Purifying A Compound Of Benzoic Acid

In order to isolate benzoic acid, benzocaine and 9-fluorenone, each component needed to be separated from one another. All three compounds began together in one culture tube, dissolved in methylene chloride and formed into a homogenous mixture. In this culture tube, two milliliters of aqueous three molar hydrochloric acid was added, which immediately formed two layers, the top acidic aqueous layer was clear in color and contained benzocaine, and the bottom organic formed was yellow and contained benzoic acid and 9-fluorenone. Benzocaine’s amino group is protonated by the aqueous layer hydronium. This protonation forms the conjugate acid of benzocaine, benzocaine hydrochloride. Thus, the conjugate acid, benzocaine hydrochloride is a salt in which is soluble in water and furthermore can be isolated from the organic mixture. When testing out the pH levels in benzocaine, the pH test strip was dark blue in color, indicating a pH level of around 5 to 7. When isolating benzoic acid, two milliliters of aqueous three molar sodium hydroxide was added, which deprotonates the carboxylic group in benzoic acid, forming its conjugate base, sodium benzoate. As with benzocaine hydrochloride, sodium benzoate is a water soluble ionic salt in the aqueous layer that can then be separated from the bottom organic layer containing the 9-fluorenone. The pH test strip was a vibrant red for benzoic acid, indicating a pH of 2. Now the 9-fluorenone is left, deionized water is added to remove any excess

It is also important that the proper solvent does dissolve impurities at room temperature but does not dissolve impurities near its boiling point. 7) Thin-layer Chromatography (TLC) was used in the experiment to identify the filtrate. TLC works by applying a sample of the filtrate onto a TLC plate that is partially submerged in a solvent in a closed jar. The filtrate then moves up the plate through capillary action, and the distance that the filtrate moved (the Rf value) is measured. This value is then compared to Rf values measured from given solutions, and the filtrate is identified by matching its Rf to the closest Rf of a given

Experiment 1: After 10% sodium bicarbonate solution adds to the dichloromethane solution, which dissolves the mixture of benzoic acid, 2-naphthol, and 1,4-dimethoxybenzene, and shake the separatory funnel, there are hissing sounds as well as when 10% sodium hydroxide solution is added. Also, when the separatory funnel is vented, gas, carbon dioxide, rushes out. The first extraction allows benzoic acid to be isolated. Through adding 10% sodium bicarbonate solution, the weak base removes the proton of benzoic acid, a stronger acid compared with 2-naphthol, which turns benzoic acid into charged form. So it dissolves in the aqueous layer while 1,4-dimethoxybenzene and 2-naphthol remain in the organic layer.

It was observed that the solution turned a strong purple tint as the reflux continued, turning extremely dark at certain points. At the end of the 15 minutes, the reflux was stopped and the round bottom flask was allowed to cool to room temperature. Afterwards, the flask was placed in an ice bath in order to allow a precipitate to form, and it was observed that an extremely slight precipitate formed at the bottom of the flask. The mixture was then poured into a Buchner funnel attached to a Buchner flask in order to perform a vacuum filtration. The collected precipitate was further washed with 10 mL of cold DI water and 10 mL of cold ethanol.

The percentage yield calculation reveals that approximately 90% of benzoic acid as white precipitate were recovered from the reaction. There were a number of factors which might have contributed to the 10% deficiency in the final yield. It needs to be mentioned though that a percentage yield of less than 100% is achieved because the drying of the solid mass after vacuum filtration was sufficient to give a practical number. During measurements of mass of benzoate and benzoic acid when it’s formed, there were obvious human errors involved. Some benzoates were lost while transferring to the conical reaction vial from the watch glasses, and further loss of the product benzoic acid might have taken place when the solution mixture was tipped on the Hirsh funnel. We couldn’t determine if the reaction was complete or not, so we might not have had all the salt converted 4. The solution might not have sufficiently and gradually cooled though every effort was made for that, hence there could be lack of benzoic acid crystals forming.

Recrystallization purifies a crude product by separating the product from impurities based on solubility. The product being purified should easily dissolve in the chosen solvent at high temperatures, but not at room temperature. Impurities should dissolve in the solvent at room temperature but not at high temperatures.

