Select an appropriate recrystallizing solvent. Separate and purify acetanilide from a mixture by recrystallization. Compare the melting points of impure and recrystallized Acetanilide

1. LAB REPORT No 1 : Purification of Acetanilide through Recrystallization
Date: August 29th
, 2016
I. PURPOSE: Selectanappropriate recrystallizingsolvent.Separate andpurifyacetanilidefroma
mixture byrecrystallization.Compare the meltingpointsof impure andrecrystallized Acetanilide
II. INTRODUCTION:
Impurities often contaminate organic compounds that
have been synthesized in the laboratory or isolated from
natural sources. Recrystallization is a purification process
used to remove impurities from organic compounds that
are solid at room temperature. This process is based on
the premise thatthe solubility of a compound in a solvent
increases with temperature. Conversely, the solubility of
the compounddecreasesasthe solutioncools,andcrystals
form.
Selecting an appropriate recrystallizing solvent to use is
probably the most difficult step of Recrystallization. The
primary consideration when choosing a recrystallizing
solvent is the extent to which the compound and
impurities are soluble in the solvent at high and low
temperatures. The graph in Figure 2 shows three possible scenarios for how the solubiliies of the
compoundandthe impurities depend on temperature. Ideally, the compound to be recrystallized
shouldbe verysoluble inthe chosensolventat elevated temperatures, but almost insoluble in the
cold solvent, as shown by line A. Impurities should be soluble in the chosen solvent at all
temperaturessothatimpuritiesstayinsolution,asshownbyline B.Alternatively,impurities should
be insoluble at all temperatures so they can be filtered from the hot solution, as shown by line C.
Miscellaneousnotesonmeltingrange depression/broadening:1.Only“soluble”impurities, which
are incorporatedintothe crystal structure at the molecularlevel,cause depressionand broadening.
An insoluble piece of metal or wood ionic salt crystal has negligible effect, because only a few
organicmoleculeswill be incontactand will be affected.2.Atthe chemical level, it is impossible to
“raise” the melting point of an already pure substance. It’s melting point can be depressed by
contamination,butnotraised.Practical:If the melting point for an unknown sample is observed to
be in between that of two candidates whose pure mp’s are known, the unknown can’t actually be
equal tothe lower-meltingcandidate.(Short of the rapid-heating effect, see later.) Most likely the
unknownsample isanimpure versionof the highermeltingcandidate. For example: Melting Range
4 suppose anunknownsample Xmeltsat148-152º, and isthoughtto be either candidate A (known
range is 141-142º) or B (knownrange is161-162º). Sample Xcannot be candidate A, but it can be an
impure and thus depressed version of candidate B. 3. Often contaminated solids are purified by
recrystallization.If the resultingmeltingrange isunchanged,the original sample probably was pure
to begin with. But if the resulting melting point gets higher, the original sample was obviously
impure.4.Whencrystals are isolatedby filtration from a solvent, it is important to allow complete
drying/evaporationof the solventinordertogeta goodmeltingrange.Residualsolventfunctionsas
a contaminantandwill depress/broadenthe meltingrange for a crystal. 5. When two chemicals are
mixed, the resulting melting point is not the average of the two mp’s. It is always depressed from

2. the meltingpointof the majorcomponentinthe mixture. This is true even if the impurity is higher
melting(whenpure) than the major component. For example, if a chemical that normally melts at
130º is contaminated by a small amount of material that when pure melts at 200º, the resulting
mixture will not melt between 130º and 200º. Rather, the melting point of the major component
will be depressed, and the observed melting range will begin lower than 130º. 6. Even when two
chemicalswithexactlythe same meltingpoint when pure are mixed, the resulting melting point is
depressed. Mixed Melting Points That mixtures have depressed melting points, even when both
components have comparable melting points when each is pure, provides a useful laboratory
technique. Consider the following situation and flow chart. If an unknown candidate X melts at a
temperature close to that of two potential candidates A and B, you can identify it by taking X+A
mixed melting point, and X+B mixed melting point. If X is equal to either candidate, one of these
mixedmelting points will not be depressed. If the mixture with X+A is not depressed, X = A. if the
mixture withX+Bisnot depressed,X=B. If bothmixturesare depressed,thenX≠A or B. (Reference
Lab Manual- Craig)
III. PROCEDURE:

