228 research outputs found
OxidatĂv katalĂzis metalloenzim modellekkel = Oxidative catalysis using metalloenzyme models
OxidatĂv katalĂzis metalloenzim modellekkel A bioszervetlen kĂ©mia egyik fontos kutatási irányzata a biomimetikus oxidáciĂłk vizsgálata. Munkánk során vizsgáltuk a pirokatechin oxidáz, fenoxazinon szintetáz, szuperoxid dizmutáz Ă©s kataláz enzimek funkcionális modellezĂ©sĂ©t mangán, vas Ă©s nikkel komplexekkel. Kimutattuk, hogy a dioximáto-vas(II) Ă©s nikkel(II) komplexek gyorsĂtják pirokatechin származĂ©kok bázis katalizált oxidáciĂłját. A reakciĂłk mechanizmusának tisztázása Ă©rdekĂ©ben indokolt volt rĂ©szletes reakciĂłkinetikai mĂ©rĂ©sek elvĂ©gzĂ©se. A ferroxim(II)komplex ([Fe(Hdmg)2(Melm)2] alkalmasnak bizonyult a fenoxazinon szintetáz modellezĂ©sĂ©re, 2-amino-fenol származĂ©kok, mint modell szubsztrátumok oxidáciĂłjában. MegállapĂtottuk, hogy a [Mn2(HL)2](BPh4)2 {ahol H2L egy ötfogĂş dioxim ligandum HON=C(CH3)C(CH3)=N-CH2CH2)2NH} szelektĂv katalizátorkĂ©nt viselkedik az adrenalin oxidáciĂłjában adrenokrommá karbonát pufferben. Kimutattuk, hogy a dioximáto-mangán(II)komplex gyorsĂtja a hidrogĂ©n peroxid bomlását vĂzzĂ© Ă©s oxigĂ©nnĂ©, Ăgy a kataláz enzim funkcionális modelljĂ©nek tekinthetĹ‘. | Oxidative catalysis using metalloenzyme models One of the major subjects of bioinorganic chemistry is the study of biomimetic oxidations. We have studied catechol oxidase, phenoxazinone synthase, superoxide dismutase and catalase enzymes using manganese, iron and nickel complexes as functional models. We have established that dioximato-iron(II) and nickel(II) complexes accelerate the base-catalyzed oxidation of catechol derivatives. For establishing the underlying mechanism, we have carried out detailed kinetic studies of the catalytic oxidation. Ferroxime(II) is a suitable model for phenoxazinone synthase in the oxidation of 2-amino-phenol derivatives as model substrates. The complex [Mn2(HL)2](BPh4)2 {where H2L is the quinquedentate dioxime ligand HON=C(CH3)C(CH3)=N-CH2CH2)2NH} was found to be a selective catalyst for the oxidation of epinephrine to adrenochrome in carbonate buffer. We have demonstrated that dioximato-manganese(II)complex accelerate the disproportionation of hydrogen-peroxide into water and dioxygen in buffered aqueous solution thus can be regarded as catalase model
Rousseau vagy az utazásról és a turizmus
Rousseau Emil vagy a nevelĂ©srĹ‘l (1762) cĂmű munkájában kĂ©pzelt regĂ©nyhĹ‘se nevelĂ©sĂ©re a könyv lapjain saját maga vállalkozott, magára öltve a házitanĂtĂł szerepĂ©t. A Rousseau által kĂ©pviselt nĂ©zetek az ellentmondásokkal Ă©s a megkĂ©rdĹ‘jelezhetĹ‘ elgondolásokkal egyĂĽtt is, jelentĹ‘s állomást jelentettek a nevelĂ©s törtĂ©netĂ©ben. A tanulmány alapjául az utazással kapcsolatos nĂ©zeteinek fejezete szolgál
Poliamin-oxim ligandumok mangánkomplexeinek előállĂtása, szerkezete Ă©s reakciĂłi = Synthesis, structure and reactivity of manganese complexes with polyamine oxime ligands
Kis molekulatömegű mangán(II)- Ă©s vas(II)komplexek a pirokatechin oxidáz Ă©s a fenoxazinon szintetáz nevű metalloenzim kismolekulájĂş funkcionális modelljeikĂ©nt működnek. KĂĽlönbözĹ‘ enzimmodell-rendszerekben vizsgáltuk a 3,5-diterc-butil-pirokatechin (H2dtbc) Ă©s a 2-amino-fenol (H3ap) O2-nel vĂ©gbemenĹ‘ biomimetikus oxidáciĂłjának kinetikáját Ă©s mechanizmusát. Ăšj dioximáto-mangán(II) dimert állĂtottunk elĹ‘, amely metanolos oldatban az [Mn] monomer komplexszĂ© disszociál. Az utĂłbbi TEA jelenlĂ©tĂ©ben felgyorsĂtja a 3,5-diterc-butil-pirokatechin (H2dtbc) Ă©s a H3ap bázis-katalizált oxidáciĂłját. E korábban nem ismert promotor hatás oka az [Mn] monomer komplex kölcsönhatása a H2dtbc-bĹ‘l keletkezĹ‘ hidroperoxiddal, ami Ăşj, gyorsabb reakciĂłutat nyit meg az oxidáciĂł számára. A ferroxim(II) komplex szintĂ©n alkalmasnak bizonyult a pirokatechin oxidáz Ă©s a fenoxazinon szintetáz modellezĂ©sĂ©re.
