Ngokwesiko, i-catalyst isebenza ngokusebenzelana okuqondile nama-reactants.Kusistimu entsha ye-noncontact catalytic (NCCS), okumaphakathi okukhiqizwa ukusabela okukodwa kwe-catalytic kusebenza njengomlamuli ukuze kunikwe amandla ukusabela okuzimele ukuze kuqhubeke.Isibonelo i-oxidation ekhethiwe ye-ethylbenzene, engeke yenzeke lapho kukhona i-Au nanoclusters noma i-cyclooctene e-solubilized, kodwa iqhubeke kalula lapho zombili zikhona ngesikhathi esisodwa.I-Au-initiated selective epoxidation ye-cyclooctene ekhiqizwe i-cyclooctenyl peroxy kanye ne-oxy radicals esebenze njengabalamuli ukuze iqalise i-ethylbenzene oxidation.Lolu hlelo oluhlanganisiwe lwandise ngempumelelo umthelela we-Au.Indlela yokusabela yasekelwa i-reaction kinetics kanye nokuhlolwa kwe-spin trap.I-NCCS inika amandla ukusabela okuhambisanayo ukuthi kuqhubeke ngaphandle kwemingcele yobudlelwano be-stoichiometric, enikeza amadigri amasha enkululeko ezinqubweni ze-industrial hydrocarbon co-oxidation.

Ngokwesiko, i-catalyst isebenzisana ngokuqondile nama-reactants (isenzo A) ukuze yenze ukuhlelwa kabusha kwebhondi okunqunywe ukusabela.Isibonelo, ku-cobalt-catalyzed oxidation ye-alkylaromatics (1) noma i-Au-catalyzed epoxidation ye-cyclooctene (2), i-catalyst isiza ukukhishwa kwe-athomu ye-hydrogen ku-hydrocarbon ukuze kuqalise ukusabela.Ekuphenduleni kweketango lamahhala, i-catalyst ibamba iqhaza ekuqhekekeni kwe-catalytic homolytic yesibopho esibuthakathaka kubaqalisi okungenzeka ukuthi kwengezwe ngamabomu noma abakhona njengokungcola okuzayo kungxube yokusabela (1, 3, 4).Ezinye izinyathelo zokusabela kwe-catalytic tandem zingase zingadingi ukuthintana okuqondile kwe-substrate-catalyst lapho ukuguqulwa kwe-substrate kunikwe amandla umkhiqizo okhiqizwe ngendlela esheshayo ezinyathelweni ezedlule (5–8).Kodwa-ke, lokhu kusabela kuvinjelwa ubudlelwano be-stoichiometric phakathi kwezinyathelo.Isibonelo, ku-Mukaiyama (ep) oxidation ye-alkene, i-catalyst iguqula i-reductant yomhlatshelo ekuphenduleni A, njenge-isobutyraldehyde, nokwakheka kwe-stoichiometric okuhambisanayo kwe-epoxide (ukusabela B) (9, 10).Nakuba kungenzeka ngokomthetho, asazi isibonelo lapho umsebenzi we-catalyst kuwukukhiqiza u-S ophakathi nendawo ekuphenduleni A, lapho u-S esebenza njengomxhumanisi ukuze aqalise noma enze enye indlela yokusabela B esikhundleni sokubamba iqhaza njenge-reagent ye-stoichiometric. , kuyilapho i-catalyst ingasebenzi ekuphenduleni B (Fig. 1).Kuhlelo olunjalo, umthelela we-catalyst unwetshwa ngale kokusabela okukhangayo A ukuze futhi kube nomthelela wokusabela B kodwa ngaphandle kokuxhumana okuqondile nama-reactants ako.Sibiza uhlelo olunjalo ngokuthi i-nocontact catalytic system (NCCS).Ku-NCCS, ububanzi bokusabela kokusabela okungu-A no-B akuboshiwe yinoma yibuphi ubuhlobo be-stoichiometric phakathi kwakho.Lokhu kuphambene nokusabela kwe-tandem.Embonini, ubuhlobo obunjalo be-stoichiometric buvame ukubeka izithiyo zezomnotho enqubweni yokukhiqiza amakhemikhali.Isibonelo esaziwa kakhulu ukukhiqizwa kwe-stoichiometric kwe-phenol ne-acetone nge-oxidation ye-benzene nge-cumene hydroperoxide emaphakathi kunqubo ye-cumene (11).

I-catalyst (Ikati) igqugquzela ukusabela A (AR ➔ S ➔AP) lapho u-S omaphakathi esebenza kahle ekuqaliseni noma ekuphenduleni kokusabela B (BR ➔ BP), nakuba ukusabela B kungenziwanga yi-catalyst.

Sithole i-NCCS enjalo lapho sihlola izici ze-catalytic zamaqoqo e-Aun e-solubilized (lapho i-n ngokuvamile yayingama-athomu ayisithupha kuya kwayisishiyagalombili) ye-oxidation ingxenye ye-ethylbenzene (EB).Sibonise ukuthi lezi Aun ezincibilikisiwe zenze ukuqaliswa kwe-epoxidation ekhethiwe ye-cyclooctene (cC8═) nge-O2 ene-~80% yokukhetha (2).Lawa maqoqo akhelwe endaweni ngesikhathi se-Au/SiO2-catalyzed cC8═ epoxidation, futhi agcina ikhono lawo lokukhiqiza i-radical Initiator cyclooctene hydroperoxy radical (cC8═OO·) kukho konke ukusabela.Amaqoqo ka-Aun ahlanganisiwe angaqoqwa engxubeni yokusabela ngemva kokususwa kwe-Au/SiO2, futhi usayizi wawo omaphakathi wanqunywa kusetshenziswa i-electron microscopy elungiswe ngendlela engafanele kanye ne-fluorescence spectroscopy (2).Ngokungeziwe kumaqoqo ka-Aun, lezi zingxube nazo zaziqukethe i-cyclooctene hydroperoxide (cC8═OOH) nemikhiqizo ye-oxidation i-cyclooctene epoxide, i-cyclooctenol, ne-cyclooctenone.I-cC8═OOH iwuhlobo oluzinzile lwe-hydrogenated lwe-cC8═OO· futhi lukhona ekugxilisweni kuka-0.2 kuya ku-0.5 M ngemva kokuguqulwa kuka-40 kuya ku-100% cC8═.Le ngxube ibizwa nge-Au + cC8═OOH-x, lapho u-x eyiphesenti le-cC8═ lokuguqulwa.Nakuba ngenani eliphansi kakhulu kanye nesikhathi eside (>amahora angu-5) sokungeniswa, i-cC8═ epoxidation ingase yenzeke nge-auto-oxidation ngaphandle kwamaqoqo ka-Aun.Izingxube ezitholwe nge-auto-oxidation ngaphandle kwe-Au zibizwa ngokuthi cC8═OOH-x.Ku-NCCS, i-Aun e-solubilized izoba yi-catalyst, i-epoxidation ye-cC8═ izoba ukusabela A, futhi i-cC8═OO· kuzoba ngu-S.

