造纸专业英语3

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1、GeneralligninreactionsinpulpbleachingThechemistryofbleachingisconcernedmainlywiththeresponseoflignintotheactionofvariousbleachingagentsbecausesuccessfulbleachingrequiresthatligninberemovedormodifiedfromthepulp.Intheorysitesorthoandparatothehydroxylandalkoxylsubstituentonthearoma

2、ticringshouldbepreferentiallyattackedbyelectrophiles.Attackofbleachingchemicalsonthecarbohydratecomponentsofpulpisunavoidableandhasthepotentialforcausingdeteriorationofpulpstrengthandyield.ortho-邻，邻位para-对位hydroxyl羟基alkoxyl烷氧基substituent取代基aromaticring芳环electrophile亲电试剂carbohydr

3、ate碳水化合物Generalligninreactionsinpulpbleaching1.ElectrophilicsubstitutionandoxidationofaromaticstructuresThegeneralsequenceiscomprisedofthreedistinctpathways:electrophilicsubstitutionatanunsubstitutedringcarbon,electrophilicsubstitutionofthe1-carbonwithdisplacementofabenzylalcoho

4、lsidechain,anddealkylation.Allofthesetransformationsproceedthroughacomplextothreedistinctcyclohexadienoylintermediates.electrophilic亲电的substituent取代基substitution;【化】取代benzyl【化】苄基,苯甲基sidechain侧链dealkylation脱烷基化作用cyclohexadienoyl环己二烯酮GeneralligninreactionsinpulpbleachingAdditional

5、substitutionmaytakeplaceatotherelectron-deficientringsitestoadegreedependingonthetypeandavailabilityofthecationicspeciesandtheincidenceofcompetingreactions.Theeffectoftheintroducedringsubstituentonligninsolubilitydependsonthehydrophilicityoftheattackingcationicspecies;forexample

6、,chlorosubstituentshaveanadverseeffectonwatersolubility;hydroxylgroupshavetheoppositeeffect.electron-deficientring缺电子环availabilityn.有效性,可利用性cationic阳离子的incidencen.发生(率)competingreaction竞争反应substituent【化】取代基hydrophilicity亲水性chloro氯代Generalligninreactionsinpulpbleaching2.Additionr

7、eactionofolefinicstructuresEthylenicgroupsareoftenpresentinthelignincomponentofpulpaspartsoflargerstructuraltypes,forexample,stilbenesandvinylarylethers.Aselectron-richentities,thesegroupsreactinitiallywithcationicbleachingspecies.additionreaction加成反应olefinic烯烃的ethylenic乙烯基的grou

8、p基团stilbene芪;1,2-二苯乙烯vinyl【化】乙烯基,乙烯树脂aryl【化】芳基,