Nickel-catalysed hydrogen exchange of aniline, phenol, and their alkylated derivatives with deuterium oxide

1967 ◽  
Vol 20 (2) ◽  
pp. 297 ◽  
Author(s):  
CG Macdonald ◽  
JS Shannon
Keyword(s):  
Aromatic Ring ◽  
Hydrogen Exchange ◽  
Deuterium Oxide ◽  
Electron Donors ◽  
Hydroxyl Groups ◽  
Exchange Reactions ◽  
Hydrogen Atoms ◽  
Catalytic Exchange ◽  
Deuterium Distribution

Selective exchange of hydrogen atoms ortho to amino or hydroxyl groups, together with benzylic hydrogen atoms in aniline, phenol, and their C- alkylated derivatives, was achieved by allowing these compounds to react with deuterium oxide over nickel on kieselguhr at 99�. In addition to the benzylic hydrogen atoms, alkyl hydrogen atoms farther from the aromatic ring underwent slower exchange. Hydrogen atoms ortho to methoxyl did not exchange. Mechanisms of the catalytic exchange reactions are discussed in the light of the results of deuterium distribution measurements and poisoning experiments with electron donors.

Catalytic deuterium exchange reactions with organics. XIII. Characteristic reactions of the Group VIII transition metals

1965 ◽  
Vol 18 (7) ◽  
pp. 1003 ◽  
Author(s):  
JL Garnett ◽  
WA Sollich
Keyword(s):  
Transition Metal ◽  
Hydrogen Exchange ◽  
Deuterium Oxide ◽  
Metal Catalysts ◽  
Transition Metal Catalysts ◽  
Group Viii ◽  
Exchange Reactions ◽  
Substitution Mechanism ◽  
Π Complex ◽  
Complex Adsorption

Activation procedures and hydrogen exchange reactions with six Group VIII transition metal catalysts (Pt, Pd, Ru, Rh, Ir, Ni) are reported for three characteristic reaction systems: (i) deuterium oxide/benzene, (ii) deuterium oxide/naphthalene, and (iii) deuterium oxide/n-octane. Results of these exchange reactions indicate that both π-complex adsorption and the dissociative π-complex substitution mechanism previously established for platinum are applicable to other Group VIII transition metal catalysts. For general catalytic labelling with isotopic hydrogen, platinum was found to be the most efficient of the catalysts investigated.

Exchange reactions of olefins with deuterium oxide on ion-exchanged X-type zeolites

1971 ◽  
Vol 321 (1545) ◽  
pp. 259-273 ◽  
Keyword(s):  
Active Sites ◽  
Deuterium Oxide ◽  
Reaction Rates ◽  
Main Reaction ◽  
Exchange Reactions ◽  
Hydrogen Atoms ◽  
Carbonium Ion ◽  
Mass Spectrometric Technique ◽  
Carbonium Ions ◽  
Cation Charge

Reactions of propylene, ethylene, but-1-ene , isobutene and isobutane with D 2 O on ion-exchanged X-type zeolites have been followed by a mass spectrometric technique. Exchange was usually the main reaction but polymerization of olefins also occurred with some catalysts. All the hydrogen atoms in isobutene were exchanged at similar rates by a stepwise process but with propylene only five atoms were replaced. Exchange was complicated by simultaneous isomerization with but-1-ene. Isobutane reacted only at high temperatures but gave multiply exchanged products. The order of activity for exchange was isobutene ⪢ but-1-ene > propylene ⪢ ethylene, isobutane, and this order appeared to reflect the relative ease of formation of carbonium ions from the hydrocarbons. The character of the exchange reactions as well as the rates were in accord with mechanisms involving carbonium ion intermediates . The order of activity of the zeolites for the exchange of propylene was CeX, LaX > NiX, CuX, CoX > CaX > NaX and a correlation was found to exist between the apparent activation energy for exchange and a function of the cation charge. Reaction rates on NiX and CeX increased with increasing degree of ion-exchange and decreased with increasing amounts of D 2 O. There was evidence that in some cases the active sites were associated with acidic OH(OD) groups rather than the cations themselves.

