James A. Happe

On the mechanism of kerogen pyrolysis

Abstract Aromaticities determined by 13 C n.m.r. are reported for five shale oil samples (Green River formation) prepared under widely different pyrolysis conditions. In the absence of high-pressure hydrogen, the total amount of aromatic carbon in the products is nearly twice that in the raw shale. This is true for a wide range of pyrolysis conditions, although the distribution of aromatic carbon between the oil and carbonaceous residue changes. High-pressure hydrogen appears to inhibit both the formation of additional aromatic carbon during pyrolysis and the coking of aromatic oil. An improved kerogen decomposition mechanism is reported that accounts for these effects and provides for changes in the aromaticity of the liquid product with pyrolysis conditions. Further work is necessary to make it quantitative and account for gas formation.

Isotropic NMR Shifts in Pyridine‐Type Bases Complexed with Paramagnetic NiII and CoII Acetylacetonates

Isotropic contact interaction shifts in the proton NMR spectra of pyridine‐type molecules coordinated with paramagnetic nickel (II) and cobalt (II) acetylacetonates have been observed. The role of π‐ and σ‐ bonding frameworks in the transfer of unpaired electron spin density from the metal ion to ligand protons is considered. Pseudocontact interactions appear to be significant in the cobalt systems but not in the nickel systems. When the pseudocontact contribution to isotropic shifts in cobalt systems is factored out there remain contact shifts which are in good agreement with the observed nickel shifts. It is concluded that the unpaired electrons in metal eg orbitals of both cobalt and nickel systems cause contact shifts in the pyridine‐type ligands whereas the t2g electron in the cobalt system does not. The t2g electron gives isotropic shifts by contributing to anisotropy in the electronic g factor.

35Cl NMR studies of the active site zinc of horse liver alcohol dehydrongenase

Abstract 35 Cl-NMR has been used to study the active site Zn ions of horse liver alcohol dehydrogenase. The Cl − probe interaction with the Zn ions is completely removed by the binding of two molecules of reduced coenzyme per molecule of enzyme. Adenosine diphosphate ribose (ADPR) also effectively removed the Cl − Zn interaction. Orthophenanthroline (OP) has no effect on the Cl − line width, but is an effective competitor with coenzyme and ADPR for the Zn ions. The OP results suggest that the Zn is octahedrally coordinated in the enzyme. The pH profile of the Cl − broadening is relatively flat from pH 5.5 to pH 9.0. It decreases above pH 9.0 with an apparent pK of 9.8 ± 0.2 in 0.5M NaCl.

The identification of a new heterocyclic amine mutagen from a heated mixture of creatine, glutamic acid and glucose

A new heterocyclic amine mutagen was isolated from a dry-heated reaction of the natural meat components creatine, glutamic acid and glucose. Heating creatine and glutamic acid alone had only one seventh of the Ames/Salmonella mutagenic activity of the glucose, creatine and glutamic acid mixture. The major mutagenic compound was purified by HPLC using the Ames/Salmonella test to guide the purification. The mutagen has a molecular weight of 244 and a composition of C12H12N4O2 as determined by high-resolution mass spectrometry. NMR and IR spectral data suggest the structure is a 2,6-diamino-3,4-dimethyl-7-oxo-pyrano[4,3-g]benzimidazole. Mutagenic activity in strains TA1538, TA98 and TA100, was approximately 7000, 5200, and 550 revertants per microgram, respectively. The formation of this mutagen from natural meat components suggests that it may be present in cooked food. The preferential formation of this mutagen with glucose shows that glucose can be important in dry-heated mutagen-forming reactions.

1H, 19F and 11B nuclear magnetic resonance characterization of BF3: amine catalysts used in the cure of C fibre-epoxy prepregs

