Asidefromyourcar’sfuel,therightsizeofthewheelsalsoplaysakeyroleinkeepingyourvehicleintip-topshape.Ifyouhavenoticed,asidefromthebrandofyourtiresthereareothermarkingsonit,particularlylettersandnumbers.Whatdotiresizenumbersmean?Andwhatdotheselettersonmytiresmean?
Thesenumbersandletterstellalotofinformationaboutthetires’purpose,itsdimensions,theloadcapacityitcouldhold,anditsdurabili...[
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格氏试剂与氧气的反应一般分为如下2个步骤： 格氏试剂与O2反应先形成过氧化物。 过氧化物与另一分子格氏试剂反应形成ROMgX。ROMgX在被水淬灭后，则生成ROH，即醇或酚。 一般而言，芳基格氏试剂比烷基格氏试剂对氧气更稳定一些。 更直观的机理如下所示： 如果有其他合适的金属离子存在下，也会发生格氏试剂的自偶联反应： 具体案例： 来自网络 参考文[
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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键被C-H键取代的脱卤反应（dehalogenationreactions）在过渡金属催化的偶联反应中，尤其是钯催化的交叉偶联反应中是很常见的竞争性反应，并导致相关杂质的形成和偶联收率的降低。Suzuki偶联，Sonogashira偶联，Heck偶联，Buchwald偶联等反应中均有可能出现掉卤素杂质。
Suzuki偶联反应中的脱卤素杂质（掉氯，掉溴，掉碘）的形成与多种反应因素有关。催化剂，配体，碱，溶剂[
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