Deuterium Exchange Reactions with Substituted Aromatics. II. The Monohalogenated Benzenes and Naphthalenes

1961 ◽  
Vol 14 (3) ◽  
pp. 441 ◽  
Author(s):  
JL Garnett ◽  
WA Sollich
Keyword(s):  
Complex Formation ◽  
Ionization Potential ◽  
Heavy Water ◽  
Product Formation ◽  
Ortho Position ◽  
Exchange Reactions ◽  
Naphthalene Derivatives ◽  
Aromatic Molecules ◽  
Π Complex ◽  
Benzene Series

The platinum-catalysed exchange between heavy water and the monohalogenated benzenes and naphthalenes has been studied at 130-180 �C. Rate of exchange is found to decrease with increasing size of halogen substituent. Naphthalene derivatives exchange more slowly than the corresponding members of the benzene series. Rate of exchange increases with increasing ionization potential. From this correlation it is postulated that chemisorption of aromatic molecules on active platinum occurs through π-complex formation. In the benzene series, exchange in the ortho-position is slower than in the meta- or para-positions which react at approximately the same speed. ortho-Exchange increases with increasing size of halogen substituent. This deuteration technique is applicable to tritium labelling especially for aromatics since radiochemical by-product formation is minimized.

Catalytic deuterium exchange reactions with organics. XL. Pyridine, the quinolines, azines, and aniline on unsupported Group VIII transition metals

1968 ◽  
Vol 21 (4) ◽  
pp. 961 ◽  
Author(s):  
GE Calf ◽  
JL Garnett ◽  
VA Pickles
Keyword(s):  
Charge Transfer ◽  
Transition Metals ◽  
Heavy Water ◽  
Heterocyclic Compounds ◽  
Group Viii ◽  
Borohydride Reduction ◽  
Exchange Reactions ◽  
Catalyst Activation ◽  
Π Complex ◽  
Sodium Borohydride Reduction

Pyridine, the quinolines, pyridazine, pyrimidine, pyrazine, s-triazine, and aniline have been exchanged with heavy water on the following Group VIII transition metals: Fe, Co, Ni, 0s. Ru, Rh, Pd, Ir, and Pt. Three types of catalyst activation have been used, including self-activation, hydrogen and sodium borohydride reduction of the inorganlo salts. Platinum is the most useful catalyst for general exchange whereas cobalt possesses valuable specificity for selective a exchange in a large number of the heterocyclic compounds. A kinetic study of the deuteration of pyridine on platinum has been performed. The exchange results have been rationalized in terms of charge-transfer adsorbed intermediates. E.s.r. has been used to support this conclusion for the interaction between pyridine and potassium chloropalladite. π-Complex mechanisms have been proposed to explain the observed deuteration behaviour.

Catalytic deuterium exchange reactions with organics. XXIII. Deformylation during the deuteration of aromatic α-hydroxy acids and related compounds

1966 ◽  
Vol 19 (2) ◽  
pp. 211 ◽  
Author(s):  
GE Calf ◽  
JL Garnett
Keyword(s):  
Carboxylic Acid ◽  
Heavy Water ◽  
Mandelic Acid ◽  
Hydroxy Acids ◽  
Exchange Reactions ◽  
Catalyst Activation ◽  
Π Complex ◽  
Complex Adsorption ◽  
Benzilic Acid ◽  
Related Compounds

The transition-metal catalysed exchange of aromatic a-hydroxy acids with heavy water has been studied. Benzilic acid and its 00'-dichloro- and pp'-dimethyl derivatives simultaneously deformylate with the formation of the corresponding diary1 ketones. Mandelic acid and derivatives are stable under these conditions and only deuterate, whereas 9-hydroxyfluorene-9-carboxylic acid decomposes quantitatively to 9-fluorenol and 9-fluorenone. Benzhydrol decomposes appreciably to benzophenone. The effect of catalyst (soluble Fe, Co, Ni, Ru, Rh, Pd, Ir, and Pt chlorides versus insoluble oxides) and the method of catalyst activation (hydrogen, sodium borohydride, and self-activation) on the exchange and deformylation reactions have been studied. The results are interpreted in terms of a mechanism based on π-complex adsorption.

Deuterium Exchange Reactions with Substituted Aromatics. III. Heterocyclics and Polycyclic Hydrocarbons

1962 ◽  
Vol 15 (1) ◽  
pp. 56 ◽  
Author(s):  
JL Garnett ◽  
WA Sollich
Keyword(s):  
Adsorption Mechanism ◽  
Lone Pair ◽  
Deuterium Exchange ◽  
Catalyst Poisoning ◽  
Polycyclic Aromatics ◽  
Exchange Reactions ◽  
Aromatic Molecules ◽  
Π Complex ◽  
Additional Interaction ◽  
A Charge

Platinum-catalysed deuterium exchange reactions between heavy-water and polycyclic aromatics and heterocyclics have been investigated. The results confirm a charge-transfer-no-bond adsorption mechanism for catalytic chemisorption. Degree of catalyst poisoning increases with decreasing ionization potential for aromatic molecules of similar complexity, e.g., anthracene and phenanthrene. As the number of nodal planes in the bonding orbitals of the more complex polycyclic aromatics increases, a decrease is observed in catalyst poisoning. Exchange of pyridine is slower than benzene and this is attributed to an additional interaction of the pyridine molecule with the catalyst through its lone-pair of electrons. The reactivity of n-octane supports extension of the authors' π-complex chemisorption theory to molecules possessing only σ-electrons. Anisole, cyclohexane, nitrobenzene, cyclohexene, and phenyl cyanide exchange in an anomalous manner.