I-auto-oxidation ye-EB ayenzeki kalula.Ku-145°C, ukusabela okungu-9% kuphela okwenzeka ku-EB ehlanzekile ngaphansi kuka-2.76 MPa O2 (12).Ngaphansi kwezimo zethu ezithambile kakhulu ze-100°C kanye ne-O2 ebabazayo ku-0.1 MPa, akuzange kube khona ukusabela okutholakalayo kwe-EB ehlanzekile okungenani amahora angu-20.Ukwengezwa komqalisi we-radical wamahhala bekudingeka ukuze lokhu kusabela kuqhubeke.Ukuqaliswa nge-2,2′-azobisisobutyronitrile (AIBN), i-radical radical initiator esebenza kakhulu, kubangele uku-oxidation okuzenzakalelayo kwe-EB ngesilinganiso sobude beketanga elingu ~3 (fig. S2A).Iketango elifushane (~1) libonwe kusetshenziswa i-tert-butyl hydroperoxide (fig. S2B), futhi kube nokusabela okuncane kakhulu okubonakalayo kusetshenziswa i-cumene hydroperoxide esebenzayo kancane.Ngakho, i-auto-oxidation ye-EB yayinomthelela omncane emiphumeleni yokusabela ebikwe ngezansi.

I-oxidation ye-aerobic engaguquki ye-EB kuya ku-EB hydroperoxide, i-acetophenone, ne-phenylethanol ifinyelelwe ngokungeza i-Au + cC8═OOH-50 equkethe ingxube ye-Aun, cC8═OOH, ne-cC8═ engaphenduliwe (Fig. 2, curve 1).Njengoba kuboniswa ukuhlola okulandelayo, lezi zingxenye ezintathu zadlala indima eyinhloko ku-EB oxidation, futhi zihambisana ne-catalyst, S, ne-AR kusistimu ye-NCCS evezwe ku-Fig.

(i) 7 ml we-EB + 3 ml we-Au + cC8═OOH-50;(ii) 7 ml we-EB + 3 ml we-Au + cC8═OOH-50 + 1.2 mmol Ph3;(iii) 7 ml we-EB + 3 ml we-Au + cC8═OOH-99 + 0.6 mmol Ph3;(iv) 7 ml we-EB + 3 ml we-cC8═OOH-50;(v) 7 ml we-EB + 3 ml we-cC8═OOH-50 + 1.5 mmol Ph3.Inani le-PPh3 elengeziwe lahlelwa ukuthi lilingane nenani le-titrated hydroperoxide (izinga lokushisa lokusabela, elingu-100°C).

Ngaphansi kwezimo zethu, akukho oxidation we-aerobic EB obonakalayo owenzekile kungxube ye-cC8═ ne-EB (okungukuthi, ngaphandle kweKati noma i-S).I-Triphenylphosphine (PPh3) iphumelela kakhulu ekususeni i-hydroperoxides.Isixazululo se-Au + cC8═OOH-99, esincishwe i-cC8═OOH ngokungezwa kwe-PPh3, equkethe u-Aun kanye ne-cC8═ encane kakhulu engasabelanga, yehlulekile ukuqalisa ukusabela kwe-EB ngisho nangemva kwamahora angu-2 (Fig. 2, curve 3), okubonisa ukuthi u-Aun iyodwa yayingasebenzi.Lo mphumela uphinde wabonisa ukuthi eminye imikhiqizo ye-cC8═ oxidation, efana ne-cyclooctene epoxide, i-cyclooctene alcohol, noma i-ketone, ayikwazanga ukuqalisa i-EB oxidation.Ngokuphambene nokuhlolwa okungenhla, ukususwa kwe-cC8═OOH nge-PPh3 ku-Au + cC8═OOH-50, ukushiya u-Aun kanye ne-cC8═ engaphenduliwe, akuzange kuvimbe ukuguqulwa kwe-EB (qhathanisa namajika 1 no-2, Fig. 2).

Lawa masethi amathathu edatha aphakamise ukusebenzisana phakathi kuka-Aun ne-cC8═ engaphenduliwe ekuqalisweni kwe-EB oxidation.Sicabange ukuthi u-Aun wenze i-oxidation ye-cC8═ ukuze yakhe i-cC8═OOH, okwaba ngumqalisi wokusabela kwe-EB.Lokhu kungase kuhlolwe ngokuqhathanisa ukusebenza kahle kokuqaliswa kwe-EB oxidation nengxube ye-cC8═OOH ne-cC8═ kodwa ngaphandle kuka-Aun ngaphambi nangemuva kokususwa kwe-cC8═OOH ne-PPh3.Ukuze silingise kangcono izimo zamasethi angaphambili okuhlolwa, sisebenzise isisombululo cC8═OOH-50 sengxube ye-cC8═OOH ne-cC8═ ukuze noma yimuphi umthelela ongaba khona wemikhiqizo ye-cC8═ epoxidation iphinde ikhiqizwe.Imiphumela ibonise ukuthi phambi kwe-cC8═OOH-50, i-EB iphendule ngokuphumelelayo (Umdwebo 2, ijika le-4).Nokho, uma i-cC8═OOH isuswe yi-PPh3, akubangakho ukusabela ngehora lokuqala nomsebenzi ocindezelwe ngokulandelayo (ijika 5).Le datha iphinde yasekela imodeli yokuthi indima ebambekayo ka-Aun bekuwukukhiqiza ngokuqhubekayo i-cC8═OOH nge-cC8═ oxidation, futhi i-cC8═OOH iqalise ukusabela kwe-EB.Iqhaza elikhulu lika-Aun laqinisekiswa ngokuqhubekayo ngokuqaphela ukuthi amazinga okuqala e-EB oxidation lapho ingekho i-cC8═OOH anda ngokukhula kwe-Aun concentration (fig. S3).

