Kev lig kev cai, lub catalyst ua haujlwm los ntawm kev sib cuam tshuam ncaj qha nrog cov reactants.Nyob rau hauv lub tshiab noncontact catalytic system (NCCS), ib qho nruab nrab uas tsim los ntawm ib tug catalytic cov tshuaj tiv thaiv yog ib tug intermediary los pab kom muaj kev ywj pheej cov tshuaj tiv thaiv mus ntxiv.Ib qho piv txwv yog kev xaiv oxidation ntawm ethylbenzene, uas tsis tuaj yeem tshwm sim nyob rau hauv lub xub ntiag ntawm solubilized Au nanoclusters los yog cyclooctene, tab sis tau npaj txhij thaum ob qho tib si nyob ib txhij.Au-initiated xaiv epoxidation ntawm cyclooctene generated cyclooctenyl peroxy thiab oxy radicals uas ua hauj lwm los ua intermediaries los pib ethylbenzene oxidation.Qhov kev sib xyaw ua ke no tau txuas ntxiv cov txiaj ntsig catalytic ntawm Au.Cov tshuaj tiv thaiv mechanism tau txais kev txhawb nqa los ntawm cov tshuaj tiv thaiv kinetics thiab spin trap thwmsim.NCCS ua rau muaj kev sib txuam ua ke mus ntxiv yam tsis muaj kev txwv ntawm kev sib raug zoo stoichiometric, muab qib tshiab ntawm kev ywj pheej hauv cov txheej txheem hydrocarbon co-oxidation.

Raws li kev lig kev cai, tus catalyst cuam tshuam ncaj qha nrog cov reactants (reaction A) kom cuam tshuam cov kev sib cog lus rov kho dua los ntawm cov tshuaj tiv thaiv.Piv txwv li, nyob rau hauv cobalt-catalyzed oxidation ntawm alkylaromatics (1) los yog Au-catalyzed epoxidation ntawm cyclooctene (2), lub catalyst pab txhawb abstraction ntawm hydrogen atom los ntawm hydrocarbon los pib cov tshuaj tiv thaiv.Nyob rau hauv cov tshuaj tiv thaiv kab mob dawb radical, tus catalyst koom nrog hauv catalytic homolytic cleavage ntawm ib tug tsis muaj zog daim ntawv cog lus nyob rau hauv cov pib uas yog ntxiv txhob txwm los yog tam sim no raws li adventitious impurities nyob rau hauv cov tshuaj tiv thaiv sib tov (1, 3, 4).Qee cov kauj ruam hauv cov tshuaj tiv thaiv catalytic tandem yuav tsis xav tau kev sib cuag ncaj qha substrate-catalyst thaum hloov pauv ntawm substrate yog qhib los ntawm cov khoom tsim catalytically hauv cov kauj ruam ua ntej (5-8).Txawm li cas los xij, cov kev cuam tshuam no raug txwv los ntawm kev sib raug zoo ntawm stoichiometric ntawm cov kauj ruam.Piv txwv li, nyob rau hauv Mukaiyama (ep) oxidation ntawm alkene, ib tug catalyst converts ib tug sacrificial reductant nyob rau hauv cov tshuaj tiv thaiv A, xws li isobutyraldehyde, nrog lub concomitant stoichiometric tsim ntawm ib tug epoxide (reaction B) (9, 10).Txawm hais tias muaj peev xwm ua tau raws li txoj cai, peb tsis paub txog qhov piv txwv ntawm qhov kev ua haujlwm ntawm lub catalyst yog los tsim ib qho nruab nrab S hauv cov tshuaj tiv thaiv A, qhov twg S ua haujlwm ua tus neeg nruab nrab los pib lossis catalyze lwm cov tshuaj tiv thaiv B es tsis txhob koom ua ib qho stoichiometric reagent. , thaum lub catalyst tsis zoo rau cov tshuaj tiv thaiv B (Fig. 1).Hauv cov tswv yim zoo li no, kev cuam tshuam ntawm cov catalyst tau txuas ntxiv dhau qhov kev cuam tshuam cov tshuaj tiv thaiv A kom tseem cuam tshuam cov tshuaj tiv thaiv B tab sis tsis muaj kev sib cuag ncaj qha nrog nws cov reactants.Peb lub tswv yim zoo li no yog noncontact catalytic system (NCCS).Hauv NCCS, qhov ntev ntawm cov tshuaj tiv thaiv A thiab B tsis raug khi los ntawm kev sib raug zoo ntawm stoichiometric ntawm lawv.Qhov no yog qhov sib piv rau cov tshuaj tiv thaiv tandem.Hauv kev lag luam, xws li kev sib raug zoo stoichiometric feem ntau cuam tshuam kev lag luam ntawm cov txheej txheem tsim tshuaj.Ib qho piv txwv paub zoo yog stoichiometric ntau lawm ntawm phenol thiab acetone los ntawm oxidation ntawm benzene ntawm cumene hydroperoxide intermediate hauv cov txheej txheem cumene (11).

Lub catalyst (Cat) catalyzes cov tshuaj tiv thaiv A (AR ➔ S ➔AP) uas qhov nruab nrab S muaj txiaj ntsig hauv kev pib lossis catalyzing cov tshuaj tiv thaiv B (BR ➔ BP), txawm hais tias cov tshuaj tiv thaiv B tsis yog catalyzed los ntawm cov catalyst.

