Ka tloaelo, catalyst e sebetsa ka ho sebelisana ka kotloloho le li-reactants.Lenaneong le lecha la nocontact catalytic system (NCCS), karolo e bohareng e hlahisoang ke karabelo e le 'ngoe e sebetsa e le mokena-lipakeng ho etsa hore karabelo e ikemetseng e tsoele pele.Mohlala ke khetho ea oxidation ea ethylbenzene, e neng e sa khone ho ba teng ha solubilized Au nanoclusters kapa cyclooctene, empa e ile ea tsoela pele habonolo ha ka bobeli li le teng ka nako e le 'ngoe.The Au-initiated selective epoxidation ea cyclooctene generated cyclooctenyl peroxy le oxy radicals e sebelitseng e le bakena-lipakeng ho qala oxidation ea ethylbenzene.Sistimi ena e kopaneng e atlehile ho atolosa phello ea matla ea Au.Mokhoa oa karabelo o ne o tšehetsoa ke reaction kinetics le liteko tsa spin trap.NCCS e etsa hore likarabelo tse tšoanang li tsoele pele ntle le lithibelo tsa likamano tsa stoichiometric, li fana ka likhato tse ncha tsa tokoloho lits'ebetsong tsa hydrocarbon co-oxidation tsa indasteri.

Ka tloaelo, catalyst e sebelisana ka ho toba le li-reactants (action A) ho etsa litlhophiso tsa bond tse laetsoeng ke karabelo.Mohlala, ho cobalt-catalyzed oxidation ea alkylaromatics (1) kapa Au-catalyzed epoxidation ea cyclooctene (2), catalyst e thusa ho ntšoa ha athomo ea haedrojene ho hydrocarbon ho qala karabelo.Karabelong ea mahala ea ketane ea radical, mokelikeli o kenya letsoho ho khaohaneng ho homolytic ha maqhama a fokolang ho ba qalang ba eketsoang ka boomo kapa ba teng e le litšila tse tlang motsoakong oa karabelo (1, 3, 4).Mehato e meng ea karabelo ea catalytic tandem e kanna ea se hloke khokahano e tobileng ea substrate-catalyst ha phetoho ea substrate e etsoa ka sehlahisoa se hlahisitsoeng ka mokhoa o ts'oanelang mehatong e fetileng (5-8).Leha ho le joalo, karabelo ena e hatelloa ke likamano tsa stoichiometric lipakeng tsa mehato.Ka mohlala, ho Mukaiyama (ep) oxidation ea alkene, catalyst e fetola sehlabelo sa sehlabelo karabelong ea A, e kang isobutyraldehyde, ka mokhoa o ts'oanang oa stoichiometric oa epoxide (reaction B) (9, 10).Le hoja ho khoneha ka molao-motheo, ha re tsebe mohlala oo ho oona mosebetsi oa "catalyst" e leng ho hlahisa S e bohareng ho arabela A, moo S e sebetsang e le mokena-lipakeng ho qala kapa ho susumetsa karabelo e 'ngoe B ho e-na le ho nka karolo e le stoichiometric reagent. , athe catalyst ha e sebetse bakeng sa karabelo ea B (setšoantšo sa 1).Ka morero o joalo, tšusumetso ea "catalyst" e atolosoa ka nģ'ane ho ts'ebetso ea A-catalyzing ho ea ho etsa karabelo ea B empa ntle le ho kopana ka ho toba le li-reactants tsa eona.Re bitsa morero o joalo a nocontact catalytic system (NCCS).Ho NCCS, boholo ba karabelo ea karabelo A le B ha bo tlanngoe ke kamano efe kapa efe ea stoichiometric lipakeng tsa bona.Sena se fapane le maikutlo a tandem.Ka indasteri, kamano e joalo ea stoichiometric hangata e beha lithibelo tsa moruo ts'ebetsong ea tlhahiso ea lik'hemik'hale.Mohlala o tsebahalang ke tlhahiso ea stoichiometric ea phenol le acetone ka oxidation ea benzene ka cumene hydroperoxide e bohareng ts'ebetsong ea cumene (11).

Catalyst (Katse) e susumetsa karabelo A (AR ➔ S ➔AP) moo S e mahareng e sebetsang hantle ho qaleng kapa ho hlabolleng karabelo ea B (BR ➔ BP), le hoja karabelo ea B e sa hlahisoe ke sesosa.

Re ile ra fumana NCCS e joalo ha re ntse re hlahloba thepa ea catalytic ea solubilized Aun clusters (moo n boholo e neng e le liathomo tse tšeletseng ho isa ho tse robeli) bakeng sa oxidation e itseng ea ethylbenzene (EB).Re bonts'itse hore Aun ena ea solubilized e ile ea etsa hore ho be le epoxidation e khethehileng ea cyclooctene (cC8═) le O2 e nang le ~ 80% selectivity (2).Lihlopha tsena li entsoe ka situ nakong ea Au/SiO2-catalyzed cC8═ epoxidation, 'me li ile tsa boloka bokhoni ba tsona ba ho hlahisa radical initiator cyclooctene hydroperoxy radical (cC8═OO·) nakong eohle ea karabelo.Lihlopha tsa Aun tse qhibilihisitsoeng li ne li ka bokelloa motsoakong oa karabelo ka mor'a ho tlosoa ha Au/SiO2, 'me boholo ba tsona bo lekantsoe ho sebelisoa microscope ea elektrone e lokisoang ka mokhoa o sa tloaelehang le spectroscopy ea fluorescence (2).Ntle le lihlopha tsa Aun, metsoako ena e ne e boetse e na le cyclooctene hydroperoxide (cC8═OOH) le lihlahisoa tsa oxidation cyclooctene epoxide, cyclooctenol, le cyclooctenone.cC8═OOH e ne e le mofuta o tsitsitseng oa hydrogenated oa cC8═OO· mme o teng maemong a 0.2 ho isa ho 0.5 M kamora phetoho ea 40 ho isa ho 100% cC8═.Motsoako ona o bitsoa Au + cC8═OOH-x, moo x e leng phesente ea cC8═ phetoho.Le hoja ka tekanyo e fokolang haholo le ka nako e telele (> 5 lihora) nako ea ho kenya letsoho, cC8═ epoxidation e ka boela ea etsahala ka auto-oxidation ntle le lihlopha tsa Aun.Metsoako e fumanoeng ka auto-oxidation ntle le Au e bitsoa cC8═OOH-x.Ho NCCS, Solubilized Aun e ne e tla ba sesosa, epoxidation ea cC8═ e tla ba reaction A, 'me cC8═OO· e tla ba S.

