Synthesis and Characterization of Dibenzalacetone

Synthesis and Characterization of Dibenzalacetone Tan Yong Jie (m15604 Synthesis and Characterization Characterization of Dibenzalacetone Dibenzalacetone Aim: Aim: The aim of this experiment is to prepare a sample of dibenzalacetone (via a reaction of acetone with benzaldehyde) and determine its yield. The purity of the product will be determined usin a meltin point apparatus and T!C will also be conducted to determine if there is contamination contamination from reactants. Intro Introdu duct ctio ion n "enzal "enzaldeh dehyd yde# e# a primar primary y compo componen nentt of bitte bitterr almon almond d oil# oil# has has a characteristic pleasant almond$li%e odor. "enzaldehyde can also be obtained from other natural sources such as from almonds# apricots# apples and cherry %ernels# which contain sinificant amounts of amydalin# a lycoside that brea%s down under  enzyme enzyme catalysi catalysis s into benzalde benzaldehyde hyde ( 1). &otably &otably on oxidation oxidation## benzalde benzaldehyde hyde is converted into an odourless benzoic acid# which is a common impurity in laboratory samples (1 (1).  'cetone is a colourless# volatile# flammable liuid that is the simplest %etone. t is miscible with water and serves as an important solvent for cleanin purposes in the laboratory. t is also an important component of nail polish removers as well as paint thinners (2  (2 ). ). Dibenzyl Dibenzyliden ideneace eacetone tone is used as a sunscreen sunscreen compone component nt and as a liand in oranometallic chemistry. t is a briht$yellow solid insoluble in water# but soluble in ethanol. Sunliht causes the compound to be converted to a cyclobutane mixture in a *+,+* +,+- cycloaddition (3 (3). Suction filtration is a method used to remove solvent from solid crystals by the application of reduced pressure in the "chner flas% ( 3). This method offers more control over the rate of filtration compared to ravity filtration. n this experiment suction filtration was used to remove the solvent from the crude product as well as the final product (3 ( 3). /ecrystallization is a purification techniue that exploits the differential solubility of  compounds in solvents of different temperatures. ' near minimum of hot solvent is added to the crude product to dissolve it and then the mixture is allowed to cool slow slowly ly to room room temp temper erat atur ure e (4). (4). 's the tempe temperat ratur ure e decre decrease ases# s# the compou compound nd becomes less soluble and as the solution becomes saturated with the compound it crystalli crystallizes zes out of the solution. solution. Since crystalli crystallizatio zation n is a very thermody thermodynami namically cally selective selective process process that excludes excludes forein particles# particles# the compound compound obtained obtained will will be pure. ' minimum of ice cold solvent is then applied to remove any impurities on the surface (4). Thin$layer chromatoraphy (T!C) is a chromatoraphy techniue used to separate non$volatile mixtures. n a lab settin# T!C can be used to determine the number of  components in a mixture# verify a substance0s identity or monitor the proress of a reaction (5  (5 ). ). T!C has wide applications includin analysis of ceramides and fatty acids# detection of pesticides or insecticides in food and water# analysin the dye comp compos osit itio ion n of fibe fibers rs in fore forens nsic ics# s# assa assayi yin n the the radi radioc oche hemi mica call puri purity ty of  radiopharmaceuticals# radiopharmaceuticals# or identification of medicinal plants and their constituents ( 5 ). ). The stationary phase used in this experiment is silica el coated on aluminium# a polar absorbent. 1n a molecular level# molecules are continuously movin bac% and forth between the free and absorbed states in a dynamic euilibrium euilibrium that depends on three three factor factors# s# namel namely y the polarit polarity y and and size size of the molecu molecule le## the polarity polarity of the stationary phase and the polarity of the solvent. Since silica is polar# more polar  molecules will be more stronly attracted to the stationary phase. The two solvents

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Synthesis and Characterization of Dibenzalacetone Tan Yong Jie (m15604 used in this experiment# hexane and ethyl acetate# are non$polar and wea%ly polar  respectively. Mechanism:

Procedure: "enzaldehyde (2.2345mol# +.2 ml) and acetone (2.2324 mol# 2.6ml) was added to a 322ml 322ml conic conical al flas%. flas%. &a17 &a17 (2.28 (2.2822m 22mol# ol# +.2) +.2) pelle pellets ts were were placed placed in ethan ethanol ol (2.99mol# +2 ml) and D water (+2 ml) and mixed well in a 322ml conical flas%. This solution was then added to the mixture of benzaldehyde and acetone and swirled continuously for 38 minutes. The product was then collected from the filter paper by sucti suction on filt filtra rati tion on usin usin  D wate waterr as poor poor solv solven ent. t. The The crud crude e prod produc uctt was was re$ re$ crystallized usin hot ethyl acetate as the solvent heated to 382;C before the solvent was removed usin suction filtration. The crystals were spread on a piece of filter  paper on a watch lass and dried under / lamp for 8 minutes. The yield and the meltin meltin point point of the product was determine determined d usin usin meltin meltin point point apparatus apparatus and weihin balance# respectively. ' small amount of the product was removed usin a capillary tube and dissolved in 3 m! of ethanol to be used for T!C analysis. thyl acetate and 42= hexane was used for T!C analysis. Results: Table 1 !bser"ed melting #oint range of #rod$ct as determined by melting #oint determination a##arat$s com#ared %ith theoretical melting #oint as determined  by (6 & &

