This experiments enables you to separate a solid-phasemixture consisting of (i) 2-methoxynaphthalene, (ii)m-nitroaniline,and also (iii) benzoic acid utilizing Separatory Funnel extractions. Since each of these chemicals have similar solubilities in water and ether, you deserve to impact a separation their chemical properties. For example, benzoic acid is insoluble in water yet the benzoate ion is soluble in water. Thus, under neutral conditions, the benzoic will certainly partition right into the ether layer. Adding NaOH will certainly neutralize the benzoic acid creating the benzoate ion, which now goes into the aqueous layer, leaving various other other 2 organic compounds in the ether. Likewise, nitroaniline is not soluble in neutral or basic conditions, but is soluble in acidic options. Making the liquid in the Separatory Funnel acidic will certainly permit the nitroaniline to be positively charged, and it will now partition right into the aqueous layer. Isolating the aqueous layers permit you to crystallize the benzoic acid and nitroaniline as define in this protocol. Final analysis of the isolated chemicals will be done using melt point analysis. You will certainly also must determine a percent yield for each.

You are watching: How does naoh affect the solubility of benzoic acid why

Benzoic Acid m-nitroaniline1 2-methoxynaphthalene
1para or meta-nitroaniline may be supplied for this experiment


In Experiments Ia and also Ib youpurified a solid by picking a solvent thata certain chemical is soluble in, but which an additional remainsinsoluble(e.g., acetone dissolved aspirin however not the NaCl or silica) and by making use of the strategy of re-crystallization you were able to isolate benzoic acid in pure form away from contaminants. However, tbelow aremany timeswhen neither of these approaches are be appropriate because you mayneedto isolate two or more solids from the same mixture that have exceptionally similar physical or chemical properties. For instance, and also both solids areorganicin nature, with similar solubility properties, or when the liquids youaretrying to separate boil at virtually the exact same temperature (distillation isaapproach we will usage in a later on experiment). Solventextraction isa procedure that will certainly work-related well in many kind of of these cases. Throughout anextractivity,one solvent is used to disfix (or partition) one or more of thecomponentsof the mixture, leaving various other components behind (in the solid phase,theliquid phase, or in one more solvent). In this experiment we will beworkingthrough "liquid-liquid" extractions, however the general ethics will certainly bethevery same for "solid-liquid" extractions as well.

Zubrick renders the importantdifference in between "extraction" and "washing".While the same series of speculative measures are mostly offered to carryoutboth of these techniques, and also they use the exact same concept, the maindifferenceis that in an extraction you are relocating a substance you desire to keepintoa new solvent, while in washing you are relocating a substance you willthrowaway into a brand-new substance. In future experiments you may be instructedto"extract the product mixture via 3, 10-mL sections, of ether," or"washthe ether extracts through 10% sodium bicarbonate, and then through water."Theseinstructions assume you understand also the distinction in between extractionandwashing.

In this experiment you will beoffered a mixture containing 2-methoxynaphthalene, m-nitroanilineand benzoic acid. The initially action in the separation will certainly be to dissolvethe whole mixture in one organic solvent (diethyl ether). You will certainly usethe chemical and also physical properties of these compounds to determineexactly how to separate them in pure create making use of extractions (and also washings,wbelow necessary), and isolate the m-nitroanilineand benzoic acid in solid form. Follow the guidelines provided in chapter15 of Zubrick in determining the solvents you will certainly usage, the order inwhich you perdevelop the extractions, and also the techniques you will usage to geteach compound earlier right into the solid form.

Day1 Do separatory funnelextractions of chemical mixture Isolate pure benzoic acid (from fundamental extractivity of the ether layer) Isolate purem-nitroaniline (from acidic extraction of the ether layer) Day2 Quantitate recoveredchemicals (recognize percent yield) Determine melt pointsfor recovered chemicals



2-methoxynaphthalene is anirritant — wear gloves while managing it. m-nitroaniline(or p-nitroaniline)is an irritant, and also is very toxic —wear gloveswhile managing it; take one-of-a-kind care not to ingest any type of of it or toinhale its vapors or dust. Benzoic acid is an irritant— wear gloves while handling it. Hydrochloric acid solutionis corrosive and toxic — wear gloves while handling it. Sodium hydroxide solution iscorrosive and also toxic — wear gloves while dealing with it. Diethyl ether (a lot of oftenjust described as ether) is highly volatile with a boiling point ofabout 35oC,and also very flammable — handle through care and also pour from thebottle in the hood.

To carry out the experiment, obtain around 3 grams (2.5-3.0 grams is acceptable) of the solid mixtureconsisting of about equal parts of:

2-methoxynaphthalenem-nitroanilinebenzoic acid

You will be separating from the above mixture pure benzoic acid and also pure m-nitroaniline.