Then, 0.100 grams of pure benzil, 0.30 mL of 95% ethanol, and a spin vane was placed into a 3-mL conical vial with an attached air condenser. The mixture was heated with an aluminum block at 100°C, while being stirred, until all the benzil had dissolved. Using a pipet, 0.25 mL of an aqueous potassium hydroxide solution was added drop wise into the conical vial through the air condenser. The mixture was boiled at 110°C while being stirred for approximately 15 minutes and the reaction mixture changed from deep blue-black to brown in color. The vial was removed from heat and allowed to cool to room temperature. The mixture was crystallized in an ice bath and the crystals were collected over a Hirsch funnel using vacuum filtration and rinsed with ice-cold 95% ethanol. The solid crystals were transferred to a 10-mL Erlenmeyer flask that contained 3 mL of 70°C water. The flask was swirled while 0.50 mL of 1 M hydrochloric acid was added to the flask. With each drop added a white precipitate formed immediately. The solution was checked to have a pH of 2, if it was not, more acid was added to the flask. The mixture was cooled to room temperature and then cooled in an ice bath. The crystals were collected by vacuum filtration using a Hirsch funnel and rinsed with ice-cold water. The pure benzilic acid crystals were weighed and a melting point was obtained.

After dissolving benzoic acid in 1.0mL CH2Cl2 and 1.0mL 10% NaHCO3 solution, two layers are created, the top layer is 10% NaHCO3 solution and the bottom is CH2Cl2.

Discussion: As seen in the melting point determination, the average melting point range of the product was 172.2-185.3ºC. The melting points of the possible products are listed as 101ºC for o-methoxybenzoic acid, 110ºC for m- methoxybenzoic acid, and 185ºC for p- methoxybenzoic acid. As the melting point of the sample

Different procedures were used to isolate benzil from the ether layer and benzoic acid from the aqueous layers. To isolate benzil, anhydrous MgSO4 was added to the flask containing the ether layer solution. MgSO4 removes the remaining water in the ether layer solution. After making sure that enough amount of MgSO4 present in the solution, the ether solution was filtered by using gravity filtration. During filtration, MgSO4 was removed from the solution and the ether solution was collected in 25 ml flask. To separate benzil from the filtered ether solution, the beaker containing the ether solution was heated until the ether evaporated. After letting the beaker to cool to room temperature, the mass of the beaker with the benzil crystals was measured. From the combined mass of the beaker and the benzil crystals and from the predetermined mass of the beaker, the mass of the collected crystals was calculated to be 0.266 gram.

The product attained was a white, dry solid. The small amount of product lost during the second recrystallization was most likely do to impurities, which were filtered away with the methanol. Impurities that contributed to the low percent yield could be due to side reactions such as methyl o-nitrobenzoate and methyl p-nitrobenzoate. Although the percent yield attained was low, the product attained was fairly pure due to similarity in melting point and IR spectrum compared to standardly accepted values for methyl m-nitrobenzoate.

Three grams of a mixture containing Benzoic Acid and Naphthalene was obtained and placed in 100 ml beaker and added 30 ml of ethyl acetate for dissolving the mixture. A small amount (1-2 drops) of this mixture was separated into a test tube. This test tube was covered and labelled as “M” (mixture). This was set to the side and used the following week for the second part of lab. The content in the beaker was then transferred into separatory funnel. 10 ml of 1 M NaOH added to the content and placed the stopper in the funnel. In the hood separatory funnel was gently shaken for approximately one minute and vent the air out for five seconds. We repeated the same process in the same manner one more time by adding 10ml of 1M NaOH.

In this lab, liquid-liquid extraction was performed to isolate a mixture of benzocaine and benzoic acid. 2.0107 grams of the mixture was first weighed out for the trials. When HCl was added to the mixture for the first acid extraction of benzocaine, an emulsion formed during inversion and venting that prevented a defined separation of the two layers. 8 mL of water was therefore added before continuing the extraction. The addition of NaOH then turned the top aqueous layer basic, indicated by the pH strips that turned blue when tested. A vacuum filtration isolated 0.29 grams of benzocaine and a MelTemp apparatus measured the crystal’s melting point ranges to be 85.1C-87.4C. For the base extraction of benzoic acid, the aqueous layers were retrieved

This process was then repeated two more times with subsequent additions of 10 mL of the 0.5M aqueous NaHCO3 and the aqueous layers drained off into the above mention labeled 100-mL beaker. Finally 5 mL of deionized water was placed into the funnel and mixed. The water was then drained off into the beaker containing the aqueous solution extracts. The solution was then saved until need later in the experiment.

The purpose of this experiment is to practice common organic laboratory techniques inside the lab to get one oriented to the basic methods of procedure that can be used for later experiments. This experiment involves the separation of benzoic acid from a more crude form, consisting of benzoic acid, methyl orange, a common acid/base indicator, and cellulose, a natural polymer of glucose (Huston, and Liu 17-24). The technique that is used to perform this separation is called extraction. Extraction is a systematic process of separating mixtures of compounds, taking advantage of the affinity differences of compounds to separate them (Padias 128-37). This technique recognizes the principle that “like dissolves in like,” that is,