Catalysis on evaporated metal films. V Reactions between cyclic hydrocarbons and deuterium

1954 ◽  
Vol 226 (1167) ◽  
pp. 472-489 ◽  
Keyword(s):  
Catalytic Activity ◽  
Molecular Geometry ◽  
Exchange Reactions ◽  
Hydrogen Atoms ◽  
Initial Product ◽  
Product Distributions ◽  
Redistribution Reaction ◽  
Multiple Exchange ◽  
Turn Over ◽  
Catalytic Exchange

Catalytic exchange reactions have been studied by means of a mass spectrometer between deuterium and cyclo Zopentane over palladium and cyclo Zohexane over rhodium, palladium, tungsten, platinum, nickel, oriented nickel and oriented rhodium. Activation energies, frequency factors and distributions of initial products were determined. The reactions involved multiple exchange by repeated second-point adsorption. Half the hydrogen atoms were readily exchanged, and a study of the temperature-dependence of the product distributions showed that it required an activation energy of 4 to 8 kcal/mole in excess of that for adcorption-desorption before the remaining half could be exchanged. Considerations of molecular geometry revealed that in order to exchange the second half of the hydrogen atoms the molecule had to ‘turn over’ on the surface, and for cyclo Zopentane the process for turning over must require second-point adsorption by the same carbon atom, but with cyclo hexane there is the alternative process of exchanging two adjacent equatorial hydrogen atoms. Theories are developed which account satisfactorily for the observed initial product distributions. The pressure-dependence of reaction rate was determined for cyclo hexane over palladium. Deuterium was strongly adsorbed and cyclo hexane weakly adsorbed. Exchange of cyclo hexane over oriented films of nickel and rhodium showed marked differences in distribution compared with unoriented films, suggesting different catalytic activity of different crystal planes. Only exchange was observed with benzene over nickel, but there was simultaneous exchange and deuteration over palladium. The initial product pattern over palladium showed that a redistribution reaction (in the sense of Wagner et al , (1952)) did not occur during deuteration and that benzene was adsorbed mainly as phenyl radicals during the exchange reaction. The reaction between cyclo propane and deuterium was examined over rhodium and simultaneous exchange and deuteration were observed. As determined by the temperature range for reaction the order of reactivity in exchange was cyclo propane > cyclo pentane > cyclo hexane, and the order of catalytic activity of the metals was similar to that observed previously for the exchange of other saturated hydrocarbons.

Hydrogen-exchange reactions via hot hydrogen atoms produced in the dissociation process of molecular hydrogen on Ir{111}

2001 ◽  
Vol 115 (21) ◽  
pp. 9947-9959 ◽  
Author(s):  
Kousuke Moritani ◽  
Michio Okada ◽  
Mamiko Nakamura ◽  
Toshio Kasai ◽  
Yoshitada Murata
Keyword(s):  
Molecular Hydrogen ◽  
Hydrogen Exchange ◽  
Exchange Reactions ◽  
Hydrogen Atoms ◽  
Dissociation Process

Transalkylierung und protonenkatalysierte C-C-Spaltung bei n-Butyl-und n-Pentylbenzol in der Gasphase / Transalkylation and Proton Catalyzed C-C-Cleavage of Gaseous n-Butyl and w-Pentyl Benzenes

1979 ◽  
Vol 34 (3) ◽  
pp. 495-501 ◽  
Author(s):  
C. Wesdemiotis ◽  
H. Schwarz ◽  
C. C. Van de Sande ◽  
F. Van Gaever
Keyword(s):  
Hydrogen Exchange ◽  
Closed Shell ◽  
Open Shell ◽  
Molecular Ions ◽  
Exchange Reactions ◽  
Intramolecular Exchange ◽  
Carbon Carbon Bond ◽  
Exchange Processes ◽  
Reaction Channels ◽  
Alkyl Benzenes

Abstract The investigation of several 13carbon and deuterium labelled n-butyl and n-pentyl benzenes demonstrate that chemical ionization (reagent gas: methane) induces specific carbon-carbon bond cleavages of the alkyl group. The extent of competing reaction channels as for instance direct alkene elimination versus dealkylation/reprotonation is analyzed. Partial hydrogen exchange processes between reagent ions and substrate molecules are restricted to the phenyl ring. Intramolecular exchange reactions between the side chain and the aromatic ring which are typical for the open shell molecular ions of alkyl benzenes are not observed for analogous closed shell cations.

