Cuyamaca College The Synthesis of Ethyl 4 Nitrocinnamic Acid Project

1. Please show your calculations for obtaining your percent yield. Include the calculations for the theoretical yield as well. Also, if something went wrong during the course of your experiment (i.e you spilled your product, did the work-up wrong, etc.) you can explain about it here. weight of empty vial =17.07g, weight of vial +product =20.10g. we used 5.66g triphenylphosphine, 2.37g of nirtobenzaldehyde, 5.2g ethyl bromacetate.

2. Analyze your NMR spectra using Mestrenova and upload a picture of it on this assignment. In your spectra, you should have the chemical shifts of each peak, and the integration underneath it as well. You also have to include an explanation matching up the peaks in your NMR spectra to that of the product, methyl benzoate. Explain why you think you matched up the peaks properly based on chemical shift, integration, and splitting pattern. If you have extra peaks in your NMR that do not match up to any proton peaks in your product, explain where they could have come from.

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An“OnWater”WittigReactionusingpͲNitrobenzaldehyde
Introduction:
TheWittigreactionisafundamentalintroductoryorganicchemistryreactionusedtoproducean
alkenefromthereactionofaphosphoniumylidewithacarbonylcompound.Organicchemistsuseitasa
toolforsimplecarbonͲcarbonbondformation.TheWittigreactionoccursinthreestages(Figure1):1)
Theformationofthephosphonium“Wittigsalt”usingaphosphineandanalkylhalide.2)Theformation
ofthephosphoniumylidebytheremovalofaprotonwithabase.3)Reactionoftheylideandacarbonyl
compoundtoproduceanalkeneproductandaphosphineoxidebyͲproduct.
Figure1:3StepsofaWittigReaction
Figure2:Synthesisof(E)ͲethylpͲnitrocinnamate
Forthislab,youwillconductan“onwater”Wittigreactiontoproduceprimarily
(E)ͲethylpͲnitrocinnamate(Figure2).Waterisnotconsidereda“solvent”inthisreactionbutrathera
“medium”sincethereagentsarequitehydrophobicandappearinsoluble.Waterisaremarkably
efficientmediumfortheWittigreactionandcanbeusedwithawiderangeofstabilizedylidesand
aldehydes.TheWittigreactionisfasterinwaterthaninorganicsolventseventhoughthereactions
seemheterogeneousinwater.Despitethereactants’poorsolubility,aqueousWittigreactionshave
veryhighyieldswithhightransͲ(E)Ͳselectivities.

Hazards:
TheSDSforeachchemicalusedshouldbeconsultedandunderstoodpriortouse.Youwillbe
usingaqueoussodiumbicarbonateasthebase,averysafeandbenignbase,alsoknownasbakingsoda.
Thealkylhalideisethylbromoacetate,apotentlachrymator.Lachrymatorscauseacutepainand
burninginthemucousmembranes(eyes,nose,andthroat).Itisalsotoxicwhendirectlyinhaledor
injested.Ethylbromoacetateandanythingusedtocontainitmustbekeptinsidethefumehoodatall
times.Cleanallglasswareusedtohandleethylbromoacetateinthesinkinyourfumehood.The
carbonylcompoundis4Ͳnitrobenzaldehydeisanirritant.Silicagel(veryfineglasspowder)isa
respiratoryhazard,similartofiberglass.Becauseglassdoesnotdissolve,prolongedexposureresultsin
particlestrappedinthelungsandcanleadtoformationsoftumors.Allmaterialsshouldbehandledwith
appropriatecaution.
ExperimentalProcedure:
Inyourhood,addϮϭ.ϲmmoltriphenylphosphineandastirbartoa100mLroundbottomflask.
Add20mLaqueoussaturatedsodiumbicarbonateandϭϱ.ϳmmolpͲnitrobenzaldehyde,thenaddyour
weighedsampleofethylbromoacetate(ϯϭ.ϰmmol)tothesolution.(Caution!Ethylbromoacetateisa
toxiclachrymator).Attachacondenserwithakeckclipandheatthesolutiontoreflux.Ifthesolution
foamsintothecondenserthenremoveitfromtheheatuntilthefoamingstops,thenreturnittothe
heat.Stirthesolutionasvigorouslyaspossiblefor30minutes(makesureitdoesNOTstopstirring!!).
Theheterogeneoussolutionmustmixwell.
After30minutesatreflux,removetheflaskfromheatandletitcooluntilyoucanhandleit.
Pourthemixturetoa125mLseparatoryfunnel.Rinsetheflasktwoorthreetimeswithaboutϭ0mLof
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400MHz1HͲNMRforEthyl4ͲNitrocinnamate

InfraredSpectrumforEthyl4ͲNitrocinnamate

400MHz1HͲNMRfor4ͲNitrobenzaldehyde

InfraredSpectrumfor4ͲNitrobenzaldehyde