8/12/2019 pre lab #5 crossed aldol condensation

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Jose Gonzalez C

Pre-Lab #5

12/04/2013

Crossed Aldol Condensation

Objectie

!ibenzalacetone "ill be reared b$ t%e crossed or &i'ed Aldol condensation o( acetone and

benzalde%$de) *odi+& %$dro'ide and a &i't+re o( et%anol and "ater ,alread$ reared. t%ese

t"o co&o+nds "ill sere as t%e base and t%e solent. resectiel$. to s$nt%esize t%e rod+ct

desired)

%eor$

%at is an Aldol condensation Aldol reaction

%e aldol condensation reresents a o"er(+l eneral &et%od (or t%e constr+ction o( carbon-

carbon bonds. is one o( t%e central t%e&es o( oranic c%e&istr$) n t%e (irst ste t%e base-

catal$zed ,*odi+& $dro'ide in o+r e'a&le aldol condensation reaction. eli&inates a roton

(ro& an al%a carbon ,adjacent to a carbon$l ro+ t%at (or&s a resonance-stabilized anion

called an enolate. "%ic% t%en carries o+t n+cleo%ilic attac at t%e carbon$l ro+ o( t%e reactant.

iin an alo'ide ion t%at abstracts a roton (ro& "ater t%+s creatin an aldol reaction) %e

aldol rod+ct o(ten +nderoes (acile eli&ination o( "ater ,a de%$dration reaction. a((ordin an

6.7-+nsat+rated carbon$l co&o+nd as t%e (inal rod+ct) 89-is *ectr+& ill %el to

deter&ine t%e di((erent conj+ation s$ste&s ,absortion leels bet"een t%e startin &aterial and

t%e (inal rod+ct)

:aterials

;enzalde%$de. acetone. 10< sodi+& %$dro'ide. et%anol)

Proced+re

A) =eaction

1) Add benzalde%$de to a 125 &l >rlen&e$er (las "it% a &anetic stirrin bar. t%en 3 &l o(benzalde%$de? 1 &l o( acetone? 25 &l o( @5< et%anol)

2) %en add 30 &l o( 10< sodi+& %$dro'ide)3) *tir "it% &anetic stirrin bar (or 5 &in+tes)

4) ilter t%e &i't+re b$ ac++& (iltration) Bo+ need to +se (ilter aer)

5) as% t%e solid "it% 20 &l o( "ater)) !isconnect t%e r+bber t+be (ro& t%e (iltration (las) %en t+rn o(( t%e ac++&)

D) ;rea + t%e cr$stal &ass ,on lare (ilter aer

8/12/2019 pre lab #5 crossed aldol condensation

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E) ei%)

@) Calc+late rod+ct $ield)

;) 89-is sectr+&1) !issole 10 & o( dibenzalacetone in 10 &L o( et%anol in an >rlen&e$er (las) *%ae t%e

(las to &ae s+re t%e sol+tion is %o&oeneo+s) rans(er 1 &L o( t%e sol+tion to a ne" (lasand dil+te it to 10 &L "it% et%anol)

2) =ecord t%e 89-is sectr+& o( t%e co&o+nd)