bluuebunny/crossref_metadata_2025 huggingface dataset:
The methylation of inorganic tin by humic materials in an aquatic environment
Authors: Shugui Dai , Guolan Huang , Yong Cai
Published: January 2005

This paper presents a study of methylation of inorganic tin (SnCl4·5H2O) by humic materials (humic and fulvic acids) isolated from the sediment of Tianjin Harbor, Tianjin, China, and the effects of pH, salinity, and the concentration of inorganic tin on the production of methyltin were investigated.

These humic materials could methylate inorganic tin, and the methyltin product was mainly monomethyltin. Low molecular weight compounds of the humus fraction (i.e. fulvic acid) were more active in the methylation, which could be facilitated by salinity and affected by pH.
A study of the partitioning and sorptive behaviour of butyltins in the aquatic environment
Authors: Dowson P H , Bubb J M , Lester J N
Published: January 2005

This study was designed to investigate the partitioning and sorptive behaviour of tributyltin(TBT), and its degradation products dibutylitin (DBT) and monobutyltin (MBT), in the aquatic environment. Factorial experiments were undertaken to determine the importance of pH and particulate matter concentration in the sorption of butyltin compounds to solid phases. Results indicate that in freshwaters MBT, and to a lesser extent TBT, will be partitioned towards the particulate phase, whereas DBT exhibits a 50:50 partitioning between particulate and solution phases. In estuarine waters, whilst MBT will almost exclusively sorb on to particulates, TBT will be predominantly in the solid‐phase fractions but 10–30% may remain in solution. DBT, in contrast, is solubilized in estuarine waters. A more detailed investigation of TBT sorption and particulate matter concentration was undertaken using adsorption isotherms on different sediment types. The results from batch isotherm tests plotted according to the Freundlich adsorption model revealed that TBT adsorption varied with sediment type, increasing in the order sandy‐silt < silty‐sand < silty‐clay. TBT sorption was found to be reversible, indicating that contaminated sediments may release TBT to overlying waters following sediment distrubance. Interstitial water partitioning studies indicate that TBT predominates in the particulate phase with partition coefficients for TBT higher than for DBT and MBT. The TBT partition coefficient in interstitial waters appears to be related to total organic carbon loadings.
Antimicorbial effects of newly synthesized organotin(IV) and organolead(IV) derivatives
Authors: Kumari Anita , Tandon J P , Singh R V
Published: January 2005

Triorganotin(IV) and triorganolead(IV) derivatives of the types Me3Sn(SCZ) and Ph3Pb(SCZ) (where SCZ− is the anion of a semicarbanzone ligand) have been synthesized by substitution reactions of trimethyltin chloride and triphenyl‐lead chloride with semicarbazones derived from heterocyclic ketones. The resulting complexes have been characterized by elemental analyses, molecualr weight determinations and conductivity measurements. The mode of bonding has been established on the basis of infrared and 1H, 13C and 119Sn NMR spectroscopic studies. Some respresentative complexes have also been evaluated for their antimicrobial effects on different species of pathogenic fungi and bacteria; the results of these investigations have been reported in the present paper.
Polygermoxanes suitable for biochemical purposes. Part I. Digermoxanes (low‐viscosity oils)
Authors: Duverneuil Gilles , Mazerolles Pierre , Perrier Elisabeth
Published: January 2005

In order to replace silicones in some of their biomedical applications, e.g. syringe lubrication, implants ets., a series of digermoxanes (R1R2R3Ge)2O (R = n–alkyl, aryl) were synthesized. These compounds are thermally stable oils; their viscosities, depending on the nature of substituents, lie in the range 1–72 cPo (mPa s) at 20°C.
The association between selenium and humic substances in forested ecosystems—laboratory evidence
Authors: Gustafsson Jon Petter , Johnsson Lars
Published: January 2005

In the soils and aquatic systems of coniferous forests, selenium is usually associated with humic substances. To clarify further some of the mechanisms involved, labelled and unlabelled selenite were added to two forest floors and to a brownwater lake. Sequential extraction procedures and chromatographic methods were used to evaluate the resulting association between selenium and humic substances. It was observed that the forest floors fixed most of the added selenite by means of microbial reductive incorporation and that selenium was preferentially incorporated into lowmolecular‐weight fractions of the humic substances. By contrast, selenium reduction was much slower in the brown‐water lake and instead, inorganic complexation of selenite to metal–humic complexes was important during the experiment, provided that the concentrations of competing ligands were low.
Simplified sample preparation for GC speciation analysis of organotin in marine biomaterials
Authors: Ceulemans M. , Witte C. , Łobiński R. , Adams F. C.
Published: January 2005

Two simple sample preparation methods for the speciation analysis of triphenyltin and butyltin compounds in marine biotissues, using tetramethylammonium hydroxide (TMAH) solubilization and enzymic hydrolysis, have been developed and compared with conventional acid digestion. Derivatization was carried out in situ using sodium tetraethylborate (NaBEt4) without prior separation of the analytes from the tissue matrix. Separation and detection was performed using capillary gas chromatography (GC) coupled to microwave‐induced plasma atomic emission spectrometry (MIP AE) allowing detection limits of 2 ng g−1 (as tin) to be reached. The accuracy of the presented methods was demonstrated by the analysis of a fish reference material (NIES No. 11). the necessity for sample clean‐up is discussed and examples of the analysis of mussel tissue are shown.
Synthesis and radiopharmacological study of new metallated thiazolidines and dithioacetals of N‐allyl‐substituted cysteamine and methylcysteamine
Authors: Rima G. , Satge J. , Sentenac‐Roumanou H. , Fatome M. , Laval J. D. , Lion C. , Alazard O. , Chabertier P.
Published: January 2005