scholarly journals F/OH ratio in a rare fluorine-poor blue topaz from Padre Paraíso (Minas Gerais, Brazil) to unravel topaz’s ambient of formation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
N. Precisvalle ◽  
A. Martucci ◽  
L. Gigli ◽  
J. R. Plaisier ◽  
T. C. Hansen ◽  
...  
Keyword(s):  
Supercritical Fluids ◽  
Fluorine Content ◽  
Minas Gerais ◽  
Hydroxyl Groups ◽  
Exchange Reactions ◽  
Silicate System ◽  
Mullite Phase ◽  
Anomalous Water

AbstractTopaz [Al2SiO4(F,OH)2] is one of the main fluorine-bearing silicates occurring in environments where variably acidic (F)/aqueous (OH) fluids saturate the silicate system. In this work we fully characterized blue topaz from Padre Paraíso (Minas Gerais, Brazil) by means of in situ synchrotron X-Ray and neutron powder diffraction measurements (temperature range 298–1273 K) combined with EDS microanalyses. Understanding the role of OH/F substitution in topaz is important in order to determine the hydrophilicity and the exchange reactions of fluorine by hydroxyl groups, and ultimately to characterize the environmental redox conditions (H2O/F) required for mineral formation. The fluorine content estimated from neutron diffraction data is ~ 1.03 a.f.u (10.34 wt%), in agreement with the chemical data (on average 10.0 wt%). The XOH [OH/(OH + F)] (0.484) is close to the maximum XOH value (0.5), and represents the OH- richest topaz composition so far analysed in the Minas Gerais district. Topaz crystallinity and fluorine content sharply decrease at 1170 K, while mullite phase starts growing. On the basis of this behaviour, we suggest that this temperature may represent the potential initial topaz’s crystallization temperature from supercritical fluids in a pegmatite system. The log(fH2O/fHF)fluid (1.27 (0.06)) is coherent with the fluorine activity calculated for hydrothermal fluids (pegmatitic stage) in equilibrium with the forming mineral (log(fH2O/fHF)fluid = 1.2–6.5) and clearly different from pure magmatic (granitic) residual melts [log(fH2O/fHF)fluid < 1]. The modelled H2O saturated fluids with the F content not exceeding 1 wt% may represent an anomalous water-dominant / fluorine-poor pegmatite lens of the Padre Paraíso Pegmatite Field.

Catalytic deuterium exchange reactions with organics. XXIV. Electron spin resonance studies of adsorption on platinum oxide

1966 ◽  
Vol 19 (4) ◽  
pp. 529 ◽  
Author(s):  
IT Ernst ◽  
JL Garnett ◽  
WA Sollich-Baumgartner
Keyword(s):  
Transition Metal Oxides ◽  
Hydrogen Exchange ◽  
Platinum Oxide ◽  
Active Species ◽  
Paramagnetic Species ◽  
Charge Transfer Complexes ◽  
Severe Reaction ◽  
Exchange Reactions ◽  
Spin Resonance ◽  
Solid Liquid

The formation of paramagnetic species on catalyst surfaces at room temperature through the interaction of polynuclear aromatics in solid, liquid, or solute form with hydrated platinum oxide (PtO2,2H2O) is reported. The results are attributed to the formation of charge-transfer complexes, where the transferred electrons couple weakly, forming essentially a "diradicaloid" complex with a low-lying, thermally populated, triplet state. The effect of solvent, particle size, oxygen, water of crystallization, and temperature on the generation and stability of these e.s.r. active species has been investigated. The possible importance of these paramagnetic species in catalytic self-activation and hydrogen exchange reactions has been discussed. The following Group VIII transition metal oxides gave no e.s.r. spectra under relatively severe reaction conditions such as 1 hr at 120�: PdO; Ru02,2H20; RuO2; Rh2O3; IrO2,2H2O; ReO2; and NiO.

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