OBJECTIVES: This experiment aims to: to: - Synthesize Synthesize benzyl benzyl acetate acetate through through Fische Fischerr Esterifc Esterifcatio ation n occurri occurring ng throug through ha nucleophilic acyl substitution mechanism - Succes Successu sully lly use use the reu reux x techniq technique ue to synt synthes hesize ize benz benzyl yl aceta acetate te - Une Uners rsta tan n mech mechan anis ism m in!ol in!ol!e !e in the rea react ctio ion n - E!aluate E!aluate e"cien e"ciency cy o Fischer ischer Esterifc Esterifcation ation as a metho metho o synthesizi synthesizing ng esters esters INTRODUCTION: Esters are some o the most #iesprea naturally-occurring compouns$ %any esters are responsible or the ragrance o o#ers an ruits li&e bananas' raspberries' an peaches an are also the primary constituent o ats an oils$ Esters are usually orme rom aci-catalyze conensation o a carboxylic aci an an alcohol #here the t#o molecules combine to orm a bigger molecule$ This type o reaction is calle a nucleo nucleophi philic lic acyl acyl substi substitut tution ion$$ Fischer ischer Esteri Esterifca fcatio tion n is the most most useul useul metho metho in synthesizing esters because o its relati!ely high yiel$ This process is one by using a carboxylic aci an an alcohol in the presence o an aci catalyst$ (n this reaction' the carboxylic aci is acti!ate #ith an aci to ma&e the acyl carbon more electrophilic$ Thus' the alcohol can attac& the acyl carbon an the eprotonation o the acyl oxygen orms the ester$ PRELAB QUESTIONS: )$ *o# is the the yiel o the the reaction reaction maximize maximize+ + *o# is the the hyrolysis hyrolysis o o benzyl acetate bac& to benzyl alcohol an acetic aci pre!ente+ Explain$ To To maximize the yiel o the reaction' reaction' the reaction reaction mixture is #ashe #ashe #ith #ater to remo!e unreacte benzyl alcohol an excess acetic aci$ , secon #ash #ith bicarbonate is also utilize to remo!e any remaining traces o acetic aci$ The ester must also be remo!e immeiately as it orms$ ,nother #ay to ri!e the reaction or#ar is to a an excess o acetic aci because it is easier to remo!e ater the reaction$ ecause esterifcation is a re!ersible reaction' it is important to remo!e compouns such as #ater an strong bases that ai in inucing the re!erse o esterifcation or hyrolysis process$ These compouns are remo!e uring the purifcation stage o the crue prouct$ p rouct$ .$ /hat is the the use o the soium soium bicarbona bicarbonate te #ash+ #ash+ /hat gas gas is prouce prouce upon upon the aition o soium bicarbonate into the organic layer+ The soium bicarbonate #ash #ash remo!es any any remaining trace o acetic acetic aci$ (t is also use to neutralize any unreacte aci$ Soium bicarbonate is a #ea&er aci thus its reaction #ith the unreacte aci catalyst #ill prouce carbonic aci #hich issociates into #ater an carbon ioxie$ Thus' soium bicarbonate must be ae beore remo!ing the aqueous layer in the last #ashing an beore rying the organic layer$ layer$ 0arbon ioxie is the gas prouce$ 1$ /hat is is the use use o soium soium chlorie chlorie in the the soium soium chlorie chlorie #ash+ #ash+ Soium chlorie increases the ionic strength o the aqueous layer$ layer$ Thereore' Thereore' the separation o the aqueous aqueous an organic layer layer #ill be easily obser!e$ Soium chlorie also ais in remo!ing polar impurities an #ater rom the crue ester$ 2$ /here /here #oul you you expect expect the organic organic layer layer to be in each each o the three three #ashing #ashing steps+ For the frst #ash #ith )3m4 col #ater' the organic layer is at the bottom o the separatory unnel because the benzyl acetate is enser than #ater$ Thus' the organic layer layer is raine into an Erlenmeyer as&$ For the secon secon an thir #ash' the organic layer is at the top o the separatory unnel because soium bicarbonate an soium chlorie both ha!e higher ensities than benzyl acetate$ Thereore' they sit at the bottom o the unnel an are raine through the stopcoc&$ 3$ /hat are are the qualitati!e qualitati!e tests tests to !eriy !eriy the presence presence o benzyl benzyl acetate acetate an benzyl benzyl alcohol+ /hat constitutes a positi!e test result+ •