ElőállĂtottunk 3 Ăşj dioximátovas(II) komplexet, amelyek pirokatechin oxidáz modellkĂ©nt működnek, egy esetben pedig dioxigenáz aktivitás is megfigyelhetĹ‘. A komplexek igen jĂłl oldĂłdnak metanolban Ă©s más oldĂłszerekben, ezĂ©rt szerkezetĂĽket oldatban határoztuk meg röntgensugár-szĂłrás segĂtsĂ©gĂ©vel.
Meghatároztuk az eddig vizsgált katalizátorainkra jellemző deutérium kinetikus izotópeffektust (KIE), amely megfelel az elméletileg várható 3-nál kisebb értéknek. | Low molecular manganese(II) and iron (II) complexes are functional models of the metalloenzymes catechol oxidase and phenoxazinone synthase. We have studied the kinetics and mechanism of the biomimetic oxidation of 3,5-ditert-butylcatechol (H2dtbc) and 2-aminophenol (H3ap) with O2. The new dioximatomanganese(II) dimer synthesized rapidly dissociates in MeOH to the monomeric complex [Mn]. In the presence of triethylamine [Mn] accelerates the base-catalzyed oxidation of H2dtbc and H3ap. This previously unknown promoter effect is due to complex formation between [Mn] and the hydroperoxide intermediate of the base-catalyzed oxidation, which opens up a new, faster reaction pathway for the oxidation. Ferroxime(II) is also a suitable model for both catecholase and phenoxazinone synthase action.
The 3 new dioximatoiron(II) complexes synthesized exhibit catecholase activity, one of them also showing dioxygenase activity. Due to their good solubility in MeOH and other common solvents, their structure was determined by X-ray scattering in MeOH solution
The deuterium kinetic isotope effects (KIE) for the catalyst complexes studied by us thus far, correspond to the theoretically expected value of less than 3
Szulfonamidszármazékok katalitikus karbonilezésének mechanizmusvizsgálata = Catalytic carbonylation of sulfonamide derivatives. Mechanistic studies
1. N-klĂłr-arĂ©nszulfonamidátok lĂ©gszáraz, vĂzmentes Ă©s rehidratált mintáit tanulmányoztuk IR-spektroszkĂłpiai Ă©s pordiffrakciĂłs mĂłdszerekkel. MegállapĂtottuk, hogy a nátriumsĂłk esetĂ©ben a vĂzleadás reverzibilis, mĂg a vĂzmentes káliumsĂłk levegĹ‘n tárolva nem rehidratálĂłdnak. A ?(OH) rezgĂ©s tartományán kĂvĂĽl a ?as(SO2) Ă©s a ?(SN) sávok is Ă©rzĂ©kenyek voltak a minták vĂztartalmára. 2. Tanulmányoztuk a kis tĂ©rigĂ©nyű bisz(dimetil-foszfino)-metán Ă©s bisz(dietil-foszfino)-metán ligandumokat tartalmazĂł [Pd2(P-P)2Cl2] komplexek reakciĂłit arĂ©nszulfonil-azidokkal. MegfigyeltĂĽk, hogy a sztĂ©rikus gátlás mĂ©rsĂ©klĹ‘dĂ©se a nitrĂ©nkomplex kĂ©pzĹ‘dĂ©sĂ©re vezetĹ‘ reakciĂł sebessĂ©gĂ©nek jelentĹ‘s növekedĂ©sĂ©t eredmĂ©nyezi, Ă©s elmarad az azidkomplexet eredmĂ©nyezĹ‘ mellĂ©kreakciĂł, melyet a [Pd2(dppm)2Cl2] dimer szulfonil-azidokkal mutatott reakciĂłiban tapasztaltunk. 3. A [Pd2(dppm)2Cl2] dimer Ă©s benzoil-azidok reakciĂłjával 9 Ăşj N-benzoil-nitrĂ©nkomplexet állĂtottunk elĹ‘, Ă©s jellemeztĂĽnk spektroszkĂłpiai Ă©s krisztallográfiai mĂłdszerekkel. Kimutattuk, hogy a hĂdhelyzetű imidonitrogĂ©natom Ă©s a karbonilszĂ©natom között kĂĽlönösen erĹ‘s p?-p? kapcsolat alakul ki, mely megakadályozza az N-C(O) kötĂ©s körĂĽli szabad rotáciĂłt. Kinetikai vizsgálataink során megállapĂtottuk, hogy a vizsgált reakciĂł követi a Hammett-egyenletet. | 1. The structural features of air dried, water free and rehydrated sodium and potassium N-chloroarenesulfonamidates were studied using IR spectroscopy and powder diffraction methods. It was observed that the water free samples of sodium salts are easily rehydrated when stored in air while the potassium salts are reluctant to absorb water under identical conditions. Beside the ?