Peb pom zoo li NCCS thaum tshawb nrhiav cov khoom catalytic ntawm solubilized Aun pawg (qhov twg n feem ntau yog rau rau yim atoms) rau ib nrab oxidation ntawm ethylbenzene (EB).Peb tau pom tias cov solubilized Aun catalyzed qhov pib ntawm kev xaiv epoxidation ntawm cyclooctene (cC8═) nrog O2 nrog ~ 80% selectivity (2).Cov pawg no tau tsim nyob rau hauv situ thaum lub sij hawm Au/SiO2-catalyzed cC8═ epoxidation, thiab lawv tuav lawv lub peev xwm los tsim cov radical pib cyclooctene hydroperoxy radical (cC8═OO·) thoob plaws hauv cov tshuaj tiv thaiv.Cov pawg Aun solubilized tuaj yeem sau rau hauv cov tshuaj tiv thaiv sib xyaw tom qab tshem tawm Au / SiO2, thiab lawv qhov nruab nrab loj tau txiav txim siab siv aberration-kho electron microscopy thiab fluorescence spectroscopy (2).Ntxiv rau Aun pawg, cov khoom sib xyaw no kuj muaj cyclooctene hydroperoxide (cC8═OOH) thiab oxidation khoom cyclooctene epoxide, cyclooctenol, thiab cyclooctenone.cC8═OOH yog daim ntawv ruaj khov hydrogenated ntawm cC8═OO· thiab tam sim no ntawm cov concentrations ntawm 0.2 txog 0.5 M tom qab 40 mus rau 100% cC8═ hloov dua siab tshiab.Qhov sib tov no hu ua Au + cC8 ═OOH-x, qhov twg x yog qhov feem pua ​​cC8═ hloov dua siab tshiab.Txawm hais tias ntawm tus nqi qeeb qeeb thiab nrog lub sijhawm ntev (> 5 teev) induction, cC8═ epoxidation kuj tuaj yeem tshwm sim los ntawm nws pib-oxidation yam tsis muaj Aun pawg.Cov khoom sib xyaw uas tau txais los ntawm auto-oxidation tsis muaj Au yog hu ua cC8═OOH-x.Hauv NCCS, tus solubilized Aun yuav yog tus catalyst, epoxidation ntawm cC8═ yuav yog cov tshuaj tiv thaiv A, thiab cC8═OO· yuav yog S.

Lub auto-oxidation ntawm EB tsis tshwm sim yooj yim.Ntawm 145 ° C, tsuas yog 9% cov tshuaj tiv thaiv tshwm sim rau qhov zoo ntawm EB hauv qab 2.76 MPa O2 (12).Nyob rau hauv peb cov mob me me ntawm 100 ° C thiab bubbling O2 ntawm 0.1 MPa, tsis muaj cov tshuaj tiv thaiv zoo ntawm EB rau tsawg kawg 20 teev.Ntxiv cov dawb radical pib xav tau rau qhov kev tawm tsam no mus ntxiv.Pib nrog 2,2′-azobisobutyronitrile (AIBN), ib tug heev reactive thermal radical pib, ua rau nws pib-oxidation ntawm EB nrog ib tug nruab nrab saw ntev ntawm ~ 3 (daim duab S2A).Cov saw luv luv (~1) tau pom tias siv cov tert-butyl hydroperoxide tsawg dua (daim duab S2B), thiab muaj cov tshuaj tiv thaiv me me uas siv cov cumene hydroperoxide tsawg tshaj plaws.Yog li, nws pib-oxidation ntawm EB muaj kev cuam tshuam me ntsis ntawm cov tshuaj tiv thaiv tau qhia hauv qab no.

Aerobic oxidation tsis tu ncua ntawm EB rau EB hydroperoxide, acetophenone, thiab phenylethanol tau ua tiav los ntawm kev ntxiv Au + cC8═OOH-50 uas muaj cov sib xyaw ntawm Aun, cC8═OOH, thiab unreacted cC8═ (Fig. 2, nkhaus 1).Raws li tau pom los ntawm cov kev sim hauv qab no, peb lub ntsiab lus no tau ua lub luag haujlwm tseem ceeb hauv EB oxidation, thiab lawv tau txuas mus rau catalyst, S, thiab AR hauv NCCS system uas tau piav qhia hauv daim duab 1.

(i) 7 ml of EB + 3 ml of Au + cC8═OOH-50;(ii) 7 ml of EB + 3 ml of Au + cC8═OOH-50 + 1.2 mmol PPh3;(iii) 7 ml of EB + 3 ml of Au + cC8═OOH-99 + 0.6 mmol PPh3;(iv) 7 ml ntawm EB + 3 ml ntawm cC8═OOH-50;(v) 7 ml ntawm EB + 3 ml ntawm cC8═OOH-50 + 1.5 mmol PPh3.Qhov ntau ntawm PPh3 ntxiv tau teem kom sib npaug ntawm qhov ntau ntawm titrated hydroperoxide (qhov kub thiab txias, 100 ° C).

Raws li peb cov xwm txheej, tsis muaj qhov pom tau aerobic EB oxidation tshwm sim hauv kev sib xyaw ntawm cC8═ thiab EB (xws li, tsis muaj Cat lossis S).Triphenylphosphine (PPh3) muaj txiaj ntsig zoo hauv kev tshem tawm hydroperoxides.A Au + cC8═OOH-99 tov, depleted ntawm cC8═OOH los ntawm PPh3 ntxiv, muaj Aun thiab me ntsis unreacted cC8═, ua tsis tau tejyam pib cov tshuaj tiv thaiv EB txawm tom qab 2 teev (Fig. 2, nkhaus 3), qhia tias Aun ib leeg ua tsis tau zoo.Cov txiaj ntsig no kuj tau qhia tias lwm cov khoom ntawm cC8 ═ oxidation, xws li cyclooctene epoxide, cyclooctene cawv, lossis ketone, tsis tuaj yeem pib EB oxidation.Nyob rau hauv sib piv rau cov kev sim saum toj no, tshem tawm cC8═OOH nrog PPh3 los ntawm Au + cC8═OOH-50, tawm hauv qab Aun thiab unreacted cC8═, tsis deter EB conversion (piv nkhaus 1 thiab 2, daim duab 2).

