The Separation and Purification of Benzoin and Benzoic Acid - Lab Report Example

The Separation and Purification of Benzoin and Benzoic Acid The main objective of the experiment was to use the separating funnel to separate two organic compounds that include Benzoic acid and Benzoin. The simplest methods utilize different solubility exhibited by most compounds in water compared to organic solvents. In this case, the experiment which I carried out was based on the fact that benzoic acid is soluble in organic solvents as well as it is easily converted to water soluble benzoate anion. In order to carry out this separation, sealable funnel that is specifically designed for the task was used. The objective of the experiment was met because I was able to separate Benzoic acid from benzoin compound. The compounds were later purified then weighted and the results were recorded. Purification of both benzoic acid and benzoin was done by crystallization. Introduction Compound separation is one of the most important activities done in chemistry laboratory (Irving, 1967). Whether the original material source is from a natural source, a sample from the environment or even the synthetic procedure product, there is normally a mixture of compounds (Van Ooyen et al., 1967). Only one specific compound may be needed or we could wish to analyze all the species present. Such separations are based on exploiting some physical variations either between the molecules in the mixture or chemically modified type. A broad array of separation techniques do exist and it exploits a range of various molecular properties, and they include size, crystal, mass, charge (for ions) and structure (Liljenzin et al., 1969). A separating funnel was used to separate 2 immiscible (benzoin and benzoic acid) solvents mixed together through shaking the sealed apparatus. During shaking and holding the separating funnel in my warm hands, the molecules were given enough kinetic energy to undergo a change from the liquid state to gas state. In the experiment, benzoic acid was converted to water-soluble benzoate anion by treating it with sodium hydroxide solution which is a strong base. In this case, benzoin remained dissolved in 1,4-Dibromobenzene because it does not dissolve in sodium hydroxide,. After the separation of organic and aqueous layers, the benzoic acid was recovered from the aqueous solution by addition of hydrochloric. Both compounds were then purified by crystallization, dried then their weights were measured and recorded as indicated in the results section. Methods The separation of Benzoin and benzoic acid The separating funnel was used to separate 2 different organic chemicals that included benzoin and benzoic acid. In the separating funnel, a compound was extracted from one solvent into another immiscible solvent through mixing of the 2 solvents. This allowed the solvents to separate. Separation was carried out by running off the lower or bottom layer (normally aqueous) through the tap below and the top layer (normally organic) were poured out from the top. Basing on the above, benzoic acid was manipulated to become soluble in the aqueous phase. In the experiment, benzoin and benzoic acid were dissolved in 1,4-Dibromobenzene.The benzoic acid was converted to water-soluble benzoate anion by treating it with sodium hydroxide solution which is a strong base. Since benzoin does not dissolve in sodium hydroxide, it had to remain dissolved in 1,4-Dibromobenzene.After organic and aqueous layers were separated, the benzoic acid was recovered from the aqueous solution by addition of hydrochloric acid as shown in figure 1 below Figure1. The recovery of benzoic acid from the aqueous solution Recovery and purification of benzoic acid Approximately 60ml of water in a 100ml beaker was prepared.2 boiling chips was added then heated to boil on a hot plate. This was for benzoic acid re-crystallization later. The aqueous layer flask was taken to steam bath in the fume hood, a few boiling chips were added then boiled off any dissolved 1,4-Dibromobenzene.The solution was then cooled and 10M HCl was slowly added with stirring until the appearance of a white precipitate was complete. The acidity of the solution was checked with litmus paper. The crystals were collected with Buchner funnel. The crude benzoic acid was transferred to a clean 100 ml conical flask and re-crystallized from the boiling water on the hot plate. The crystals were washed with cold water then dried at the pump. The weights and the characteristics (pure white or yellow tinge) of the crystals were recorded. Recovery and purification of benzoin The benzoin that remained in the 1,4-Dibromobenzene layer was washed with 10 ml of saturated NaCl solution. This was done to reduce the amount that was dissolved in the 1,4-Dibromobenzene.The stopper was removed and the lower layer was run off into a conical flask for disposal. The 1,4-Dibromobenzene from the top of the separating funnel was carefully poured into the flask that was labeled 1,4-Dibromobenzene layer. Anhydrous sodium sulfate