Aldol Condensation: Synthesis of Dibenzalacetone using the Claisen-Schmidt Reaction
Abstract: In this experiment, dibenzalacetone as prepared !ia an aldol condensation reaction beteen acetone and benzaldehyde" Acetone and benzaldehyde ere mixed ith sodium hydroxide and ethanol, and mixed !igorously for #$ minutes" %he crystals ere rinsed ith ith ater then centrifuged" %his as repeated a total of three times" %he dibenzalacetone as then characterized using melting point analysis" %he obser!ed melting point as &#"'(C- )$&" *(C compared to a cited !alue of ))$(C" ))$(C" %he sample as not completely dry and could ha!e contributed to the loer and broader obser!ed melting point" %he percent yield as ))+ ))+ " %his percentage occurred because of the excess moisture in the sample"
ig )" ./uation of Acetone Acetone and 0enzaldehyde to form Dibenzalacetone Dibenzalacetone
Introduction: Dibenzalacetone, or D0A, is often used as an ingredient in sunscreen lotions and sprays because it has spectral properties that ma1e it capable of absorbing 23 light" It is also 1non to possess anti-inflammatory properties and can therefore
be used to treat pain, selling and inflammation" ) Dibenzalacetone can also be used as a ligand in organometallic chemistry, and its deri!ati!es are often utilized as polymer crosslin1ers" * %his experiment demonstrated the Claisen-Schmidt condensation of mixed aldols" .nolate ions ere ere formed hen the molecules ith hydrogens hydrogens alpha to carbonyl groups ere reaction ith a base 45a67"8
Fig. 2 Acetone reaction reaction and Sodium Hydroxide Reaction Reaction
9hen an enolate forms from an aldehyde, it normally reacts ith unreacted aldehydes to form an aldol additioncondensation" ;etones are less reacti!e toard nucleophilic additions and therefore, the enolate formed from a 1etone can be used to react ith an aldehyde" %his is 1non as the Claisen-Schmidt reaction" 9hen the product formed still has a reacti!e alpha hydrogen and and a hydroxide ad
Fig. 3 Claisen-Schmidt Reaction
0ecause of the symmetry of acetone, the reaction can no be repeated on the other side of the carbonyl hich then form the final product, dibenzalacetone"
=rocedure: $"**$>g of benzaldehyde as transferred to a centrifuge tube" )"> ml of ethanol and *"$ ml of #? sodium hydroxide ere measured then transferred to the centrifuge tube !ia clean, dry syringes" 2sing a micropipette syringe, $"$+# ml of acetone ere measured then in
After the final rinse rinse and remo!al remo!al of excess excess li/uid, li/uid, the crystals crystals ere ere remo!ed remo!ed from the centrifuge tube, placed on a filter in a sealed 7irsch filter, then !acuumed" After !acuuming, !acuuming, the the crystals crystals ere ere remo!ed from the 7irsch 7irsch filter filter and placed placed beteen > paper filters to absorb the excess moisture" %he crystals ere then eighed" After eighing eighing the the crystals, crystals, the melting melting point point as determined determined using a 3ernie 3ernierr melt station and 3ernier abBuest *"
Results and Calculations: ?ass of product: $")>@> g %heoretical ield: $")@$+ g =ercent ield: ))>"&& ))>"&&
Finding Limiting Reagent
Acetone $"$+#m ) mol A ) mole prdct prdct **@g **@g prdct 'E"$ 'E"$E E g ) mol mol A F $"*E)' g dibenzalacetone 0enzaldehyde $"**> g 0 ) mol 0 ) mole prdct **@g prdct 'E"$E g 0 * mol 0 F $"@#'E g dibenzalacetone %he limiting reagent for this reaction is acetone as it yields the least amount of dibenzalacetone"
Aldol Condensation: Synthesis of Dibenzalacetone Theoretical Yield Yield
Acetone $"$+#m ) mol A ) mole prdct prdct **@g **@g prdct 'E"$ 'E"$E E g ) mol mol A F $"*E)' g dibenzalacetone
Percent Yield Yield
4mass of D0A crystals8 4theoretical yield8
F
$"#*&@ g D0A $"*E)' g D0A
x )$$ F
F ))+"$* yield Discussion and Conclusions: In this experiment, an aldol condensation as carried out under basic conditions" In these types of reactions, carbonyl compounds act as either the enolate ion or the electrophile, or sometimes both" %he carbonyl compound hich becomes the enolate ion must possess at least ) G-carbon" In this experiment, the enolate ion originates from acetone because benzaldehyde lac1s an G-carbon" 0enzaldehyde, therefore, acts as the electrophile in this reaction" %he enolate ion deri!ed from acetone then reacts ith benzaldehyde to form a Hhydroxy1etone" %his H-hydroxy1etone ill then undergo dehydration to form an enome, a con
References 1
Smerbec1, R" 3" =ittz, ." =" 4)&E>8" 2"S" =atent 5o" @,'E+,*>$" 9ashington, DC: 2"S" =atent and %rademar1 6ffice"
*
7eidt, =" C" .lliott ?" " 4*$$)8" 2"S" =atent 5o" >,)&@,>)'" 9ashington, DC: 2"S" =atent and %rademar1 6ffice"
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