Auto-oxidation ea EB ha e etsahale habonolo.Ka 145°C, ke karabelo ea 9% feela e etsahetseng bakeng sa EB e makhethe tlasa 2.76 MPa O2 (12).Tlas'a maemo a rona a bobebe haholo a 100 ° C le ho phatloha ha O2 ho 0.1 MPa, ho ne ho se na karabelo e bonoang ea EB e makhethe bonyane lihora tse 20.Ho ne ho hlokahala ho eketsoa ha "free radical initiator" hore karabelo ena e tsoele pele.Ho qalisoa ka 2,2'-azobisisobutyronitrile (AIBN), e leng mokelikeli o matla oa mocheso o matla haholo, o ile oa fella ka auto-oxidation ea EB ka bolelele ba ketane ea ~ 3 (fig. S2A).Ho ile ha hlokomeloa ketane e khuts'oane (~1) ho sebelisoa tert-butyl hydroperoxide (fig. S2B), 'me ho ne ho e-na le karabelo e fokolang haholo e ka bonoang ho sebelisoa cumene hydroperoxide e sebetsang ka tlase.Kahoo, auto-oxidation ea EB e ne e e-na le tšusumetso e fokolang ho liphello tsa karabelo tse tlalehiloeng ka tlase.

Motsoako o tsitsitseng oa aerobic oxidation oa EB ho EB hydroperoxide, acetophenone, le phenylethanol o ile oa finyelloa ka ho eketsa Au + cC8═OOH-50 e nang le motsoako oa Aun, cC8═OOH, le cC8═ e sa sebetseng (Setšoantšo sa 2, curve 1).Joalokaha ho bontšitsoe ke liteko tse latelang, likarolo tsena tse tharo li ile tsa phetha karolo ea bohlokoa ho EB oxidation, 'me li ne li lumellana le catalyst, S, le AR tsamaisong ea NCCS e bontšitsoeng setšoantšong sa 1.

(i) 7 ml ea EB + 3 ml ea Au + cC8═OOH-50;(ii) 7 ml ea EB + 3 ml ea Au + cC8═OOH-50 + 1.2 mmol Ph3;(iii) 7 ml ea EB + 3 ml ea Au + cC8═OOH-99 + 0.6 mmol Ph3;(iv) 7 ml ea EB + 3 ml ea cC8═OOH-50;(v) 7 ml ea EB + 3 ml ea cC8═OOH-50 + 1.5 mmol Ph3.Palo ea PPh3 e ekelitsoeng e ne e behiloe ho lekana le palo ea titrated hydroperoxide (mocheso oa ho arabela, 100 ° C).

Tlas'a maemo a rona, ha ho na oxidation ea aerobic EB e hlokomelehang e etsahetseng motsoakong oa cC8═ le EB (ke hore, ntle le Cat kapa S).Triphenylphosphine (PPh3) e sebetsa haholo ho tlosa hydroperoxides.Tharollo ea Au + cC8═OOH-99, e felisitsoeng ke cC8═OOH ke tlatsetso ea PPH3, e nang le Aun le cC8═ e nyenyane haholo e sa sebetseng, e hlotsoe ho qala karabelo ea EB esita le ka mor'a lihora tse 2 (Setšoantšo sa 2, curve 3), e bontšang hore Aun e le 'ngoe e ne e sa sebetse.Sephetho sena se boetse se bontšitse hore lihlahisoa tse ling tsa cC8═ oxidation, tse kang cyclooctene epoxide, cyclooctene alcohol, kapa ketone, ha lia ka tsa khona ho qala EB oxidation.Ho fapana le teko e ka holimo, ho tlosoa ha cC8═OOH le Pph3 ho tloha Au + cC8═OOH-50, ho siea Aun le cC8═ e sa sebetseng, ha hoa ka ha thibela phetoho ea EB (bapisa li-curves 1 le 2, Fig. 2).

Lihlopha tsena tse tharo tsa data li khothalelitse ho sebelisana lipakeng tsa Aun le cC8═ e sa sebetseng qalong ea EB oxidation.Re hakanya hore 'Mangoane o ile a etsa hore oxidation ea cC8═ e thehe cC8═OOH, eo e neng e le mothehi oa karabelo ea EB.Sena se ka lekoa ka ho bapisa katleho ea ho qala EB oxidation le motsoako oa cC8═OOH le cC8═ empa ntle le 'Mangoane pele le ka mor'a ho tlosoa ha cC8═OOH le Pph3.Ho etsisa maemo a liteko tsa pejana hantle, re sebelisitse tharollo cC8═OOH-50 bakeng sa motsoako oa cC8═OOH le cC8═ e le hore phello efe kapa efe e ka bang teng ea lihlahisoa tsa cC8═ epoxidation e ka hlahisoa hape.Liphello li bontšitse hore ka pel'a cC8═OOH-50, EB e ile ea itšoara hantle (setšoantšo sa 2, curve 4).Leha ho le joalo, haeba cC8═OOH e tlositsoe ke Pph3, ho ne ho se na karabelo bakeng sa hora ea pele le ts'ebetso e hatelitsoeng ka mor'a moo (curve 5).Lintlha tsena li boetse li tšehetsa mohlala oa hore karolo ea bohlokoa ea Aun e ne e le ho tsoela pele ho hlahisa cC8═OOH ka cC8═ oxidation, le cC8═OOH e qalile karabelo ea EB.Karolo ea catalytic ea Aun e ile ea tiisoa ka ho eketsehileng ka ho hlokomela hore litekanyetso tsa pele tsa EB oxidation ha ho se na cC8═OOH li eketsehile ka ho eketseha ha Aun concentration (fig. S3).

