制药工程专业英语第6单元

1、PART2BIOCHEMICALPHARMACEUTICALSUnit6IsolationofCaffeinefromTeaInthisexperiment，Caffeinewillbeisolatedfromtealeaves.Themajorproblemoftheisolationisthatcaffeinedoesnotoccuraloneintealeaves，butisaccompaniedbyothernaturalsubstancesfromwhichitmustbeseparated.Themajorcomponentoftealeavesiscellulose，whichi

2、sthemajorstructuralmaterialofallplantcells.Celluloseisapolymerofglucose.Sincecelluloseisvirtuallyinsolubleinwater，itpresentsnoproblemsintheisolationprocedure.Caffeine，ontheotherhand，iswatersolubleandisoneofthemajorsubstancesextractedintothesolutioncalledtea.”Caffeinecomprisesasmuchasp5ercentbyweight

3、oftheleafmaterialinteaplants.Tanninsalsodissolveinthehotwaterusedtoextracttealeaves.Thetermtannindoesnotrefertoasinglehomogeneouscompound，oreventosubstanceswhichhavesimilarchemicalstructure.Itreferstoaclassofcompoundswhichhavecertainpropertiesincommon.Tanninsarephenoliccompoundshavingmolecularweight

4、sbetween500and3000.Theyarewidelyusedtotan”leatheTrh.eyprecipitatealkaloidszandproteinsfromaqueoussolutions.Tanninsareusuallydividedintotwoclasses:thosewhichcanbehydrolyzedandthosewhichcannot.Tanninsofthefirsttypewhicharefoundinteagenerallyyieldglucoseandgallicacidwhentheyarehydrolyzed.Thesetanninsar

5、eestersofgallicacidandglucose.Theyrepresentstructuresinwhichsomeofthehydroxylgroupsinglucosehavebeenesterifiedbydigalloylgroups.Thenon-hydrolyzabletanninsfoundinteaarecondensationpolymersofcatechin.Thesepolymersarenotuniforminstructure，butcatechinmoleculesareusuallylinkedtogetheratringpositions4and8

6、.Whentanninsareextractedintohotwater，thehydrolyzableonesarepartiallyhydrolyzed，meaningthatfreegallicacidisalsofoundintea.Thetannins，byvirtueoftheirphenolicgroups，andgallicacidbyvirtueofitscarboxylgroups，arebothacidic.Ifcalciumcarbonate，abase，isaddedtoteawater，thecalciumsaltsoftheseacidsareformed.Caf

7、feinecanbeextractedfromthebasicteasolutionwithchloroform，butthecalciumsaltsofgallicacidandthetanninsarenotchloroformsolubleandremainbehindintheaqueoussolution.Thebrowncolorofateasolutionisduetoflavonoidpigmentsandchlorophylls，aswellastheirrespectiveoxidationproducts.Althoughchlorophyllsaresomewhatch

8、loroformsoluble，mostoftheothersubstancesinteaarenot.Thus，thechloroformextractionofthebasicteasolutionremovesnearlypurecaffeine.Thechloroformiseasilyremovedbydistillation(by61C)toleavethecrudecaffeine.Thecaffeinemaybepurifiedbyrecrystallizationorbysublimation.68CatechinGallicAcidInasecondpartofthisex

9、periment，Caffeinewillbeconvertedtoaderivative.Aderivativeofacompoundisasecondcompound，ofknownmeltingpoint，formedfromtheoriginalcompoundbyasimplechemicalreaction.Intryingtomakeapositiveidentificationofanorganiccompound，itisoftencustomarytoconvertitintoaderivative.Ifthefirstcompound，Caffeineinthiscase

10、，anditsderivativebothhavemeltingpointswhichmatchthosereportedinthechemicalliterature(e.g.，ahandbook)，itisassumedthatthereisnocoincidenceandthattheidentityofthefirstcompound，Caffeine，hasbeendefinitelyestablished.Caffeineisabaseandwillreactwithanacidtogiveasalt.Usingsalicylicacid，aderivativesaltofCaff

11、eine，Caffeinesalicylate，willbemadeinordertoestablishtheidentityoftheCaffeineisolatedfromtealeaves.SpecialInstructionsBecarefulwhenhandlingchloroform.Itisatoxicsolvent，andyoushouldnotbreatheitexcessivelyorspillitonyourself.Whendiscardingspenttealeaves，donotputtheminthesinkbecausetheywillclogthedrain.

