The decreasing concentration of starting material paminobenzoic acid and increasing concentration of product benzocaine impedes the reaction from moving to the forward direction. The longer the reaction takes place, less and less products will form. The stretch at A lot of starting material remain with the products. But it does not show up in the IR spectrum. No O-H stretch around means no carboxylic acid exists in the sample.
The reason lies in the difference of solubility between two compounds in the basic environment. The starting material, p-aminobenzoic acid, is very soluble in the basic solution when it is deprotonated by the base and forms the water-soluble carboxylate anion. On the other hand, the benzocaine lacks the acidic protons and cannot be deprotonated by the base.
Since final pH of the solution was made to 8, all the starting material exist as an anion rather than the solid. And when the reaction mixture was filtrated , the products can be isolated from starting material. The NMR spectrum of the product shows 4 peaks that integrate to 2 protons each and one peak that integrate to 3 protons.
The two doublets, 7. The peaks form 7. Because the amine group is an electron-donating activating group while the ester group is an electronwithdrawing deactivating group. The ester group is more electronegative than amine group. Any protons near electronegative groups will have higher chemical shift. The single- split peak at 5. The - protons next to the ester group appear from4. The methyl protons appear as triplet at 1. All of these peaks mentioned above match very well with the expecting shifts and splitting pattern for benzocaine.
There are 2 impurity peaks and one solvent peak in the NMR spectrum. The peak from 2. As the NMR tube is not dried thoroughly , some acetone which is used to wash the NMR tube does not evaporate completely. The remaining acetone show up at 2. The other impurity at 3.
It neither came from starting material nor came from the solvent. The melting point of the isolated product is C which matches well with the literature value 4. Though the measured data is a little bit lower than the literature value, the result is acceptable as vacuum evaporation is not perfect separation method. Trace amounts of Sodium Bicarbonate may affect the melting point of product.
A mixed melting point test can be performed to further confirm the identity of Benzocaine. The GC data only showed one peak at It further suggests the purity of isolated Benzocaine. It also showed one peak.
The yield is quite reasonable as the fischer esterification is a reversible reaction. Temperature , concentration of products and reactants and even pressure will affect the extent of reaction. References : 1.
Volume , Issues 12, 14 June , Pages 2. Anesth Prog. Volume 53 Issue2 Philip A. Gilderhus , Carol A. Than the samples obtained by thermal activation for the activated carbons thermally activated, the values for acid and basic groups are low-between 0,20 and 0,72 meq g-l Directory of Open Access Journals Sweden Flavia M. Amaral Full Text Available Intestinal infection caused by Giardia lamblia represents a serious public health problem, with increased rates of prevalence in numerous countries.
Increased resistance of the parasite and the side-effects of the reference drugs employed in the treatment of giardiasis make necessary to seek new therapeutic agents. Natural products, especially of plant origin, represent excellent starting point for research. The objective of this study is to review the literature on plant extracts, fractions and chemical constituents whose giardicidal activity has been investigated in vitro. The review describes one hundred and fifty-three plant species from 69 sixty-nine families that were evaluated for their giardicidal activity.
Because the amine group is an electron-donating activating group while the ester group is an electronwithdrawing deactivating group. The pure products university of south florida application essay topic were analyzed by IR spectral data, showing a fingerprint of the compound.
Gilderhus , Carol A. Safety Precautions Ethanol is flammable. Anesth Prog. Empty the filtrate into the aqueous waste container 1, then replace the empty Erlenmeyer flask and continue pulling a vacuum on the product to allow it to dry for ca. Related documents.
Curry Woods III pages 4. Overall, the product was successfully acquired.
Benzocaine is synthesized with p-aminobenzoic acid, ethanol, and sulfuric acid as a catalyst.
Copy the reaction and the reaction table below in your own writing into your notebook and complete all empty cells in the table. Figure 2: The mechanism walkthrough of the esterification of benzocaine. For example, it can be used to relive pain due to the oral injection. Heat the mixture gently until the reaction commences, and remove the flame. This can be accomplished by physical e.
After cooling to room temperature, distilled water is added to the reaction mixture in a beaker 50mL. Volume 53 Issue2 Philip A.
Second, the tetrahedral intermediate is formed by nucleophilic attack of ethanol on the p-aminobenzoic acid. A precipitate is expected to form. K values for the formation of esters of acetic acid Alcohol ethanol t-butanol Ester Equilibrium Constant K ethyl acetate 3. Furniss, Antony J. Solvent question. Discussion: The Fischer Esterification reaction proceeded without any notable chemical issues.
K values for the formation of esters of acetic acid Alcohol ethanol t-butanol Ester Equilibrium Constant K ethyl acetate 3. The negative charge of the carbon previously known as the carbonyl carbon results in the formation of a double bond to the hydroxyl group. The K values were determined experimentally from systems at equilibrium and may be taken as a measure of the efficiencies of the esterification processes. The methyl protons appear as triplet at 1. Upon the completion of reaction, saturated sodium bicarbonate 1M was added dropwise until the pH of solution was around 8.
Obtain the mass of product and calculate the percent yield. Allow to cool somewhat and decant the liquid into a 1-litre beaker; wash the residual tin by decantation with 15 ml of water, and add the washings to the contents of the beaker.
One hundred and one compounds isolated from plant species, classified by chemical class, are presented. Safety glasses and gloves are mandatory. Because the product benzocaine is not removed from the mixture, the concentration of product increases during the whole process of the reaction. Nusstein, J.