Karolo e ikhethang ea Aun ho NCCS ena e bonts'itsoe ka ho hlahloba Co e le sesebelisoa se seng, se ileng sa khethoa hobane cobalt acetate le cobalt cycloalkanecarboxylate (13) ke li-catalyst tsa indasteri bakeng sa phetoho ea EB ho acetophenone e nang le molek'hule O2, e sebetsang tlas'a maemo a thata 'me e hloka ho ba teng ha li-ion tsa acid le bromide.Li-co complexes li boetse li sebelisetsoa ho khetha aerobic EB oxidation ka pel'a organocatalyst N-hydroxyphthalimide (NHPI) kapa sehlabelo sa sehlabelo (14, 15).Leha ho le joalo, tlas'a maemo a rona a karabelo, boteng ba Co/ZSM-5 ha boa ka ba fella ka oxidation efe kapa efe e bonoang ea EB, cC8═, kapa motsoako oa bona bonyane lihora tse 6.Ka mantsoe a mang, Co e le 'ngoe ha e khone ho qala karabelo ea oxidation.Leha ho le joalo, boteng ba Aun le cC8═, e nolofalitse karabelo ea oxidation.Ho itšetlehile ka boemo, cC8═ kapa EB e ile ea arabela ka makhetlo a mararo ho isa ho a mahlano ka potlako ha Co/ZSM-5 e le teng, 'me ntlafatso e ile ea eketseha ka palo ea Co/ZSM-5 (tafole S2, liteko tsa 6 ho isa ho 8).Kabo ea sehlahisoa sa EB oxidation le eona e fetohile ka mokhoa o itseng ka pel'a Co/ZSM-5.Ho eketsa palo ea Co/ZSM-5 ho ekelitse lihlahisoa tsa acetophenone, 'me, ho isa tekanyong e fokolang, lihlahisoa tsa phenylethanol ka litšenyehelo tsa EB hydroperoxide (tafole S3, liteko tsa 6 ho ea ho 8), ho lumellana le taba ea hore Co catalyzed decomposition ea EB hydroperoxide ho acetophenone le phenylethanol le oxidation ea morao-rao ho acetophenone.Molemong oa boiketlo, re kenyelelitse Co/ZSM-5 motsoakong oa rona oa karabelo ho khutsufatsa nako ea karabelo.

Ntho e khethollang pakeng tsa NCCS le mekhoa ea ho itšoara ka tandem ke hore nakong ea pele, ha ho na kamano ea stoichiometric pakeng tsa liketso A le B (setšoantšo sa 1).Ho netefatsa hore maikutlo a rona a etsahetse ka NCCS, re ile ra leka phello ea ho fetola karolelano ea cC8═ ho EB ka ho beha leihlo litekanyetso tsa bona tsa karabelo.Setšoantšo sa 3 se bontša liphello tsa ho fetola mahloriso a pele a cC8═ ha u ntse u boloka mohopolo oa pele oa EB le maemo a mang a karabelo kamehla.Lintlha li bonts'a hore ho ne ho se na kamano e tsitsitseng ea stoichiometric pakeng tsa bongata ba li-reactants tse peli tse ileng tsa arabela, ho tiisa hore mokhoa oa ho itšoara o fapane le leano la setso la tandem reaction.Sehlopha se ts'oanang sa liteko moo likhatiso tsa EB tsa pele li neng li fapane ha ho ntse ho lokisoa likhatiso tse ling li fihlile qetong e ts'oanang.Ho tsoa ho lintlha tsena, litekanyetso tsa pele tsa karabelo li ne li baloa (Letlapa la 1 le tafole S2, liteko tsa 4 le 5) 'me li bontšoa ho fapana ka tsela e fapaneng bakeng sa cC8═ le EB.Ho ne ho se na tšebelisano-'moho mabapi le litekanyetso tsa karabelo lipakeng tsa maikutlo ana a mabeli e le hore ha karabelo e le 'ngoe e tsoela pele ka potlako, e 'ngoe e ne e tlameha ho lieha ka ho lekana.Litekanyetso ka bobeli li ka eketseha ka nako e le 'ngoe, joalo ka ha ho bonts'itsoe ke liteko tsa 4 le 5 tafoleng ea S2.Ho ka lebelloa phapanyetsano haeba EB le cC8═ li qothisana lehlokoa le sebaka se tšoanang sa catalytic reaction kapa lipakeng.Qeto ena e boetse e lumellana le 'nete ea hore liketso tsa nako e le 'ngoe tsa EB le cC8═ ha lia ka tsa e-ba le phello kapa e nyenyane haholo kabong ea bona ea lihlahisoa ka bomong, joalokaha ho bontšitsoe ho Lethathamo la 1 le tafoleng ea S3.

Khatiso ea pele ea cC8═ e ne e le 0.34 M (A), 1.05 M (B), le 1.75 M (C).Decane e ne e sebelisetsoa ho etsa phapang ea bophahamo ba cC8═ e sebelisitsoeng.Maemo a mang: 32 mg ea Co/ZSM5, 100°C.