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The *yroxamic ,ci test can help !eriy the presence o an ester in the benzyl acetate prouct$ , positi!e result is seen i the test prouces a re!iolet solution$ %ean#hile' a 0hromic ,ci test is use to chec& or the presence o an alcohol$ , positi!e result is inicate by the presence o blue-green precipitate$ ( the 0hromic ,ci test results in a positi!e test result' then the benzyl acetate prouct still contains traces o benzyl alcohol an #as not ully synthesize$
REAGENTS: REAGENTS
PHYSICAL AND CHEMICAL PROPERTIES
SAFETY PRECAUTIONS
Benzyl Acetate (IUPAC) [C9H10O2]
Molecular Wei!t" 1#0$1% &'ol Boilin Point" 21 oC Meltin Point" #1oC *en+ity" 1$0# &c' ,olu-ility" $1 '&'. (2# oC) in /ater Aearance" Colorle++ liui /it! earli3e oor4 -itterunent ta+te
,3in an eye irritant" 5lu+! /it! /ater 5or at lea+t 1# 'in+$ t!en et 'eical a++i+tance Ine+tion (!azarou+)" o not inuce 6o'itin unle++ in+tructe -y 'eical er+onnel In!alation (!azarou+)" to 5re+! air4 i6e o7yen4 +ee3 'eical a++i+tance Co'-u+ti-le
Acetic Aci (IUPAC) [C 2H8O2]
Molecular Wei!t" 0$0#2 &'ol Boilin Point" 11:$9 oC Meltin Point" 1$oC *en+ity" 1$0# &c' Aearance" Colorle++ liui or cry+tal+ /it! a +our4 6inearli3e oor
,oiu' Bicar-onate & ,oiu' !yroen car-onate (IUPAC) [;aHCO]
Molecular Wei!t" %8$00: &'ol Boilin Point" %#1 oC Meltin Point" #0oC *en+ity" 2$1 &c' ,olu-ility" %$: &100'. (20 oC) o5 /ater Aearance" W!ite cry+talline o/er or ranule+4 oorle++4 +aline an +li!tly al3aline ta+te Molecular Wei!t" #%$88 &'ol Boilin Point" 18# oC Meltin Point" %00$:oC *en+ity" 2$1: &c' ,olu-ility" $0 &100 (2# oC) o5 /ater Aearance" Colorle++ to /!ite cry+talline +oli4 +alty ta+te
,3in an eye irritant" 5lu+! /it! /ater i5 contact ,eriou+ +3in contact" Wa+! /it! i+in5ectant +oa an co6er conta'inate +3in /it! anti -acterial crea'$ ,ee3 'eical ai Ine+tion (!azarou+)" o not inuce 6o'itin unle++ in+tructe -y 'eical er+onnel In!alation (!azarou+)" re'o6e to 5re+! air4 i6e o7yen4 +ee3 'eical a++i+tance ,3in an eye irritant" 5lu+! /it! /ater i5 contact Ine+tion" o not inuce 6o'itin unle++ in+tructe -y 'eical er+onnel In!alation" re'o6e to 5re+! air4 i6e o7yen4 +ee3 'eical a++i+tance
,oiu' C!lorie (IUPAC) [Cl;a]
,ul5uric Aci (IUPAC) [H 2,O8]
Molecular Wei!t" 9%$0:9 &'ol Boilin Point" : oC Meltin Point" 10$1oC *en+ity" 1$%8 &c' ,olu-ility" 'i+ci-le (20 oC) in /ater
,3in an eye irritant" 5lu+! /it! /ater i5 contact ,eriou+ +3in contact" Wa+! /it! i+in5ectant +oa an co6er conta'inate +3in /it! anti -acterial crea'$ ,ee3 'eical ai Ine+tion" o not inuce 6o'itin unle++ in+tructe -y 'eical er+onnel In!alation" re'o6e to 5re+! air4 i6e o7yen4 +ee3 'eical a++i+tance ,3in an eye irritant (6ery !azarou+)" 5lu+! /it! /ater i5 contact ,eriou+ +3in contact" Wa+! /it! i+in5ectant +oa an co6er conta'inate +3in /it! anti
Aearance" Oorle++ colorle++ oily !yro+coic liui
-acterial crea'$ ,ee3 'eical ai Ine+tion (6ery !azarou+)" o not inuce 6o'itin unle++ in+tructe -y 'eical er+onnel In!alation (6ery !azarou+)" re'o6e to 5re+! air4 i6e o7 yen4 +ee3 'eical a++i+tance
