造纸专业英语4

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1、RecationofcarbohydrateswithbleachingagentsandalkaliAlthoughthechemistryofpulpbleachingmainlyinvolvesthereactionsofligninwithbleachingchemicals,carbohydratesneverthelessundergoconcurrenttransformationsduringbleachingthatoftenhaveanimportantbearingonthestrengthpropertiesan

2、dyieldoftheresultingpulp.Theimpactofthesereactionsbecomesincreasinglymoresignificantasthelignincontentofthepulpdecreases.concurrent同时发生的，并存的；nevertheless还是,然而bearing关系,影响;方面;意义RecationofcarbohydrateswithbleachingagentsandalkaliThereactivesitesforattackbyelectrophilicblea

3、chingspeciesoncarbohydratesareacetal(glycosidic)linkages,reducingend-groupsandenonestructuresformedinitiallybyattackofanelectrophilicbleachingspecies.Thereactionsofcarbohydrateswithbleachingchemicalsmaybeconvenientlyclassifiedaccordingtowhethertheyoccuratacetalsitesorels

4、ewhere.acetal缩醛glycosidic[生化]糖苷的enone烯酮Recationofcarbohydrateswithbleachingagentsandalkali1.reactionsatacetalsitesInafreeradicalchainprocess,thechlorineradicalabstractsahydrogenatomfromtheC-1atomoftheglycosideforminganorganicradicalwhichthenreactswithelementalchlorinetor

5、egeneratechlorineradicalsandformachlorinatedanhydroglucoseunit.Inanensuinghydrolysisstep,theacetallinkageisdirectlycleavedandanaldonicacidendgroupisultimatelyformed.chlorinatevt.使氯化,用氯消毒anhydroglucose【化】葡糖酐aldonicacid醛酮酸aldonicacidChemicalstructureofgluconicacid,thealdon

6、icacidderivedfromglucose.UronicacidRecationofcarbohydrateswithbleachingagentsandalkaliIntheozonationofcarbohydratemodelcompoundsandcellulose,thedominantreactionsintheinitialphaseareionicandinvolveadirectattackontheacetallinkage.TheC-Hbondisattackedbyozoneandahydrotrioxid

7、eisformedbya1,3-dipolaradditionmechanism.Thehydrotrioxideundergoesfragmentationtothelactonewithreleaseofoxygenwhichmaybeinthesingletform.ozonation臭氧化，臭氧处理lactone内酯singlet【物】单线;独态triplet三线态Recationofcarbohydrateswithbleachingagentsandalkali2.Reactionatnon-acetalsitesOxida

8、tionofhydroxylgroupsTheoxidationofasecondaryalcoholgroupisinitiatedbyabstractionofahydrogenatomfromahyd