The first step is where the substrate enters the active site on the enzyme. It is held there by hydrophobic interactions between the exposed non-polar groups of the enzyme residues and the side chain of the substrate. The second step is where the hydroxyl group on Serine 195, aided by the histidine-serine hydrogen bonding, preforms its nucleophilic attack on the carbonyl carbon of an aromatic amino acid. While this happens, it also transfers the hydroxyl hydrogen to the histidine nitrogen. The nucleophilic attack pushes the carbonyl electrons onto the carbonyl oxygen, which forms a short-lived intermediate.
If this happens, the mixture boils and it would be necessary to start the experiment all over again. After obtaining an homogeneous mixture, the flask was placed in an ice bath during five minutes next to a graduated cylinder containing 5.0 mL of concentrated sulfuric acid. The temperature of the ice bath was recorded to be 1.1 °C. Likewise, a second graduated cylinder containing 1.8 mL of nitric acid and 2.5 mL of sulfuric acid was immersed in the cold ice bath to keep the three different solutions at the same temperature. Thereafter, the cold 5.0 mL of H2SO4 were added to the erlenmeyer flask containing the acetanilide solution, which remained in the cold water for approximately another 4 minutes.
Experiment Scheme1 Equation 1. Esterification of acetic acid to form isopentyl acetate. The experiment to attain isopentyl acetate contained various steps and processes. First, we assembled the reflux apparatus by using a 25-mL round-bottom flask, water-cooled condenser, and heating mantel.
The crude tetraphenylnaphthalene in a 25-ml Erlenmeyer flask and dissolved in boiling isopropyl alcohol (12 ml). The solution was cooled to room temperature and further cooled in an ice bath for 30 minutes. Crystallization of colorless crystals occurred. The product was collect in a Hirsch funnel and washed with isopropyl alcohol. The solid was left to dry over the weekend.
Experimental Methods: 1. SYNTHESIS OF 4-BENZOYL BUTYRIC ACID METHYL ESTER Materials required * 5 oxopentanoic acid : 2 gm (Aldrich) * Methanol : 50 ml * Acetic Acid (Rankem) Procedure: * 2 grams of 5 oxopentanoic acid was weighed and placed in a round bottom flask and then to it 50 ml of methanol was added. It was placed on a hot plate and the temperature was increased to 50 degrees under ambient air conditions. * To the RB, 2 ml of acetic acid was added and then by attaching a condenser the entire reaction was put on refluxing at 70 degrees Celsius in an oil bath. * For work up: * The reaction media was concentrated till about 10 ml and then dry silica gel was added.
Two drops of iodine- potassium was then added to the mixture. The procedure was repeated with the rest of the samples and isopropyl with varying drops of sodium hydroxide. Eight drops of sodium hydroxide was added to formaldehyde, 9 drops to cyclohexanone, 15 drops to benzaldehyde, and 7 drops to isopropyl. It was observed that both cyclohexanone and benzaldehyde formed a yellow layer that lasted only for a few seconds before disappearing completely while the formaldehyde mixture produce a yellow precipitate. Both acetone and isopropyl mixtures were heated since no precipitate was observed.
( CALCULATIONS) The equipment used for the procedure is as followed: scale, graduated cylinder, beakers, Erlenmeyer flask, hot plate and titration pipette. The chemicals used in the procedure are as followed: pure Na2CO3, distilled water, phenolphthalein concentrated 1% in 50% ETOH/50% H2O, and 0.02 M concentrated HCl. __ g 〖Na〗_2 〖CO〗_3 × ((1 mol 〖Na〗_2 〖CO〗_3)/(105.99 g 〖Na〗_2 〖CO〗_3 ))= ___ mols 〖Na〗_2 〖CO〗_3 ___ mols 〖Na〗_2 〖CO〗_3 × ((2 mol HCl)/(1 mol 〖Na〗_2 〖CO〗_3 ))= ____ mols HCl ((___ mols HCl)/(___ L HCl))= ___ M (mol/L) HCl * The above procedure
[Figure 1] 2.2.1. Chloromethylation of poly sulphone 5 g of polysulphone was dissolved in 75 mL of chloroform at 70°C. After complete dissolution of polymer, a mixture of paraformaldehyde (3.4 g) and chlorotrimethylsilane (14.7) mL was prepared as the chloromethylating agent with constant stirring which was followed by the addition of 5% of stannous chloride (by weight, of polymer) as catalyst with stirring at 70°C and allowed to react for 18 h. Then the polymer was precipitated in methanol to eliminate
Results and discussion Stirring of L with 4-methylaniline and 4-methoxyaniline in equimolar proportion in water at room temperature for 72 h without any Lewis acid catalyst gives L.H2O and L respectively (Scheme 1). The yield of L.H2O is 90% and that of L 70%. These are obtained in 60% yield when the reactants are refluxed in water for 14 h. But the yield goes on decreasing when increasingly more refluxing time is used. Earlier Moody et al have  studied opening of the epoxide ring in L in connection with their total synthesis of the pentacyclic marine alkaloid ascididemin from 1,10-phenanthroline (phen).
Enthalpy of neutralization The purpose of this experiment is to determine the enthalpy change for the reaction between aqueous sodium hydroxide (NaOH) and aqueous hydrochloric acid (HCl). Introduction A neutralization reaction is a chemical reaction where a base and an acid react with each other. The products will always be water and a salt. The balanced reaction equation for this experiment is the reaction below (Enthalpy of neutralization, 2018). 〖NaOH〗_((aq))+〖HCl〗_((aq))→〖NaCl〗_((aq))+H_2 O_((l)) In aqueous solutions the substances that are involved will experience dissociation, which changes the ionization state of the substances (Neutralization, 2018).