Abstract 1H, 19F and 11B nuclear magnetic resonance studies are reported which characterize the complexes of boron trifluoride with monoethylamine and with piperidine, BF3:NH2C2H5 and BF3:NHC5H10, respectively. These complexes are used as catalysts for the cure of high performance C fibre-epoxy composities from prepregs. The chemical compositions of commercial BF3:amine complexes are variable and contain BF4− and BF3(OH)− salts together with other unidentified highly reactive species. The BF3:amine complexes, which are susceptible to hydrolysis, also partially convert to the BF4− salt (i.e. BF4−NH3+C2H5) upon heating. This salt formation is accelerated in dimethyl sulphoxide solution and in the presence of the epoxides that are present in commercial prepregs. Commercial C fibre-epoxy prepregs are shown to contain either BF3:NH2C2H5 or BF3:NHC5H10 species together with their BF4− salts and a variety of boron-fluorine or carbon-fluorine prepreg species. Considerable variation in the relative quantities of BF3:amine to its BF4− salt was observed from prepreg lot to lot, which will cause variable viscosity-time-temperature prepreg cure profiles. It is concluded that the chemically stable and mobile BF4− salt is the predominant catalytic species, acting as a cationic catalyst for the prepreg cure reactions. During the early stages of cure the BF3:amine catalysts convert to the BF4− salts in the presence of epoxides, whereas the BF3-prepreg species are susceptible to catalytic deactivation and immobilization.

Identification of the mutagenic quinoxaline isomers from fried ground beef.

Two mutagens isolated from fried-beef patties were compared to a series of synthetic structural isomers of 2-aminodimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-aminotrimethylimidao[4,5-f]quinoxaline (DiMeIQx). Comparison by NMR spectrometry and HPLC coelution showed that one beef mutagen (molecular weight of 213) was identical to the 8-MeIQx isomer not the 7-Me isomer. Another quinoxaline beef mutagen, having 3 methyl groups (molecular weight of 227), had an NMR spectrum different from the 5,8- or 7,8-DiMeIQx isomers, but not clearly distinguishable from the 4,8- or 4,7-DiMeIQx isomers. The HPLC separation of the DiMeIQx isomers and subsequent addition of the beef mutagen showed the beef-derived compound to coelute with the 4,8-DiMeIQx and not with the 4,7-DiMeIQx. The number and position of methyl groups was responsible for a 7-fold range of mutagenic response in the Ames/Salmonella assay. In conclusion, the major quinoxaline mutagens isolated from fried beef were identified as 8-MeIQx and 4,8-DiMeIQx isomers.

Methylcobalamin methylation of chloroplatinate: bound chloride, valence state, and relative mutagenicity

Abstract A methyl‐Pt compound formed by incubating K2PtCl6 with methylcobalamin (MeB‐12) is further characterized with respect to its chloride content, its Pt oxidation state, and its electro‐phoretic mobility. The complexed chloride has been determined from nuclear magnetic resonance (NMR) spectra of the Cl displaced by competing thiocyanate (SCN ) anions. Release of 3 chlorides per Pt combined with a Me/Pt ratio of 1.0 indicates a metal coordination number of 4. This is in agreement with X‐ray photoelectron spectra (ESCA) which show that the majority of the Me‐Pt product contains Pt in the +2 valence state. Based on this data and the anionic nature of the product at pHs from 2.5–7.5 it 2‐is presently represented as MePtCl3. In comparison to the closely related complexes K2PtCl4 and K2PtCl6, MePtCl3 ‐2 is slightly less cytotoxic to an auxotrdphic Chinese hamster ovary cell line (CHO AUXB1). All three of these chloro‐Pt compounds at concentrations of 15–70 μ? induce a 6–10 fold increase in the frequency o...

Platinum tetrachloride: Mutagenicity and methylation with methylcobálamin

It was reported earlier that methylcobalamin (MeB‐12) plus K2PtCl6 or Na2PtCl6 under acidic conditions yields a single square planar Pt2+ species, MePtCl2‐ 3. A reaction between MeB‐12 and PtCl4 in...

Proton Resonance Shifts for the Systems HNO3–H2O and HNO3–KNO3

Proton resonance shifts have been measured for the concentrated region of the nitric acid‐water system and also for the system nitric acid‐KNO3. The nitrate ion is very effective in unshielding the protons of nitric acid and further information is presented on the solvation of this ion in the anhydrous acid. Chemical shifts in nitric acid‐water solutions are interpreted in terms of the associated nature of nitric acid. The effect of the self‐ionization of anhydrous nitric acid on the chemical shift for this liquid is evaluated. Also, it was found that the chemical shift could be used for very accurate analysis of nitric acid‐water mixtures in the concentrated acid region.