Lintlha tsena li lumellana le morero oa mechine o bontšitsoeng ho 4, moo mehato ea bohlokoa bakeng sa NCCS e hatisoang 'me libapali tse ka sehloohong li totobatsoa (leano le feletseng le bontšitsoeng ho feiga. S8).Mochine ona, lihlopha tsa Aun li qala potoloho ea cC8═ epoxidation ka ho hlahisa cyclooctenyl radicals (I) le cyclooctene peroxy radicals (II).Li-radicals tsena tse peli li nka karolo ho cC8═ epoxidation cycle, joalo ka ha e ne e thehiloe pejana (2, 16).Ha EB e le teng, II e fetoha molek'hule ea mahareng le shuttles lipakeng tsa cC8═ epoxidation cycle le EB oxidation cycle.Ka potoloho ea EB, II e sebetsana le EB ho theha phenylethyl radical, eo hang-hang e etsang phenylethyl peroxy radical (III) ka karabelo le O2, kaha liketso tse matla tsa carbon-centered le O2 li tsejoa e le tse bonolo haholo (1).Ka mor'a moo hydrogen abstraction ka III e etsa phenylethyl hydroperoxide mme qetellong acetophenone le phenylethanol.III e ka boela ea itšoara ka potlako ka cC8═, e fetohang tsela ea ho tlatsa II e sebelisoang ke potoloho ea oxidation ea EB.Kahoo, karabelo ea oxidation ea EB ha e tsamaee le khatello ea stoichiometric ea cC8═ epoxidation reaction, 'me ha ho na "trade-off" ka litekanyetso tsa karabelo ea EB le cC8═ joalokaha ho ne ho ka lebelloa haeba ba ne ba hlōlisana bakeng sa reagent e tšoanang. kapa sebaka sa marang-rang se sebetsang.Hobane II e nka karolo mohatong oa ho qala ho EB le cC8═ oxidation cycles empa e seng ka kotloloho mehatong ea ho theha sehlahisoa, ho koala ha likarolo tsena tse peli ha ho ame kabo ea sehlahisoa.

Cyclooctene peroxy radical (II) ke mokena-lipakeng ea ka sehloohong ea qalang EB oxidation.II e ka nchafatsoa ka karabelo ea EB peroxy radical (III) le cC8═.Ka holimo ka ho le letšehali, lihlopha tsa 'Mangoane li qala potoloho ea cC8═ epoxidation (potoloho ka ho le letšehali).Potoloho e ka ho le letona e bontša mehato ea EB oxidation.Ke mehato ea mantlha feela e bonts'itsoeng ea bohlokoa bakeng sa NCCS.

Ho netefatsa ho thehoa ha li-intermediate tsa nakoana tse hlalositsoeng ho 4, re kentse leraba la spin 5,5-dimethyl-1-pyrroline N-oxide (DMPO) ho motsoako oa karabelo ho etsa li-adducts tsa nako e telele tsa nitroxide radical spin le li-radicals tsa mahala li teng bakeng sa ho fumanoa ka X-band electron paramagnetic resonance (EPR) spectroscopy.E le taolo, ha ho li-radicals tse neng li ts'oaroe ke DMPO ka tharollo ea acetone le decane ntle le C8═ kapa EB (fig. S4-3).Ha DMPO e ne e eketsoa motsoakong oa karabelo o nang le cC8═OOH le cC8═ (fig. S4-1), sephetho sa EPR spectrum se ile sa etsisoa hantle e le kakaretso ea mefuta e meholo e ikhethang ea paramagnetic (A setšoantšong, ~86% ea kakaretso. ketsiso e matla) le mefuta e 'meli e menyenyane (B le C, ~ 5 le ~ 9% ea matla a papiso ea kakaretso, ka ho latellana), e fanang ka bopaki bo tobileng ba sebopeho se matla nakong ea karabelo.Motheong oa papiso ea boleng ba hyperfine coupling ho ea li-adducts tse tsejoang tsa DMPO (tafole S1), mofuta oa C o ile oa abeloa DMPO/ROO• adduct, ho hlakile hore cyclooctene 3-peroxy radical (II) e bonts'itsoeng e le mokena-lipakeng lipakeng tsa tse peli. karabelo (sa feiga. 4).Mefuta ea A le B li ile tsa abeloa li-adducts tse peli tse fapaneng hanyane tsa DMPO/RO•, moo R e neng e bua ka karolo ea hydrocarbon.E ka 'na ea e-ba e' ngoe ea mefuta ea RO• e hlalositsoeng ho Fig. 4 kapa alkoxy radicals e hlahisoang ho tloha DMPO/ROO• adduct decay [DMPO/ROO• adducts e tsejoa e le e sa tsitsang le ho bola ho lumellana le alkoxy radical adduct (17, 18)] kapa motsoako wa tsona ka bobedi.Ha EB e ne e boetse e kenyelelitsoe motsoakong oa karabelo, sephetho sa EPR se ile sa etsisoa hantle le mefuta e mengata ea A′, e neng e tšoana haholo le mefuta ea A (DMPO/RO•), le mefuta e 'meli e menyenyane ea B le C e nang le litlatsetso tse nyane tse tšoanang. (sa feiga. S4-2 le tafole S1).Hobane ho kenyelletsoa ha EB ho ne ho lebeletsoe ho khanna ho thehoa ha phenylethyl peroxy radicals (III), mefuta ea A′ e ne e ka 'na ea e-ba motsoako oa RO• e hlahisitsoeng karabelong hammoho le leha e le efe phenylethyl peroxy adduct, eo hamorao e ileng ea senyeha ho phenylethyl oxy DMPO adduct.

Ho sebelisa EB-d10 joalo ka reactant le ho beha leihlo deuterium labeling lihlahisoa tsa cC8═ ho ka bona hore na ho bile le karabelo ea EB ka cC8═ based carbon radicals.Liphello tsa teko e joalo li bontšitse hore ho ne ho se na deuterium incorporation ho cyclooctene epoxide (feiga. S5 le S6).Phenylethanol e ile ea boloka tsohle tsa deuterium ho EB reactant, 'me tse ling tsa li-deuteron tsa sehlopha sa methyl tsa acetophenone li ne li fapanyetsana, tse neng li ka etsahala ka spectrometer e kholo.Kahoo, ho ne ho se na bopaki ba karabelo pakeng tsa EB-d10 le cyclooctenyl radical, e neng e tla hlahisa deuteron ho lihlahisoa tsa cC8═.