Indima eyingqayizivele ka-Aun kule NCCS yaboniswa ngokuhlola i-Co njengenye i-catalyst, eyakhethwa ngenxa yokuthi i-cobalt acetate ne-cobalt cycloalkanecarboxylate (13) zingama-industrial catalysts ekuguquleni i-EB ibe i-acetophenone nge-molecule O2, esebenza ngaphansi kwezimo ezinzima futhi idinga ukuba khona kwe-asidi ne-bromide ions.Ama-Co complexes nawo asetshenziselwa i-aerobic EB oxidation ekhethiwe lapho kukhona i-organocatalyst N-hydroxyphthalimide (NHPI) noma i-reductant yomhlatshelo (14, 15).Kodwa-ke, ngaphansi kwezimo zethu zokusabela, ukuba khona kwe-Co/ZSM-5 akuzange kubangele noma yikuphi ukutholakala kwe-oxidation ye-EB, cC8═, noma ingxube yabo okungenani amahora angu-6.Okusho ukuthi, i-Co iyodwa ayikwazanga ukuqalisa noma yikuphi ukusabela kwe-oxidation.Kodwa-ke, phambi kwabo bobabili u-Aun kanye ne-cC8═, kwenze kwaba lula ukusabela kwe-oxidation.Kuye ngesimo, i-cC8═ noma i-EB iphendule ngokushesha izikhathi ezintathu kuya kweziyisihlanu lapho i-Co/ZSM-5 ikhona, futhi ukuthuthukiswa kukhuphuke ngenani le-Co/ZSM-5 (ithebula S2, ukuhlolwa 6 kuya ku-8).Ukusatshalaliswa komkhiqizo we-EB oxidation nakho kwashintsha ngandlela thize phambi kwe-Co/ZSM-5.Ukwandisa inani le-Co/ZSM-5 kwandisa ukukhiqizwa kwe-acetophenone futhi, ngezinga elincane, isivuno se-phenylethanol ngezindleko ze-EB hydroperoxide (ithebula S3, ukuhlolwa kwe-6 kuya ku-8), ngokuhambisana neqiniso lokuthi i-Co catalyzed ukubola kwe-EB hydroperoxide i-acetophenone ne-phenylethanol kanye ne-oxidation yakamuva ku-acetophenone.Ngenxa yokufaneleka, sifake i-Co/ZSM-5 kungxube yethu yokusabela ukuze sifinyeze isikhathi sokusabela.

Isici esihlukanisayo phakathi kwe-NCCS nezinhlelo zokusabela kwe-tandem ukuthi ekuqaleni, abukho ubuhlobo be-stoichiometric phakathi kokusabela A no-B (Fig. 1).Ukuze siqinisekise ukuthi ukusabela kwethu kwenzeke nge-NCCS, sihlole umphumela wokushintsha isilinganiso se-cC8═ kuya ku-EB ngokuqapha izilinganiso zabo zokusabela ezingazodwana.Umfanekiso wesi-3 ubonisa imiphumela yokushintsha ukugxila kwe-cC8═ kokuqala kuyilapho kugcinwa ukugxiliswa kwe-EB kokuqala nezinye izimo zokusabela zingashintshi.Idatha ibonisa ukuthi abukho ubudlelwano obugxilile be-stoichiometric phakathi kwamanani ama-reactants amabili asabelayo, okuqinisekisa ukuthi iphethini yokusabela ihluke ohlelweni lwendabuko lokusabela kwe-tandem.Isethi efanayo yokuhlola lapho ukugxila kwe-EB kokuqala kwahlukahluka ngenkathi kulungiswa okunye ukugxila kufinyelele esiphethweni esifanayo.Kusukela kule datha, izilinganiso zokuqala zokusabela zibaliwe (Ithebula 1 nethebula S2, ukuhlolwa 4 no-5) futhi ziboniswa zihluka ngokuhlukile ku-cC8═ kanye ne-EB.Kwakungekho ukuhwebelana kumazinga okusabela phakathi kwalokhu kusabela okubili kangangokuthi lapho ukusabela okukodwa kuqhubeka ngokushesha, okunye kwakumele kuhambe kancane ngokulinganayo.Zombili izilinganiso zokusabela zingakhula ngesikhathi esisodwa, njengoba kuboniswa ukuhlolwa 4 no-5 kuthebula elithi S2.Kuzolindeleka ukuhwebelana uma i-EB ne-cC8═ ziqhudelana endaweni efanayo yokusabela noma okumaphakathi.Lesi siphetho siphinde sihambisane neqiniso lokuthi ukusabela kanyekanye kwe-EB kanye ne-cC8═ akuzange kube nomthelela noma omncane kakhulu ekusabalaliseni umkhiqizo ngamunye wabo, njengoba kuboniswe kuThebula 1 nakuthebula S3.

Ukugxila kwe-cC8═ kwasekuqaleni kube ngu-0.34 M (A), 1.05 M (B), kanye no-1.75 M (C).I-Decane yasetshenziswa ukwenza umehluko wevolumu ye-cC8═ esetshenzisiwe.Ezinye izimo: 32 mg Co/ZSM5, 100°C.