New germa‐ and silathiazolidines or germa‐ and siladithioacetals with N‐allyl‐substituted cysteamine and methylcysteamine ligands have been synthesized and their pharmacological properties (toxicity, radioprotective activity) have been studied. A notable decrease in the toxicity and a rather large increase in the radioprotective activity of these new organometallic derivatives compared to N‐allyl‐substituted cysteamine and methylcysteamine were observed.
The hydrodechlorination of chloroaromatic and unsaturated chloroaliphatic compounds using a nickel boride reagent
Authors: Yale M. , Keen C. , Bell N. A. , Drew P. K. P. , Cooke M.
Published: January 2005

A nickel boride reagent, prepared in situ by the reaction of nickel chloride with sodium borohydride, has been used to hydrodechlorinate and hydrogenate chloroaromatic compounds. The same reagent can also dechlorinate chloro‐olefinic compounds but chloroalkanes do not react. The reactions can be sustained by addition of hydrogen gas and the ratio of the aromatic to aliphatic hydrocarbons produced can be varied by addition of sodium hydroxide to the reaction mixture and by the duration of the reaction. The reactivity of polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), chlorobenzene and tetrachloroethylene have been studied. Capillary gas chromatography was used to follow the course of reactions and gas chromatography‐mass spectroscopy (GC–MS) was used for product identification.
Arsenobetaine and other arsenic species in mushrooms
Authors: Byrne A. R. , Šlejkovec Z. , Stijve T. , Fay L. , Gössler W. , Gailer J. , Lrgolic K. J.
Published: January 2005

Arsenic species in arsenic accumulating mush‐ rooms (Sarcosphaera coronaria, Laccaria amethystina, Sarcodon imbricatum, Entoloma lividum, Agaricus haemorrhoidaius, Agaricus placomyces, Lycoperdon perlatum) were determined. HPLC/ICP MS and ion‐exchange chromatogra‐ phy–instrumental neutron activation analysis (NAA) combinations were used. The remarkable accumulator Sarcosphaera coronaria (up to 2000 mg As kg−1 dry wt) contained only methylarsonic acid, Entoloma lividum only arsenite and arsenate. In Laccaria amethystina dimethylarsinic acid was the major arsenic compound. Sarcodon imbricatum and the two Agaricus sp. were found to contain arsenobetaine as the major arsenic species, a form which had previously been found only in marine biota. Its identification was confirmed by electron impact MS.
Synthesis and characterization of 7‐(CH3)3N‐4‐ {2,4‐(NO2)2C6H3S}‐nido‐7‐CB10H11 and its Biodistribution in C57B16 Mice Bearing B16 Melanoma
Authors: Morris John H. , Peters Gavin S. , Koldaeva Elena , Spryshkova Raisa , Borisov Gergy
Published: January 2005

7‐(CH3)3N‐4‐{2,4‐(NO2)2C6H3S}‐nido‐7‐CB10H11 has been synthesized through a Friedel‐Crafts substitution reaction on 7‐(CH3)3N‐nido‐7‐ CB10H12. A biodistribution study in mice with implanted B16 melanoma indicates that the compound locates in neoplastic tissue at concentrations which suggest that its use in 10B neutron capture therapy may be feasible.
On the reactions of molybdenum and tungsten carbonyls with trimethyl‐ and triethyl‐aluminium
Authors: Pasynkiewicz S. , Jankowski J.
Published: January 2005

Reactions of hexacarbonylmolybdenum, hexacarbonyltungsten and arene complexes of tricarbonylmolybdenum and tricarbonyltungsten with trimethyl‐ and triethyl‐aluminium have been studied. It has been found, based on IR and NMR spectra, that trialkylaluminium does not form complexes with hexacarbonyls of molybdenum and tungsten. Arene (mesitylene, toluene and benzene) complexes of tricarbonylmolybdenum form 1 : 1 complexes with triethylaluminium, and arene complexes of tricarbonyltungsten form complexes with trimethyl‐ and triethyl‐aluminium. Regardless of the molar ratios of reactants (arene)M(CO)3/AlEt3, only one of the three CO groups bonded to molybdenum or tungsten forms a complex with AlEt3. Fast exchange between free and complexed trialkylaluminium and an exchange of trialkylaluminium between all three carbonyl groups have been observed in benzene, toluene and decalin solutions. In the 1H NMR spectra of the products of the reactions of (mesitylene)Mo(CO)3 with AIEt3 and AIMe3, signals at –9 to –14ppm (characteristic for molybdenum hydrides) were present. It confirmed an alkylation of molybdenum followed by β‐ or α‐hydrogen elimination with the formation of the corresponding molybdenum hydrides, the actual catalyst of aromatic hydrocarbon hydrogenation.
Metabolism of arsenic compounds by the blue mussel mytilus edulis after accumulation from seawater spiked with arsenic compounds
Authors: Gailer Jürgen , Lrgolic K. J. , Francesconi Kevin A. , Edmondsxs John S.
Published: January 2005

Blue mussels (Mytilus edulis) were exposed to 100 μg As dm−3 in the form of arsenite, arsenate, methylarsonic acid, dimethylarsinic acid, arsenobetaine, arsenocholine, trimethylarsine oxide, tetramethylarsonium iodide or dimethyl‐(2‐hydroxyethyl)arsine oxide in seawater for 10 days. The seawater was renewed and spiked with the arsenic compounds daily. Analyses of water samples taken 24 h after spiking showed that arsenobetaine and arsenocholine had been converted to trimethylarsine oxide, whereas trimethylarsine oxide and tetramethylarsonium iodide were unchanged. Arsenobetaine was accumulated by mussels most efficienty, followed in efficiency by arsenocholine and tetramethylarsonium iodide. None of the other arsenic compounds was significantly accumulated by the mussels. Extraction of mussel tissues with methanol revealed that control mussels contained arsenobetaine, a dimethyl‐(5‐ribosyl)arsine oxide and an additional arsenic compound, possibly dimethylarsinic acid. Mussels exposed to arsenobetaine contained almost all their experimentally accumulated arsenic as arsenobetaine, and mussels exposed to tetramethylarsonium iodide contained it as the tetramethylarsonium compound. Mussels exposed to arsenocholine had arsenobetaine as the major arsenic compound and glycerylphosphorylarsenocholine as a minor arsenic compound in their tissues. The results show that arsenobetaine and arsenocholine are efficiently accumulated from seawater by blue mussels and that in both cases the accumulated arsenic is present in the tissues as arsenobetaine. Consequently arsenobetaine and/or arsenocholine present at very low concentrations in seawater may be responsible for the presence of arsenobetaine in M. edulis and probably also among other marine animals. The quantity of arsenobetaine accumulated by the mussels decreases with increasing concentrations of betaine. HPLC‐ICP‐MS was found to be very powerful for the investigation of the metabolism of arsenic compounds in biological systems.
Catalytic asymmetric synthesis of propranolol and metoprolol using a La–Li–BINOL complex
Authors: Sasai Hiroaki , Suzuki Takeyuki , Itoh Noriie , Shibasaki Masakatsu
Published: January 2005