Obse Observ rved ed melt meltin ing g poi point nt rang range( e(°C °C))

110'11&1

Theo Theore reti tica call mel melti ting ng poin point( t(°C °C))

110'111

Table  Yield of #rod$ct as determined $sing molar mass calc$lations ass$ming #rod$ct is 100) #$re (calc$lations sho%n belo% table&

Mass of watch Mass of watch glass and filter glass, filter paper paper and product *4&*15g *4&+01g .olar ratio /enzaldehyde  cetone  1

Mass of  Theoretical Mass product of product

% Yield

0&*,6g

16&,

&-5g



.ass of /enzaldehyde  1&042  3 &0,g  o of moles of /enzaldehyde  &0,106&11  &0,106&11 3 0&01-6mol mol (* s&f& 





Synthesis and Characterization of Dibenzalacetone Tan Yong Jie (m15604 .ass of cetone  0&+-12 0&,0 3 0&6*,g  o of moles of cetone cetone  0&6*, 5,&0, 3 0&010-mol (*s&f& Com#o$nd cetone /enzaldehyde  $mber of moles 0&0100&01-6 Theoretical .ol atio(eaction 1  stoichiometry .olar ratio 0&0100&00-, Sim#lified .olar ratio 1 &1 1 



/enzaldehyde is the limiting reagent& Therefore molar ratio of #rod$ct (Dibenzalacetone  /enzaldehyde is 11& Theoretical n$mber of moles of #rod$ct 3 0&00-,0 mol Theoretical .ass of #rod$ct 0&00-,2 *4&- 3 &-6g Table * !bser"ations recorded for reaction ste#s Ste# .i7t$re of reactants in 100 ml conical flas8  Collection of cr$de #rod$ct by s$ction filtration

!bser"ation 9eat %as #rod$ced and a yello%  #reci#itate %as formed in a clear sol$tion&  small amo$nt of yello% crystal %as collected on the filter #a#er& The filtrate %as clo$dy and yello% %ith lost #rod$ct&  min$te amo$nt of yello% solid %as reco"ered from the filter #a#er&

Collection of #$re #rod$ct after recrystallization and s$ction filtration 0&5cm

Sol"ent front

*&5cm

/aseline 2 

2 C

2

1cm

:

;ig$re 1 Dra%ing of T
Table 4 f "al$es for the reactant and #rod$ct in 10) ethyl acetate and -0) he7ane& nalyte f   eactant' /enzaldehyde 1&+*&5 3 0&4,6 Co's#ot' S#ot f$rther from baseline 1&,*&530&514 (/enzaldehyde :rod$ct' Dibenzalacetone 1&4*&530&4 *

Synthesis and Characterization of Dibenzalacetone Tan Yong Jie (m15604 Co's#ot' S#ot closer to baseline (:rod$ct 

