Inthis experiment, an acid base extraction was done in order to separate amixture of benzoic acid, 4- chloroaniline and naphthalene. Find the meltingpoints of each of the compounds and compare with the actual melting points. Toseparate these organic compounds, it is a must to use solvent- solvent extractionthat will help attain product purification. In order to follow through with theextraction, the solvents must be immiscible (Korry).
Korry also mentions thatin this experiment, the mixture will react with HCl in order to react withamine (which has a nitrogen in it) which at the end will give solid salts thatcan be weighed. The extraction includes a separatory funnel, it plays the mostimportant role in this experiment, which helps separate two compounds byshaking it. Acid- base extraction is used for separating different organiccompounds that have same functional group (Libretexts). This extraction helpsseparate acid, base and a neutral compound. In this extraction, organic acidand organic base can be separated from organic solvent through the process ofadding aqueous solution to it (from WayBack Machine).
Experimental Section (Weldegirma, 12-13) : 1) Solid mixture (acid, base, and neutral)of 3 grams was collected. 30 mL diethyl ether was added to dissolve.2) Both, the mixture and the ether wereadded into the separatory funnel with 20 mL of fresh ether. 30 mL of 5% HCl wasadded. Capped the funnel.
3) Shook vigorously, uncap the vent, repeata few times until separate layers of the mixture was seen.4) Top layer was benzoic acid. Drew thebottom layer into a 125 mL Erlenmeyer flask which contained protonated amine.5) This was in Flask #1. 6) Then 3 M NaOH was added, dropwise, untilthe solution turned basic.
7) The solid amine, 4- chloroanilineappeared at the base. Used pH strip to determine if it was basic yet. Placed inice for 15 minutes.8) Used vacuum filter, rinsed with coldwater to get the remaining solution out. 9) Obtained dry crystal out, allowed to airdry, then measured its weight. 10) Back to separatory funnel, added 50 mL 5%NaOH.
Capped it. Shook vigorously, uncap the vent, repeated few times until twolayers were observed.11) Naphthalene, organic layer, appeared onthe top. Acid, aqueous layer, appeared on the bottom. The bottom layer wasdrawn out. 12) This was in Flask #2.
Added 6 M HCl. Putin ice bath for 10- 15 minutes, used the pH strip to check the acidity of it.Repeated steps 8 and 9.13) Naphthalene, left in the separatoryfunnel, added 20 mL NaCl which removed the traces of water. Repeated step 3.14) Drew the bottom layer out, and discardedit in aqueous waste.
Drew the organic layer, the top layer, into flask #3.15) Added , then waited 15 minutes. Transferredflask #3 into a tared 125 mL vacuum flask.16) Rinse the drying agent with 10-15 mLfresh diethyl ether.
Using vacuum pump, all the liquid was evaporated untilonly solid remained, which was weighed. Table of Chemicals: Benzoic Acid: 4- Chloroaniline: Naphthalene: Physical properties: Carboxylic acid, white crystal Physical properties: an amine, white or pale yellow solid Physical properties: aromatic hydrocarbon, white crystal with mothball odor Molar Mass: 122.12 g/mol Molar Mass: 127.57 g/mol Molar Mass: 128.
17 g/mol Melting point: 122°C Boiling point: 480.6 °F Melting point: 68-71°C Boiling point: 449.6 °F Melting point: 80°C Boiling point: 424.4 °F Results: # Benzoic Acid 4- Chloroaniline Naphthalene Mass: 1 g 1 g 1 g Mass recovered: 1.002 g 0.882 g 0.519 g Percent Recovery*: 100.
2% 88.2% 51.9% Melting Point: 122°C 68-71°C 80°C Melting Point found: 123°C 72°C 80°C *PercentRecovery for Benzoic Acid: * 100% = * 100% = 100.
2%PercentRecovery for 4- Chloroaniline: = * 100% = 88.2%PercentRecovery for Naphthalene: =* 100% = 51.9%Discussion:Theexperimental results obtained for benzoic acid, 1.002 g (100.2%) was more than1 g (100%) due to error such as not letting it air dry for enough time whichcauses the solid to still contain a little bit of liquid in it. It could havealso had a little bit of base in it, from the first flask. The results for 4-Chloroaniline obtained was 0.882 g (88.
2%) which was less than 1 g (100%). Thiscould have been due to not letting it sit in the ice bath for enough time, ormoving too quickly through the vacuum flask. The value obtained for naphthalenewas 0.519 g (51.9%) which was almost half of 1 g (100%).
The error that mayhave caused this vast difference in the percent recovery is due to the waitingfor all of the liquid to evaporate from the flask which may have caused thesolution to evaporate more than it was acquired. Due to experimental error ofturning on and turning off the vacuum flask during the process, it may havecaused more solution to evaporate rather than be obtained. The melting pointfor benzoic acid is 122°C and was found to be 123°C. There isa difference of 1°C and it may have been due an error whilefinding the melting point. 4- Chloroaniline has a range of melting pointbetween 68-71°C and the melting point found was 72°C. Theobtained melting point was 1°C higher than the range, which can be dueto experimental error while finding the melting point. The melting point ofnaphthalene is 80°C and was found to be 80°C, whichmeans that there was no difference in the literature value and the experimentalvalue of naphthalene.
Conclusion: Thetheory of this experiment was an easy way to separate acid, base and a neutralcompound from the mixture of them. The compounds in the mixture were immisciblewhich means that they can be separated much easily. In the lab, HCl and NaOHwere added to the mixture in order to separate the base from the mixture first,then the acid was separated. The procedure used in this lab can be used indaily life, for example: in order to separate oil from water, this method canbe used. There are many other separations that can be performed using thistechnique, because the less dense liquid will form its layer on the top of thedenser liquid. The lab successfully accomplished the aim of the experiment whichwas to separate acid, base and a neutral compound using acid- base extractionmethod.