The La–Li–(R)‐BINOL complex prepared from either lanthanum(III) chloride [LaCl3 · 7H2O] or [La(O‐i‐Pr)3] has made possible effective catalytic asymmetric syntheses of therapeutically important ß‐blockers such as propranolol and metoprolol. The possible stereochemical course of asymmetric nitroaldol reactions has been also clarified.
Syntheses of monodispersed methyl methacrylate oligomers via organolanthanide complexes and introduction of hydroxyl groups into the oligomer
Authors: Ihara Eiji , Taguchi Motoko , Yasuda Hajime
Published: January 2005

Methyl methacrylate (MMA) oligomers (Mn ≃ 2500) with a narrow molecular weight distribution (Mw/Mn>1.10) were synthesized by using a Cp*2SmMe(THF) initiator (Co=η −C). The oligomerization proceeds via a samarium enolate as the propagating species and the reaction of the living oligomer with p‐tolualdehyde produced p‐tolyl hydroxymethyl‐terminated oligoMMA.
Carbon–Halogen bond cleavage reaction catalyzed by organoyttrium hydride (in situ) and lanthanide alkoxides
Authors: Qian Changtao , Zhu Chengjian , Zhu Dunming
Published: January 2005

Organic halides can be ubiquitous long‐lived contaminants to the environment. Dehalogenation of organic halides with sodium hydride (NaH) as reductant catalyzed by two varieties of lanthanides was reported in respect of environmental remediation. The first catalyst is a dicyclopentadienyl yttrium halide, and organoyttrium hydride was thought to be the reactive species. The second catalyst is a lanthanide isopropoxide which showed higher catalytic reactivity, and an aggregate is involved in the suggested mechanism.
Acetalization of ketones and aldehydes catalyzed by lanthanoid trisulfonates
Authors: Okano Tamon , Michihashi Tomonori , Kiji Jitsuo
Published: January 2005

Lanthanoid sulfonates are found to be good catalysts for the acetalization of aldehydes and ketones with methyl orthoformate in methanol. The catalytic activity of Ln(OTf)3 (OTf, trifluoromethanesulfonate) increases in the order of La<Sm<Gd<Er<Yb. As sulfonates such as trifluoromethylsulfonates and (1S)‐10‐camphorsulfonates are more soluble in organic solvents than the chlorides, the acetalization in ether or dichloromethane and the exchange reaction of alkoxy groups between acetals and alcohols can be achieved under mild conditions.
Photomodulation of conformational states. IV. Integrin‐binding RGD‐peptides with (4‐aminomethyl)phenylazobenzoic acid as backbone constituent
Authors: Milbradt Alexander G. , Löweneck Markus , Krupka Simone S. , Reif Maria , Sinner Eva‐Kathrin , Moroder Luis , Renner Christian
Published: January 2005

In previous studies we have investigated octapeptides backbone‐cyclized by (4‐amino)phenyl azobenzoic acid (APB) or (4‐aminomethyl)phenylazobenzoic acid (AMPB) and containing the active‐site sequence Cys‐Ala‐Thr‐Cys‐Asp from the thioredoxin reductase. The conformational and redox properties of these peptides were strongly dependent on the isomeric state of the azobenzene chromophore. Using the same approach we were successful in constructing photoresponsive ligands for αvβ3 integrin containing the Arg‐Gly‐Asp (RGD) sequence as binding motif. For achieving maximal conformational restriction of the peptide a reduced ring size compared to our previous azobenzene peptides was employed in the cyclic peptide c[Asp‐D‐Phe‐Val‐AMPB‐Lys‐Ala‐Arg‐Gly‐]. Conformational properties of the trans and cis isomers of this peptide in solution were investigated by CD and NMR and were found to differ markedly from the thioredoxin derived azobenzene peptides. In a second peptide, c[Asp‐D‐Phe‐Val‐Lys‐AMPB‐Ala‐Arg‐Gly‐], shifting the position of the chromophore lead to a marked decrease in affinity. With the availability of the x‐ray structure of a cyclic RGD‐pentapeptide bound to αvβ3 integrin (PDB entry 1L5G) modeling of possible bound conformations for trans and cis isomers of both azobenzene peptides was possible. Notably, both peptides in either isomeric form share the same overall conformation in the bound state according to our molecular dynamics simulations. © 2005 Wiley Periodicals, Inc. Biopolymers 77: 304–313, 2005
Biomedical informatics and granularity
Authors: Kumar Anand , Smith Barry , Novotny Daniel D.
Published: January 2005

An explicit formal‐ontological representation of entities existing at multiple levels of granularity is an urgent requirement for biomedical information processing. We discuss some fundamental principles which can form a basis for such a representation. We also comment on some of the implicit treatments of granularity in currently available ontologies and terminologies (GO, FMA, SNOMED CT). Copyright © 2004 John Wiley & Sons, Ltd.
The seventh annual Bio‐Ontologies meeting
Authors: Lord Phillip , Stevens Robert
Published: January 2005

