ACID-BASE EXTRACTION

ACID-BASE EXTRACTION

Abstract

The experimental goal and purpose are to separate benzoic acid, p -nitroaniline, naphthalene based on the property solubility of acid, base, and salt. Through vacuum filtration, 43.1%    yield of benzoic acid was collected from acid extract, 49.6% of naphthalene and 91.4% of p-nitroaniline.

Introduction

The goal of the experiment is to separate benzoic acid, p- nitroaniline and naphthalene based on their solubilities of acid, base and salt. The liquid-liquid extraction separates compounds based on the relative solubility of two different immiscibleliquids. (Celius, Peterson, Anderson-Wile, & Kraweic-Thayer, 2018).  Usually polar and non- polar compounds. There is a transfer of species from aqueous to organic driven by chemical potential. The solvent which is supplemented in the solute is the extract. Acid-base extraction separates organic compounds based on their acid-base properties by introducing a proton into the compound making it a positive ion or removing a proton making it a negative ion.pKa data predicts reactivity by determining the direction of acid-base equilibrium (.Ma, Wei, Liu, Liu, & Zong,2019). In weak acid and base, the equilibrium lies to the left. HCl and NaOH are Bronsted acid and bases respectively and so do not react upon exposure to neutral substances. To achieve the separation of neutral compounds, the liquid-liquid extraction method is used.Acid-base extraction is applied in organic chemistry to isolate compounds and natural products such as alkaloids from crude oil.

Experimental

Benzoic acid

p-Nitroaniline

Naphthalene

Distilled water

6M HCL

6M NaOH

Ethyl acetate

Anhydrous magnesium sulfate for removing water

Ethanol for recrystallization

Separatory funnel

Erlenmeyer flask for keeping the extract.

Hirsch funnels for vacuum filtration.

Rovatap for evaporation of a solution..

Procedure

Part 1: extraction

1gram of benzoic acid, P-nitroaniline, naphthalene was transferred into 60ML separatory funnel using 10ml ethylacetate.5ml of distilled water and 6M HCL was added into the mixture. the bottom layer was drained into Erlenmeyer flask and was marked as HCL extract. The second step was repeated and the two aqueous combined. 5ml of distilled water and 6M NaOH was added to the funnel shaken and then transferred into Erlenmeyer flask and was marked as NaOH extract. The procedure was repeated and the two aqueous extract combined. The organic layer was poured into 50mL Erlenmeyer flask then marked as an organic extract. Separatory funnel was rinsed with ethyl acetate. water traces were removed by adding magnesium sulfate. The drying agent was separated by gravity filtration and the filtrate was collected in a 25mL pear-shaped flask.

Part 2: Isolation

Hydroxide extract was cooled and neutralized using 6M HCL till the mixture is strongly acid. The solid was isolated by vacuum filtration using the Hirsch funnel it was washed with a small amount of cold water, then the solid was dried and the mass recorded. The crude yield was calculated. The HCL extract was cooled and neutralized using 6M NaOH till the mixture is strongly basic. The solid precipitate was isolated, p-nitroaniline, dried by vacuum filtration. The dried mass was recorded and the crude yield was calculated. Ethyl acetate was evaporated from the organic solution on a rotavap and naphthalene was obtained, dried and the crude yield was calculated.

Part 3: purification by crystallization.

Purification of crude benzoic acid by recrystallization from hot water: the solid crude was separated by hot filtration through a conical funnel plugged with cotton. The filtrate was allowed to cool in room temperature the cooled in ice afterward it was dried in the lamp before determining the melting points.it was followed by purification of crude p-nitroaniline and naphthalene by recrystallization from ethanol. Then the crystals were dried using a lamp before weighing and determining the melting points.

Results and Discussion

Discussion

The percentage yield of crude naphthalene was 49.6%, benzoic acid was 43.1% and p-nitroaniline was 91.4%. The melting points of benzoic acid p-nitroaniline and naphthalene were 120, 145,85 degrees Celsius respectively.

Reference:

Celius, T. C., Peterson, R. C., Anderson-Wile, A. M., & Kraweic-Thayer, M. (2018). From Observation to Prediction to Application: A Guided Exercise for Liquid-Liquid Extraction. Journal of Chemical Education, 95(9), 1626-1630.

Ma, Z. H., Wei, X. Y., Liu, G. H., Liu, Z. Q., Liu, F. J., & Zong, Z. M. (2019). Insight into the Compositions of the Soluble/Insoluble Portions from the Acid/Base Extraction of Five Fractions Distilled from a High-Temperature Coal Tar. Energy & Fuels, 33(10), 10099-10107.