Le datha ihambisana nohlelo lokumaka oluboniswe ku-Fig. 4, lapho izinyathelo ezibalulekile ze-NCCS zigcizelelwa khona futhi abadlali abayinhloko bagqanyiswe (isikimu esiphelele siboniswa kufig. S8).Kulo mshini, amaqoqo e-Aun aqala umjikelezo we-cC8═ epoxidation ngokukhiqiza ama-cyclooctenyl radicals (I) kanye ne-cyclooctene peroxy radicals (II).Lawa ma-radicals amabili abe esebamba iqhaza kumjikelezo we-cC8═ we-epoxidation, njengoba kwasungulwa ngaphambilini (2, 16).Uma i-EB ikhona, i-II iba i-molecule ephakathi futhi ishuthe phakathi komjikelezo we-cC8═ epoxidation kanye nomjikelezo we-EB oxidation.Emjikelezweni we-EB, i-II ihlangana ne-EB ukuze yakhe i-phenylethyl radical, eyenza ngokushesha i-phenylethyl peroxy radical (III) ngokusabela nge-O2, njengoba ukusabela okunamandla okugxiliswe ku-carbon ne-O2 kwaziwa njengokulula kakhulu (1).Ukukhishwa kwe-hydrogen okulandelayo nge-III kwenza i-phenylethyl hydroperoxide futhi ekugcineni i-acetophenone ne-phenylethanol.I-III futhi ingasabela ngokushesha nge-cC8═, okuba indlela yokugcwalisa i-II esetshenziswa umjikelezo we-EB oxidation.Ngakho, ukusabela kwe-EB oxidation akuhambisani nokucindezelwa kwe-stoichiometric kwe-cC8═ epoxidation reaction, futhi akukho "trade-off" kumazinga wokusabela we-EB kanye ne-cC8═ njengoba bekungalindeleka uma bebeqhudelane nge-reagent efanayo. noma isayithi elisebenzayo le-catalytic.Ngenxa yokuthi u-II ubamba iqhaza esinyathelweni sokuqala kuyo yomibili imijikelezo ye-EB kanye ne-cC8═ ye-oxidation kodwa hhayi ngokuqondile ezinyathelweni zokwenziwa komkhiqizo, ukuhlanganisa kwayo okubili okusabela akuthinti ukusatshalaliswa komkhiqizo.

I-Cyclooctene peroxy radical (II) ingumxhumanisi oyinhloko oqalisa i-EB oxidation.II ingenziwa kabusha ngokusabela kwe-EB peroxy radical (III) nge-cC8═.Phezulu kwesokunxele, amaqoqo ka-Aun aqala umjikelezo we-cC8═ we-epoxidation (umjikelezo kwesokunxele).Umjikelezo ongakwesokudla ubonisa izinyathelo ze-EB oxidation.Kuboniswa kuphela izinyathelo eziyinhloko ezibalulekile ze-NCCS.

Ukuqinisekisa ukwakheka kwama-radical intermediate esikhashana njengoba kuhlongozwa ku-Fig. 4, sengeze i-spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) kungxube yokusabela ukuze kwakheke ama-nitroxide radical spin adducts ahlala isikhathi eside. ama-radicals wamahhala akhona ukuze atholwe nge-X-band electron paramagnetic resonance (EPR) spectroscopy.Njengokulawula, awekho ama-radicals abanjwe yi-DMPO esixazululweni se-acetone ne-decane ngaphandle kwe-C8═ noma i-EB (fig. S4-3).Ngenkathi i-DMPO yengezwa engxubeni yokusabela equkethe i-cC8═OOH ne-cC8═ (fig. S4-1), umphumela we-EPR spectrum ulingiswe kahle njengesamba sohlobo olukhulu oluhlukile lwe-paramagnetic (A esithombeni, ~86% yenani eliphelele ukuqina kokulingisa) kanye nezinhlobo ezimbili ezincane (B no-C, ~5 kanye no-~9% wengqikithi yokuqina kokulingisa, ngokulandelanayo), okunikeza ubufakazi obuqondile bokwakheka okukhulu phakathi nokusabela.Ngokwesisekelo sokuqhathanisa amanani okuhlanganisa i-hyperfine nalawo ezithako ze-DMPO ezaziwayo (ithebula S1), uhlobo C lwabelwa isithasiselo se-DMPO/ROO•, ngokusobala i-cyclooctene 3-peroxy radical (II) eboniswa njengomxhumanisi phakathi kwalokhu okubili. ukusabela (Fig. 4).Izinhlobo A no-B zabelwe izengezo ezimbili ze-DMPO/RO• ezihluke kancane, lapho u-R ebhekisela ku-hydrocarbon moiety.Kungaba olunye lwezinhlobo ze-RO• ezichazwe ku-Fig. 4 noma ama-alkoxy radicals akhiqizwa kusuka ku-DMPO/ROO• i-adduct decay [DMPO/ROO• adducts aziwa ngokungazinzi futhi abola ku-alkoxy radical adduct ehambisanayo (17, 18)] noma inhlanganisela yakho kokubili.Lapho i-EB iphinde ifakwe engxubeni yokusabela, umphumela we-spectrum we-EPR ulingiswe kahle nezinhlobo eziningi ze-A′, ezazifana kakhulu nezinhlobo ezingu-A (DMPO/RO•), kanye nezinhlobo ezimbili ezincane ezithi B no-C ezineminikelo emincane efanayo. (umkhiwane S4-2 kanye nethebula S1).Ngenxa yokuthi ukufakwa kwe-EB bekulindeleke ukuthi kuqhube ukwakheka kwe-phenylethyl peroxy radicals (III), uhlobo lwe-A′ cishe lwaluyingxube ye-RO• ekhiqizwe ekuphenduleni kanye nanoma iyiphi i-phenylethyl peroxy adduct, kamuva yabola ku-phenylethyl oxy DMPO adduct.

Ukusebenzisa i-EB-d10 njenge-reactant kanye nokuqapha ilebula ye-deuterium emikhiqizweni ye-cC8═ kungathola ukuthi kukhona yini ukusabela kwe-EB nge-cC8═ esekelwe ku-carbon radicals.Imiphumela yokuhlolwa okunjalo ibonise ukuthi kwakungekho ukufakwa kwe-deuterium ku-cyclooctene epoxide (amakhiwane S5 kanye ne-S6).I-Phenylethanol igcine yonke i-deuterium ku-reactant ye-EB, kanti amanye ama-deuteron eqembu le-methyl ye-acetophenone ayeshintshile, okungenzeka ku-mass spectrometer.Ngakho-ke, abukho ubufakazi bokusabela phakathi kwe-EB-d10 ne-cyclooctenyl radical, ebingathula i-deuteron emikhiqizweni ye-cC8═.