The Annual Bio‐Ontologies Meeting has now reached its seventh consecutive year, running as a special interest group (SIG) of the much larger ISMB conference. This year's meeting in Glasgow had approximately 100 attendees. Since the advent of the Gene Ontology, which coincided with the first Bio‐Ontologies Meeting, we have seen a year‐on‐year strengthening of the field; bio‐ontologies has moved from being dominated by computer science to be led by biological applications; discussion is less about ‘what is an ontology?’ and more about ‘how to build an ontology which is fit for purpose?’. This strengthening of the field can be seen elsewhere. Both the main ISMB conference and this year's Pacific Symposium on Biocomputing (PSB) have seen a large number of submissions to their ontologies track. For the first time a selection of the papers from the SIG is being published in this issue of Comparative and Functional Genomics. We hope that this will complement the publications of the larger conferences, bringing to a wider audience the cutting edge research that characterizes the Bio‐Ontologies SIG. Copyright © 2004 John Wiley & Sons, Ltd.
Analysis of single‐locus tests to detect gene/disease associations
Authors: Roeder Kathryn , Bacanu Silviu‐Alin , Sonpar Vibhor , Zhang Xiaohua , Devlin B.
Published: January 2005

A goal of association analysis is to determine whether variation in a particular candidate region or gene is associated with liability to complex disease. To evaluate such candidates, ubiquitous Single Nucleotide Polymorphisms (SNPs) are useful. It is critical, however, to select a set of SNPs that are in substantial linkage disequilibrium (LD) with all other polymorphisms in the region. Whether there is an ideal statistical framework to test such a set of ‘tag SNPs’ for association is unknown. Compared to tests for association based on frequencies of haplotypes, recent evidence suggests tests for association based on linear combinations of the tag SNPs (Hotelling T2 test) are more powerful. Following this logical progression, we wondered if single‐locus tests would prove generally more powerful than the regression‐based tests? We answer this question by investigating four inferential procedures: the maximum of a series of test statistics corrected for multiple testing by the Bonferroni procedure, TB, or by permutation of case‐control status, TP; a procedure that tests the maximum of a smoothed curve fitted to the series of of test statistics, TS; and the Hotelling T2 procedure, which we call TR. These procedures are evaluated by simulating data like that from human populations, including realistic levels of LD and realistic effects of alleles conferring liability to disease. We find that power depends on the correlation structure of SNPs within a gene, the density of tag SNPs, and the placement of the liability allele. The clearest pattern emerges between power and the number of SNPs selected. When a large fraction of the SNPs within a gene are tested, and multiple SNPs are highly correlated with the liability allele, TS has better power. Using a SNP selection scheme that optimizes power but also requires a substantial number of SNPs to be genotyped (roughly 10–20 SNPs per gene), power of TP is generally superior to that for the other procedures, including TR. Finally, when a SNP selection procedure that targets a minimal number of SNPs per gene is applied, the average performances of TP and TR are indistinguishable. Genet. Epidemiol. © 2005 Wiley‐Liss, Inc.
Reactions of unsymmetrically substituted allyl radicals with methyl radicals
Authors: Montague D. C.
Published: January 2005

The Hg(63P1) photosensitized decompositions of 3‐methyl‐1‐butene, 2‐methyl‐2‐butene, 3,3‐dimethyl‐1‐butene, and 2,3‐dimethyl‐1‐butene have been used to generate 1‐methylallyl, 1,2‐dimethylallyl, 1,1‐dimethylallyl, and 1,1,2‐trimethylallyl radicals in the gas phase at 24 ± 1°C. From a study of the relative yields of the CH3 combination products, the relative reactivities of the reaction centers in each of these unsymmetrically substituted ambident radicals have been determined. The more substituted centers are found to be the less reactive, and this is ascribed primarily to greater steric interaction at these centers during reaction. Measurement of the ratio of trans‐ to cis‐2‐pentene formed from the 1‐methylallyl radical, combined with published values for this ratio at higher temperatures, enabled the differences in entropy and heat of formation of the trans‐ and cis‐forms of this radical to be calculated as 0.62 ± 0.85 J mol−1 K−1 and ‐ 0.63 ± 0.25 kJ mol−1, respectively, at 298K. Approximate values of the disproportionation/combination ratios for reaction of CH3 with 1,1‐dimethylallyl and 1‐methylallyl have been estimated and used to compute rate constants for the recombinations of tert‐butyl and isopropyl radicals that are in agreement with recently published data.
Thermolysis of dimethyl sulfoxide
Authors: Thyrion F. C. , Debecker G.
Published: January 2005

The thermal decomposition of dimethyl sulfoxide at small extent of reaction has been studied at temperatures of 297‐350°C and pressures of 10–400 Torr. The major products CH4, C2H4, and SO2 were shown to follow first‐order kinetics. The activation energies for production of each was about 48 kcal·mole−1. A chain mechanism has been postulated in the light of the results of isotopic substitution experiments.
Investigation of the rate coefficient for O(3p) + NO2 → O2 + NO
Authors: Slanger Tom G. , Wood Bernard J. , Black Graham
Published: January 2005

Measurements of the rate coefficient of the reaction (O3P) + NO2 → O2 + NO have been made at 296°K and 240°K, using the technique of NO2* chemiluminescent decay. Values of 9.3 × 10−12 cm3 molec−1 sec−1 at 296°K and 10.5 × 10−12 cm3 molec−1 sec−1 at 240°K were obtained, in excellent agreement with the recent results of Davis, Herron, and Huie [1]. The earlier lower values may have resulted from loss of NO2 on surfaces.
Recalculation of data on the thermal decomposition of 1,1‐difluoroethane and 1,1,1‐trifluoroethane
Authors: Tsang Wing
Published: January 2005