REFERENCES: Guidote AM, del Rosario DR, Abuzo AL. Experiencing Organic Chemistry. Quezon City: Office of Research and Publications, Ateneo de Manila University; 2005. [Author Unknown]. Pubchem compound database [Internet]. USA: National Centre for Biotechnology Information; 2005 March 25 [updated 2017 March 26; cited 2017 March 26]. Available from: https://pubchem.ncbi.nlm.nih.gov/compound/benzyl_acetate [Author Unknown]. Sciencelab.com [Internet]. USA: Sciencelab.com, Inc.; unknown first publication [cited 2017 March 26]. Available from: http://www.sciencelab.com/msds.php?msdsId=9923066 [Author Unknown]. Pubchem compound database [Internet]. USA: National Centre for Biotechnology Information; 2004 September 16 [updated 2017 March 25; cited 2017 March 26]. Available from: https://pubchem.ncbi.nlm.nih.gov/compound/acetic_acid [Author Unknown]. Sciencelab.com [Internet]. USA: Sciencelab.com, Inc.; unknown first publication [cited 2017 March 19]. Available from: http://www.sciencelab.com/msds.php?msdsId=9922769 [Author Unknown]. Pubchem compound database [Internet]. USA: National Centre for Biotechnology Information; 2005 March 27 [updated 2017 March 25; cited 2017 March 26]. Available from: https://pubchem.ncbi.nlm.nih.gov/compound/sodium_bicarbonate [Author Unknown]. Sciencelab.com [Internet]. USA: Sciencelab.com, Inc.; unknown first publication [cited 2017 March 26]. Available from: http://www.sciencelab.com/msds.php?msdsId=9927258 [Author Unknown]. Pubchem compound database [Internet]. USA: National Centre for Biotechnology Information; 2005 March 25 [updated 2017 March 25; cited 2017 March 26]. Available from: https://pubchem.ncbi.nlm.nih.gov/compound/sodium_chloride [Author Unknown]. Sciencelab.com [Internet]. USA: Sciencelab.com, Inc.; unknown first publication [cited 2017 March 26]. Available from: http://www.sciencelab.com/msds.php?msdsId=9927593 [Author Unknown]. Pubchem compound database [Internet]. USA: National Centre for Biotechnology Information; 2004 September 16 [updated 2017 March 25; cited 2017 March 26]. Available from: https://pubchem.ncbi.nlm.nih.gov/compound/sulfuric_acid [Author Unknown]. Sciencelab.com [Internet]. USA: Sciencelab.com, Inc.; unknown first publication [cited 2017 March 26]. Available from: http://www.sciencelab.com/msds.php?msdsId=9925146 De Guzman JV. Scribd [Internet]. Unknown Place: Scribd Inc.; 2015 April 08 [cited 2017 March 26]. Available from: https://www.scribd.com/doc/295968779/SYNTHESIS-OF-BENZYL-ACETATE-THROUGH-FISCHERESTERIFICATION-REACTION -
PROCEDURES:
Pour #$#'. o5 acetic aci an # ro+ (<0$2'.) o5 concentrate +ul5uric aci into =B>$ ,lo/ly a 8$#'. o5 -enzyl alco!ol into 'i7ture an +/irl it$
Attac! /ater conen+er 6ertically o6er 'out! o5 roun -otto' 5la+3$ C!ec3 +etu 5or lea3+ an !eat =B> to +lo/ -oil$ Continue !eatin =B> o6er lo/'eiu' !eat 5or an !our$$
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,ecure +etu /it! cla'+ on nec3 o5 =B> an on -oy o5 conen+er
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=eulate !eat in orer to re6ent 5or'ation o5 +oli -yrouct+
.et 'i7ture in =B> cool o/n an ecant into +earatory 5unnel$ Wa+! =B> /it! 1#'. col /ater an u+e to /a+! 'i7ture in +earatory 5un
*rain oranic layer into clean an ry @rlen'eyer 5la+3 an i+car aueou+ la yer$ Wa+! oranic layer /it! 10'. # ;aHCO an t!en /it! 10'. 10 ;aCl$
*ecant oranic layer into @rlen'eyer 5la+3 an ry o6er +oiu' +ul5ate$ *i+till it i5 nece++ary an +tore in +cintillatin 6ial$ Per5or' ualitati6e te+t+$
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?!e orer o5 t!e oranic an aueou+ layer+ in +earatory 5unnel c!ane+ t!rou!out e7eri'ent ue to c!anin en+ity o5 aueou+ layer
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Ma3e +ure layer+ are roerly ienti5ie