Peb cov ntaub ntawv no qhia txog kev sib koom ua ke ntawm Aun thiab unreacted cC8═ hauv kev pib ntawm EB oxidation.Peb xav tias Aun catalyzed lub oxidation ntawm cC8 ═ rau tsim cC8═OOH, uas yog tus pib ntawm EB cov tshuaj tiv thaiv.Qhov no tuaj yeem kuaj tau los ntawm kev sib piv cov txiaj ntsig ntawm kev pib EB oxidation nrog kev sib xyaw ntawm cC8═OOH thiab cC8═ tab sis tsis muaj Aun ua ntej thiab tom qab tshem tawm cC8═OOH nrog PPh3.Txhawm rau ua kom zoo tshaj plaws ntawm cov kev sim ua ntej, peb siv cov tshuaj cC8═OOH-50 rau kev sib xyaw ntawm cC8═OOH thiab cC8═ kom txhua yam ua tau ntawm cC8═ epoxidation cov khoom yuav rov tsim dua.Cov txiaj ntsig tau pom tias nyob rau hauv lub xub ntiag ntawm cC8═OOH-50, EB tau txais txiaj ntsig zoo (Daim duab 2, nkhaus 4).Txawm li cas los xij, yog tias cC8═OOH raug tshem tawm los ntawm PPH3, tsis muaj qhov cuam tshuam rau thawj teev thiab txo qis kev ua haujlwm tom qab (khoov 5).Cov ntaub ntawv no tau txhawb nqa tus qauv ntxiv tias lub luag haujlwm catalytic ntawm Aun yog los txuas ntxiv tsim cC8═OOH ntawm cC8═ oxidation, thiab cC8═OOH pib EB cov tshuaj tiv thaiv.Lub luag haujlwm catalytic ntawm Aun tau lees paub ntxiv los ntawm kev saib xyuas tias qhov pib ntawm EB oxidation thaum tsis muaj cC8═OOH nce nrog nce Aun concentration (daim duab S3).

Lub luag haujlwm tshwj xeeb ntawm Aun hauv NCCS no tau pom los ntawm kev tshuaj xyuas Co raws li kev hloov pauv hloov pauv, uas tau xaiv vim tias cobalt acetate thiab cobalt cycloalkanecarboxylate (13) yog cov khoom siv hluav taws xob rau kev hloov pauv ntawm EB rau acetophenone nrog molecular O2, ua haujlwm nyob rau hauv cov xwm txheej hnyav thiab yuav tsum tau ua. muaj cov kua qaub thiab bromide ions.Co complexes kuj siv rau kev xaiv aerobic EB oxidation nyob rau hauv lub xub ntiag ntawm ib tug organocatalyst N-hydroxyphthalimide (NHPI) los yog ib tug sacrificial reductant (14, 15).Txawm li cas los xij, nyob rau hauv peb cov kev mob tshwm sim, lub xub ntiag ntawm Co / ZSM-5 tsis ua rau muaj kev kuaj pom oxidation ntawm EB, cC8═, los yog lawv cov sib tov rau tsawg kawg 6 teev.Ntawd yog, Co ib leeg tsis tuaj yeem pib ua cov tshuaj tiv thaiv oxidation.Txawm li cas los xij, nyob rau hauv lub xub ntiag ntawm ob qho tib si Aun thiab cC8 ═, nws yooj yim rau oxidation cov tshuaj tiv thaiv.Nyob ntawm qhov xwm txheej, cC8═ lossis EB reacted peb mus rau tsib zaug sai dua thaum Co/ZSM-5 nyob, thiab qhov kev txhim kho tau nce ntxiv nrog tus nqi ntawm Co/ZSM-5 (cov lus S2, kev sim 6 txog 8).EB oxidation khoom faib kuj hloov me ntsis nyob rau hauv lub xub ntiag ntawm Co/ZSM-5.Ua kom tus nqi ntawm Co/ZSM-5 nce acetophenone tawm los thiab, kom tsawg dua, phenylethanol yields ntawm tus nqi ntawm EB hydroperoxide (table S3, thwmsim 6 txog 8), raws li qhov tseeb tias Co catalyzed decomposition ntawm EB hydroperoxide rau. acetophenone thiab phenylethanol thiab oxidation tom kawg rau acetophenone.Rau qhov ua tau raws li qhov xav tau, peb suav nrog Co/ZSM-5 hauv peb cov tshuaj tiv thaiv sib xyaw kom luv lub sijhawm cov tshuaj tiv thaiv.

Qhov txawv ntawm NCCS thiab tandem cov tshuaj tiv thaiv kab mob yog qhov qub, tsis muaj kev sib raug zoo ntawm cov tshuaj tiv thaiv A thiab B (Daim duab 1).Txhawm rau kom ntseeg tau tias peb cov kev cuam tshuam tshwm sim ntawm NCCS, peb tau sim cov txiaj ntsig ntawm kev hloov pauv ntawm cC8═ rau EB los ntawm kev saib xyuas lawv tus kheej cov tshuaj tiv thaiv.Daim duab 3 qhia cov txiaj ntsig ntawm kev hloov pauv qhov pib cC8═ concentration thaum ua kom qhov pib EB concentration thiab lwm yam tshuaj tiv thaiv tsis tu ncua.Cov ntaub ntawv qhia tias tsis muaj kev sib raug zoo stoichiometric ntawm qhov ntau ntawm ob lub reactants reacted, paub meej tias cov qauv tshuaj tiv thaiv txawv ntawm cov tshuaj tiv thaiv tandem.Ib qho piv txwv ntawm cov kev sim uas thawj zaug EB concentrations tau sib txawv thaum kho lwm cov concentrations tuaj txog ntawm tib qhov kev txiav txim siab.Los ntawm cov ntaub ntawv no, thawj zaug cov tshuaj tiv thaiv tau suav nrog (Table 1 thiab cov lus S2, kev sim 4 thiab 5) thiab pom tias sib txawv rau cC8═ thiab EB.Tsis muaj kev lag luam tawm hauv cov tshuaj tiv thaiv ntawm ob qhov kev tshwm sim xws li thaum ib qho kev tawm tsam sai dua, lwm qhov yuav tsum tau qeeb qeeb.Ob leeg cov tshuaj tiv thaiv tuaj yeem nce ib txhij, raws li qhia los ntawm kev sim 4 thiab 5 hauv rooj S2.Kev lag luam tawm yuav xav tau yog tias EB thiab cC8═ sib tw rau tib qhov chaw tshuaj tiv thaiv catalytic lossis nruab nrab.Qhov kev txiav txim siab no kuj tseem ua tau raws li qhov tseeb tias qhov kev tawm tsam ib txhij ntawm EB thiab cC8═ tsis muaj qhov cuam tshuam me me rau lawv tus kheej cov khoom faib, raws li qhia hauv Table 1 thiab cov lus S3.

Initial cC8═ concentrations yog 0.34 M (A), 1.05 M (B), thiab 1.75 M (C).Decane tau siv los ua qhov sib txawv ntawm qhov ntim ntawm cC8═ siv.Lwm yam mob: 32 mg ntawm Co/ZSM5, 100 ° C.

