Experiment7- Separation of Organic Compounds in a solid mixture by protontransfer chemical reactions (Acid-base reactions)
Themain objective of caring out this experiment was to separate andisolate benzoic ethyl14-aminobezoate, acid and 9-fluorenone from a1:1:1 mixture using the process of proton transfer chemicalreactions. Each component was extracted from the mixture usingacid-base reactions. Sodium hydroxide and hydrochloric acid were thetwo main solution used in this experiment to separate the chemicalsfrom the mixture. To obtain the basic compound 2ml of 3 M HCL wasadded to the mixture using a graduated cylinder and shaken for about4-5 minutes. The aqueous solution obtained was placed in a water bathand 6M NaOH added drop wise and finally vacuum filtration was used toobtain the solid from the solution. For acid compound 2 ml of 3 MNaOH was added to methyl chloride solution and a similar extractionprocess was carried out. 9-Fluorenone was collected by adding waterto wash the remaining methyl chloride solution. Once the solidportions were completely isolated, the percent recovery was done byweighing the three chemical compounds individually.
Benzoicacid was the primarily acidic component, ethyl14-aminobezoate was thebasic component and 9-fluorenone was the neutral component in the1:1:1 mixture. The percentage yield that was recovered for each ofthe three chemical compound ethyl 4-aminobezoate, benzoic acid and9-fluorenone was 44%, 56% and 82% respectively. The melting point foreach chemical component varied with ethyl 4-aminobezoate having themelting point range of 88⁰C – 92.2⁰C, benzoic acid having themelting point range of 121.6⁰C – 122.9⁰C, and finally9-fluorenone having the melting point range of 79.1⁰C – 88.5 ⁰C.The literature values for each were: ethyl14-aminobezoate being88⁰C-90⁰C,benzoic acid being 121⁰C-123⁰Cand 9-fluorenone having a melting point range between 82⁰C-85⁰C.The literature melting point values correlated well with theexperimental melting point values. The percent recovered for each ofthe three chemical components was within the accepted value, anydiscrepancies with the amount of percent recovered or the meltingpoint was due to error that occurred during the experiment.
Theobjective of caring out this experiment was to extract threedifferent chemical components from 1:1:1 mixture containing9-fluoerenone, ethyl 4-aminoacidbenzoate and Benzoic acid. The 1:1:1mixture was separated and isolated using an acid-base liquid toliquid extraction method. There are two types of liquid to liquidextraction methods which are also used in this experiment the firsttype of extraction uses polarity where water is used to extractorganic components from a mixture by extracting the very high polarmaterials in the solution such as in organic salts. The second typeof liquid to liquid extraction uses the chemical properties of thecompound. Acid extraction is used to separate basic compounds fromthe organic mixture.
Benzoicacid (a Carboxylic acid) is referred to as "weak acids"because it incompletely ionizes in water because of the reversibilityof its reaction with water that forms hydronium ion, H3O+. Weak acidsyield significantly less than one H3O+ ion in solution for each acidmolecule dissolved in water. The structure of benzoic acid consistsof a large, non-polar benzene ring attached to a small, polarcarboxylic acid functional group (C6H5COOH). The intermolecularforces within a benzoic acid are London dispersion bonds,dipole-dipole bonds, and hydrogen bonds. The Reactions of benzoicacid can occur at either the aromaticring orat the carboxylgroup:The ability of Benzoic acid (a carboxylic acid) to ionize and behaveas acids is a direct function of the electronic properties andbonding order of the atoms that make up the carboxyl (COOH) moiety.This functional group consists of a carbonyl group that has anelectron deficient carbon atom due to pi bonding (double bond) toelectronegative oxygen. This carbonyl carbon also is directly linkedto, and in conjugation with, a second electronegative oxygen atombearing a hydrogen atom. This electronic arrangement allows for lossof a proton and ionization because electron density is "pulled"from the hydroxyl hydrogen through the conjugated carboxyl group, andthe charge formed upon ionization (in the conjugate base) isstabilized by resonance delocalization. The conjugate base is a saltand is water soluble therefore, it is removed from the organicsolvent layer. Reacidification of this basic aqueous layer willregenerate the organic acid, which will precipitate from the aqueoussolution due to the acid`s limited solubility in water.
Ethyl4-aminobenzoate is classified as a weak base. A weak base is a basethat produces fewer hydroxide ions in water solution than there areparticles of base dissolved. In this experiment Ethyl 4-aminobenzoatereacts with 2ml of 3M HCL by picking up a proton. The proton istransferred to a basic compound, but not to a neutral or the acidicone in the 1:1:1 mixture. The basic compound (ethyl 4-aminobenzoate)becomes ionic, and more water-soluble. A mineral base NaOH is addedto take away the proton in order to obtain pure form of ethyl4-aminobenzoate from the ions. 9-fluorenone is the neutral compoundsince it does not react with either the acids or the base.
Thedata yielded from this experiment included 9-fluorenone weighing41mg, benzoic acid weighing 28mg and ethyl 4-aminobenzoate weighing22mg. From the calculations, the percentage recovery for 9-fluorenonewas 82%, benzoic acid was 56% and ethyl 4-aminobenzoate was 44%. Thepercentage yield for all the three components was 61%, this valueideally is suppose to be 100% according to the literature value. Thiscould have come about for a multitude of reasons. To begin with,during vacuum filtration, the entire compound was not adequatelytransferred onto the filter paper- some was lost to the sides.Therefore, the mass recovered would be lower. Also, during the actualseparation of the water mixture from ether solution, some of thesolution was spilt while transferring the solution to a beaker.Similar to before, this would cause the mass recovered to be lower.
Theoriginal composition of the mixture obtained was also not known.Though it was assumed to be a perfect 1:1:1 ratio of acid to base toneutral, it cannot be determined if the solution obtained was aperfect 1:1:1 ratio. Therefore, the percentage recovers could bepotentially higher for some and lower for others. Lastly, theequipment used was not perfectly cleaned. Therefore containments mayhave been mixed up with the reaction which would cause vivid changesin the data if reactions occurred before they were supposed to. If alittle HCl was still left after the first initial addition, the HClcould have caused a precipitate to form at the wrong point in time.Therefore, the experiment was not perfect because many uncertaintiesare present about the errors in the lab but can be considered asuccess because the compounds were separated from the originalmixture.
Inthis experiment, the start melting point for 9-fluorenone was lowerthan the literature value and the finish melting point was higherthan the literature value, while the melting points for benzoic acidand ethyl 4-aminobenzoate were in the range of melting points inregards to the literature values. 9-fluorenone was supposed to havemelting point range of 82⁰C – 85⁰C, in this experiment themelting point range achieved was 79.1⁰C – 88.5⁰C. The possiblereason for why 9-fluorenone had a lower start melting point could bebecause of the inaccurate weights achieved for during the experiment.The skewed percent yield recovered values can also explain how theexperimentally achieved start melting point of 9-fluorenone is lowerand end melting point is higher than what the literature value says.Another reason why this melting points for these chemical componentswere not exact to the literature values melting point range could bedue to impurities in the chemical components. To avoid errors andskewed results the extraction process should have been done betterand more accurately. Overall, this experiment went smoothly and asplanned.