3. 2.1. Reagents: Acetone,PetroleumEther,Pentane andwater
2.2. Procedure Part 0:
a. Weight100 mg of acetanilide
b. Divide intofourtesttube.
c. Prepare the solvents:Acetone,PetroleumEther,
Pentane andwater
d. Add2ml of eachsolventineverytesttube.
e. Observe andrecord.
f. Take the testtubessolutionsandsettheminhotwater
and coldwater.
g. Observe andrecord.
2.3. Procedure Part 1:
a) Taking125 mL Erlenmeyer
b) Add50 mL of waterand 2 gr of Acetanilide
c) Mixingwithwater
d) Agitate inthe hot plate withstirringbarfor5
minutes.
e) Observe andrecord.
f) Take the solutionandfilterbythe vacuum
filtrationasthe figure No3.
g) Collectthe precipitate inyour filtrationpaper
and store.
IV. ResultOBSERVATIONS
Part 0.: SELECTION SOLVENT
At the room temperature,we noticethe acetanilidedissolveimmediatelyinacetone withaclear
solution,acetanilide inethanolisapartial soluble because the solutionis clearwhite,petroleum
etherandethanol withacetanilide show notsolubility.The solutionisclearandthe acetanilide
isin the bottomof the bothtesttube.
At the coldtemperature,the solubilityinwater decreasebecause the solutionbecameand
clear,for petroleumetherthe solutionbecome more clearandclearthatshowsitis not soluble
incold temperature,thenthe testtube withacetoneshowsusthe acetanilide issoluble with
acetone at thistemperature.
At the hot temperature,inthe testtube withwater,the acetanilide starttodissolve littleby
little andmore if we agitate the testtube,inethanol the solubilityincrease because the solution
become inclearwhite indicatingthe acetanilide solubility,inacetone the testtube isclearall
the time showus the solubilityinacetone.Finallyinpetroleumeter,the acetanilidekeepina
solutionclearwhite.
For our observation,we concludedthistable.

4. Solubility Test (cold) Solubility Test (hot)
Water insoluble soluble
pet ether insoluble insoluble
ethanol fairly soluble readily soluble
acetone very soluble readily soluble
Part 1: RECRYSTALLIZATION
In our recrystallizationprocess,we observethe acetanilide becomemore soluble inhotwater.Our
crystalsoverflowthe filterpaperandwe lostsome crystalsinthe vacuumfiltration.
Part 2: MeltingPoint:
We use the meltingpointapparatusandrecognize the purityof our
acetanilide recoverybecauseithasan exactmeltingpointthatshowsthe
msdsfor acetanilide.
V. CALCULATION
We recover1.3659 gramsof Acetanilide by114.3 °C.
Our recoverycrystal was
Our data is: Amountpure productrecovered=1.3659 g
Amountof crude material used= 2.0011g
% recovery= (1.3659/2.0011 )x100 = 68.3 %
We notice we lostcrystal bythe transferthe containertoweight.

5. VI. CONCLUSION
In this experiment we use a technique called purification by
recrystallization. The choice of solvent is perhaps the most critical step
in the process of recrystallization since the correct solvent must be
selectedtoforma productof high purity and in good recovery or yield.
The small loss in yield is made up by the high gain in purity. Also, we
notice Acetanilide is soluble in water in some amount. Acetanilide is
soluble in ethanol, diethyl etherandacetone, andbenzeneandlesssoluble inpetroleum eter and
pentane. We observe the temperature influence in its solubility because acetanilide is more
soluble in hot water and in the other soluble.
Even after a solid has been recrystallized, it may still not be pure. Thus, it is important to
determine the purityof the sample, and one of the easiest methods to do this is by determining
the meltingpointof the solid. In our experiment, acetanilide shows a 114.3 °C that is exactly the
same from the MSDS table of acetanilide (reference 4)
VII. REFERENCES
1. ANALYTICALCHEMISTRY FOR TECHNICIANS.ThirdEdition.LewisPublishers.2003.Pages337-
341
2. Laboratory TechniquesinOrganicChemistry.Morhigandothers.1 st.Edition.W.H.
FreemanandCompany.2014. Pag: 180-184
3. Lab Manual -Fall,2016. Dr. CraigP. Jasperse MinnesotaState UniversityMoorhead.
Departmentof Chemistry..
http://web.mnstate.edu/jasperse/Chem355/Chem355%20Labbook.pdf
4. Material SafetyData SheetAcetanilide MSDS -
http://www.sciencelab.com/msds.php?msdsId=9927060