Cov ntaub ntawv no tau ua raws li cov txheej txheem kev siv tshuab uas tau pom hauv daim duab 4, uas cov kauj ruam tseem ceeb rau NCCS tau hais txog thiab cov neeg ua haujlwm tseem ceeb tau hais txog (cov txheej txheem ua tiav ntau dua yog pom hauv daim duab S8).Hauv cov txheej txheem no, cov pawg Aun pib lub voj voog cC8═ epoxidation los ntawm kev tsim cov cyclooctenyl radicals (I) thiab cyclooctene peroxy radicals (II).Ob lub radicals no ces koom rau hauv lub voj voog cC8═ epoxidation, raws li tau tsim ua ntej (2, 16).Thaum EB tam sim no, II dhau los ua ib qho nruab nrab ntawm cov molecule thiab shuttles ntawm cC8═ epoxidation voj voog thiab EB oxidation voj voog.Nyob rau hauv lub voj voog EB, II reacts nrog EB los tsim ib tug phenylethyl radical, uas tam sim ntawd tsim ib phenylethyl peroxy radical (III) los ntawm cov tshuaj tiv thaiv nrog O2, raws li carbon-centered radical tshua nrog O2 paub tias yuav yooj yim heev (1).Tom qab hydrogen abstraction los ntawm III daim ntawv phenylethyl hydroperoxide thiab nws thiaj li acetophenone thiab phenylethanol.III kuj tuaj yeem hnov ​​​​mob sai nrog cC8═, uas dhau los ua txoj hauv kev kom rov ua dua II uas tau noj los ntawm EB oxidation voj voog.Yog li, EB oxidation cov tshuaj tiv thaiv tsis yog nrog los ntawm cov tshuaj tiv thaiv stoichiometric ntawm cC8═ epoxidation cov tshuaj tiv thaiv, thiab tsis muaj "kev lag luam tawm" hauv cov tshuaj tiv thaiv ntawm EB thiab cC8═ raws li xav tau yog tias lawv tau sib tw rau tib reagent. los yog catalytic active site.Vim tias II koom nrog cov kauj ruam pib hauv ob qho tib si EB thiab cC8═ oxidation cycles tab sis tsis ncaj qha rau hauv cov khoom tsim cov kauj ruam, nws txoj kev txuas ntawm ob qhov kev cuam tshuam tsis cuam tshuam rau cov khoom faib khoom.

Cyclooctene peroxy radical (II) yog tus tseem ceeb intermediary uas pib EB oxidation.II tuaj yeem rov tsim dua los ntawm cov tshuaj tiv thaiv ntawm EB peroxy radical (III) nrog cC8═.Nyob rau sab laug sab laug, Aun pawg pib lub voj voog cC8═ epoxidation (lub voj voog ntawm sab laug).Lub voj voog ntawm sab xis qhia cov kauj ruam rau EB oxidation.Tsuas yog cov kauj ruam tseem ceeb ntawm NCCS tau pom.

Txhawm rau txheeb xyuas qhov tsim ntawm transient radical intermediates raws li tau hais tseg hauv daim duab 4, peb ntxiv cov ntxiab 5,5-dimethyl-1-pyrroline N-oxide (DMPO) rau cov tshuaj tiv thaiv sib tov los tsim cov nitroxide radical spin adducts ntev ntev nrog rau Cov dawb radicals tam sim no rau kev kuaj pom nrog X-band electron paramagnetic resonance (EPR) spectroscopy.Raws li kev tswj hwm, tsis muaj cov radicals raug kaw los ntawm DMPO hauv cov tshuaj acetone thiab decane yam tsis muaj C8═ lossis EB (daim duab S4-3).Thaum DMPO tau ntxiv rau cov tshuaj tiv thaiv sib xyaw uas muaj cC8═OOH thiab cC8═ (daim duab S4-1), qhov tshwm sim EPR spectrum tau zoo simulated raws li qhov sib npaug ntawm cov kab mob sib txawv loj (A hauv daim duab, ~ 86% ntawm tag nrho. simulation siv) thiab ob hom me (B thiab C, ~ 5 thiab ~ 9% ntawm tag nrho cov simulation siv, feem), muab pov thawj ncaj qha ntawm kev tsim radical thaum cov tshuaj tiv thaiv.Raws li kev sib piv ntawm hyperfine coupling qhov tseem ceeb rau cov neeg paub DMPO adducts (table S1), hom C tau raug xa mus rau DMPO / ROO• adduct, plausibly lub cyclooctene 3-peroxy radical (II) tau piav qhia ua tus intermediary ntawm ob. cov tshuaj tiv thaiv (Daim duab 4).Hom A thiab B tau raug xa mus rau ob qhov sib txawv me ntsis DMPO/RO• adducts, qhov twg R hu ua hydrocarbon moiety.Lawv tuaj yeem yog ib hom RO• uas tau piav qhia hauv daim duab 4 los yog alkoxy radicals uas tsim los ntawm DMPO/ROO• adduct decay [DMPO/ROO• adducts paub tias tsis ruaj khov thiab decompose rau qhov sib thooj alkoxy radical adduct (17, 18)] los yog sib tov ntawm ob qho tib si.Thaum EB kuj tseem suav nrog hauv cov tshuaj tiv thaiv sib xyaw, qhov tshwm sim EPR spectrum tau zoo simulated nrog feem ntau hom A', uas zoo ib yam li hom A (DMPO / RO•), thiab ob hom haiv neeg B thiab C nrog cov kev pab cuam me me. (fig. S4-2 and table S1).Vim hais tias suav nrog EB tau xav tias yuav tsav qhov tsim ntawm phenylethyl peroxy radicals (III), hom A' yog qhov sib xyaw ntawm RO• tsim nyob rau hauv cov tshuaj tiv thaiv nrog rau ib qho phenylethyl peroxy adduct, uas tom qab lwj mus rau phenylethyl oxy DMPO adduct.