Ukusebenza kwesu le-NCCS kwanwetshwa ukuze kuhlolwe i-Au + cC8═OOH-100–assisted aerobic oxidation ye-4-methylanisole.Ngenxa yamabhondi ayisisekelo e-C─H aqinile kule molecule, ukusabela kwe-oxy-functionalization kwenziwa ezingeni lokushisa eliphezulu.Amazinga okuqala okuguqulwa kwe-4-methylanisole kuya ku-4-anisaldehyde aqhathaniswa nokusabela okuqalwe ngo-Aun kanye nokungeza noma ngaphandle kwe-cC8═ (cC8═OOH ikhishwe nge-PPh3).Ngokufanayo ne-EB oxidation, lapho ingxube yokusabela ingenayo i-cC8═ futhi ingenayo i-cC8═OOH, izinga lokuqala le-oxidation lalihamba kancane kakhulu (fig. S7).Lapho i-cC8═ ingezwa engxubeni yokusabela, izinga le-oxidation lokuqala lathuthukiswa ngokuphawulekayo.Ngakho, amaqoqo e-Aun akwazile ukukhiqiza i-cC8═OOH kusukela ku-cC8═ eyengeziwe ukuze kuqalwe i-oxidation ye-4-methylanisole njengoba kulindelekile ku-NCCS.

Sengiphetha, sibonise umqondo we-NCCS.Isebenzisa i-oxidation kanyekanye ye-cyclooctene ne-EB kanye ne-cyclooctene ne-4-methylanisole, i-NCCS yaboniswa ukunika amandla i-co-oxidation yama-hydrocarbons ngaphandle kwezithiyo zobudlelwane be-stoichiometric bezinqubo zendabuko ze-co-oxidation.Lokhu kunikeza izinga lenkululeko elalingatholakali ngaphambilini ekusebenzeni kwezimboni kangangokuthi inqubo yezomnotho ayisaboshiwe isidingo sezimakethe ezivumayo zemikhiqizo ekhiqizwe ngamanani e-stoichiometric.

Imithombo nokuhlanzeka kwamakhemikhali asetshenzisiwe kwakungokulandelayo: HAuCl4•3H2O (≥99.9% isisekelo se-trace metals, Sigma-Aldrich), i-silica evuthayo (CAB-O-SIL90, Cabot Corporation), i-ethylenediamine (≥99% ReagentPlus, Sigma-Aldrich) , i-ethanol (200 grade, Decon Labs), cobalt(II) nitrate hexahydrate (≥98%, Sigma-Aldrich), Nano H-ZSM-5 (P-26, ACS Material), decane (≥99% ReagentPlus, Sigma- Aldrich), i-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), i-hydrogen peroxide (30% isixazululo samanzi, i-Fisher Chemical), i-potassium hydroxide (i-reagent grade, 90%, Sigma-Aldrich), sodium sulfate (Food Chemicals Codex/United States Pharmacopeia–grade, Fisher Chemical), tetrahydrofuran (>99%, Sigma-Aldrich), tert-butyl hydroperoxide (~5.5 M in decane , Sigma-Aldrich), PPh3 (>98.5%, Sigma-Aldrich), d-chloroform (99.8 atomic % D, Sigma-Aldrich), HCl (38% w/w, Fisher Chemical), HNO3 (68 kuya ku-70% w /w, I-Fisher Chemical), imichilo yokuhlola ye-peroxide ye-EM Quant, nesihlungi sesirinji (i-polyvinylidene difluoride membrane, 0.25 mm/0.2 μm, Acrodisc).

Au/SiO2.I-silica esekelwe igolide nanoparticle catalyst yalungiswa nge-Au(en)2Cl3 isandulela ngokuya ngendlela eyakhiwe ngu-Zhu et al.(19) futhi ilungiswe ngu-Qian et al.(2).Ukucacisa kabanzi, isixazululo se-Au(III) chloride trihydrate salungiswa ngokuncibilikisa u-0.5 g we-HAuCl4•3H2O engxubeni equkethe u-10 ml we-ethanol no-2 ml wamanzi.Ngemva kokwenza isisombululo se-homogeneous, i-0.23 ml ye-ethylenediamine (en = i-ethylenediamine) yengezwe kusixazululo se-dropwise ukuze kwakhiwe i-Au(III) ethylenediamine chloride [Au(en)2Cl3] ngokushintshaniswa kwe-ligand.I-Au(en)2Cl3 eyenziwe njengalokhu iqoqwe ngokuhlunga futhi yagezwa ngo-300 ml we-ethanol.Ukuze ufake i-Au kusekelo lwe-silica, isixazululo samanzi esingu-4.2 mM Au(en)2Cl3 salungiswa ngokuncibilikisa u-46.3 mg we-Au(en)2Cl3 ku-26 ml wamanzi acwengiwe e-distilled (DDI).Isixazululo esakhiwe njengesakhiwe sagcinwa ku-40 ° C endaweni yokugeza yamafutha.Khona-ke, i-1 g ye-silica ene-fumed yengezwe kwisisombululo esishisayo ngenkathi inyakaza.Lapho zonke izisekelo ze-silica sezicwiliswe ekhambi, ingxube yasuswa kubhavu wamafutha futhi ipholiswe ekamelweni lokushisa.Ngokulungisa i-pH yengxube ibe ngu-9 ngokungezwa kwe-dropwise kwesisombululo se-aqueous esingu-0.75 M en, ukukhangisa okungcono kwezakhiwo zegolide ze-cationic endaweni eshajelwe kabi kufinyelelwe.Ngemva kokugqugquzela amahora angu-2 ekamelweni lokushisa, ingxube ihlungiwe futhi igezwe nge-500 ml yamanzi e-DDI.Ukuze kukhishwe izinsalela ezingafuneki (Cl, en, okunye ukungcola), ikhekhe lokuhlunga laphinde lahlakazwa ku-200 ml wamanzi e-DDI ku-40°C.Okokugcina, i-Au/SiO2 eyakhiwe yaqoqwa ngokuhlunga futhi yagezwa ngamanye ama-500 ml amanzi e-DDI futhi yomiswa emoyeni ubusuku bonke.Ukubalwa kwe-nanoparticles yegolide esekelwa i-silica kwenziwa kushubhu ye-U ngaphansi kokugeleza kwe-O2/O3 (~300 ml/min) ngenani lokugxuma elingu-0.12°C/min kuze kube ngu-150°C.I-catalyst igcinwe ebumnyameni ku-5 ° C.Ukulayishwa kwegolide, njengoba kulinganiswa nge-plasma optical emission spectrometry ehlanganisiwe ngokungenisa, bekuyisisindo esingu-1.2 % (wt %), kanti isilinganiso sikasayizi wezinhlayiyana zegolide esikalwa ngokuskena i-electron microscopy (STEM) sasicishe sibe ngu-2 nm.