Under normal problems, all three of your organic compounds will certainly disfix in the organic layer (the diethyl ether), not the aqueous layer. The only method to sepaprice the organic compounds from each various other is to rely on their chemical properties, not just physical properties. To this end, you have to always remember that neutral organic compounds execute not disfix to an excellent extent in aqueous options. Alternatively, charged organic compounds will often dissettle in aqueous solvents bereason they are ions. Conversely, neutral organic compounds disfix in organic solvents (e.g., diethyl ether) whereas charged organic compounds will certainly not disdeal with (or stay dissolved) in organic solvents.

It is feasible to pressure an organic compound, that is charged, out of the organic phase right into the aqueous phase. This process is generally perdeveloped utilizing a Separatory Funnel. When a compound leaves one phase and also goes right into the other phase, this process is described as partitioning. For example, when the benzoate ion, derived from benzoic acid, leaves the ether phase and goes into the aqueous phase, we describe this as partitioning into the aqueous phase.

The numbers below display just how this is done in order to isolate different compounds based upon their acid-base properties. Benzoic acid is soluble in ether, but once neutralized and also converted into benzoate ion, it is now soluble in water, so will partition right into the reduced aqueous phase, leaving uncharged organic compounds in the ether. Once the aqueous layer is isolated, benzoic acid is conveniently isolated once the benzoate ion is converted back right into benzoic acid following the addition of 6 M HCl.


m-nitroaniline is soluble in ether, even when the aqueous layer is standard, because a base continue to be base in base. However before, as soon as a solution of 1 M HCl is added to the Separatory Funnel, the amino group accepts a proton which produces a charged molecule. This charged molecule then partitions right into the aqueous layer, and can be accumulated. When the aqueous layer has actually 6 M NaOH added to you, the m-nitroaniline is regenerated, and since it is currently insoluble in water, you can collect it as a solid.


The basic dominance you need to remember is that uncharged organic compounds stay in the organic (e.g., ether) layer. Charged organic compounds partition right into the aqueous layer. It does not issue whether the organic compound acquires a positive or negative charge, it will certainly partition into the aqueous layer, out of the organic layer. Acids (i.e., benzoic acid) are converted right into their negatively charged ions in the existence of base, and partition right into the aqueous layer. Bases (e.g., m-nitroaniline, which is a base because it is a proton acceptor) come to be positively charged when reacted with an acid, and this positively charged ion will now partition right into the aqueous layer. Charged molecules partition right into the aqueous layer and also uncharged molecules partition right into the organic layer.

Isolation of Benzoic Acid

Using a powder funnel (a plastic funnel through a more comprehensive opening and that fits in the ground-glass opening of your Separatory Funnel) add all of your mixture to the Separatory Funnel. Add the complying with to the Separatory Funnel:

30 mL of diethyl ether (the ether bottle must be kept in the hood and always rearea the lid after dispensing)30 mL 1.0 M NaOH

By including the NaOH to the organic compound mixture (through diethyl ether), you will convert the benzoic acid (uncharged) right into sodium benzoate (negatively charged), which is now soluble in aqueous solutions. The various other organic compounds, which continue to be neutral in standard options stay uncharged in the diethyl ether layer. The negatively charged benzoate ion currently partitions right into the reduced aqueous layer as soon as you shake the contents of the Separatory Funnel. Be specific that you thoapproximately mixture the contents of the Separatory Funnel to allow reliable partitioning of the benzoate ion into the aqueous layer.

Once you check out the appearance of two unique layers in the Separatory Funnel (upper organic layer and also reduced aqueous layer), you have the right to collect the reduced aqueous layer which contains the benzoate ion. To collect the lower layer, initially rerelocate the ground-glass stopper, and then open up the stopcock valve. Let the lower aqueous layer drain out until the optimal organic layer simply reaches the stopcock worth opening. Cshed the stopcock valve, and prepare to isolate the nitroaniline.

In order to collect your benzoic acid, you must convert the benzoate ion (which is entirely soluble in water) earlier to benzoic acid (which is greatly insoluble in water). To effect this convariation, you have to initially include acid to the benzoate solution, which will certainly then allow benzoic acid to form.

Using the 6 M HCl solution add sufficient acid to convert every one of the benzoate ion to benzoic acid. As a first approximation, you will require around 5 mL of the 6 M HCl to neutralize your solution. Keep including 6 M HCl till the solution is acidic, based upon litmus paper. When you think you having actually an acidic solution add around 2 mL even more 6 M HCl, because you cannot have actually also a lot acid. A bit expression you can remember is: "acid remains acid in acid."

Collect your solid benzoic acid above making use of vacuum filtration through a typical Buchner Funnel filtration setup. For this specific experiment, carry out not save the filter paper in the cooktop as it will certainly decompose at a high temperature once the paper is acidic. So, just scrape your solid benzoic acid right into an evaporating dish (or 100-mL beaker) and also place it in the drying range till the next lab duration.