12、Disposeoftheminawastecontainer.ProcedurePlace25gofdrytealeaves，25gofcalciumcarbonatepowder，and250mlofwaterina500mlthreeneckroundbottomflaskequippedwithacondenserforreflux.Stoppertheunusedopeningsintheflaskandheatthemixtureunderrefluxforabout20minutes.UseaBunsenburnertoheat.Whilethesolutionisstillhot

13、，filteritbygravitythroughaflutedfilterusingafastfilterpapersuchasE&DNo.617orS&SNo.595.Youmayneedtochangethefilterpaperifitclogs.Coolthefiltrate(filteredliquid)toroomtemperatureand，usingaseparatoryfunnel，extractittwicewith25mlportionsofchloroform.Combinethetwoportionsofchloroformina100mlroundbottomfl

14、ask，Assembleanapparatusforsimpledistillationandremovethechloroformbydistillation.Useasteambathtoheat.Theresidueinthedistillationflaskcontainsthecaffeineandispurifiedasdescribedbelow(crystallization).Savethechloroformthatwasdistilled.Youwillusesomeofitinthenextstep.Theremaindershouldbeplacedinacollec

15、tioncontainer.69Crystallization(Purification)Dissolvetheresidueobtainedfromthechloroformextractionoftheteasolutioninabout10m1ofthechloroformthatyousavedfromthedistillation.Itmaybenecessarytoheatthemixtureonasteambath.Transferthesolutiontoa50mlbeaker.Rinsetheflaskwithanadditional5m1ofchloroformandcom

16、binethisinthebeaker.Evaporatethenowlight-greensolutiontodrynessbyheatingitonasteambathinthehood.Theresidueobtainedonevaporationofthechloroformisnextcrystallizedbythemixedsolventmethod.Dissolveitinasmallquantity(about2to4ml)ofhotbenzeneandaddjustenoughhighboiling(60Cto90C)petroleumether(orligroin)tot

17、urnthesolutionfaintlycloudy.Alternatively，acetonemaybeusedforsimplecrystallizationwithoutasecondsolvent.CoolthesolutionandcollectthecrystallineproductbyvacuumfiltrationusingaHirschfunnel.Crystallizetheproductthesamewayasecondtimeifnecessary，andallowtheproducttodrybyallowingittostandinthesuctionfunne

18、lforawhile.Weightheproduct.Calculatetheweightypercentageyieldbasedonteaanddeterminethemeltingpoint.Ifdesired，theproductmaybefurtherpurifiedbysublimationasdescribedinthenextexperiment.TheDerivativeDissolve0.20gofCaffeineand0.15gofsalicylicacidin15mlofbenzeneinasmallbeakerbywarmingthemixtureonasteamba

19、th.Addabout5mlofhighboiling(60Cto90C)petroleumetherandallowthemixturetocoolandcrystallize.Itmaybenecessarytocoolthebeakerinanicewaterbathortoaddasmallamountofextrapetroleumethertoinducecrystallization.CollectthecrystallineproductbyvacuumfiltrationusingaHirschfunnel.Drytheproductbyallowingittostandin

20、theair，anddetermineitsmeltingpoint.Checkthevalueagainstthatintheliterature.Submitthesampletotheinstructorinalabeledvial.SelectedfromPaviaDonaldL.IntroductiontoOrgantcLaboratoryTechniques:aContemporaryApproach.W.B.SaundersCompany,1976.ExercisesAnswerthefollowingquestions:68Canyoulistseveralplantsthat

21、containcaffeine?Whatkindofmethodcanbeusedtoisolatecaffeinefromtea?Howdoesmanusecaffeineinthedailylife?Competingthefollowingparagraph.ChooseNotMoreThanThreeWordsfromthepassageforeachanswer.Theactiveingredientthatmakesteaandcoffeevaluabletomanis.Caffeineisan，aclassofnaturallyoccurringcompoundscontaini

22、ngnitrogenandhavingthepropertiesofanorganicaminebase.Teaandcoffeearenottheonlyplantsourcesofcaffeine.Othersinclude:kolanuts，mateleaves，guaranaseeds，andinsmaallamount，cocoabeans.Place35gofgroundcoffeeaboilingstoneand125mlofwaterintoa500mlroundbottomflaskequippedwithaforreflux.theunusedopeningsinthefl

23、askandheatthemixtureunderforabout20minutes.Useatoheat.Duringtheheatingperiod，assembleavacuumfiltrationapparatus.Whenboilingactionhasstoppedandthecoffeegroundshavesettledsomewhat，butwhilethesolutionisstillhot，filterthesolutionthroughabyvacuumfiltration.PutthefollowingintoChinese:celluloseglucosechlor