Co/ZSM-5.I-Nano H-ZSM-5 yenziwa i-calcined ku-U-tube ngaphansi kwe-O2/O3 flow (~300 ml/min) enezinga lokukhuphuka elingu-2°C/min kuze kube ngu-200°C futhi libanjwe ku-200°C ihora elingu-1 ukuze lisuswe. izifanekiso ezisele.I-Co/ZSM-5 ilungiselelwe ubumanzi bokuqala.Isibonelo, i-5 wt % yokulayisha i-Co/ZSM-5 yalungiswa ngokwengeza isixazululo se-nitrate esingu-0.72 M cobalt (II) [250 mg ye-cobalt(II) nitrate hexahydrate ku-1.2 ml wamanzi e-DDI] kuya ku-1 g we-nano H- I-ZSM-5 ngenkathi uphendukisa ngokucophelela i-beaker.I-slurry yomiswa ngaphansi kwesibani, futhi kwakhiwa impushana ebomvana.I-powder eyenziwe njenge-as-formed yabe ilayishwa ku-tube yokubala eqondile futhi ihlanzwa ngaphansi kokugeleza kwe-argon (100 ml/min) ihora elingu-1 ukuze kuncishiswe umswakama.I-catalyst elungiselelwe njenge-catalyst yabe ibalwa ngaphansi kokugeleza komoyampilo (60 ml/min) ngezinga lokugxuma lika-10°C/min kuya ku-450° (elibanjwe ku-250°C, 350°C, kanye no-450°C ihora elingu-1 lilinye) .I-Co/ZSM-5 etholiwe inokulayisha kwe-cobalt engu-5 wt %.Okunye okulayishiwe okubili, okungu-3 no-7 wt %, kulungisiwe.Womathathu ama-catalysts abonakala ngokuncishiswa okuhleliwe kwezinga lokushisa kwe-H2, i-x-ray diffraction, i-x-ray photoelectron spectroscopy, kanye ne-ultraviolet-visible spectroscopy.

Isihlungi esiqukethe noma.I-Au-containing filtrate (Au + cC8═OOH-x) ibisendaweni ekhiqizwe kusuka ku-Au/SiO2-catalyzed cC8═ ukuphendula kwe-epoxidation ngokuya ngenqubo eyenziwe ngu-Qian et al.(2) Ngaphambi kokusabela, i-cC8═ yahlanzwa ukuze kukhishwe isizinzisi esengezwe ngumkhiqizi.Ngokuvamile, u-50 ml wesisombululo esingu-3 M potassium hydroxide (KOH) wengezwe ku-50 ml we-cC8═ eflaskini.Ngemuva kokuxuba okwanele nokugqugquzela ngamandla, ungqimba lwe-organic luqoqwe ngokuhlukaniswa.Le nqubo iphindwe ngomunye u-50 ml we-3 M KOH kanye namanye amabili ama-50 ml amanzi e-DDI.I-cC8═ yabe yomiswa nge-sodium sulfate ubusuku bonke.Ukuze ususe ngokuphelele i-stabilizer, i-cC8═ eyomile ihlanjululwe emanzini okugeza amafutha cishe ku-180 ° C, futhi ingxenyenamba eyaphuma ku-145 ° C iqoqwe.I-cC8═ (10 ml) ehlanzekile ne-decane (1 ml) ixutshwe kureactor equkethe u-80 mg we-Au/SiO2 catalyst eshiwo ngenhla.I-cC8═ epoxidation reaction yenziwa ngaphansi kokugeleza komoyampilo (30 ml/min) ku-100°C, futhi ukuguqulwa kwaqashwa yi-GC.Lapho ukuguqulwa okufunayo sekufinyelelwe, ingxube yokusabela yaqoqwa futhi i-catalyst eqinile yasuswa ngokuhlunga okushisayo kusetshenziswa isihlungi sesirinji.I-Solubilized Au concentration evamile eyanqunywa i-plasma mass spectrometry ehlanganiswe ngokungenisa yayicishe ibe ngu-80 ng/ml, futhi usayizi weqoqo le-Au wanqunywa i-fluorescence spectroscopy kanye ne-aberration-corrected transmission microscopy kusukela kuma-athomu e-Au kuye ku-~0.7 nm.I-cC8═OOH-x ilungiswe ngendlela efanayo ngaphandle kokusebenzisa i-Au/SiO2 catalyst.Kokubili izixazululo ze-Au + cC8═OOH-x ne-cC8═OOH-x iqukethe imikhiqizo ye-cC8═ oxidation, ehlanganisa i-cyclooctene oxide, i-cyclooctene 3-hydroperoxide, i-2-cycloocten-1-ol, i-2-cycloocten-1-one, kanye nenani lokulandelela I-1,2-cyclooctanediol.

