CHM 556 ORGANIC CHEMISTRY II EXPERIMENT 4: THEALDOL CONDENSATION CONDENSATION REACTION: PREPARATION OF BENZALACETOPHENONES (CHALCONES)
NAME AMAR SAFWAN BIN MOHD ALI HANAPIAH (201522222) LAB PARTNER ARTNER SALMA IZZATI BINTI SINAR MASH!RI (2015"#$") (2015"#$") N!R!L SHAZREENA BINTI Z!L%AFLY (201525"246) CLASS: AS245#D1 LECT!RE&S NAME: PN' N!R IC%Y BIH!D
LABORATORY REPORT MARKING SCHEME
Objective of the Experiment !ntroduction Experimental #rocedure $esults and Observations &alculations 'iscussion &onclusion nsers to *uestions $eferences #re+laboratory preparations ,aboratory techni-ues otal otal Marks
Full Marks Mark(s) (to be filled by lecturer) 1. ". 1. %. %. ". 1. %. 1. ". 1. "
Objective
#erf #erfor ormi min/ n/
aldo aldoll
cond conden ensa sati tion on
reac reacti tion on
bet betee een n
%+ni %+nitr trob oben en0a 0ald ldeh ehy yde
and and
acetophenone in the presence of base (ethanol) to produce an 2 3+unsaturated ketone (%+ nitrochalcone) and calculate the percenta/e yield of the crude and purified product and obtain the 4M$ spectrum for the pure product. Introduction
n aldol condensation is an or/anic reaction in hich an enol or an enolate ion reacts ith a carbonyl compound to form a 3+hydroxyaldehyde or 3+hydroxyketone2 folloed by a dehydration to /ive a conju/ate enone. 5en0aldehyde reacts ith a ketone in the presence of base to /ive 2 3+unsaturated ketones. his reaction is an example of a crossed aldol conden condensati sation on here here the interm intermedia ediate te dehyd dehydrat rates es to produc producee the resonan resonance+s ce+stab tabili0 ili0ed ed unsaturated ketone. 6etone loses a proton from an +carbon to form an enolate ion2 hich attacks the carbonyl carbonyl carbon of the aldehyde to yield2 after protonation2 protonation2 2 3+hydoxy 3+hydoxy ketone. he intermediate is2 for aromatic aldehyde at least2 instable and under/oes base+catalysed dehydration to yield the unsaturated product.
ldol condensations are important in or/anic synthesis2 providin/ a /ood ay to form carbon7carbon bonds. For example2 the $obinson annulation reaction se-uence features an aldol condensation8 the 9ieland+Miescher ketone product is an important startin/ materia l for many or/anic syntheses. ldol condensations are also commonly discussed in university level or/ani or/anicc chemistry chemistry classes classes as a /ood /ood bond+f bond+form ormin/ in/ reactio reaction n that that demons demonstrat trates es import important ant reaction mechanisms. !n its usual form2 it involves the nucleophilic addition of a ketone enolate to an aldehyde to form a 3+hydroxy ketone2 or :aldol: (aldehyde ; alcohol)2 a structural unit found in many naturally occurrin/ molecules and pharmaceuticals.
Procedure
1. .<=1=/ .<=1=/ of %+nitrobe %+nitroben0alde n0aldehyde hyde as mix mix ith .>m, .>m, acetophen acetophenone one and ?m, ?m, of @=A @=A ethanol in a conical flask. he mixture as stirred until the entire solid is dissolved. ". .=m, .=m, of sodium sodium hydroxid hydroxidee solution (>/ (>/ 4aOB solid solid in 1m, ater) as added added into the mixture and the stirrin/ process continued. %. 1m 1m, of ice ice ater ater as as adde added d and and scra scratc tchi hin n/ as as perf perfor orm med to ind induce uce to crystalli0ation process. ?. he mixture mixture then as transferred transferred into into a beaker beaker containin/ containin/ 1=m, 1=m, of ice ater. ater. =.
he mixture mixture as as filtered to to collect the solid solid by usin/ usin/ 5uchner 5uchner funnel funnel filtration filtration set. set.