Ho sebetsa ha leano la NCCS ho ile ha atolosoa ho hlahloba Au + cC8═OOH-100-assisted aerobic oxidation ea 4-methylanisole.Ka lebaka la maqhama a matla a mantlha a C─H molek'huleng ena, karabelo ea oxy-functionalization e entsoe ka mocheso o phahameng.Litefiso tsa pele tsa phetoho ea 4-methylanisole ho 4-anisaldehyde li ne li bapisoa bakeng sa karabelo e qalileng le Aun le ebang ke ka cC8═ tlatsetso kapa ntle le eona (cC8═OOH e tlositsoe ka Pph3).Ho tšoana le EB oxidation, ha motsoako oa karabelo o ne o se na cC8═ mme o se na cC8═OOH, sekhahla sa pele sa oxidation se ne se lieha haholo (sa feiga. S7).Ha cC8═ e eketsoa motsoakong oa karabelo, sekhahla sa pele sa oxidation se ile sa ntlafatsoa ka mokhoa o hlakileng.Ka hona, lihlopha tsa Aun li ile tsa khona ho hlahisa cC8═OOH ho tloha ho cC8═ e eketsehileng ho qala oxidation ea 4-methylanisole joalokaha ho lebeletsoe ho NCCS.

Qetellong, re bonts'itse mohopolo oa NCCS.Ho sebelisa oxidation ea nako e le 'ngoe ea cyclooctene le EB hammoho le cyclooctene le 4-methylanisole, NCCS e bontšitsoe ho nolofalletsa co-oxidation ea li-hydrocarbon ntle le lithibelo tsa likamano tsa stoichiometric tsa mekhoa ea setso ea ho kopanya.Sena se fana ka tekanyo e neng e sa fumanehe ea tokoloho ts'ebetsong ea indasteri hoo moruo oa ts'ebetso o seng o sa tlameletsoe ke tlhokahalo ea mebaraka e ntle bakeng sa lihlahisoa tse hlahisoang ka chelete ea stoichiometric.

Mehloli le bohloeki ba lik'hemik'hale tse sebelisitsoeng e ne e le tse latelang: HAuCl4•3H2O (≥99.9% trace metal basis, Sigma-Aldrich), fumed silica (CAB-O-SIL90, Cabot Corporation), ethylenediamine (≥99% ReagentPlus, Sigma-Aldrich) , 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), 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 (kereiti ea reagent, 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 ho 70% w / w, Fisher Chemical), EM Quant peroxide strips test strips, and syringe filter (polyvinylidene difluoride membrane, 0.25 mm / 0.2 μm, Acrodisc).

Au/SiO2.Khauta e tšehelitsoeng ke silika ea nanoparticle catalyst e lokiselitsoe ka Au(en)2Cl3 precursor ho latela mokhoa o entsoeng ke Zhu et al.(19) mme e fetotsoe ke Qian et al.(2).E le ho toba haholoanyane, tharollo ea Au(III) chloride trihydrate e ile ea lokisoa ka ho qhaqha 0.5 g ea HAuCl4•3H2O ka motsoako o nang le 10 ml ea ethanol le 2 ml ea metsi.Ka mor'a ho etsa tharollo ea homogeneous, 0.23 ml ea ethylenediamine (en = ethylenediamine) e ile ea eketsoa ka tharollo ea dropwise ho theha Au (III) ethylenediamine chloride [Au (en) 2Cl3] ka phapanyetsano ea ligand.As-formed Au(en)2Cl3 e ile ea bokelloa ka ho sefa le ho hlatsuoa ka 300 ml ea ethanol.Ho kenya Au holim'a tšehetso ea silica, 4.2 mM Au(en)2Cl3 tharollo ea metsi e ile ea lokisoa ka ho qhibiliha 46.3 mg ea Au(en)2Cl3 ka har'a 26 ml ea metsi a qhibilihisitsoeng deionized (DDI).Tharollo e entsoeng ka mokhoa o entsoeng e ne e bolokiloe ho 40 ° C ka ho hlapa ka oli.Joale, 1 g ea silika e fumed e ile ea ekeletsoa ho tharollo ea preheated ha e ntse e susumetsa.Hang ha litšehetso tsohle tsa silica li qoelisoa ka har'a tharollo, motsoako o ne o ntšoa ka har'a bateng ea oli 'me oa pholile mocheso oa kamore.Ka ho fetola pH ea motsoako hore e be 9 ka ho eketsoa ha lerotholi la 0.75 M en aqueous solution, ho ile ha finyelloa mokhoa o betere oa li-complexes tsa khauta tsa cationic sebakeng se qosoang hampe.Ka mor'a ho hlohlelletsa lihora tse 2 mocheso oa kamore, motsoako o ne o tlhotliloeng mme o hlatsuoa ka 500 ml ea metsi a DDI.Ho tlosa masalla a sa batleheng (Cl, en, ditshila tse ding), kuku e sefang e ile ya qhalwa hape ka 200 ml ya metsi a DDI ka 40°C.Qetellong, Au/SiO2 e entsoeng ka mokhoa o hlophisitsoeng e ile ea bokelloa ka ho sefa 'me ea hlatsuoa ka 500 ml e' ngoe ea metsi a DDI 'me ea omisoa moeeng bosiu bo le bong.Calcination ea chefo ea nanoparticles ea khauta e tšehetsoeng ke silika e ile ea etsoa ka U-tube tlas'a O2 / O3 phallo (~ 300 ml / min) ka sekhahla sa 0.12 ° C / min ho fihlela 150 ° C.The catalyst e ne e bolokoa lefifing ka 5 ° C.Ho laeloa ha khauta, joalo ka ha ho lekantsoe ke plasma optical emission spectrometry, e ne e le boima ba 1.2% (wt%), 'me boholo ba karoloana ea khauta e lekantsoeng ka ho skena electron microscopy (STEM) e ne e le 2 nm.