Siv EB-d10 ua cov tshuaj reactant thiab saib xyuas deuterium labeling hauv cC8═ cov khoom tuaj yeem kuaj xyuas seb puas muaj cov tshuaj tiv thaiv EB nrog cC8═ raws cov pa roj carbon radicals.Cov txiaj ntsig ntawm qhov kev sim no tau pom tias tsis muaj deuterium koom nrog hauv cyclooctene epoxide (fig. S5 thiab S6).Phenylethanol khaws tag nrho cov deuterium hauv EB reactant, thiab qee qhov ntawm deuterons hauv methyl pawg ntawm acetophenone tau sib pauv, uas tuaj yeem tshwm sim hauv qhov loj spectrometer.Yog li, tsis muaj pov thawj ntawm cov tshuaj tiv thaiv ntawm EB-d10 thiab cyclooctenyl radical, uas yuav qhia deuteron rau hauv cov khoom cC8.

Qhov kev siv tau ntawm NCCS lub tswv yim tau txuas ntxiv los tshuaj xyuas Au + cC8═OOH-100-pab aerobic oxidation ntawm 4-methylanisole.Vim yog qhov muaj zog thawj C─H daim ntawv cog lus hauv cov molecule no, cov tshuaj tiv thaiv oxy-functionalization tau ua nyob rau ntawm qhov kub siab dua.Tus nqi pib ntawm kev hloov pauv ntawm 4-methylanisole mus rau 4-anisaldehyde tau muab piv rau cov tshuaj tiv thaiv pib nrog Aun thiab nrog lossis tsis muaj cC8═ ntxiv (cC8═OOH raug tshem tawm nrog PPh3).Zoo ib yam li EB oxidation, thaum cov tshuaj tiv thaiv sib xyaw tsis muaj cC8═ thiab tsis muaj cC8═OOH, tus nqi pib oxidation qeeb heev (daim duab S7).Thaum cC8═ tau ntxiv rau cov tshuaj tiv thaiv sib tov, qhov pib oxidation tau pom zoo txhim kho.Yog li, pawg Aun muaj peev xwm tsim cC8═OOH los ntawm kev ntxiv cC8═ los pib oxidation ntawm 4-methylanisole raws li xav tau hauv NCCS.

Hauv kev xaus, peb tau pom lub tswv yim ntawm NCCS.Siv tib lub sijhawm oxidation ntawm cyclooctene thiab EB nrog rau cyclooctene thiab 4-methylanisole, NCCS tau pom tias yuav pab kom co-oxidation ntawm hydrocarbons yam tsis muaj kev sib raug zoo stoichiometric kev txwv ntawm cov txheej txheem co-oxidation.Qhov no muab yav dhau los tsis muaj kev ywj pheej hauv kev ua lag luam xws li cov txheej txheem kev lag luam tsis muaj kev cuam tshuam los ntawm kev xav tau kev lag luam zoo rau cov khoom lag luam tsim tawm hauv cov nyiaj stoichiometric.

Cov peev txheej thiab purity ntawm cov tshuaj siv tau raws li hauv qab no: HAuCl4•3H2O (≥99.9% trace hlau hauv paus, Sigma-Aldrich), fumed silica (CAB-O-SIL90, Cabot Corporation), ethylenediamine (≥99% ReagentPlus, Sigma-Aldrich) , ethanol (200 qib, Decon Labs), cobalt (II) nitrate hexahydrate (≥98%, Sigma-Aldrich), Nano H-ZSM-5 (P-26, ACS Khoom), decane (≥99% ReagentPlus, Sigma- Aldrich), dodecane (≥99% ReagentPlus, Sigma-Aldrich), cis-cyclooctene (95%, Alfa Aesar), EB (99.8% anhydrous, Sigma-Aldrich), EB-d10 (99 atomic % D, Sigma-Aldrich) 4-methylanisole (99%, Sigma-Aldrich), acetophenone (99% ReagentPlus, Sigma-Aldrich), 1-phenylethanol (98%, Sigma-Aldrich), hydrogen peroxide (30% aqueous solution, Fisher Chemical), potassium hydroxide (qib reagent, 90%, Sigma-Aldrich), sodium sulfate (Food Chemicals Codex / United States Pharmacopeia-qib, Fisher Chemical), tetrahydrofuran (> 99%, Sigma-Aldrich), tert-butyl hydroperoxide (~ 5.5 M hauv decane , Sigma-Aldrich), PPh3 (> 98.5%, Sigma-Aldrich), d-chloroform (99.8 atomic % D, Sigma-Aldrich), HCl (38% w/w, Fisher Chemical), HNO3 (68 txog 70% w /w, Fisher Chemical), EM Quant peroxide test strips, thiab syringe lim (polyvinylidene difluoride membrane, 0.25 mm / 0.2 μm, Acrodisc).

Au/SiO 2.Lub silica-txhawb kub nanoparticle catalyst tau npaj nrog Au (en) 2Cl3 precursor raws li txoj kev tsim los ntawm Zhu li al.(19) thiab hloov kho los ntawm Qian et al.(2).Txhawm rau kom paub meej ntxiv, Au (III) chloride trihydrate tov tau npaj los ntawm kev sib cais 0.5 g ntawm HAuCl4•3H2O hauv qhov sib xyaw uas muaj 10 ml ntawm ethanol thiab 2 ml dej.Tom qab tsim cov tshuaj homogeneous, 0.23 ml ntawm ethylenediamine (en = ethylenediamine) tau ntxiv rau cov tshuaj dropwise los ua Au(III) ethylenediamine chloride [Au(en)2Cl3] los ntawm ligand exchange.Raws li-formed Au(en)2Cl3 tau sau los ntawm kev pom thiab ntxuav nrog 300 ml ntawm ethanol.Txhawm rau tso Au mus rau kev txhawb nqa silica, 4.2 mM Au (en) 2Cl3 aqueous tov tau npaj los ntawm kev sib cais 46.3 mg ntawm Au (en) 2Cl3 rau hauv 26 ml ntawm distilled deionized (DDI) dej.Cov tshuaj raws li tsim tau khaws cia ntawm 40 ° C hauv cov roj da dej.Tom qab ntawd, 1 g ntawm fumed silica yog ntxiv rau cov tshuaj preheated thaum stirring.Thaum tag nrho cov kev txhawb nqa silica tau muab tso rau hauv qhov kev daws teeb meem, qhov sib tov raug tshem tawm ntawm cov roj da dej thiab txias rau chav tsev kub.Los ntawm kev kho cov pH ntawm cov sib tov mus rau 9 nrog dropwise ntxiv ntawm 0.75 M en aqueous tov, ib tug zoo dua adsorption ntawm cov cationic kub complexes rau qhov tsis zoo nqi nto yog tiav.Tom qab stirring rau 2 teev nyob rau hauv chav tsev kub, qhov sib tov yog lim thiab ntxuav nrog 500 ml ntawm DDI dej.Txhawm rau tshem tawm cov khoom seem tsis xav tau (Cl, en, lwm yam impurities), lub ncuav mog qab zib lim tau rov ua dua hauv 200 ml ntawm DDI dej ntawm 40 ° C.Thaum kawg, cov txheej txheem Au/SiO2 tau sau los ntawm kev pom thiab ntxuav nrog lwm 500 ml ntawm DDI dej thiab ziab hauv huab cua thaum hmo ntuj.Calcination ntawm silica-txhawb kub nanoparticles catalyst tau ua nyob rau hauv U-tube nyob rau hauv O2 / O3 txaus (~ 300 ml / min) nrog ib tug ramping tus nqi ntawm 0.12 ° C / min txog 150 ° C.Cov catalyst tau khaws cia hauv qhov tsaus ntuj ntawm 5 ° C.Kub loading, raws li ntsuas los ntawm inductively coupled plasma optical emission spectrometry, yog 1.2 qhov hnyav % (wt %), thiab qhov nruab nrab kub particle loj ntsuas los ntawm scanning kis electron microscopy (STEM) yog nyob ib ncig ntawm 2 nm.