>. he solid solid collecte collected d as alloed alloed to dry in oven oven ith temper temperatu ature re of about CD& CD& for % minutes. he ei/ht of the solid product as recorded. <. he entire entire solid solid (1.>%%/ (1.>%%/)) as recrystal recrystalli0e li0ed d ith ith ?".=m, ?".=m, hot hot methan methanol ol solution solution22 and the solid as filtered a/ain. he solid as dried a/ain in oven at temperature of about CD& overni/ht to make sure complete dryin/ process. C. he dried dried solid produ product ct (%+nitrocha (%+nitrochalcone) lcone) as as ei/hed ei/hed and the the percenta/e percenta/e yield yield as calculated.
$' he meltin/ point and 4M$ test ere done ith the solid product (%+nitrochalcone).
Cacuation!
Molar mass of acetophenone 1"/mol Molar mass of %+nitrobel0aldehyde 1=1/mol Molar mass of %+nitrochalcone "=%/mol 'ensity of acetophenone 1.%/cm % g 151 g / mol 0.75
Mol of %+nitroben0aldehyde
.?@>m, of acetophenone .>cm % of acetophenone Mass of acetophenone .>cm % G 1.%/cm% .>1C/
g 120 g / mol 0.618
Mol of acetophenone
.=1=mol
Result and observation: i.
Observation C*+,*-.. .*+/ /+,. / ,-.3 -** /3- 7,-87//-
9, 9/-, /3- / 9 .+ 3,;3,;- .*+/' Description Weight of 3-nitrobenzaldehyde Weight of crude solid Weight of crude solid to recrystallize Weight of dry pure product
Weight (g) 0.7555 1.171 0.500 0.!513
M.. 9 7,+8/ (#</,83*8-) = 0'251#> M-*/> 7/ 9 7,+8/ (#</,83*8-) (#</,83*8-) =5 ?C
"ercentage yield #
mass mass of produc product t molarmass of product massofst mass ofstartin arting g material material molar mass massof of starting starting material material
$ 100%
0.2513 g 253 g / mol
#
0.7555 g
$ 100%
151.12 g / mol
# 1.&&%
ii.
NMR result for chalcone
Signal Signal 1H +@*-/
Chemic Chemical al shift shift (ppm) (ppm) '"4<'1
Freuen reuenc! c! ("#) ("#) 15'6
"i#cu##ion
he result for meltin/ point that obtain from the experiment is =< o&2 and the meltin/ point from the reference is 1?>o&. !t is due to some error hile handlin/ this experiment. Errors may occur durin/ the filtration process by usin/ the 5uchner funnel vacuum filtration. he pressure used to collect the solid is too hi/h until the filter paper form holes that can pass throu/h the solid ith the li-uid into the conical flask. his then ill make the actual yield mass ill decrease. o make sure there is no error in ei/hin/ the product2 the solid must be dry at least overni/ht to evaporate all the ater moisture. From the 4M$ result the 1B doublet doublet si/nal si/nal as observ observed ed ith ith fre-uen fre-uency cy of 1=.>B0 1=.>B0.. From From the literatu literature re revie revie22 the fre-uency of si/nal for trans compound is beteen 1"+1CB02 so that it is proven that the compou compound nd yield yield is that that trans+co trans+comp mpoun ound. d. his his fre-uen fre-uency cy is compare compared d to cis+com cis+compou pound nd fre-uency that is loer2 >+1"B0. here some error in the inte/ration of this 4M$ peaks based on the result that obtain. !t is due to some human error durin/ run the sample in 4M$. o overcome this error2 hen run the sample in the machine need to follo the procedure to avoid the error in inte/ration of 4M$ peaks. he mechanism of this reaction is sho on beloH
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Reference:
1' CHM CHM 556 556 O, O,> > 8 8 C3- C3-. ./, /, 2 *-8/ *-8/+, +,- //-. . 7,-7 7,-7, ,- - @ P,9' 9' F+' 2' T'W' 'W' G, G,3 3 S* S*. . C,> C,> B' F,3*- ,3*- O, O,> >8 8 C3-. C3-./, /, A. A. 3 W*- S. S. 2011' #' A** 8-./
16112014
3//7:-'7-',>A**8-./' 4' C3*8- C3*8- 16112014 16112014 3//7:-' 3//7:-'7 7-' -',> ,> C3*8 C3*8-' -'