1&4*&530&4

Discussion: This e7#eriment is a mi7ed aldol condensation reaction& >t is also 8no%n as a Claisen' Schmidt reaction= %hich in"ol"es a reaction bet%een an aldehyde (benzaldehyde and a 8etone 8etone (acetone (acetone catalysed by a base (a!9& (a!9& This reaction is e7othermic e7othermic and th$s releases the heat obser"ed d$e to the t%o dehydration reactions and formation of ne%  bonds in a stable #rod$ct Dibenzalacetone %hich has higher melting and boiling  #oints than the reactants& The e7tensi"e con?$gation of dibenzalacetone ca$ses it to absorb light in the "isible s#ectr$m at @400 nm= res$lting in a yello% colo$r& This is d$e to the delocalisation of electrons in the A clo$d that res$lts in a lo%ering of the  #romotional energy reB$ired for an electron to ?$m# into a higher energy orbital& /ased on the beer eB$ation the energy is lo% eno$gh s$ch that "isible light has eno$ eno$gh gh ener energy gy to allo allo% % the the elect electro rons ns to be #rom #romot oted ed to the the ne7t ne7t orbi orbita tal= l= and and absorbance of #$r#le light near 400nm res$lts in a yello% colo$r& Dibenzalacetone  #reci#itates o$t of the sol$tion beca$se it is not sol$ble in %ater&  1 molar ratio of acetone to benzaldehyde is $sed so that the aldol condensation %ill occ$r on both sides of acetone and yield the most #rod$ct& 9o%e"er= it might still  be #ossible that mono's$bstit$ted acetone (benzylideneacetone might be contaminatin contaminating g in the #rod$ct& /enzylideneac /enzylideneacetone etone has a m$ch lo%er boiling #oint at near *-'4 C com#ared to dibenzaleacetone& >t is of a #aler yello% com#ared to dibenzaleacetone& >n addition= it is also E acti"e d$e to the #resence of the benzene ring& Th$s T
;or T
Synthesis and Characterization of Dibenzalacetone Tan Yong Jie (m15604 containing 8etonealdehyde gro$#& ;rom the T
Improvements Hash #rod$c #rod$ctt crystal crystalss %ith %ith D> %ater  %ater  tho thoro$g ro$ghl hly y to rem remo"e any any sodi sodi$m $m com# com#o$ o$nd nd im#$ im#$rit ritie iess befo before re dryin drying g $nder > lam#& se a lo%er   concentration of a!9& (Ta8e note that lo%er concentrations of base may slo% formation of #rod$ct and th$s lead to side reactions ecr ecry ystal stalli liza zati tion on $sin $sing g a less less stee stee# # cool coolin ing g c$r" c$r"e& e&  cont contro rolle lled d cool coolin ing g c$r"e that has a less stee# tem#erat$re gradient can be $sed for recrystallization  by #lacing the #rod$ct in a %ater bath on a hot #late and red$cing the tem#erat$re grad$ally o"er a long #eriod of time to 0 GC& Crystal Crystalliza lizatio tion n %as slo% slo% and crystal crystalss se a seed crystalI  sam#le of #$re failed to a##ear after 15 min$tes& Dibenz Dibenzalac alaceto etone ne #re#ar #re#ared ed before before the sol$ sol$ti tion on can can be $sed $sed as a n$cle n$cleati ation on factor to allo% the Dibenzalacetone to form aro$nd the crystal& >deally a s$#er  sat$rated sol$tion sho$ld be #re#ared by $sing a minimal amo$nt of ethyl acetate d$ring recrystallization ste#&

The seed crystal is caref$lly s$s#ended in the the sol$ sol$ti tion on and and the the cont contai aine nerr is co"ered in al$mini$m foil in order to 8ee# 8ee# o$t d$st d$st and red$ce tem#er tem#erat$ at$re re fl$ct$ations& The #rod rod$ct is im# im#$re d$e to the dd a trace amo$nt of acti"ated carbon  #resence obser"ed of colo$red to the the hot hot sol$ sol$ti tion on foll follo% o%ed ed by hot hot im#$rities& filtrat filtration ion to remo"e remo"e the charco charcoal& al& The The acti acti" "ated ated carb carbo on abso absorb rbss org organic anic com#o$nds to the s$rface b$t also leads to the loss of yield& Th$s a small amo$nt sho$ld only be $sed if colo$red im#$rit im#$rities ies s$ch s$ch as #olar #olar or #olym #olymeric eric com#o$nds are dete etermi rmined to be  #resent& The yield is lo% at only 16&,)& 9$man error Some of the #rod$ct mi7t$re %as s#lit onto the table& Cold sol" sol"en entt %as %as not not adde added d to filte filterr #a#e #a#er  r   before s$ction filtrationI #rod$ct 5

Synthesis and Characterization of Dibenzalacetone Tan Yong Jie (m15604 esca esca#e #ed d into into the the filt filtra rate te&& Sol$ Sol$ti tion on emember to #erform ste#s according to logboo8 and be more caref$l&

onclusions: Dibenzalacetone %as s$ccessf$lly synthesised %ith a yield of 16&,) and a melting  #oint range of 110'11 110'11&1GC& &1GC& !uestions: "# s mentioned before= benzylideneacetone %ill be #rod$ct formed&

 /enzylideneacetone $#

eferences: (1) 7olleman# '. <.? @iber# >. Inorganic Chemistry ? San Dieo: 'cademic Aress# +223? pp 3B   9+. 9+. (2) !yday# A. '. odine and odine Compounds. n Ullmann's Encyclopedia of Indstrial Chemistry ? @iley$C7# @einheim# +228? pp 96+942. (3) Ereenwoo Ere enwood# d# &orman &o rman &.? >arnshaw# 'lan. Chemistry of the Elements (+nd Elements  (+nd ed.)? "utterworth$7einemann "utterworth$7einemann## 344B? pp 39B$38. (4) 7aynes# @illiam F. C!C "and#oo$ of Chemistry and %hysics (&2nd ed.)? ed.) ? "oca /aton#
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Synthesis and Characterization of Dibenzalacetone Tan Yong Jie (m15604 (5) Chan /. Chemistry 1th edition? edition ? FcEraw$7ill: +232? pp 845+. Dibenzalacetone  rg. *ynth. *ynth. 1!"# 1!"# 2 # 35B. (6) Conard# C. /.? Dolliver# F. '. Dibenzalacetone

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