Co/ZSM-5.Nano H-ZSM-5 tau calcined nyob rau hauv U-tube nyob rau hauv O2 / O3 txaus (~ 300 ml / min) nrog tus nqi ntawm 2 ° C / min mus txog 200 ° C thiab tuav ntawm 200 ° C rau 1 teev kom tshem tawm residual templates.Co/ZSM-5 tau npaj los ntawm kev ntub dej.Piv txwv li, 5 wt % loading Co/ZSM-5 tau npaj los ntawm kev ntxiv 0.72 M cobalt (II) nitrate tov [250 mg ntawm cobalt (II) nitrate hexahydrate hauv 1.2 ml ntawm DDI dej] rau 1 g ntawm nano H- ZSM-5 thaum ua tib zoo tig lub beaker.Lub slurry tau qhuav nyob rau hauv ib lub teeb, thiab ib tug uniform liab hmoov tau tsim.Tom qab ntawd cov hmoov nplej ua tiav tau muab tso rau hauv lub raj calcination ncaj thiab purged nyob rau hauv argon flow (100 ml / min) rau 1 teev kom txo cov av noo.Cov catalyst raws li npaj tau ces calcined nyob rau hauv oxygen txaus (60 ml / min) nrog ib tug ramping tus nqi ntawm 10 ° C / min rau 450 ° ( tuav ntawm 250 ° C, 350 ° C, thiab 450 ° C rau 1 teev txhua). .Cov tau txais Co/ZSM-5 muaj cobalt loading ntawm 5 wt%.Ob qhov chaw thau khoom, 3 thiab 7 wt %, kuj tau npaj.Tag nrho peb cov catalysts tau tus yam ntxwv los ntawm H2 qhov kub-txhim kho qhov txo qis, x-ray diffraction, x-ray photoelectron spectroscopy, thiab ultraviolet-pom spectroscopy.

Au-muaj filtrate.Lub Au-muaj filtrate (Au + cC8═OOH-x) yog nyob rau hauv situ generated los ntawm Au/SiO2-catalyzed cC8═ epoxidation cov tshuaj raws li tus txheej txheem tsim los ntawm Qian li al.(2) Ua ntej cov tshuaj tiv thaiv, cC8═ raug ntxuav kom tshem tawm cov chaw tsim khoom-ntxiv stabilizer.Feem ntau, 50 ml ntawm 3 M poov tshuaj hydroxide (KOH) tov tau ntxiv rau 50 ml ntawm cC8 ═ hauv ib khob.Tom qab sib tov txaus thiab muaj zog nplawm, cov organic txheej tau sau los ntawm kev sib cais.Cov txheej txheem no tau rov ua dua nrog lwm 50 ml ntawm 3 M KOH thiab ob qho ntxiv 50 ml ntawm DDI dej.Lub cC8═ tau qhuav nrog sodium sulfate ib hmos.Txhawm rau kom tshem tawm tag nrho cov stabilizer, cov qhuav cC8═ tau muab tso rau hauv cov roj da dej ntawm thaj tsam 180 ° C, thiab cov feem uas tawm ntawm 145 ° C tau sau.Purified cC8═ (10 ml) thiab decane (1 ml) tau muab sib xyaw rau hauv lub reactor uas muaj 80 mg ntawm Au/SiO2 catalyst aforementioned.Cov tshuaj tiv thaiv cC8═ epoxidation tau ua raws li cov pa oxygen txaus (30 ml / min) ntawm 100 ° C, thiab kev hloov pauv tau raug saib xyuas los ntawm GC.Thaum qhov kev hloov pauv xav tau mus txog, cov tshuaj tiv thaiv sib xyaw tau sau thiab cov khoom siv hluav taws xob tau raug tshem tawm los ntawm kev lim dej kub siv lub syringe lim.Qhov feem ntau solubilized Au concentration uas tau txiav txim los ntawm inductively coupled plasma huab hwm coj spectrometry yog hais txog 80 ng / ml, thiab lub Au pawg loj yog txiav txim los ntawm fluorescence spectroscopy thiab aberration-kho kis electron microscopy xws li ntawm Au atoms rau ~ 0.7 nm.cC8═OOH-x tau npaj zoo sib xws yam tsis siv Au/SiO2 catalyst.Ob lub Au + cC8═OOH-x thiab cC8═OOH-x cov kev daws teeb meem muaj cC8═ oxidation cov khoom, uas suav nrog cyclooctene oxide, cyclooctene 3-hydroperoxide, 2-cycloocten-1-ol, 2-cycloocten-1-one, thiab cov kab ntawm 1,2-cyclooctanediol.