Disagreements in rate constants and parameters between published results on the decomposition of 1,1‐difluoroethane and 1,1,1‐trifluoroethane are shown to originate from incorrect specification and setting of reaction conditions in one of the studies. When corrected, applicable results are in excellent agreement.
Kinetics of diffusion‐controlled reaction between chemically asymmetric molecules. II. Approximate steady‐state solution
Authors: Šolc K. , Stockmayer W. H.
Published: January 2005

The previously published equation for the rate of a diffusion‐limited bimolecular reaction between chemically asymmetric molecules is studied numerically for the case that one of the reactant molecules is uniform. The results are reproduced quite well by a simple approximate chemical‐kinetic steady‐state scheme and, in principle, allow estimates of the size of the reactive region and of the activation‐controlled rate to be made from the observed dependence of rate on solvent viscosity. The simple scheme is easily generalized to the case of two nonuniform reactants. In general, restriction of reactivity to some fraction of the molecular surface (i.e., a steric factor) must reduce the observable reaction rate, but to an extent which is moderated by the rotational diffusion of the reactant molecules.
Kinetics and mechanism of the substitution of olefinic ligands by triphenylantimony in (π‐monoolefin) tetracarbonyliron complexes
Authors: Cardaci G.
Published: January 2005

The kinetics of the reaction

have been studied in toluene solution. The reaction occurs by a dissociative mechanism and the observation of an appreciable mass law retardation effect shows that Fe(CO)4 is produced as an intermediate. Analysis of the effect of the substituent X on the stability of the complexes leads to the conclusion that π‐backbonding between the metal and the olefinic ligand is the major cause of the M‐olefin bond strength.
Kinetics of the reactions of 2,4,6‐tri‐t‐butylphenoxyl with cumene hydroperoxide, cumylperoxyl radicals, and molecular oxygen
Authors: Griva A. P. , Denisov E. T.
Published: January 2005

Reactions of 2,4,6‐tri‐t‐butylphenoxyl (TBP) with cumene hydroperoxide (ROOH), cumylperoxyl radicals (RO2), and molecular oxygen in benzene solution have been investigated kinetically by the ESR method. The rate constant of the reaction TBP + ROOH magnified image has been estimated in the temperature range 27°‐75°C: log10(k−7/M−1sec−1) = (7.1 ± 0.4) ‐ (10.9 ± 0.6 kcal mole−1)/θ

The ratio of the rate constants of reactions TBPH + RO2 magnified image products has been determined from the experimental dependence of the rate constant of reaction TBP with ROOH on [TBPH]0/[TBP]0. Putting k7 = 4.0 × 103M−1sec−1, we obtain k8 = (2.0 ± 0.2) × 108M−1sec−1 at 30°C. The reaction of TBP with O2 obeys the kinetic law −d[TBP]/dt = k′[O2][TBP]2. This is in accordance with scheme TBP + O2 ← TBP ⃛O2 [I]; TBP ⃛O2 + TBP · products, log10 (k′/M−2sec−1) = (−14.5 ± 0.9) + (27.2 ± 1.4)/θ at 66°−78°C, where ° = 2.303RT.
A simple empirical method for the estimation of activation energies in radical molecule metathesis reactions
Authors: Alfassi Ze'ev B. , Benson Sidney W.
Published: January 2005

Several new empirical methods are presented for the prediction of activation energies E of the metathetical transfer reaction of single bonded atoms in radical‐molecule reactions of the type A· + BC → AB + C· The methods assign additive contributions to E for the endgroups A· and C·, neglecting the effect of the transferred atom B. Most of the predicted values agree to within l kcal mol−1 with the experimental activation energies (average error = 0.82 and standard deviation = 1.02 kcal mol−1). This is comparable to the best of the more complex schemes available for such estimation.
Kinetics into the steady state. I. study of the reaction of oxygen atoms with methyl radicals
Authors: Slagle Irene R. , Pruss Frank J. , Gutman David
Published: January 2005

The exponential relaxation of CH3, produced by the reaction O + C2H4 → CH3 + HCO, to its steady‐state concentration was quantitatively monitored after the reactants were mixed. The relaxation profiles yield the rate constant of the reaction O + CH3 → H2CO + H equal to (1.85 ± 0.28) × 10‐10 cm3/molecule‐sec at 300°K. Ancillary experiments yielded values for the rate constant for the reaction of O atoms with C2H4 at 300°K, the average of which is 7.7 × 10‐12 cm3/molecule‐sec. The experimental technique, which employs a fast‐flow reactor coupled to a photoionization mass spectrometer, is described in detail and its potential discussed.
Electron spin resonance and kinetic study of the photolysis of p‐Flouranil (tetrafluoro‐p‐benzoquinone) in dioxane
Authors: Vyas H. M. , Wan J. K. S.
Published: January 2005

The photochemistry of p‐fluoranil in dioxane was studied by electron spin resonance (ESR) and the ESR‐rotating sector technique. The transient photoradical is identified as the p‐tetrafluorobenzosemiquinone neutral radical with a hyperfine splitting of 1.1 gauss for the hydroxy proton and the fluorine hyperfine splittings of 3.8 and 14.1 gauss for the meta and ortho fluorines, respectively. The radicals decayed by self‐disproportionation with a second‐order rate constant at room temperature of approximately 3.2 × 109M−1s−1. The activation energy of the decay process is found to be about 2.4 ± 0.4 kcal/mole.
Kinetics of reactions of Schiff base complexes of iron(II). V. Reactions of the complex of the hexadentate ligand NN‴‐bis‐[α‐(2‐pyridyl)benzylidene]triethylenetetramine in acid solution and with hydroxide, cyanide, and peroxodisulphate
Authors: Gardner E. R. , Mekhail F. M. , Burgess J.
Published: January 2005

