Asidefromyourcar’sfuel,therightsizeofthewheelsalsoplaysakeyroleinkeepingyourvehicleintip-topshape.Ifyouhavenoticed,asidefromthebrandofyourtiresthereareothermarkingsonit,particularlylettersandnumbers.Whatdotiresizenumbersmean?Andwhatdotheselettersonmytiresmean?
Thesenumbersandletterstellalotofinformationaboutthetires’purpose,itsdimensions,theloadcapacityitcouldhold,anditsdurabili...[
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格氏試劑與氧氣的反應一般分為如下2個步驟： 格氏試劑與O2反應先形成過氧化物。 過氧化物與另一分子格氏試劑反應形成ROMgX。ROMgX在被水淬滅後，則生成ROH，即醇或酚。 一般而言，芳基格氏試劑比烷基格氏試劑對氧氣更穩定一些。 更直觀的機理如下所示： 如果有其他合適的金屬離子存在下，也會發生格氏試劑的自偶聯反應： 具體案例： 來自網絡 參考文[
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TheBarton–McCombiedeoxygenationisanorganicreactioninwhichahydroxyfunctionalgroupinanorganiccompoundisreplacedbyahydrogentogiveanalkylgroup.ItisnamedafterBritishchemistsSirDerekHaroldRichardBartonandStuartW.McCombie.Thereactionmechanismconsistsofacatalyticradicalinitiationstepandapropagationstep.Thealcohol(1)isfirstconvertedintoareactivecarbonothioylintermediatesuchasathionoesterorxanthate2.H...[
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Stryker'sreagent([(PPh3)CuH]6),alsoknownastheOsborncomplex,isahexamericcopperhydrideligatedwithtriphenylphosphine.Itisabrickred,air-sensitivesolid.Stryker'sreagentisamildlyhydridicreagent,usedinhomogeneouscatalysisofconjugatereductionreactionsofenones,enoates,andrelatedsubstrates.
Thecompoundcaneffectregioselectiveconjugatereductionsofvariouscarbonylderivativesincludingunsaturatedal...[
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Diethylaluminumcyanide("Nagata'sreagent")istheorganoaluminumcompoundwithformula((C2H5)2AlCN)n.Thiscolorlesscompoundisusuallyhandledasasolutionintoluene.Itisareagentforthehydrocyanationofα,β-unsaturatedketones.
Synthesis
Diethylaluminumcyanidewasoriginallygeneratedbytreatmentoftriethylaluminumwithaslightexcessofhydrogencyanide.Theproductistypicallystoredinampoulesbeca...[
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TheNicholasreactionisanorganicreactionwhereadicobaltoctacarbonyl-stabilizedpropargyliccationisreactedwithanucleophile.Oxidativedemetallationgivesthedesiredalkylatedalkyne.ItisnamedafterKennethM.Nicholas.ThePauson–Khandreaction(orPKRorPK-typereaction)isachemicalreactiondescribedasa[2+2+1]cycloadditionbetweenanalkyne,analkeneandcarbonmonoxidetoformaα,β-cyclopentenone.IhsanUllahKhand...[
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TheBabler-DaubenOxidationisthecatalyticchromium-mediated1,3-oxidativetranspositionofallylicalcohols.Generalfeatures:1.Thereactionproducesthedesiredenoneproductinhighyields,anditdoesn’trequireair-freeconditionsnorheating.2.AcommonsolventisanhydrousDCMorchloroform.3.Themaindrawbackistheuseofthehighlytoxicoxidizingagent,PCC.4.Besides,theBabler-Daubenoxidationofsecondaryallylicalcoholsprovesmore...[
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Sincethediscoveryofthepalladium-catalyzedSuzukiMiyaurareaction,organoboronateshavebeendevelopedaspowerfulreagentsforcarbon-carbonbondformationduetotheirstability,nontoxicity,andfunctionalgroupcompatibility.Althoughnumerousligandsystemshavebeendevelopedforawidearrayofcouplingpartners,reactionofelectron-deficientboronatessuchas2-pyridylremainschallenging2andofhighinteresttothesyntheticcommunity,part...[
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Forsubstratesthatbearmorethanonehalide/triflate,theabilitytoeffectselectivemonofunctionalizationthroughSuzukicrosscouplingcanbeapowerfultool.Forpalladiumcatalysts,thegeneralorderofreactivityisthefollowing:I>BrJOTf.Cl.IthasbeenestablishedthatwiththePd2(dba)3/P(t-Bu)3catalystsystemitispossibletocarryouthighlyselectivemonofunctionalizationsofdifunctionalizedarenes(Table7).Notsurprisingly,aniodoand...[
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C-X鍵被C-H鍵取代的脫鹵反應（dehalogenationreactions）在過渡金屬催化的偶聯反應中，尤其是鈀催化的交叉偶聯反應中是很常見的競爭性反應，並導致相關雜質的形成和偶聯收率的降低。Suzuki偶聯，Sonogashira偶聯，Heck偶聯，Buchwald偶聯等反應中均有可能出現掉鹵素雜質。
Suzuki偶聯反應中的脫鹵素雜質（掉氯，掉溴，掉碘）的形成與多種反應因素有關。催化劑，配體，堿，溶劑[
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