Co/ZSM-5.Nano H-ZSM-5 e ne e calcined ka U-tube tlas'a phallo ea O2 / O3 (~ 300 ml / min) e nang le sekhahla sa 2 ° C / min ho fihlela 200 ° C 'me e tšoaretsoe 200 ° C bakeng sa hora ea 1 ho tlosa. mesaletsa dithempleite.Co/ZSM-5 e lokisitsoe ke metsi a qalang.Ka mohlala, 5 wt % loading Co/ZSM-5 e lokiselitsoe ka ho eketsa tharollo ea 0.72 M cobalt (II) nitrate [250 mg ea cobalt (II) nitrate hexahydrate ka 1.2 ml ea metsi a DDI] ho 1 g ea nano H- ZSM-5 ha u ntse u potoloha beaker ka hloko.Letlapa le ne le omisitsoe ka tlas'a lebone, 'me ho thehoa phofo e pinki e tšoanang.Phofo e entsoeng e ne e kenngoa ka har'a tube e otlolohileng ea calcination 'me e hloekisoa tlas'a phallo ea argon (100 ml / min) bakeng sa hora ea 1 ho fokotsa mongobo.Sehlahisoa se lokiselitsoeng ka nako eo se ne se calcined tlas'a phallo ea oksijene (60 ml / min) ka lebelo la ho phalla ha 10 ° C / min ho 450 ° (e tšoaretsoeng 250 ° C, 350 ° C, le 450 ° C bakeng sa 1 hora ka 'ngoe) .Co/ZSM-5 e fumanoeng e na le cobalt loading ea 5 wt%.Meroalo e meng e 'meli, 3 le 7 wt %, le eona e ile ea lokisoa.Li-catalyst tse tharo kaofela li ne li khetholloa ka ho fokotsa mocheso o hlophisitsoeng oa H2, ho fapana ha x-ray, x-ray photoelectron spectroscopy, le spectroscopy e bonahalang ea ultraviolet.

Filtrate e nang le Au-containing.Au-containing filtrate (Au + cC8═OOH-x) e ne e le sebakeng se hlahisitsoeng ke Au/SiO2-catalyzed cC8═ epoxidation reaction ho latela mokhoa o entsoeng ke Qian et al.(2) Pele ho karabelo, cC8═ e ile ea hloekisoa ho tlosa stabilizer e ekelitsoeng ke moetsi.Ka kakaretso, 50 ml ea tharollo ea 3 M potassium hydroxide (KOH) e kentsoe ho 50 ml ea cC8═ ka botlolong.Ka mor'a ho kopanya ho lekaneng le ho sisinyeha ka matla, lesela la manyolo le ne le bokelloa ka ho arohana.Mokhoa ona o ile oa phetoa ka 50 ml e 'ngoe ea 3 M KOH le tse ling tse peli tsa 50 ml tsa metsi a DDI.Joale cC8═ e ile ea omisoa ka sodium sulfate bosiu bo le bong.E le ho tlosa ka ho feletseng stabilizer, cC8═ e omisitsoeng e ne e silafalitsoe ka ho hlapa ka oli hoo e ka bang 180 ° C, 'me karoloana e ileng ea tsoa ho 145 ° C e ile ea bokelloa.Li-cC8═ tse hloekisitsoeng (10 ml) le decane (1 ml) li ne li kopantsoe ka har'a mochine o nang le 80 mg oa li-catalyst tsa Au/SiO2 tse boletsoeng ka holimo.CC8═ epoxidation reaction e ile ea etsoa tlas'a phallo ea oksijene (30 ml / min) ho 100 ° C, 'me phetoho e ne e hlahlojoa ke GC.Hang ha phetoho e lakatsehang e fihletsoe, motsoako oa karabelo o ile oa bokelloa 'me motsoako o tiileng o ile oa tlosoa ka ho hloekisa ho chesang ho sebelisa sesepa sa syringe.Maemo a tloaelehileng a solubilized Au a ileng a khethoa ke plasma mass spectrometry ea inductively e ne e ka ba 80 ng/ml, 'me boholo ba sehlopha sa Au bo ile ba khethoa ke fluorescence spectroscopy le aberration-corrected transmission microscopy ho tloha ho Authoms ho ea ho ~ 0.7 nm.cC8═OOH-x e lokisitsoe ka mokhoa o ts'oanang ntle le ho sebelisa catalyst ea Au/SiO2.Ka bobeli litharollo tsa Au + cC8═OOH-x le cC8═OOH-x li na le lihlahisoa tsa oxidation tsa cC8═, tse neng li kenyelletsa cyclooctene oxide, cyclooctene 3-hydroperoxide, 2-cycloocten-1-ol, 2-cycloocten-1-one, le trace amount. ea 1,2-cyclooctanediol.