spatulaful was added then swirled. Sodium sulfate grain was seen moving freely during swirling the flask. The sodium sulfate was removed by gravity filtering the benzoin solution via a fluted filter paper. Into a 100ml conical flask, a few boiling chips were added and the 1,4-Dibromobenzene was boiled off on the steam bath in the fume hood. This resulted to a yellowish sludge (crude product).The conical flask was then removed from the steam bath. Benzoin was re-crystallized from ethanol on the steam bath. The crystals ware washed with small amount of ethanol then dried at the pump. The weight of the crystals including the description (yellow or white) were recorded Results The weights of pure precipitate of both benzoic acid and benzoin were determined after the subsequent steps of separation and purification. Before the determination of both precipitate weights. For aqueous solution or layer, the weights of 25 ml flask and the mixture (both layers) were determines as 227.106g and 0.865g respectively. From these, the weight of the precipitate(benzoic acid) was determined as (27.215-27.100) =0.109g).The melting point was as well determined as 132oc.For the case of organic layer, the weights of 25 ml flask and both flask and precipitate was 27.121g and 27.204g respectively. Basing on this, the weight of the precipitate (benzoin) was determined as (27.204-27.121) =0.082g).Its melting point was determined as 132oc.Percentage yield of benzoic acid was: (0.109/0.4325)x100 =25%.While the Percentage yield of benzoin: (0.062g/0.346g)x100 =24%. The benzoic acid crystals were washed with cold water then dried at the pump. The characteristics of benzoic acid crystals were observed as pure white while for benzoin crystals were observed as yellow. The benzoin crystals ware washed with small amount of ethanol then dried at the pump. Discussion The main objective of the experiment was to use the separating funnel to separate two organic compounds that include Benzoic acid and Benzoin. Compound separation is one of the most important activities done in chemistry laboratory. The simplest methods utilize different solubility exhibited by most compounds in water compared to organic solvents. In this case, the experiment carried out was based on the fact that benzoic acid is soluble in organic solvents as well as it is easily converted to water soluble benzoate anion. The separating funnel was used to separate 2 different organic chemicals that included benzoin and benzoic acid. In the separating funnel, a compound was extracted from one solvent into another immiscible solvent through mixing of the 2 solvents. This allowed the solvents to separate. Despite the experiment limitations, the results came out as expected and the crystals were obtained following extraction and separation of both compounds that included benzoic acid and benzoin. For instance, Benzoin was re-crystallized from ethanol on the steam bath. The crystals ware washed with small amount of ethanol then dried at the pump. On the other hand, the crystals were washed with cold water then dried at the pump. The weights and the characteristics (pure white or yellow tinge) of the crystals were recorded. There are probable limitations that could have caused in accurate results of the experiment and include the following; firstly, the measuring equipment such as weighing scale may have not been calibrated and this might result to giving wrong weights’ values that can lead to recording of wrong precipitates weight values. Secondly, wrong measurements of the solvent and solutions volumes due to human error or faulty measuring equipment could result to wrong results recording during the experiment. Thirdly, low quality of the solutions due to poor storage could contribute to wrong results. The results might have been different due to experimental errors that include human error as well as uncertainties inherent in the experimental process. Conclusion Basing on the results, it can be concluded that the experiment objective was met since benzoic acid was separated from benzoin then both compounds were purified and weighted. However, the results can be improved from the previous one if the laboratory protocol is strictly followed. For instance, some of the measuring equipments were not calibrated, therefore, it was appropriate to calibrate it in order to determine if it was accurate. In doing these, the results could be more reliable. The quality of all the compounds used was supposed to be checked to know if it was up to the required standards. The storage conditions have an effect on the compounds used. Works Cited Irving, H. p. 91, ISEC’66, Solvent Extraction Chemistry Dyrssen, D.; Liljenzin, J. O.; Rydberg, J. Eds.; North Holland, Amsterdam (1967).Print Liljenzin, J. O.; Stary, J.; Rydberg, J. ISEC’68, Solvent Extraction Research, Kertes, A. S.; Marcus, Y., Eds., J. Wiley and Sons, New York, 1969.Print Van Ooyen, J.; Dyrssen, D.; Liljenzin, J. O.; Rydberg, J. (Eds.) Solvent Extraction Chemistry (ISEC 1966), North-Holland Publ. Co., Amsterdam, 1967.Print Read More