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1、第三章.辐射化学的基本过程辐射的作用使介质分子电离、激发形成原初化学产物:活性粒子,包括电子、离子、激发分子、自由基等,分子辐射化学产额用G值表示。G值定义为体系中吸收100eV能量所变化(形成或破坏)的分子数。1一、离子1、离子的生成正离子:主要由辐射从分子中逐出电子产生的。MM++e-这一过程称电离,它主要产生正离子和电子,是电离辐射与物质相互作用的特征反应之一,也是整个辐解过程的关键一步。2这一反应的特点在于:1)、离子具有较高的能量,通常处于振动激发态和电子激发态。2)、在分子型离子(正的或负的)中,电荷可分布在整个离子或局限于一个基
2、团或原子上。这一反应看似简单,实际上是比较复杂的,就有机物中最简单的甲烷分子来讲,其辐解就有几种产物。3Chapter4RADIATIONCHEMISTRYOFSMALLMOLECULES4Astudyoftheradiationchemistryofsmallmoleculesishelpfulinunderstandingtheradiationchemistryofpolymers.Forexample,smallmoleculescontaincharacteristicgroupssuchascarboxyl(羧基),carbony
3、l(羰基),ester(酯),amide(氨基),andhalide(卤化物).Theradiationchemistryofsuchgroupingsinsmallmolecularissimilartotheirchemistryinlargemolecules,butthesmallermoleculesmaybemoreconvenienttoinvestigatebecauseofgreateaseofanalysisandhandling.Furthermore,theradiationchemistryoftheolefins(
4、烯烃类)isobviouslypertinenttopolymerchemistry,becauseolefinicmonomersarecommonlyemployedinradiation-inducedpolymerizationreactions.*Smallmolecule------lessthanpolymericinsize.5Asanotherexample,theradiationchemistryofsaturatedaliphatichydrocarbonshasbeenstudiedextensively(脂肪族烃类
5、研究最广泛),anditshowsmanyfeaturesexhibitedbyhydrocarbonpolymerssuchaspolyethyleneandpolypropylene.Whenanionizingrayorparticlespassthroughanorganicliquid,theprimaryprocessesthattakeplaceleadtotheproductionofexitedmolecules,electrons,ions,andfreeradicals.61.Primaryprocessofionizi
6、ngradiation:(1).BasicreactionsExcitation:MM*(4–1)Ionization:M*M++e-(4–2)A++B(4–3)Iondissociation:M+C++D(4–4)Neutralization:M++e-M**(4–5)Dissociation:A*andA**A+B(4–6)C+D(4–7)FreeradicalsMolecularproducts7(2).Chargetransfer:A++BA+B+(4–8)Example:C2H2++C6H6C2H2+C6H6+8(3).Whenwa
7、terisirradiated,theexitedmoleculesformeddirectlyaregenerallyignored,theideabeingthattheyreturndirectlytothegroundstatewithoutdecompositionorelsedissociationintoHandOHradicals,whichhavelittleextraenergyandrecombinewithintheircageofwatermoleculeswithoutcausinganynetchemicalch
8、ange.Theexcitedwatermoleculesmayreacttogivepartofmolecularproductyieldbythereactio