The preparation and characterization of the iron(II) complex of the hexadentate Schiff base ligand NN‴‐bis‐[α‐(2‐pyridyl)benzylidene]triethylenetetramine are reported. Kinetic patterns and rate constants for aquation of this complex, and for its reactions with hydroxide, cyanide, and peroxodisulphate have been determined. Activation parameters for the reaction with cyanide, in aqueous solution, are ΔH‡ = 24.3 kcal/mole and ΔS‡ = +1 cal/deg‐mole.
Pathways of proton transfer in acetal hydrolysis
Authors: Dunn Ben M.
Published: January 2005

The process of acetal hydrolysis is analyzed in terms of the competing steps of proton transfer and heavy atom reorganization. The results of this analysis are portrayed in a series of three‐dimensional reaction coordinate diagrams. The observed pathway of hydrolysis (A‐1, general acid catalyzed, or spontaneous) is shown to depend on the energy of the various possible intermediates in these reactions.
Molecular relaxation processes in triatomic molecules. II. The N2–CO2 system
Authors: Thommarson Ronald L. , Berend George C , Benson Sidney W.
Published: January 2005

Translation–vibration (T–V) and vibration–vibration (V–V) energy transfer processes in the N2–CO2 system were investigated using classical trajectory techniques. Two empirical interaction potentials were employed. One is comprised of independent, atom–atom Morse‐type functions operating between nonbonded atoms. The other included these atom–atom Morse functions plus Coulombic terms to account for the quadrupole–quadrupole intertion. Both interaction potentials led to similar T–V results. However, the result that CO2(v3) is excited ∼103 times more efficiently than N2(v = 1) was obtained, which is at variance with existing analytical theories of T–V energy transfer employing purely repulsive short‐range potentials. Different V–V energy transfer probabilities were obtained from the two interaction potentials. The most important finding is that only when electrostatic orientation effects are combined with short‐range repulsive interactions is the near‐resonant

V–V transfer found to be the dominant energy transfer path. This interaction potential also crudely accounts for the negative temperature dependence observed for this near‐resonant V–V transfer at low temperatures (300–1000°K).
Determination of D[C6F5‐I] by the toluene carrier method
Authors: Krech Michael J. , Price Stanley James W. , Yared Wayne F.
Published: January 2005

The pyrolysis of C6F5I has been studied by the toluene carrier method over the temperature range of 900–978°K with contact times of 0.4–2.0 seconds and total pressures of 11.2–19.5 torr. Percent decomposition ranged from 8.6 to 97.7%. With toluene‐to‐C6F5I molar ratios of greater than 150, 85–100% of the C6F5 released abstracts a hydrogen atom from toluene to produce C6F5H. No significant quantities of I2 were observed and the only major gaseous product was HI. Within the limits of the experimental method the decomposition of C6F5I was first order and homogeneous.

Least squares analysis of log k1 and 103/T(C6F5I → C6F5 + I) values gives

while a weighted line of best fit yields.

Based on this latter equation D[C6F5I] at 298°K is estimated as 66.2 kcal/mole.
Oxidation of hydrocarbons in the presence of added hydroperoxide. On the determination of rate constants by the hydroperoxide method
Authors: Niki Etsuo , Okayasu Kisaburo , Kamiya Yoshio
Published: January 2005

Oxidation of tetralin in the presence of tert‐butyl hydroperoxide and tetralyl hydroperoxide, initiated with azobisisobutyronitrile, was studied at 60°C in order to examine the complications involved in the hydroperoxide method devised by Howard and Ingold. From literature data on absolute rate constants and our rates of oxidation, cross termination rate constants and contributions of each elementary propagation and termination step were computed. It was confirmed that this method was quite useful in determining the cross propagation rate constant, but it was also demonstrated that the rate of oxidation should be measured at very low conversion and with quite high concentrations of hydroperoxide, especially when the peroxy radical derived from the added hydroperoxide has a much lower termination rate constant than that from the oxidizing substrate.
Communication to the editor pentyl radical isomerizations: Evidence for a 1,2 or 1,3 hydrogen migration
Authors: Tardy D. C.
Published: January 2005

Vibrationally excited pentyl‐1, ‐2, and ‐3 radicals were formed selectively by the addition of thermal H atoms to the various pentene isomers with approximately 47 kcal/mole of vibrational energy. Decomposition products other than those expected, along with their pressure dependences, support the fact that either 1,2 or 1,3 hydrogen migrations with either a 3‐ or 4‐member cyclic transition state is occurring with a ka of approximately 3 × 105 or 6 × 105 sec−1. A corresponding critical energy of 33 or 31 kcal/mole is found.
The thermochemical kinetics of retro‐ “ene” reactions of molecules with the general structure (allyl) XYH in the gas phase. IX. The thermal unimolecular decomposition of ethyallylether in the gas phase
Authors: Egger Kurt W. , Vitins Peter
Published: January 2005

The thermal decomposition of ethylallylether (EAE) has been studied in the gas phase over the temperature range of 560–648°K. Propylene and acetaldehyde are the only reaction products observed. The reaction is apparently homogeneous in nature and independent of the pressure of EAE and of added foreign gases. The experimetally determined first‐order rate constants, using the internal standard technique, fit the Arrhenius relationship log k(s−1) = 11.84 ± 0.29 − (43.57 ± 0.77 kcal/mole)/2.303RT. Independently the same rate constants are obtained, based on the amounts of products formed. The observed activation parameters are in general agreement with expectations based on the concept of a 6‐center 1,5‐H‐shift retro‐“ene” reaction mechanism, and they agree with previous results obtained for the similar reactions involving alkylallylamines and olefins.
On the accuracy of the hydroperoxide method of determining absolute rate constants for hydrogen atom abstraction by the tert‐butylperoxy radical
Authors: Howard J. A. , Chenier J. H. B.
Published: January 2005

Measurements of rates of oxygen absorption and steady‐state peroxy radical concentrations for the autoxidation of tetralin in the presence of tert‐butyl hydroperoxide have shown that the rate constant for reaction of the tert‐butylperoxy radical with tetralin at 60°C is approximately 11.0 M−1 s−1. This rate constant is about a factor of 4 larger than the value recently reported by Niki, Okayasu, and Kamiya for this reaction.