Inqubo evamile.Ukusabela kwe-oxidation ye-EB kwenziwe ebumnyameni kureactor eyicylindrical enezintamo ezintathu efakwe ishubhu elihle le-frit glass disperser (Chemglass Life Sciences) kanye necondenser egcinwe ku-−10°C.Ngokusabela okuvamile, u-7 ml we-EB, 1 ml we-decane, no-3 ml we-filtrate (Au + cC8═OOH-x noma cC8═OOH-x) alayishwe kureactor kanye ne-Teflon-coated magnetic stirrer.Uma kusetshenziswa, u-32 mg we-5% Co/ZSM-5, ngaphandle uma kucaciswe ngenye indlela, yengezwe.Ngemuva kokuthi ukusethwa kokusabela kuqoqwe, ingxube yokusabela yazinziswa ngaphansi kokugeleza kwe-N2 imizuzu engu-20 kubhavu kawoyela elishiswe ngaphambilini.Lapho izinga lokushisa le-condenser namafutha okugeza lizinzile, ukugeleza okuqhubekayo kwe-O2 kunikezwa ku-30 ​​ml / min.Ingxube yokusabela (0.1 ml) yathathwa ngezikhathi ezihlukene ukuze ihlaziywe (isisefo sesirinji sasetshenziswa lapho kuhileleka ama-catalyst aqinile), yahlakazwa ngo-0.7 ml we-d-chloroform, futhi yahlaziywa nge-1H nuclear magnetic resonance (NMR).

Ukuhlonza umkhiqizo kanye nomthamo.Ama-aliquots engxube yokusabela ahlanjululwe nge-tetrahydrofuran futhi ahlaziywa nge-gas chromatography–mass spectrometry (GC-MS; Agilent GC-7890A, MS-5975).Ngokusabela kwe-EB, i-acetophenone ne-1-phenylethanol zihlonzwe njengemikhiqizo ehamba phambili.I-1H-NMR ne-13C-NMR (uhlelo lwe-400 MHz Agilent DD2-MR400) zisetshenziswe ukuze kuqhutshekwe kuqinisekiswe ubunikazi bomkhiqizo.I-1-Phenylethyl hydroperoxide, engazange itholwe yi-GC-MS ngenxa yokungaqini kokushisa kwayo, ikhonjwe yi-NMR ukuthi ibe omunye umkhiqizo ovelele.Yomithathu imikhiqizo yalinganiswa nge-1H-NMR kusetshenziswa i-decane njengendinganiso yangaphakathi (fig. S1).Ukulahlekelwa okuhwamukayo kwanqunywa ngokuhlukana futhi kwasetshenziselwa ukulungisa ukugxiliswa komkhiqizo.Ngemva kokulungiswa kokulahlekelwa kokuhwamuka, akukho ukungalingani kwekhabhoni okuphawulwe ngokusabela kwe-EB.Ngokusabela kwe-cyclooctene, i-cyclooctene oxide, i-cyclooctane-1,2-diol, i-2-cycloocten-1-ol, ne-2-cycloocten-1-one ilinganiselwe yi-GC.I-Cyclooctene 3-hydroperoxide ibingazinzile futhi ibolile kukholomu ye-GC ngakho-ke ayizange ibonwe.Kube khona cishe u-10% wokulahleka kwekhabhoni ekuguqulweni okuphelele ngisho nangemva kokunxephezela ukulahleka kokuhwamuka, okungachazwa ngokwakhiwa kwenani elincane lemikhiqizo engakhonjiwe ene-oxidized kakhulu.

Ukuguqulwa nokubala kokukhetha.Isilinganiso sendawo ye-GC noma ye-NMR ye-molecule yenzuzo ku-decane yangaphakathi evamile isetshenziswe ukubala ukuguqulwa nokukhetha.Nakuba i-condenser yokupholisa yasetshenziswa, bekusadingeka ukunxephezela ukulahleka kokuhwamuka ngenxa yezinga lokushisa eliphezulu lokusabela kanye nesikhathi eside sokusabela.Amajika okulungisa okuhwamukayo atholwe kukho kokubili i-EB kanye ne-cC8═ ngaphansi kwe-nitrogen egelezayo futhi ajwayeleke ukuya esilinganisweni se-EB/decane noma i-cC8═/decane.Ngenxa yokuthi i-EB ne-cC8═ zinamaphoyinti abilayo afanayo, izici zokulungisa ezijwayelekile ezitholiwe bezingu-0.0044 (isilinganiso esijwayelekile sehlile ngehora).

Ukulinganisa kwe-hydroperoxide.Ukuhlushwa kwe-hydroperoxide kwalinganiswa ngezindlela ezimbili zokulinganisa:

1) Triphenylphosphine (PPh3) titration.I-PPh3 (0.1 M ku-EB) yasetshenziselwa ukulinganisa amasampula e-hydroperoxide angaziwa, futhi indawo yokugcina ikhonjwe ngomugqa wokuhlola we-EM Quant peroxide.I-31P-NMR isetshenziselwe ukuqinisekisa ukususwa okuphelele kwezinhlobo ze-hydroperoxide.

2) I-iodometric titration.Isampula (0.2 ml) ixutshwe kanye ne-1 ml ye-CHCl3/acetic acid (v/v = 1:2) kanye ne-6 ml yesisombululo se-1 M KI.Ingxube yanyakaziswa ebumnyameni amahora angu-2 yabe isifakwe i-titrated ngo-0.005 M Na2S2O3 phambi kwamaconsi ambalwa esixazululo sesitashi.Iphuzu lokugcina lafinyelelwa lapho ingxube ingenambala.

Zombili izindlela zazihambisana ngaphakathi;nokho, imiphumela yabo ihluke ngo-5 kuya ku-10%.Ngenxa yokuthi i-Au + cC8═OOH-x ne-cC8═OOH-x esetshenziswe kule phrojekthi yenziwe nge-cC8═OOH-initiated oxidation, ukugxiliswa kwe-hydroperoxide kwakuhluka kusukela kuqoqo kuya kwelinye kodwa kwakuhlale kungaphakathi kwebanga elingu-0.2 ukuya ku-0.5 M ukuze kulungiswe kabusha. cC8═OOH-40 kuya ku-cC8═OOH-100 amasampuli.Ukugxila kwe-hydroperoxide kwehla kancane kancane ngesikhathi sokugcinwa.