Mokhoa o akaretsang.EB oxidation reactions e ile ea etsoa lefifing ka har'a reactor e melala e meraro ea cylindrical e nang le tube e ntle ea frit glass dissperser (Chemglass Life Sciences) le condenser e bolokiloeng ho −10°C.Ka karabelo e tloaelehileng, 7 ml ea EB, 1 ml ea decane, le 3 ml ea filtrate (Au + cC8═OOH-x kapa cC8═OOH-x) li ile tsa kenngoa ka har'a reactor hammoho le Teflon-coated magnetic stirrer.Haeba e sebelisitsoe, 32 mg ea 5% Co/ZSM-5, ntle le ha ho boletsoe ka tsela e fapaneng, e ile ea eketsoa.Ka mor'a hore setupo sa karabelo se bokelloe, motsoako oa karabelo o ile oa tsitsisoa tlas'a phallo ea N2 bakeng sa 20 min ka bateng ea oli e futhumetseng.Hang ha mocheso oa condenser le bate ea oli o tsitsitse, ho phalla ha O2 kamehla ho ne ho fanoa ka 30 ml / min.Motsoako oa karabelo (0.1 ml) o nkiloe ka linako tse fapaneng bakeng sa tlhahlobo (sefefo sa syringe se ne se sebelisoa ha li-catalysts tse tiileng li ameha), sa qhibiliha ka 0.7 ml ea d-chloroform, 'me sa hlahlojoa ke 1H nuclear magnetic resonance (NMR).

Boitsebiso ba sehlahisoa le quantification.Li-aliquots tsa motsoako oa karabelo li ile tsa hlapolloa ka tetrahydrofuran 'me tsa hlahlojoa ka khase ea chromatography-mass spectrometry (GC-MS; Agilent GC-7890A, MS-5975).Bakeng sa karabelo ea EB, acetophenone le 1-phenylethanol li ile tsa khetholloa e le lihlahisoa tse hlahelletseng.1H-NMR le 13C-NMR (400 MHz Agilent DD2-MR400 system) li ile tsa sebelisoa ho netefatsa boitsebiso ba lihlahisoa.1-Phenylethyl hydroperoxide, e sa kang ea fumanoa ke GC-MS ka lebaka la ho se tsitse ha mocheso, e ile ea khetholloa ke NMR hore e be sehlahisoa se seng se ka sehloohong.Lihlahisoa tsohle tse tharo li ne li lekantsoe ke 1H-NMR ho sebelisa decane e le maemo a ka hare (fig. S1).Tahlehelo ea mouoane e ile ea khethoa ka thoko 'me ea sebelisoa ho lokisa likhahla tsa sehlahisoa.Kamora ho lokisoa bakeng sa tahlehelo ea mouoane, ha ho ho se leka-lekane ha khabone bakeng sa karabelo ea EB.Bakeng sa karabelo ea cyclooctene, cyclooctene oxide, cyclooctane-1,2-diol, 2-cycloocten-1-ol, le 2-cycloocten-1-one li ne li lekantsoe ke GC.Cyclooctene 3-hydroperoxide e ne e sa tsitsa mme e senyehile ka har'a kholomo ea GC kahoo ha ea ka ea fumanoa.Ho bile le tahlehelo e ka bang 10% ea khabone nakong ea phetoho e felletseng esita le ka mor'a ho lefella tahlehelo ea mouoane, e ka hlalosoang ka ho thehoa ha lihlahisoa tse nyenyane tse sa tsejoeng tse nang le oxidized haholo.

Palo ea ho sokoloha le khetho.Karolelano ea sebaka sa GC kapa NMR ea molek'hule ea thahasello ho decane e tloaelehileng e ka hare e ile ea sebelisoa ho bala phetoho le khetho.Leha ho ne ho sebelisoa condenser e pholileng, ho ne ho ntse ho hlokahala ho lefella tahlehelo ea mouoane ka lebaka la mocheso o phahameng oa karabelo le nako e telele ea karabelo.Li-curve tsa tokiso ea mouoane li ile tsa fumanoa bakeng sa EB le cC8═ tlas'a naetrojene e phallang 'me tsa tloaeleha ho ea ho tekanyo ea EB/decane kapa cC8═/decane.Hobane EB le cC8═ li na le lintlha tse belang tse tšoanang, lintlha tse tloaelehileng tsa tokiso tse fumanoeng e ne e le 0.0044 (karolelano e tloaelehileng e fokotsehile ka hora).

Tekanyetso ea hydroperoxide.Motsoako oa hydroperoxide o lekantsoe ka mekhoa e 'meli ea titration:

1) Triphenylphosphine (PPh3) titration.Pph3 (0.1 M ho EB) e ne e sebelisetsoa ho titrate lisampole tse sa tsejoeng tsa hydroperoxide, 'me ntlha ea ho qetela e ile ea khetholloa ka EM Quant peroxide strip strip.31P-NMR e ne e sebelisetsoa ho tiisa ho tlosoa ka ho feletseng ha mefuta ea hydroperoxide.

2) Titration ea iodometric.Mohlala (0.2 ml) o ne o kopantsoe hammoho le 1 ml ea CHCl3 / acetic acid (v / v = 1: 2) le 6 ml ea 1 M KI tharollo.Motsoako o ile oa tsosoa lefifing ka lihora tse 2 ebe o titrated ka 0.005 M Na2S2O3 ka pel'a marotholi a seng makae a tharollo ea starch.Qetello e fihlile ha motsoako o fetoha o se nang 'mala.

Mekhoa eo ka bobeli e ne e lumellana ka hare;leha ho le joalo, liphetho tsa bona li fapane ka 5 ho isa ho 10%.Hobane Au + cC8═OOH-x le cC8═OOH-x tse sebelisitsoeng morerong ona li entsoe ka cC8═OOH-initiated oxidation, mahloriso a hydroperoxide a ne a fapane ho tloha ho batch empa a ne a lula a le ka har'a 0.2 ho isa ho 0.5 M bakeng sa ho lokisoa bocha cC8═OOH-40 ho cC8═OOH-100 disampole.Motsoako oa hydroperoxide o ile oa fokotseha butle-butle ka nako ea polokelo.