ChemInform Abstract: π-Complex Formation and Collapse in Electrophilic Halogenation of Aromatic Substrates.

ChemInform ◽  
1987 ◽  
Vol 18 (47) ◽  
Author(s):  
O. M. E. EL-DUSOUQUI ◽  
K. A. M. MAHMUD ◽  
Y. SULFAB
Keyword(s):  
Complex Formation ◽  
Aromatic Substrates ◽  
Π Complex

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.

Proximity Effect in Arene Pi-Complex Formation

1966 ◽  
Vol 21 (9) ◽  
pp. 823-827 ◽  
Author(s):  
Minoru Tsutsui ◽  
Morris N. Levy
Keyword(s):  
Complex Formation ◽  
Proximity Effect ◽  
Grignard Reagent ◽  
Reaction System ◽  
Coupling Reaction ◽  
Reaction Products ◽  
Hydrogen Elimination ◽  
Trans Stilbene ◽  
Π Complex ◽  
Aryl Grignard Reagent

A proximity effect in arene π-complex formation from the reaction system of an aryl Grignard reagent and anhydrous chromic chloride was investigated. The yields of arene π-complexes and any accompanying reaction products were compared by the systematic variation of the aryl Grignard reagent employed. Phenyl Grignard gave the best yield of π-complex followed by the benzyl, mesityl and β-ethyl phenyl analogues. The styryl and phenylacetylenyl analogues did not form any π-complexes.The coupling reaction of benzyl groups gave a new π-complex, π-bibenzyl-π-toluene chromium, along with toluene, bibenzyl and trans-stilbene.Trans-stilbene was found without forming a trace amount of cis-stilbene. A mechanism for this stereospecific and α-hydrogen elimination coupling reaction is proposed.

scholarly journals Complex formation in a liquid-liquid extraction-chromogenic system for vanadium(IV)

2019 ◽  
Vol 17 (1) ◽  
pp. 599-608 ◽  
Author(s):  
Kiril B. Gavazov ◽  
Vassil B. Delchev ◽  
Nikolina P. Milcheva ◽  
Galya K. Toncheva
Keyword(s):  
Complex Formation ◽  
Ground State ◽  
Experimental Spectrum ◽  
Molar Absorptivity ◽  
Equilibrium Geometry ◽  
Ortho Position ◽  
Unusual Structure ◽  
Tetrazolium Chloride ◽  
State Equilibrium ◽  
Equilibrium Geometries

AbstractThe azo dye 4-(2-thiazolylazo)orcinol (TAO) and the cationic ion-pair reagent 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) were examined as constituents of a water-chloroform extraction-chromogenic system for vanadium(IV). The effects of TAO concentration, TTC concentration, pH and extraction time were examined. Under the optimum conditions the extracted complex has a composition of 1:2:1 (V:TAO:TTC). The absorption maximum, molar absorptivity and constant of extraction were determined to be λmax=544 nm, ε544=1.75×104 dm3 mol–1 cm–1 and Log Kex=4.1. The ground state equilibrium geometries of the possible monoanionic VIV-TAO 1:2 species were optimized by the HF method using 3-21G* basis functions. Their theoretical time dependent electronic spectra were simulated and compared with the experimental spectrum. The best fit was obtained for the structure in which one of the TAO ligands is tridentate, but the other is monodentate (bound to VIV through the oxygen which is in the ortho-position to the azo group) and forms a hydrogen bond N–H...O=V through its protonated heterocyclic nitrogen. Based on this unusual structure, which can explain some peculiarities of the complex formation between VIV and commonly used azo dyes, the ground state equilibrium geometry of the whole ternary 1:2:1 complex was computed at the HF and BLYP levels.

Catalytic deuterium exchange reactions with organics. XXVII. The alkylbenzenes on self-activated Group VIII transition metals

1966 ◽  
Vol 19 (12) ◽  
pp. 2299 ◽  
Author(s):  
BD Fisher ◽  
JL Garnett
Keyword(s):  
Transition Metal Oxides ◽  
Exchange Process ◽  
Kinetic Studies ◽  
Platinum Oxide ◽  
Activation Process ◽  
Group Viii ◽  
Exchange Reactions ◽  
Π Complex ◽  
Cis And Trans ◽  
In Cis

Exchange reactions between heavy water and the alkylbenzenes have been investigated on the following self-activated Group VIII transition metal oxides: PtO2,2H2O; PdO; Rh2O3; IrO2,2H2O; RuO2,H2O; ReO2; and Ni2O3. All oxides except Ni2O3 are self-activated by benzene up to 180�. Order of ease of self-activation is Pt > Pd > Rh, Ru, Ir > Re > Ni. Trends in deuteration rates of the alkylbenzenes on self-activated platinum oxide are generally similar to those obtained on hydrogen prereduced platinum. At 130�, some differences in reactivity are observed and these are attributed to reagent displacement effects from the presence of small percentages of dimer (1%) associated with the self-activation process. Compared with hydrogen prereduced catalysts, significant differences in isotope orientation are observed with certain alkylbenzenes on self-activated catalysts. Multiple deuteration effects which are accentuated on self-activated catalysts have been used to confirm isotope orientation and also the participation of a π-complex mechanism for the exchange process. Isomerization and exchange in cis- and trans-stilbenes on self-activated platinum have also been interpreted by the dissociative n-complex substitution mechanism. The advantages of self-activated catalysts in general deuterium and tritium labelling work have been evaluated. Possible correlations between exchange results and electron spin resonance data for charge-transfer adsorption on the above oxides are discussed. Preliminary kinetic studies with self-activation are also reported.

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