实验一对硝基苯乙腈的制备

1实验一、对硝基苯乙腈的制备8h教学目的123．进一步巩固和熟悉硝化反应的实验操作以及混酸配制方法4p-NITROBENZYLCYANIDE[α-Tolunitrile,p-nitro-]原料与试剂浓硫酸CP27.5mL浓硝酸CP27.5mL苯乙腈CP10g95％乙醇CP50mL1.ProcedureIna250-ml.round-bottomedflask,fittedwithastopperholdingadroppingfunnelandamechanicalstirrer,isplacedamixtureof27.5cc.(0.43moles)ofconcentratednitricacid(sp.gr.1.42)(Note1)and27.5cc.(0.49moles)ofconcentratedsulfuricacid(sp.gr.1.84).Thisiscooledto10°inafreezingmixture,and10g.(0.85mole)ofbenzylcyanide(freefromalcoholandwater)(Note2)isruninslowly,atsucharatethatthetemperatureremainsatabout10°anddoesnotexceed20°.Afterallthebenzylcyanidehasbeenadded(aboutonehour),theicebathisremoved,andthemixtureisstirredforonehourandthenpouredonto120g.ofcrushedice.Apastymassslowlyseparates;morethanhalfofthismassisp-nitrobenzylcyanide,theotherconstituentsbeingo-nitrobenzylcyanide,andavariableamountofanoilwhichresistshydrolysis;apparentlynodinitrocompoundsareformed.Themassisfilteredonaporcelainfunnelwithsuction,pressedwelltoremoveasmuchoilaspossible,anddissolvedin50cc.ofboiling95percentalcohol.On2cooling,p-nitrobenzylcyanidecrystallizes;themotherliquor,ondistillation,givesanimpurealcoholwhichcanbeusedforthenextrun.Recrystallizationfrom55cc.of80percentalcohol(sp.gr.0.86to0.87)yields7.0–7.5g.(50–54percentofthetheoreticalamount)ofaproductwhichmeltsat115–116°.Thisproductissatisfactoryformostpurposes,andincidentallyforthepreparationofp-nitrophenylaceticacid.Occasionallyitmustbefreeevenfromtracesoftheorthocompound;ifso,itshouldbecrystallizedagainfrom80percentalcohol;itthenmeltsat116–117°.2.Notes1.Fumingnitricacidmaybeused,buttheproceduredescribedislessexpensive.2.Theyieldof7.0–7.5g.isobtainedfrombenzylcyanide,whichboilsovera5°range,preparedasdescribedonp.107.Verypurebenzylcyanidewillgiveaslightlyhigheryield,whereascommercialgradesmaygiveonly5.0g.ofp-nitrobenzylcyanideandmuchoil.3.Thereactionhasbeenalsocarriedoutwith500g.ofbenzylcyanide.Undertheseconditionsa5-l.flaskwasused,anditrequiredtwoandone-halfhourstoaddthebenzylcyanide.Theyieldofproductwas325–370g.(47–54percentofthetheoreticalamount).3.Discussionp-Nitrobenzylcyanidehashithertobeenpreparedbytheactionoffumingnitricacid1onbenzylcyanide.Thispreparationisreferencedfrom:Org.Syn.Coll.Vol.1,406ReferencesandNotesSalkowski,Ber.17,505(1884);Pschorr,Ber.33,170(1900);KoesslerandHanke,J.Biol.Chem.39,585(1919);RobertsonandStieglitz,J.Am.Chem.Soc43,180(1921);Baker,Cooper,andIngold,J.Chem.Soc.426(1928).复习思考题1、简述硝化反应的原理。2、常见的硝化反应有那些方法？各有什么优缺点？3、本实验中可能的副反应是什么？如何尽量避免副产物的生成？4、本实验中的主要副产物是什么？如何进行分离？3实验二、对硝基苯乙酸的制备8h教学目的；1．通过本实验，掌握由腈制备羧酸的基本原理；2．熟悉和掌握羧酸的制备方法及各自特点；3．进一步巩固和熟悉由腈水解制备羧酸――p-NITROPHENYLACETICACID[α-Toluicacid,p-nitro-]原料与试剂浓硫酸CP30mL水28mL＋160mL对硝基苯乙腈自制10g1.ProcedureIna1-l.round-bottomedflaskisplaced10.0g.(0.062mole)ofp-nitrobenzylcyanide.Asolutionof30cc.(0.54moles)ofconcentratedsulfuricacid(sp.gr.1.84)in28cc.ofwaterisprepared,andtwo-thirdsofthissolutionispouredontothep-nitrobenzylcyanide.Themixtureisshakenwell,untilthesolidisallmoistenedwiththeacid.Anysolidmaterialadheringtothewallsofthevesselisnowwasheddownintotheliquidwiththeremainderoftheacid;theflaskisattachedtoarefluxcondenser,thenset,withoutshaking,overa10-cm.holeinalargesheetofasbestosboardwhichrestsonatripod,andheateduntilthemixtureboils(Note1).Theboilingiscontinuedforfifteenminutes(Note2).Thereactionmixture,whichbecomesratherdark,isdilutedwithanequalvolumeofcoldwaterandcooledto0°orbelow.Thesolutionisfiltered;theprecipitateiswashedseveraltimeswithicewaterandthendissolvedin160cc.ofboilingwater(Note3).Thissolutionisfilteredasrapidlyaspossiblethroughalargefoldedfilter,preferablywithasteamfunnel(Note4).Inspiteofallprecautions,however,somesolidusuallyseparatesonthefilter.Thismustberedissolvedin4aminimumquantityofboilingwater,andthissolutionthenfilteredintothemainsolution.Thep-nitrophenylaceticacidseparatesinlong,paleyellowneedles,whichmeltat151–152°.Theyieldis10.3–10.6g.(92–95percentofthetheoreticalamount).2.Notes1.Iftheflaskisnotprotectedwithanasbestosboardortheequivalent,decompositionoccurswherethesubstanceissuperheatedonthesidewallsoftheflask.Ifcrystalsofthecyanideareallowedtoremainontheupperwallsoftheflask,theyarenoteasilywasheddownandsoarenothydrolyzed.2.Inmakingexperimentswith500g.ofp-nitrobenzylcyanide,itwasfoundthatthetimeforhydrolysiswasaboutthesameaswhensmalleramountswereused.3.Ifagoodgradeofcyanideisused,itisnotnecessarytoaddanimalcharcoalinordertoobtaintheacidinapurestate.Withtechnicalp-nitrobenzylcyanide,afewgramsofanimalcharcoalareaddedindissolvingtheprecipitate.4.Thesolubilitycurveofp-nitrophenylaceticacidisverysteepattemperaturesnear100°,sothatthefilteringoftheboilingsolutionshouldberapid.3.Discussionp-Nitrophenylaceticacidcanbepreparedbythenitrationofphenylaceticacid1andbythehydrolysisofitsnitrilewithhydrochloricacid.2Thispreparationisreferencedfrom:Org.Syn.Coll.Vol.1,52Org.Syn.Coll.Vol.1,396Org.Syn.Coll.Vol.3,444References1.Maxwell,Ber.12,1765(1879);Borsche,Ber.42,3596(1909).2.Gabriel,Ber.15,834(1882).复习思考题1、简述由腈制备羧酸的基本原理。2、羧酸的制备方法都有哪些？各有什么优缺点？3、本实验中可能的副反应是什么？如何提高收率？