24、oformbeakercrystallizationpurificationapparatusfilterpaperhydroxylgroupcarboxylgroupbenzeneacetoneevaporationinsolublecondensationresidue第2部分生化制药6单元的分离从茶叶中的咖啡因在这个实验中，咖啡因会被孤立于茶叶。在的主要问题：隔离是，咖啡因不会出现在茶叶单，而是由其他的，它必须伴随着分离的天然物质。对茶叶的主要成分是纤维素，这是所有植物细胞的主要结构材料。纤维素是葡萄糖的聚合物。由于纤维素几乎不溶于水，它提出了在隔离程序没有问题。咖啡因，另一方面，易溶于

25、水，是提取到解决方案的主要物质之一，被称为“茶”。咖啡因包括高达5通过在茶树叶片材料的重量百分比。鞣质也溶于热水用于提取茶叶。单宁一词不是指为一个单一的化合物，甚至有相似的化学物质的结构。它是指一种化合物具有某些共同属性的类。单宁分子量之间有酚类化合物500和3000。它们被广泛用于“晒黑”皮革。他们从水溶液中沉淀alkaloidsz和蛋白质。单宁通常分为两类：那些可以水解，哪些不能。第一种类型的单宁是茶中通常会产生葡萄糖和没食子酸水解时，。这些单宁是没食子酸和葡萄糖酯。它们代表，其中在一些葡萄糖的羟基被酯化digalloyl群体结构。非水解性单宁是茶中的儿茶素缩合聚合物。这些聚合物的结构不统

26、一，但儿茶素分子在环通常与位置4和8在一起。当单宁分为热水提取，部分水解水解的是，这意味着自由没食子酸也发现茶叶中。凭借他们的酚羟基，单宁酸，没食子酸的羧基凭借其，都是酸性的。如果碳酸钙，一个基地，被添加到茶水，这些酸的钙盐的形成。咖啡因可以用氯仿提取茶叶基本解决方案，但没食子酸的钙盐和单宁酸不溶于氯仿，并保持在水溶液中落后。一个茶解褐色是由于黄酮类色素，叶绿素，以及他们各自的氧化产物。叶绿素虽然有点溶于氯仿，茶叶中的其它物质大多数都不是。因此，基本解决氯仿萃取去除茶几乎纯咖啡因。氯仿很容易去除蒸馏(由61C)离开原油咖啡因。咖啡因可能是重结晶纯化或升华。儿茶素没食子酸在本次实验的第二部分，咖

27、啡因会被转换为衍生工具。衍生的一种化合物是第二个化合物，已知熔点，从一个简单的化学反应形成的原始化合物。在努力做一个积极的鉴定一种有机化合物，它往往是习惯性地转换成一个派生它。如果第一个化合物，咖啡因在这种情况下，它的衍生物都有匹配熔点在化学文献（例如，一本手册），这是假设是没有巧合，报道的第一个化合物，咖啡因身份已绝对成立。咖啡因是一种基础，并将与酸反应，让盐。使用水杨酸，盐衍生物的咖啡因，咖啡因水杨酸，将在以确定身份的咖啡因从茶叶孤立。特别说明时要小心处理氯仿。它是一种有毒溶剂，你不应该过分或吸到它洒在自己身上。当丢弃花茶叶，不要放在水槽里，因为他们会阻塞排水管。他们掷入垃圾容器。程序放在

28、一个500毫升三颈圆底与一个装有回流冷凝器的烧瓶干茶叶25克，25克碳酸钙粉，水250毫升。塞烧瓶中加热回流20分钟左右的混合物未使用的开口。使用本生灯加热。虽然解决办法仍然是热的，它靠重力过滤槽过滤器通过使用快速滤纸，女fE&D第617和S&S的第595号。您可能需要更改滤纸如果木屐。冷却过滤（过滤液体）到室温，用分液漏斗中，用25毫升氯仿提取部分两次。结合氯仿中的两个100毫升的圆底烧瓶部分，组建一个简单的蒸馏设备和蒸馏除去氯仿。使用热蒸汽浴室。蒸馏烧瓶中的残留物含有咖啡因和被提纯如下（结晶）中所述。这是保存蒸馏氯仿。您将在下一步中使用了一些。其余应放置在一个集合容器。69结晶（净化）解散的茶溶液对氯仿，您从氯仿萃取蒸馏保存10m1取得的残留物。它可能需要加热的混合物上的蒸气浴。转移到一个50毫升的烧杯的解