The present work emphasizes that great care should be taken when the hydroperoxide method is used to estimate cross‐propagation rate constants for a substrate as reactive as tetralin at a temperature as high as 60°C.
The kinetics and mechanism of the slow oxidation of hydrogen
Authors: Shakhnazaryan I. K. , Sachyan G. A. , Philipossyan A. G. , Nalbandyan A. B.
Published: January 2005

A low‐temperature matrix isolation method has been developed which makes possible the isolation and detection of HO2 radicalsfrom a gas‐phase radical chain‐reaction system containing atomic H, O and OH radicals as well. The formation of HO2 radicals is demonstrated in the rarified hydrogen flame. The same radicals are observed to exist during the slow oxidation reaction of hydrogen between the second and third inflammation limits

The kinetics of accumulation of HO2, H2O2, and H2O has been studied as a function of total pressure, composition of reacting mixtures, temperature, and diameter and the treatmentof the surface of the reaction vessel. It has been established that in a reactor treated with boric acid, the concentration of HO2 radicalsis in the order of 101 2–101 4 particles/cm3. The kinetic relationship obtained confirms the necessity of including the following step in the mechanism of slow oxidation of hydrogen:

For a quantitative description of the experimental results, calculationsof the complete mechanism of the slow reaction are performed by computer methods. The values of the rate constants of the elementary reactions that enter into the mechanism proposed were taken from published data. Some of them were varied by small intervals to give a better agreement with experimental values. The agreement justifies the mechanism proposed for the experimental conditions employed.
Ozone–olefin reactions in the gas phase 1. Rate constants and activation energies
Authors: Becker K. H. , Schurath U. , Seitz H.
Published: January 2005

Reactions of ozone with simple olefins have been studied between 6 and 800 mtorr total pressure in a 220‐m3 reactor. Rate constants for the removal of ozone by an excess of olefin in the presence of 150 mtorr oxygen were determined over the temperature range 280 to 360° K by continuous optical absorption measurements at 2537 Å. The technique was tested by measuring the rate constants k1 and k2 of the reactions (1) NO + O3 → NO2 + O2 and (2) NO2 + O3 rarr; NO3 + O2 which are known from the literature. The results for NO, NO2, C2H4, C3H6, 2‐butene (mixture of the isomers), 1,3→butadiene, isobutene, and 1,1 ‐difluoro‐ethylene are 1.7 × 10−1 4 (290°K), 3.24 × 10−17 (289°K), 1.2 × 10−1 4 exp (–4.95 ± 0.20/RT), 1.1 × 10−1 4 exp (–3.91 ± 0.20/RT), 0.94 × 10−1 4 exp ( –2.28 ± 0.15/RT), 5.45 ± 10−1 4 exp ( –5.33 ± 0.20/RT), 1.8 ×10−17 (283°K), and 8 × 10−20 cm3/molecule ·s(290°K). Productformation from the ozone–propylene reaction was studied by a mass spectrometric technique. The stoichiometry of the reaction is near unity in the presence of molecular oxygen.
Rate constant for H+H+Ar = H2 + Ar from 1300 to 1700 K
Authors: Mallard W. G. , Owen J. H.
Published: January 2005

Shock tube experiments on the decay of OH‐radical concentration after shock‐initiated combustion of H2:O2:Ar = 10:1:89 mixtures were analyzed to give the rate constant 1 × 1015 cm6mol−2s−1for the reaction H + H + Ar = H2 + Ar overthe temperature range 1300 to 1700 K.
The temperature dependence of vibration–vibration energy exchange between CO and COS
Authors: Richman Dennis C. , Lev‐on Miriam , Millikan Roger C.
Published: January 2005

The present study reports the measurement of the V–V energy transfer rates for the CO*COS system in the temperature range of 195 to 370°K. The measured rates exhibit a slight inverse temperature dependence. The experimental results are compared to prediction based on a model of long‐range dipole–dipole interactions between colliding molecules. The effect of single quantum rotational transitions is compared to that of multiquantum rotational transitions.
Absolute rate constants for the reactions O(3P) atoms with HCl and HBr
Authors: Brown Raymond D. H. , Smith Ian W. M.
Published: January 2005

A flow tube method has been used to determine rate constants for the elementary reactions:
equation image
Oxygen atoms were produced by adding a small excess of NO to a stream of partially dissociated nitrogen, and their reaction with hydrogen halide was monitored by observing the intensity of the NO + O afterglow. Experiments were carried out at temperatures from 293 to 440°K with HCl, and from 267 to 430°K with HBr. The role of secondary reactions was minimised and the residual effects were allowed for. The rate constants for the primary reactions could be matched by Arrhenius expressions:

where the units are cm3/molec·sec and the errors correspond to a standard deviation.
The kinetics of the Diels–Alder addition of cyclopentadiene to acetylene and the decomposition of norbornadiene
Authors: Walsh Robin , Wells Jean M.
Published: January 2005

The title reactions have been investigated in a static system. The addition of acetylene to cyclopentadiene (CPD) results in formation of norbornadiene (BCH), cycloheptatriene (CHT), and toluene (T), while BCH decomposition produces CPD, C2H2, CHT, and T. Kinetic studies, comprising both product–time evolution and initial pressure variation, support a mechanism
equation image
These reactions are almost certainly homogeneous and molecular in nature. Least mean square analysis of the data yield for temperatures of 525–656°K, log k−1 (1./mole·s)=7.51±0.05− (24.19±0.15 kcal/mole)/RT ln 10, and for temperatures of 584–630°K,
Kinetics and mechanism of the pyrolysis of pentachloroethane
Authors: Houser Thomas J. , Cuzcano Teodomiro
Published: January 2005