Cov txheej txheem dav dav.EB oxidation cov tshuaj tiv thaiv tau ua nyob rau hauv qhov tsaus ntuj nyob rau hauv ib tug peb-caj dab cylindrical reactor nruab nrog ib tug zoo frit iav disperser raj (Chemglass Life Sciences) thiab ib tug condenser tuav ntawm -10 ° C.Hauv cov tshuaj tiv thaiv ib txwm, 7 ml ntawm EB, 1 ml ntawm decane, thiab 3 ml ntawm filtrate (Au + cC8═OOH-x los yog cC8═OOH-x) tau ntim rau hauv lub reactor ua ke nrog Teflon-coated magnetic stirrer.Yog tias siv, 32 mg ntawm 5% Co / ZSM-5, tshwj tsis yog tau teev tseg, tau ntxiv.Tom qab kev teeb tsa cov tshuaj tiv thaiv tau sib sau ua ke, cov tshuaj tiv thaiv sib xyaw tau ruaj khov nyob rau hauv N2 ntws rau 20 min hauv cov roj da dej preheated.Thaum qhov kub thiab txias ntawm lub condenser thiab roj da dej tau ruaj khov, qhov O2 tsis tu ncua tau muab nkag ntawm 30 ml / min.Cov tshuaj tiv thaiv sib xyaw (0.1 ml) tau coj mus rau lub sijhawm sib txawv rau kev tshuaj xyuas (lub koob txhaj tshuaj lim tau siv thaum cov khoom siv catalysts koom nrog), yaj hauv 0.7 ml ntawm d-chloroform, thiab tshuaj xyuas los ntawm 1H nuclear magnetic resonance (NMR).

Kev txheeb xyuas cov khoom thiab qhov ntau.Aliquots ntawm cov tshuaj tiv thaiv sib tov yog diluted nrog tetrahydrofuran thiab soj ntsuam los ntawm roj chromatography-mass spectrometry (GC-MS; Agilent GC-7890A, MS-5975).Rau EB cov tshuaj tiv thaiv, acetophenone thiab 1-phenylethanol tau txheeb xyuas tias yog cov khoom lag luam tseem ceeb.1H-NMR thiab 13C-NMR (400 MHz Agilent DD2-MR400 system) tau siv los ntxiv kom paub meej cov khoom cim.1-Phenylethyl hydroperoxide, uas tsis tau kuaj pom los ntawm GC-MS vim nws cov thermal instability, tau txheeb xyuas los ntawm NMR los ua lwm yam khoom tseem ceeb.Tag nrho peb cov khoom raug ntsuas los ntawm 1H-NMR siv decane raws li tus qauv sab hauv (daim duab S1).Qhov kev poob evaporative tau txiav txim siab cais thiab siv los kho cov khoom ntim.Tom qab kho cov evaporative poob, tsis muaj cov pa roj carbon imbalance tau pom rau EB cov tshuaj tiv thaiv.Rau cov tshuaj tiv thaiv cyclooctene, cyclooctene oxide, cyclooctane-1,2-diol, 2-cycloocten-1-ol, thiab 2-cycloocten-1-ib tau raug ntsuas los ntawm GC.Cyclooctene 3-hydroperoxide tsis ruaj khov thiab decomposed hauv GC kem thiab yog li tsis pom.Muaj li ntawm 10% carbon poob ntawm tag nrho cov hloov dua siab tshiab txawm tias tom qab them nyiaj rau qhov evaporative poob, uas tuaj yeem piav qhia los ntawm kev tsim cov khoom me me ntawm cov khoom tsis muaj oxidized heev.

Conversion thiab selectivity xam.GC los yog NMR cheeb tsam piv ntawm molecule ntawm kev txaus siab rau cov txheej txheem sab hauv decane tau siv los xam qhov hloov dua siab tshiab thiab xaiv.Txawm hais tias siv lub condenser txias, nws tseem yuav tsum tau them nyiaj rau evaporative poob vim qhov kub thiab txias thiab cov tshuaj tiv thaiv ntev.Evaporative kho curves tau txais rau ob qho tib si EB thiab cC8═ nyob rau hauv ntws nitrogen thiab normalized rau qhov piv ntawm EB/decane los yog cC8═/decane.Vim tias EB thiab cC8═ muaj cov ntsiab lus kub zoo sib xws, qhov kev kho qhov qub qub tau txais yog ob qho tib si 0.0044 (qhov piv txwv qis dua ib teev).

Quantification ntawm hydroperoxide.Qhov concentration ntawm hydroperoxide yog xam los ntawm ob txoj kev titration:

1) Triphenylphosphine (PPh3) titration.PPh3 (0.1 M hauv EB) tau siv los titrate tsis paub cov qauv hydroperoxide, thiab qhov kawg taw tes tau txheeb xyuas nrog EM Quant peroxide kuaj strip.31P-NMR tau siv los lees paub qhov kev tshem tawm tag nrho ntawm hom hydroperoxide.

2) Iodometric titration.Cov qauv (0.2 ml) tau sib xyaw ua ke nrog 1 ml ntawm CHCl3 / acetic acid (v / v = 1: 2) thiab 6 ml ntawm 1 M KI kua.Cov sib tov yog nplawm nyob rau hauv qhov tsaus ntuj rau 2 teev thiab ces titrated nrog 0.005 M Na2S2O3 nyob rau hauv lub xub ntiag ntawm ob peb tee ntawm starch tov.Qhov kawg taw tes tau mus txog thaum sib tov ua tsis muaj xim.

Ob txoj hauv kev tau zoo ib yam;Txawm li cas los xij, lawv cov txiaj ntsig txawv ntawm 5 mus rau 10%.Vim tias Au + cC8═OOH-x thiab cC8═OOH-x siv hauv qhov project no tau tsim los ntawm cC8═OOH-pib oxidation, hydroperoxide concentration txawv ntawm batch rau batch tab sis yeej ib txwm nyob rau hauv thaj tsam ntawm 0.2 txog 0.5 M rau freshly npaj. cC8═OOH-40 to cC8═OOH-100 samples.Cov hydroperoxide concentration maj mam poob nrog lub sijhawm cia.