Ukuhlolwa kwe-EPR spin trap.I-DMPO (23 μl) yengezwe ku-1 ml yesampula ukuze kufinyelelwe ekuhlanganiseni kwe-DMPO okungu-0.2 M, futhi u-20 mg we-Co/ZSM-5 wengezwe engxubeni yesampula eshubhuni yokuhlola.Ingxube yenziwe nge-sonicated iminithi elingu-1 ukuze kumiswe i-catalyst, futhi lokhu kwalandelwa ukushisisa ku-60°C imizuzu engu-10.I-aliquot yengxube idluliselwe kushubhu ye-borosilicate yeshubhu ye-capillary eyindilinga (u-1.50 ngaphakathi ububanzi × 1.80 ngaphandle ububanzi, I-Wale Apparatus), eyayivalwe ekugcineni - leli shubhu labe selifakwa ku-Wilmad quartz X-band EPR tube ( Sigma-Aldrich).Isampula iqandiswe ngokucwiliswa kweshubhu le-EPR ku-liquid N2.Ngokushesha ngaphambi kokulinganisa i-spectra ye-EPR, isampula yancibilika.Izilinganiso ze-Continuous-wave (CW) X-band EPR zenziwa kuzinga lokushisa legumbi kusibukeli esilungisiwe se-Varian E-4 kusetshenziswa umunwe we-Dewar.

Ukuhlolwa kokulebula kwe-Isotopic.I-Deuterated EB (d10-EB) isetshenziswe ekuhlolweni kwengxube engu-6 ml ye-cC8═OOH-45, 5 ml ye-d10-EB, 1 ml ye-decane, kanye no-60 mg we-Co-ZSM-5 (7%). , ku-120°C, no-6 ml we-cC8═OOH-45, 5 ml we-EB-d10, kanye no-1 ml we-dodecane.Ukunxephezela ukwehla kwezinga lokusabela ngenxa ye-kinetic isotope effect, i-co-oxidation yenziwa ekushiseni okuphezulu okungu-120°C.Ama-aliquots esampula athathwe ngaphambi nangemuva kwamahora angama-24 okusabela futhi ahlaziywa yi-2H-NMR ne-GC-MS.

I-spectrum ye-2H-NMR (i-fig. S5, i-spectrum 2) ibonise iziqongo ezintsha ezimbalwa ngemva kokusabela, okungekho ngaphambi kokusabela, ku-δ1.50, δ1.58, δ4.94, δ7.42 kuya ku-δ7.72, kanye no-δ8.04 .Ngenxa yokuncishiswa kwe-J-coupling njalo nokuzwela kwe-2H-NMR, amaphethini okuhlukanisa awazange axazululwe.Iziqongo kokuthi δ8.04 kanye no-δ7.42 kuye ku-δ7.72 zabelwe ama-deuteron eringi yephunga elimnandi ye-acetophenone;iziqongo ku-δ1.50 kanye no-δ4.94 zabelwe i-methyl ne-benzylic deuteron ye-1-phenylethanol, ngokulandelana;futhi inani eliphakeme elingu-δ1.58 labelwa i-deuteron ku-D2O elakhiwe ngenxa yokubola kwe-hydroperoxide.Ayikho i-deuteron etholakele ehlotshaniswa nemikhiqizo ye-cyclooctene epoxidation, futhi ukwakheka kwamanzi ancishisiwe kubonise ukuthi abathwali be-radical chain abavelele ekuphenduleni kwe-co-oxidation babeyi-peroxy ne-alkoxy esekelwe.

I-spectra ye-GC-MS yemikhiqizo iboniswa kumfanekiso.I-S6.I-Acetophenone-d8 (m/e 128, ikhishwe ngokuphelele, i-fig. S6A, m/e 127 kanye ne-126) yabonwa.Kusukela kuphethini yokuqhekeka, konke ukushintshaniswa kwe-HD kwenzeke endaweni ye-methyl.Ngaphezu kwalokho, i-1-phenylethanol-d9 (m/e 131) (fig. S6B) ukuphela kwemikhiqizo ehoxisiwe etholiwe.Ayikho i-deuterium etholwe ku-cyclooctene oxide (fig. S6C), umkhiqizo omningi kakhulu ovela ku-cyclooctene epoxidation.I-1-Phenylethanol-d9 ingakhiwa ngokusabela kwe-phenylethoxy radical ne-cyclooctene.

Izinto ezingeziwe zalesi sihloko zitholakala ku-http://advances.sciencemag.org/cgi/content/full/6/5/eaax6637/DC1

Umdwebo S5.2H-NMR ngaphambi (i-spectrum 1, ebomvu) nangemuva (i-spectrum 2, eluhlaza) ukusabela kwe-co-oxidation yamahora angu-24.

Isifanekiso S7.Ukuqhathaniswa kokuguqulwa kokuqala kwe-4-methyl anisole okuqaliswe kusetshenziswa i-Au + cC8═OOH-100, kususwe i-cC8═OOH.

Lena indatshana yokufinyelela evulekile esatshalaliswa ngaphansi kwemigomo yelayisensi ye-Creative Commons Attribution-NonCommerce, evumela ukusetshenziswa, ukusatshalaliswa, nokukhiqizwa kabusha kunoma iyiphi imidiya, inqobo nje uma ukusetshenziswa okuwumphumela kungekona okokuhweba futhi inqobo nje uma umsebenzi wokuqala ufanelekile. ikhonjiwe.

QAPHELA: Sicela ikheli lakho le-imeyili kuphela ukuze umuntu omncomayo ikhasi azi ukuthi ubufuna alibone, nokuthi aliyona i-imeyili eyimfucuza.Asithathi noma yiliphi ikheli le-imeyili.

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

Kusistimu ye-catalytic engathinteki, abaxhumanisi abasuselwe ku-Au-catalyzed cyclooctene epoxidation effects ethylbenzene oxidation.

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

Kusistimu ye-catalytic engathinteki, abaxhumanisi abasuselwe ku-Au-catalyzed cyclooctene epoxidation effects ethylbenzene oxidation.

© 2020 Inhlangano YaseMelika Yokuthuthukiswa Kwesayensi.Wonke Amalungelo Agodliwe.I-AAAS inguzakwethu we-HINARI, AGORA, OARE, CHORUS, CLOCKSS, CrossRef kanye ne-COUNTER.Science Advances ISSN 2375-2548.