The rate of the inhibited pyrolysis of pentachloroethane was studiedover the temperature range of 820 to 865°K using the toluene‐carrier technique in a stirred‐flow reactor. The pyrolysis rate was found to be first order in reactant, and the rate constant is described by k=1011.6±0.7 exp [(−48,200±2600)/RT] sec−1. An increase by a factor of 6.6 in the surface/volume of the reactor had a negligible effect on the rate. This observation, in addition to a reevaluation of earlier kinetic data for the pyrolysis of pentachloroethane, lead to the following conclusions concerning the pyrolysis mechanism. The initiation and termination as well as the propagation reactions were homogeneous, the termination involved both Cl and C2Cl5 radicals (crosstermination), and autocatalysis was caused by interaction between chlorine and pentachloroethane rather than by dissociation of molecular chlorine.
The Influence of solvent and crown polyethers on the nucleophilic reactivity of potassium tert‐Butylperoxide, potassium tert‐Butoxide, and some other oxygen bases
Authors: Curci Ruggero , di Furia Fulvio
Published: January 2005

The rates of reaction of t‐BuOOK, t‐BuOK, n‐BuOOK, and p‐MeC6H4OKwith p‐nitrophenyl diphenylphosphinate 1 and with p‐nitrophenyl benzoate 2 have been measured in toluene both in the absence and in the presence of crown polyether dicyclohexyl‐18‐crown‐6 3a. The rates of nucleophilic displacementon 1 by HOO−, t‐BuOO−, and some “nonalpha” oxyanions in water have also been determined. Solvent transfer from water to toluene results in increasing the nucleophilic reactivity of the t‐butyl hydroperoxide anion. Rate ratios QQa are given which allow one to estimate the enhanced reactivity of t‐BuOO− (an α‐nucleophile) compared to oxygen nucleophiles of comparable base strength toward 1 and 2. These are for substrate 1, Qα (water) ≃ 6.5 and Qα (toluene) ≃ 2.7; for substrate 2, Qα (water) ≃ 5.5 and Qα (toluene) ≃ 5. The hypothesis is advanced that solvation is not a major factor in determining the α‐effect of the t‐butylhydroperoxide anion.
Rate constants for the decarboxylation of the t‐butoxicarbonyl radical and concurring radical terminations directly obtained by kinetic ESR
Authors: Rüegge D. , Fischer H.
Published: January 2005

Rate constants of various simultaneous reactions of t‐butoxicarbonyl and t‐butyl radicals generated by photolysis of t‐butylpivalate in n‐heptane are directly determined by kinetic electron spin resonance. The temperature dependence of the decarboxylation reaction t‐BuOĊO → t‐Bu. + CO2 obeys log )K/S−1( = 13.8−49.0/θ where θ = 2.303 RT/kJ . mol−1. The self‐ and cross‐termination of the radicals are diffusion limited.
Kinetics and mechanism of the explosive reaction of carbon monoxide and oxygen
Authors: Ahmed S. , Back M. H.
Published: January 2005

A new technique is described for quantitative measurement of the conditions of reactant concentration at ignition in mixtures of carbon monoxide and oxygen. A thin film of carbon covering the surface of a quartz reaction vessel reacted with oxygen to form carbon monoxide and small quantities of water. Explosions were observed above 900 K over the pressure range 15–100 torr with ratios of CO/O2 far below those hitherto explored. The onset of explosion was favored by the addition of hydrogen, methane, and water and was inhibited by the addition of inert gases. A simple mechanism predicts the occurrence of an explosion over a wide range of product composition and total pressure.
The intimate ion pair mechanism in the maximally inhibited elimination kinetics of methyl 4‐chlorobutyrate and methyl 5‐chlorovalerate in the gas phase
Authors: Chuchani Gabriel , Dominguez Rosa M. , Rotinov Alexandra
Published: January 2005

The gas phase elimination of methyl 4‐chlorobutyrate and methyl 5‐chlorovalerate has been reexamined, in a static system and seasoned vessel, over the temperature range of 419.6–472.1°C and pressure range of 45–108 torr. The reactions, under maximum inhibition with propene, are homogeneous, unimolecular, and obey a first‐order rate law. The rate coefficients are given by the following Arrhenius equations: for methyl 4‐chlorobutyrate, log (k1(s−1) = (13.41 ± 0.60) ‐ (226.8 ± 8.2) kJ/mol/2.303RT; and for methyl 5‐chlorovalerate, log k1(s−1) = (13.20 ± 0.02) ‐ (227.6 ± 0.3) kJ / mol / 2.303RT. The pyrolysis rates are found to be about a half of the rates reported in a previous work. As already advanced, the carbomethoxy substituent appears to provide anchimeric assistance in the elimination process, where normal dehydrochlorination and lactone formation arise from an intimate ion pair type mechanism. The partial rates towards each of these products have been determined and reported.
Effects of alkenes on the thermal decomposition of propane part II. Influence of ethylene
Authors: Dombi A. , Huhn P.
Published: January 2005

Experiments with propane‐ethylene mixtures in the temperature range 760–830 K resulted in refinement of the role of ethylene inhibition in the decomposition of propane. The source of the rate‐reducing effect of ethylene is the reaction
equation image
This replaces the decomposition chains more slowly by means of the reactions
equation image

equation image

equation image
than H‐atoms do by direct H‐abstraction from propane. Analysis of the ratios of the product formation rates showed that the selectivity of the ethyl radical for the abstraction of hydrogen of different bond strengths from propane was practically the same as that of the H‐atom. The ratio of the rate constants of hydrogen addition to ethylene and methyl‐hydrogen abstraction from propane by the H‐atom (3) was determined

as was that of the decomposition and the similar H‐abstraction of the ethyl radical

Interpretation of the influence of ethylene required the completion of the mechanism with further initiation of the reaction
equation image
besides termination via ethyl radicals.