Isolation of m-Nitroaniline

After you have actually removed the benzoic acid from the ether layer (by the addition of NaOH above), you are left through an ether layer still containing the nitroaniline and also methoxynaphthlene. In order to impact the removal of the nitroaniline, you count on the reality that nitroaniline functions as a Bronsted-Lowry base (proton acceptor) a lot like exactly how ammonia (NH3) accepts a proton to end up being the ammonium ion (NH4+). In the instance of the nitroaniline accepting a proton, it becomes the nitroanilinium ion. As such, as soon as you include a solution of 1 M HCl to the ether layer, you transform the neutral nitroaniline into the charged nitroanilinium ion, which have the right to then partition into the acidic aqueous layer.

Add 30 mL of the 1 M HCl solution to the Separatory Funnel. Following this addition, replace the ground-glass stopper

Caution:After using ether, save the lid on the ether bottle as soon as not in usage.

Disfix the solids in theseparatory funnel by including the stopper and mixing thoroughly. You cancarry out your separatory funnel extractions in the lab (external of the hood),yet any kind of open up containers via ether need to be tackled in the hood (you canremove the stopper to the separatory funnel in the lab withoutproblem).

Using well-known chemical andphysical properties for these compounds build an extraction plan inorder to sepaprice the 3 solids, and also to isolate each compound insolid form. For instance, what are the physical properties ofthese compounds, what are their solubilitiesor their absence ofsolubility in specific solvents (e.g., in ether or aqueous solvents).The extractivity and washing solvents accessible are: water; 10% sodiumbicarbonate solution; 6 M sodium hydroxide solution; 6 M hydrochloricacid solution. Use 6 M HCl or 6 M NaOH to neutralize your aqueous remedies gathered containing either the benzoate ion (extractivity in base) or the nitroanilinium ion (extractivity in acid) in the aqueous options.

Once you have successfullyextracted either the m-nitroanilineor benzoic acid right into among the aqueous extraction solvents, you willshould isolate that chemical in pure solid form. All of theorganic chemicals will certainly be initially soluble in the organic solvent(diethyl ether). For instance, just how have the right to you pressure the benzoicacid to be partitioned (extracted) into one of the extractivity or washoptions for purification? Once it is in the appropriatesolution as a dissolved solute, how have the right to you convert it right into aninsoluble solid to isolate and characterize?

After you have isolated boththe m-nitroanilineand also benzoic acid in pure develops, you have the right to discard the staying organicliquid, containing the 2-methoxynaphthalene in the organic liquid wastecontainer.

How a lot m-nitroanilinedid you recover? How much benzoic acid did you recover? Whatare the physical properties of these compounds that you observed(shade, crystal form, etc.)? What is the melting point foreach these compounds? How carry out these values compare to the literaturevalues?Do you think that you isolated these compounds in pureform, based upon the oboffered melting points?

Guidelinesfor doing separatory funnel extractions:

Read chapters 15 and also 16 in Zubrick.

Acid and Base Solution Information Acids Uses of acid solution Base Uses of standard remedies

6 M HCl

Use this solution onlyto neutralize a straightforward solution never for extractions 6 M NaOH Use this solution onlyto neutralize an acidic solution never for extractions
1.0 M HCl Use this solution forwashes and extractions (e.g., in a separatory funnel) never forneutralizations 1.0 M NaOH Use this solution forwashes and also extractions (e.g., in a separatory funnel) never before forneutralizations
10%NaHCO3(sodium bicarbonate solution) deserve to be provided to neutralize an acidicsolution within a separatory funnel, if you want to finish up via a solutionclose to neutral pH. To remove the NaHCO3,simply use 2-3 DI water washes, effectively washing the etherlayer and also gaining rid of the bicarbonate ion. Do not use sodium bicarbonate solution to neutralize an acidic solution not in a separatory funnel.

CheckingpH (acidity or basicity) of a solution.

See more: What Molecule Provides Long Term Energy Storage For Plants, Macromolecules Part B Flashcards

Litmus paper is an effectiveand inexpensive approach to recognize if a solution is either basic oracidic. Use litmus paper in this experiment to identify if you havedeveloped an acidic or standard solution.

Red litmus paper is used tomonitor for basic solutions (red paper transforms blue in base) Blue litmus paper is offered tomonitor for acidic solutions (blue paper transforms red in acid)

Chemicals and Equipment Used for Experiment
6 M HCl 6 M NaOH 1.0 M HCl 1.0 M NaOH 10% NaHCO3 Diethyl ether Benzoic acid m-nitroaniline 2-methoxynaphthlene separatory funnel

Chemicals, Reagents, and Supplies Compound MW Amount mmol mp bp Density ηD msds Benzoic Acid 122.12 --- --- 122.4 249.4 1.2659 --- view m-Nitroaniline 138.12 --- --- 114 331.7 1.424 --- view 2-methoxynaphthlene 158.2 --- --- 73-75 274 n/a --- view Diethyl ether 74.12 30 mL --- -116.3 34.6 0.7134 --- view HCl view NaOH view Compound g/mol grams or mL 10-3 M oC oC g/mL ηD msds