(OH) region between 3600-2900 cm1, the ?as(SO2) and ?(SN) bands were also sensitive to the water content of the samples. 2. The interaction of arenesulfonyl azides with dimeric palladium complexes incorporating sterically less demanding bis(dimethylphosphino)methane or bis(diethylphosphino)methane ligands was studied. The reduced bulkiness of the bridging ligands was reflected by an increased reaction rate and, as opposed to the reaction of the [Pd2(dppm)2Cl2] dimer with the same reagents, by the lack of a side reaction resulting in azide complexes. 3. Nine N-benzoyl nitrene complexes were synthesized by reacting the [Pd2(dppm)2Cl2] dimer with benzoyl azides. The novel compounds were characterized by spectroscopic and crystallographic methods. It was demonstrated that a p?-p? interaction between the bridging imido nitrogen atom and the carbonyl carbon atom results in unusually short N-C(O) bonds, which hampers the free rotation about this bond. The reaction was found to obey the Hammett equation
„...felkelés Magyarországon." A Szabad Európa Rádió Magyar Osztálya munkatársainak visszaemlékezései az 1956-os forradalom napjaira
Chiral resolution with supercritical carbon dioxide based on diastereomer salt formation
The efficient, environmentally benign synthesis of chiral compounds is a key issue in the chemical industry, especially in the pharmaceutical, food or pesticide
sectors. Reducing or eliminating the use of organic solvents and simplifying downstream processing can significantly alleviate the environmental impact of
chemical technologies. Supercritical carbon dioxide (scCO2), used as a solvent or reaction medium, addresses both issues.
In our work, we have investigated the resolutions of three racemic compounds: ibuprofen (IBU), cis-permethric acid (cPA) and cis-chrysanthemic acid
(cCA). The former is a widely marketed analgesic and anti-inflammatory agent, the latter two are important precursors in the manufacturing of synthetic pyrethroid-type pesticides. As resolving agents, we have used (R)-1-phenylethanamine (PhEA) and (S)-2-(N-benzylamino)butan-1-ol (BAB). The resolving agents were typically added in
half-mole equivalent quantity (according to the Pope–Peachy method), resulting in partial diastereomer salt formation. This was followed by supercritical fluid extraction (SFE) to separate the unreacted enantiomers from the diastereomeric salts.
We have used two experimental approaches, improving on our earlier where the diastereomers were prepared by vacuum evaporation of organic solvent from a
solution of the starting materials. The in situ method eliminates the use of organic solvents entirely, the starting materials are loaded into a high-pressure reactor and reacted in scCO2 directly. The antisolvent approach, involves preparing a concentrated solution of the starting materials in an organic solvent, and contacting it with scCO2, causing the precipitation of the diastereomeric salts. Although the use of
organic solvents is reduced, the main advantage of this method is a significant decrease in reaction times.
The in situ method was successfully applied to all three racemic compounds at 100–200 bar and 35–55 °C. IBU with PhEA, yielded diastereomers with ~60% enantiomeric excess (ee), albeit with 100–120 h reaction time. cPA and cCA were resolved using BAB, yielding diastereomer salts of >70% ee in <5 h reaction time.
Antisolvent resolution was successfully applied to cPA and IBU with PhEA, yielding diastereomers of >90% and >70% ee, respectively in <3 h reaction time
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