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CHEM 242L Exp. 4 Report/ Synthesis of Oil of Wintergreen Name Score: 20 1) Assess the effectiveness of the experiment and your technique by A) reporting the yield of each step in grams and percent as well as the overall percent yield (What is "overall percent yield?). SHOW ALL CALCULATIONS! B) Give a complete analysis of the identity and purity of your final product and any isolated intermediates 2 What was the purpose of the addition of the 2M NaOH and the 6M HCl during the procedure for Part 1? As part of your explanation, provide a chemical cquation for cach reaction 3) Draw the mechanism for the hydrolysis of Acety lsalicylic acid to Salicylic acid. 4) Provide the product of the follow reaction sequence: H,O / NaOH SOC2 ROH OR2 SYNTHESIS OF OIL OF WINTERGREEN Experiment 4 Introduction In this experiment, methyl salicylate (oil of wintergreen) is formed from acetyl salicylic acid (aspirin) by a multi step reaction sequence. A saponification is followed by the conversion of a carboxylic acid to an acid chloride and an esterification. Your goal is to complete this synthesis with the highest possible yield and to convincingly prove the identity of the final product. You will submit the final product to the instructor. transformations can be found in your organic chemistry text) 1) Description of Transformations (Note: Details and mechanisms for these Transformation 1: Esters can be hydrolyzed either by aqueous base or by aqueous acid to yield a carboxylie acid and an alcohol. The word "saponification" is from the Latin sapo or soap since soaps are in fact synthesized by saponification which quite simply means to hydrolyze an ester in a basic solution. In this step, the ester is hydrolyzed in an aqueous solution with sodium hydroxide serving as the base. Transformation 2: The treatment of a carboxylic acid with thionyl chloride (SOCI2) is a common method for converting carboxylic acids to acid chlorides. It is important to note that SO2 and HCl are anticipated byproducts of this reaction. Acid chlorides are among the most reactive of the carboxylic acid derivatives. Due to the partial positive charge of the carbonyl carbon of acid chlorides, they are susceptible to 2) attack by nucleophiles resulting in a substitution of the chloride. 3) Transformation 3: In this reaction, an acid chloride is converted to an ester. The reaction proceeds by an attack of the alcohol (methanol) oxygen on the carbonyl carbon of the acid chloride followed by the elimination of hydrogen chloride (HCI). Due to the reactive nature of acid chlorides, the process typically occurs quite rapidly as well as irreversibly. ext, 20 mL of a I M sulfuric acid solution is placed in the addition mixture to dissolve the magnesium salts. The of magnesium salts. The resulting solution is This causes formation of a precipitate greenish yellow. N funnel and added dropwise to the reaction stir bar is removed, a nd the contents of the flask are transferred to a separatory funnel three ether layers are combined and dried with anhydrous sodium sulfate. The ether and ethanol are removed using a rotary evaporator to give a slightly viscous yellow liquid alcohol). The crude alcohol product should be analyzed to verify the formation of the target alcohol. The product is stored in a sealed vial and saved for the dehydration portion e lower aqueous layer is removed and extracted twice with 15 mL portions of ether of the experiment PART 2 - The Dehydration of 3-methyl-2-phenyl-2-butanol Procedure Wear safety glasses during the entire chemicals. All chemicals, reactions and procedures should be used or performed in the hood. All organic wastes should be put in the hazardous waste bottle unless otherwise stated. laboratory period and use gloves when handling any A magnetic stir bar, 0.64 g of the alcohol from the Grignard reaction, 20 mL of toluene, and 0.05 g of toluenesulfonic acid are placed in a 50 mL flask fitted with a reflux condenser. The solution is refluxed with stirring. The initial yellow of the solution may change to a deep purple as the reaction proceeds. After 5 minutes at reflux, 4 drops of th reaction mixture are removed via disposable pipette and placed in a small test tub containing 0.5 mL of dichloromethane and 0.5 mL of 10% sodium bicarbonate. The test tube is capped and the contents are gently shaken. Upon settling, two layers reform in the tube: an aqueous layer on top and a clear organic layer on the bottom. A pipette is used t take a sample from the lower dichloromethane layer. This sample is then analyzed by GC-MS. Additional samples are taken from the reaction mixture in a similar manner every 5 minutes for a total of 30 minutes. The samples need not be analyzed immediately since the sodium bicarbonate solution was used to neutralize the toluenesulfonic acid. The GC-MS may only be necessary for the analysis of the initial sample and subsequent samples may be analyzed on the GC Report For this experiment, write a full report as described in Appendix B of your laboratory manual. Attention to detail is essential. Consider and elaborate on all relevant aspects of the seven required sections to be included in the report. Mechanisms of the reactions being explored should be included as well as assignment of all distinguishing spectroscopic features. Explain the change in product ratios observed during the dehydration reaction in terms of kinetics and thermodynamic 20 addition of small portions of hot water until the solid is mostly dissolved. Allow the mixture to cool to room temperature slowly then chill in an ice bath until there is no further formation of precipitate. Collect the solid by vacuum filtration and rinse with cold water. Determine the yield of salicylic acid and verify its identity before proceeding to part two of the experiment Esterification of Salicylic Acid to yield Methyl Salicylate (Part 2): Note: Thionyl chloride is volatile, has extremely irritating vapors and reacts violently with water use with extreme caution! In a round bottom flask, add 2-înL thionyl chloride (in the hood) followed by the salicylic acid and reflux the mixture for about 15 minutes at which point the entire solid should be dissolved. Allow the solution to cool. Then slowly, in the hood, and with occasional swirling, add 3 mL methanol down through the condenser Heat this to boiling for a few minutes, then cool and transfer it to a separatory funnel. Add 6-mL of diethyl ether followed by 6-mL of water. Separate the two layers. Repeat the extraction 1 more time by adding a fresh 6-mL portion of ether to the original water layer.. Combine the ether extract layers and wash one time with 29mL of 10% aqueous sodium bicarbonate solution. When first adding the sodium bicarbonate solution, stir carefully so that it does not overflow, and only after the bubbling has subsided should you cap and shake, venting frequently, and then remove the aqueous layer to a separate container. Place the ether layer in a small Erlenmeyer, add drying agent to remove any residual water. Decant the ether layer containing the methyl salicylate into a tared round bottomed flask and evaporate the ether using the rotary evaporator. Weigh the flask and its contents and determine the yield. Obtain IR, GC-MS and NMR data on the product.

Answer 1

4) Oil of winter green is otherwise known as methyl salicylate.

It is obtained by the esterification reaction between salicylic acid and methanol in presence of acetic anhydride.

Since it is obtained as oil from leaves of winter green plant 'gaultheria fragrantissima' which is available in Nepal forest, it is also known as oil of winter green.

The reactions are as follows

十 CHa".ON oleyte aisl meitangl CCOH サー+ aspisine acehc auol Cooh oけ aspiuine MechauipM HYC CCOH ocoCH3 ts pixim altylate acetate Yけ 내.z mixed anh dide

4) Ester hydrolysis produces alcohol and carboxylic acid. This carboxylic acid and alcohol reacts with socl2 to form acid chloride and alkyl halide.

​​​​​​This acid chloride reacts with R2OH to form again ester.

​​​​​​The reaction is as follows

alcoh어 2 auio esteu Sovl İtaten esteレ