EPR spin trap kev sim.DMPO (23 μl) tau ntxiv rau 1 ml ntawm cov qauv kom ncav cuag DMPO concentration ntawm 0.2 M, thiab 20 mg ntawm Co / ZSM-5 tau ntxiv rau cov qauv sib xyaw hauv lub raj kuaj.Qhov sib tov yog sonicated rau 1 min kom ncua cov catalyst, thiab qhov no tau ua raws li cua sov ntawm 60 ° C rau ~ 10 min.Ib qho aliquot ntawm cov khoom sib tov tau hloov mus rau hauv ib puag ncig borosilicate tubing capillary raj (1.50 sab hauv txoj kab uas hla × 1.80 sab nraud txoj kab uas hla, Wale Apparatus), uas tau raug kaw ntawm ib kawg - lub raj no ces muab tso rau hauv Wilmad quartz X-band EPR raj ( Sigma-Aldrich).Cov qauv no tau khov los ntawm immersion ntawm EPR raj hauv kua N2.Tam sim ntawd ua ntej ntsuas EPR spectra, tus qauv tau thawed.Nruam-yoj (CW) X-band EPR ntsuas tau ua nyob rau hauv chav tsev kub ntawm qhov hloov pauv Varian E-4 spectrometer siv tus ntiv tes Dewar.

Isotopic labeling kev sim.Deuterated EB (d10-EB) tau siv rau hauv kev sim ntawm kev sib xyaw ntawm 6 ml ntawm cC8═OOH-45, 5 ml ntawm d10-EB, 1 ml ntawm decane, thiab 60 mg ntawm Co-ZSM-5 (7%). , ntawm 120 ° C, nrog 6 ml ntawm cC8 OOH-45, 5 ml ntawm EB-d10, thiab 1 ml ntawm dodecane.Txhawm rau them nyiaj rau qhov txo qis ntawm cov tshuaj tiv thaiv vim yog cov nyhuv kinetic isotope, co-oxidation tau ua tiav ntawm qhov kub siab dua ntawm 120 ° C.Aliquots ntawm cov qauv tau coj ua ntej thiab tom qab 24 teev ntawm cov tshuaj tiv thaiv thiab tshuaj xyuas los ntawm 2H-NMR thiab GC-MS.

Lub 2H-NMR spectrum (daim duab. S5, spectrum 2) pom ob peb lub ncov tshiab tom qab cov tshuaj tiv thaiv, tsis tshwm sim ua ntej cov tshuaj tiv thaiv, ntawm δ1.50, δ1.58, δ4.94, δ7.42 txog δ7.72, thiab δ8.04 .Vim tias qhov txo qis J-coupling tas li thiab rhiab heev ntawm 2H-NMR, cov qauv sib cais tsis raug daws.Lub ncov ntawm δ8.04 thiab δ7.42 rau δ7.72 tau muab rau cov deuterons ntawm lub nplhaib aromatic ntawm acetophenone;lub ncov ntawm δ1.50 thiab δ4.94 tau muab rau methyl thiab benzylic deuteron ntawm 1-phenylethanol, raws li;thiab lub ncov ntawm δ1.58 raug xa mus rau deuteron hauv D2O tsim los ntawm hydroperoxide decomposition.Tsis muaj deuteron tau pom muaj cuam tshuam nrog cov khoom ntawm cyclooctene epoxidation, thiab qhov tsim ntawm cov dej deuterated qhia tau hais tias cov tseem ceeb radical saw carriers nyob rau hauv cov tshuaj tiv thaiv co-oxidation yog peroxy thiab alkoxy.

GC-MS spectra ntawm cov khoom yog qhia nyob rau hauv daim duab.S6.Acetophenone-d8 (m/e 128, tag nrho deuterated, fig. S6A, m/e 127 thiab 126) tau pom.Los ntawm cov qauv tawg, tag nrho HD pauv tau tshwm sim ntawm txoj haujlwm methyl.Tsis tas li ntawd, 1-phenylethanol-d9 (m / e 131) (daim duab S6B) tsuas yog cov khoom lag luam deuterated.Tsis muaj deuterium tau pom nyob rau hauv cyclooctene oxide (daim duab S6C), cov khoom siv ntau tshaj plaws los ntawm cyclooctene epoxidation.1-Phenylethanol-d9 tuaj yeem tsim los ntawm cov tshuaj tiv thaiv ntawm phenylethoxy radical nrog cyclooctene.

Cov ntaub ntawv ntxiv rau tsab xov xwm no muaj nyob ntawm http://advances.sciencemag.org/cgi/content/full/6/5/eaax6637/DC1

Fig. S5.2H-NMR ua ntej (spectrum 1, liab) thiab tom qab (spectrum 2, ntsuab) 24-teev co-oxidation cov tshuaj tiv thaiv.

Daim duab S7.Kev sib piv ntawm kev hloov pauv thawj zaug ntawm 4-methyl anisole pib siv Au + cC8═OOH-100, nrog cC8═OOH tshem tawm.

Qhov no yog ib tsab xov xwm qhib tau muab faib raws li cov ntsiab lus ntawm Creative Commons Attribution-NonCommercial daim ntawv tso cai, uas tso cai rau siv, faib, thiab luam tawm nyob rau hauv ib qho nruab nrab, tsuav yog qhov tshwm sim ntawm kev siv tsis yog rau kev lag luam kom zoo dua thiab muab cov haujlwm qub kom zoo. hais.

CEEB TOOM: Peb tsuas yog thov koj qhov chaw nyob email kom tus neeg uas koj tab tom qhia nplooj ntawv kom paub tias koj xav kom lawv pom nws, thiab nws tsis yog ntawv xa tuaj.Peb tsis ntes ib qho email chaw nyob.

Los ntawm Anyang Peng, Mayfair C. Kung, Robert RO Brydon, Matthew O. Ross, Linping Qian, Linda J. Broadbelt, Harold H. Kung

Hauv qhov tsis sib cuag catalytic system, intermediaries muab los ntawm Au-catalyzed cyclooctene epoxidation cuam tshuam ethylbenzene oxidation.

Los ntawm Anyang Peng, Mayfair C. Kung, Robert RO Brydon, Matthew O. Ross, Linping Qian, Linda J. Broadbelt, Harold H. Kung

Hauv qhov tsis sib cuag catalytic system, intermediaries muab los ntawm Au-catalyzed cyclooctene epoxidation cuam tshuam ethylbenzene oxidation.

© 2020 American Association rau Advancement of Science.Txhua txoj cai.AAAS yog ib tug khub ntawm HINARI, AGORA, OARE, CHORUS, CLOCKSS, CrossRef thiab COUNTER.Science Advances ISSN 2375-2548.