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.

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.

Carbonyl halides of the Group VIII transition metals. II. Aquo adducts of Halobis(triphenylphosphine)dicarbonyls of cobalt(I)

1968 ◽  
Vol 21 (4) ◽  
pp. 891 ◽  
Author(s):  
JA Bowden ◽  
R Colton
Keyword(s):  
Solid State ◽  
Transition Metals ◽  
Group Viii ◽  
Exchange Reactions

Aquo adducts of halobis(triphenylphosphine)dicarbonylcobalt(1), Co(CO)2- (PPh3)2(H2O)X (X = Cl, Br, I), have been prepared by direct halogenation of the cation CO(CO)3(PPh3)2+, followed by addition of water. All of the compounds are stable in the solid state but they appear to undergo exchange reactions in solution.

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.

Catalytic deuterium exchange reactions with organics. XLII. The picolines, lutidines, thiophen, and furan on unsupported Group VIII transition metals

1968 ◽  
Vol 21 (5) ◽  
pp. 1221 ◽  
Author(s):  
GE Calf ◽  
JL Garnett
Keyword(s):  
Transition Metals ◽  
Lone Pair ◽  
Nickel Chloride ◽  
Platinum Oxide ◽  
Transition Metal Catalysts ◽  
The Novel ◽  
Group Viii ◽  
Exchange Reactions ◽  
Alkyl Groups ◽  
Nitrogen Lone Pair

The picolines (methylpyridines), lutidines (dimethylpyridines), thiophen, and furan have been exchanged with heavy water on a variety of Group VIII transition metals. Platinum is the most reactive general labelling catalyst for the picolines and lutidines, whereas cobalt catalyses exchange exclusively in the positions α to the nitrogen atom. The labelling pattern in the picolines and lutidines is similar to that of the alkylbenzenes in that (i)positions ortho to a methyl group are severely deactivated and (ii)positions flanked by two methyl groups are completely deactivated. Compensation effects are observed involving steric hindrance to adsorption from the alkyl groups and enhanced strength of adsorption from the nitrogen lone pair. The compensation effect in this charge-transfer adsorption slightly favours the nitrogen lone pair. Thiophen and furan generally do not exchange appreciably with pre-reduced Group VIII transition metal catalysts. Thiophen exchanges rapidly on self-activated platinum oxide whereas self-activated iridium oxide is the most useful for furan. With nickel chloride, furan exchanges exclusively in the or positions. A theory is proposed to account for the novel exchange in both thiophen and furan.

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.

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