mixture was gently stirred using a glass stirring rod and Sodium hydroxide solution (20%) was tardily added to the mixture until a neutral pH was attained.The mixture was allowed to stand for 5 minutes before the contents were poured into a beaker containing approximately 70 cm3 of ice, the reaction watercrafts was rinsed with distilled piss and the washings were transferred into the beaker to reach an approximate volume of 150cm3.The crop was filtered using a Buchner funnel (washed with some cold water) ensuring that the moisture is completely sucked out.The product was then transferred onto a overtake glass and dried in an oven at a temperature no greater than 60oC. The dry mass was then noted and the product submitted for analysis.Steps1-10 were repeated using Isopropyl alcoholic drink instead of Methylated spirits and the melting point for the product was attained.Mechanism of actionStep one portrays the protonation of the nose candyyl oxygen on 4-aminobenzoic acid where the sulfuric acid acts as the H+ donor (t he regeneration of this proton would establish the Sulphuric acid as a catalyst). This proton transfer results in a delocalisation of positive stir which bedevils rise to the presence of the three resonance structures portrayed in step 1- resonance. Of these three structures, the spunk structure (where the positive charge is localised onto the cytosine atom) allows for the esterification to proceed as its partial positive charge allows Nucleophilic attack by the Oxygen atom on Methanol as seen in step two. next this nucleophilic attack, a protonation and de-protonation occurs (which has a net effect of proton transfer) thus leading to the formation of a water molecule on the carbon atom which cleaves off in the hydrolysis in step 3. This hydrolysis results in a delocalisation of positive charge which gives rise to the presence of the three resonance structures portrayed in step 4- resonance. Of these structures, the middle structure where the positive charge is localised onto t he carbon atom allows for a de-protonation to occur as the Hydrogen atom donates its electrons to the positive carbon thus neutralising the carbon and forming a double bond. This de-protonation also results in the regeneration of the Sulphuric acid proton which protonated the reactant in step 1 thus establishingResultsWeek one division contributeMass of reactant 3gMass of product obtained 2.38gRMM reactant 137RMM product 165Reactant/product moles 0.022Theoretical yield= 3.62g% Yield = (Actual yield / theoretical yield) * 100 = 65.75%Week two percentage yieldMass of reactant 3gMass of product obtained 2.79gRMM reactant 137RMM product 179Reactant/product moles 0.022Theoretical yield= 3.92% Yield = (Actual yield / theoretical yield) * 100 = 71.18%Melting point observational product 1MP 85.9-88.4oCLiterature product 1MP 88-90oCExperimental product 2 MP 83.5-84.1oCLiterature product 2 MP 84oCH NMR4-amino benzoic acidBenzocaine13CNMR4-amino benzoic acidBenzocaineDEPT-1354-amino benzoic acidBenzocaineAnalysisThe melting points for both products were average reading from three attempts and are fair within the literature range. This can be attributed to accurate measurements, clean utensils (thus avoiding impurities) and sufficient drying.At roughly 66% and 71% the percentage yields for products one and two severally are reasonably low. This may be due to a number of problems such as, incomplete transfer of reactant into the reaction vessel, not transferring all of the reaction vessel washings for filtering, incorrect filtering technique where some product was allowed to pass through instead of being retained e.g. filtering too fast or incomplete transfer of the product from the filter paper after filtration.With reference to the HNMR tables, I have deduced corresponding H atom based on integration, splitting and chemical channelize. The chemical shift of an atom depends on the extent of protect it has, for sheath a H atom attached to an Oxygen (e.g. H atom numb er 6 on 4-amino benzoic acid) has less screen due to the Oxygen atoms electronegativity whereas a H atom attached to a C atom has more shielding as carbon is not electronegative and in the case of H atoms number 2 and 3, they are also surrounded by other atoms which give them some shielding. I found locating H atoms 2 and 3 particularly tricky as their quintet splitting pattern and integration of 3 where very misleading however their chemical shift reaffirmed their identity as it is relatively to the left thus indicating a fair amount of shielding.With reference to the 13CNMR tables I was able to deduce the corresponding Carbon atoms based on two properties, chemical shift and peak height. The chemical shift (in accordance to the level of shielding/position of the C atoms) allowed me to locate peaks for carbonyl carbons (Carbon number 7 in both reactant and product) and more shielded carbon aand the height/integration of the peaks which corresponds to the number heat content atoms attached to the C atom in question.With reference to the DEPT-135 tables I was able to distinguish the difference between the C atoms in accordance with the different number of H attached to each C atom. This technique portrays CH and CH3 atoms as positively phased and CH2 atoms negatively phased. For atoms with the same phasing, I used the chemical shift ( as with 13 CNMR ) to distinguish between the C atoms in question.In this esterification, the product was maintained in a pH of 7-8. This was done in order to prevent a nucleophilic attack from hydroxide ions which would hydrolyse the product which and reverse the esterification thus converting the product back into the reactant.Rf values can be used to deduce the signboard of a molecule, where a low Rf value can indicate a wintry molecule. This is based on how the molecule interacts with the mobile and stationary phases. For example a low Rf value is a result of the molecule interacting with the polar stationary phase/silica a nd not travelling very far up the plate allowing us to deduce that its polar. Based on this theory and the fact that polarity increases with RMM a larger molecule would be more polar and thus have a lower Rf. I would therefore predict that Isopropyl 4-Aminobenzoate would have a lower Rf value than Benzocaine due to its larger RMM making it more polar than Benzocaine.ReferencesUNCP. (2014). CNMR spectroscopy. Available http//www2.uncp.edu/home/mcclurem/courses/chm550/nmr_lec4.pdf. move accessed 06/03/2014.Chemspider. (2014).4-Aminobenzoic acid.Available http//www.chemspider.com/953. Last accessed 06/03/2014.Chemspider. (2014).benzocaine.Available http//www.chemspider.com/Chemical-Structure.13854242.html?rid=752b9fda-5ccb-49f3-bf93-47ceb79356b4. Last accessed 06/03/2014.Jim Clark. (2002).THE MECHANISM FOR THE ACID CATALYSED HYDROLYSIS OF ESTERS.Available http//www.chemguide.co.uk/physical/catalysis/hydrolyse.htmltop. Last accessed 06/03/2014.Chemspider. (2014).4 aminobenzoic acid.Av ailable http//www.chemspider.com/953. Last accessed 06/03/2014.Chemspider. (2014).Isopropyl 4-Aminobenzoate.Available http//www.chemspider.com/Chemical-Structure.78903.html. Last accessed 07/03/2014.