Liteko tsa EPR spin trap.DMPO (23 μl) e kenyelelitsoe ho 1 ml ea sampuli ho finyella DMPO concentration ea 0.2 M, 'me 20 mg ea Co / ZSM-5 e kenyelelitsoe ho motsoako oa sampole ka tube ea teko.Motsoako ona o ne o sonicated bakeng sa 1 min ho emisa mokelikeli, 'me sena se ile sa lateloa ke ho futhumatsa ka 60 ° C bakeng sa ~ 10 min.Sekhahla sa motsoako se ile sa fetisetsoa ka har'a tube e chitja ea borosilicate tubing capillary tube (1.50 ka hare ho bophara ba × 1.80 ka ntle ho bophara, Wale Apparatus), e neng e tiisitsoe ka lehlakoreng le leng - tube ena e ile ea kenngoa ka Wilmad quartz X-band EPR tube ( Sigma-Aldrich).Mohlala o ile oa hoamisoa ke ho qoelisoa ha tube ea EPR ka har'a mokelikeli oa N2.Hang pele ho lekanya ponahalo ea EPR, sampole e ile ea qhibiliha.Litekanyo tsa Continuous-wave (CW) X-band EPR li ne li etsoa ka mocheso oa kamore ho Varian E-4 spectrometer e fetotsoeng ho sebelisoa monoana oa Dewar.

Teko ea Isotopic labeling.Deuterated EB (d10-EB) e sebelisitsoe tekong ea motsoako oa 6 ml ea cC8═OOH-45, 5 ml ea d10-EB, 1 ml ea decane, le 60 mg ea Co-ZSM-5 (7%). , ka 120 ° C, e nang le 6 ml ea cC8═OOH-45, 5 ml ea EB-d10, le 1 ml ea dodecane.Ho lefella ho fokotseha ha sekhahla sa karabelo ka lebaka la kinetic isotope effect, co-oxidation e ile ea etsoa ka mocheso o phahameng oa 120 ° C.Li-aliquots tsa sampole li nkiloe pele le ka mor'a lihora tse 24 tsa karabelo mme tsa hlahlojoa ke 2H-NMR le GC-MS.

2H-NMR spectrum (fig. S5, spectrum 2) e bonts'itse litlhōrō tse 'maloa tse ncha ka mor'a karabelo, e seng teng pele ho karabelo, ho δ1.50, δ1.58, δ4.94, δ7.42 ho δ7.72, le δ8.04 .Ka lebaka la ho fokotseha ha J-coupling kamehla le kutloisiso ea 2H-NMR, mekhoa ea ho arohana ha ea ka ea rarolloa.Litlhōrō tsa δ8.04 le δ7.42 ho ea ho δ7.72 li ne li abetsoe li-deuteron tsa reng e nkhang hamonate ea acetophenone;litlhōrō tsa δ1.50 le δ4.94 li ile tsa abeloa methyl le benzylic deuteron ea 1-phenylethanol, ka ho latellana;'me tlhoro ea δ1.58 e ile ea abeloa deuteron ho D2O e entsoeng ka ho bola ha hydroperoxide.Ha ho deuteron e ileng ea fumanoa e amahanngoa le lihlahisoa tsa cyclooctene epoxidation, 'me ho thehoa ha metsi a fokolitsoeng ho bontša hore li-carriers tse ka sehloohong tsa ketane ea li-co-oxidation li ne li thehiloe peroxy le alkoxy.

GC-MS spectra ea lihlahisoa e bontšitsoe feiga.S6.Acetophenone-d8 (m/e 128, deuterated ka ho feletseng, feiga. S6A, m/e 127 le 126) e ile ea hlokomeloa.Ho tloha mokhoeng oa ho senya, phapanyetsano eohle ea HD e etsahetse sebakeng sa methyl.Ho phaella moo, 1-phenylethanol-d9 (m/e 131) (fig. S6B) e ne e le eona feela lihlahisoa tsa deuterated tse fumanoeng.Ha ho deuterium e ileng ea fumanoa ka cyclooctene oxide (fig. S6C), sehlahisoa se ngata ka ho fetisisa se tsoang ho cyclooctene epoxidation.1-Phenylethanol-d9 e ka thehoa ho tloha karabelo ea phenylethoxy radical le cyclooctene.

Boitsebiso bo tlatselletsang bakeng sa sengoloa sena bo fumaneha ho http://advances.sciencemag.org/cgi/content/full/6/5/eaax6637/DC1

Setšoantšo sa S5.2H-NMR pele (spectrum 1, red) le ka morao (spectrum 2, green) 24-hour co-oxidation reaction.

Setšoantšo sa S7.Papiso ea liphetoho tsa pele tsa 4-methyl anisole e qalileng ho sebelisoa Au + cC8═OOH-100, e nang le cC8═OOH e tlosoa.

Ena ke sengoloa se fumanehang habonolo se abuoang tlas'a lipehelo tsa laesense ea Creative Commons Attribution-NonCommercial, e lumellang ts'ebeliso, kabo, le ho ikatisa ka mokhoa ofe kapa ofe, ha feela sephetho e se molemong oa khoebo mme ha feela mosebetsi oa mantlha o nepahetse. qotsitsoe.

ELA HLOKO: Re kopa feela aterese ea hau ea lengolo-tsoibila hore motho eo u mo buellang leqephe a tsebe hore u ne u batla hore a le bone, le hore ha se mangolo-tsoibila a se nang thuso.Ha re nke aterese efe kapa efe ea lengolo-tsoibila.

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

Ka mokhoa o sa tsitsang oa catalytic, li-intermediaries tse nkiloeng ho Au-catalyzed cyclooctene epoxidation effects ethylbenzene oxidation.

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

Ka mokhoa o sa tsitsang oa catalytic, li-intermediaries tse nkiloeng ho Au-catalyzed cyclooctene epoxidation effects ethylbenzene oxidation.

© 2020 Mokhatlo oa Amerika oa Ntlafatso ea Mahlale.Litokelo tsohle li sirelelitsoe.AAAS ke molekane oa HINARI, AGORA, OARE, CHORUS, CLOCKSS, CrossRef le COUNTER.Science Advances ISSN 2375-2548.