bluuebunny/crossref_metadata_2025 huggingface dataset:
Periodontal disease in the oldest‐old living in Kungsholmen, Sweden: findings from the KEOHS project
Authors: Holm‐Pedersen Poul , Russell Stefanie Luise , Avlund Kirsten , Viitanen Matti , Winblad Bengt , Katz Ralph V.
Published: May 2006

Aims: The Kungsholmen Elders Oral Health Study evaluated the oral health status of generally healthy, community‐dwelling persons aged 80 years and over living in Stockholm, Sweden. This paper reports periodontal disease findings and evaluates the distribution by sociodemographic factors.

Methods: Eligible persons were identified through the Kungsholmen Project, an ongoing, longitudinal, population‐based study of older adults. A total of 121 study subjects received a periodontal examination.

Results: The mean pocket probing depth was 2.6 mm and the mean clinical attachment loss was 3.7 mm. Gingival bleeding was common. Over half of all study participants met the criteria used for “serious periodontitis” (SP). In the best fit adjusted odds ratio (OR) model, males were 3.1 times more likely than females to have “SP” (OR=3.1, 95% CI 1.2, 8.0), a statistically significant observation. A sub‐analysis of the differences in proportion of participants with SP revealed that the difference by sex also increased by age.

Conclusions: These findings document the substantial and ongoing impact of periodontal disease in a sample of generally healthy, community dwelling older adults and underscore the importance of continued periodontal disease prevention and treatment in the oldest‐old.
Incidence of bacteremia after chewing, tooth brushing and scaling in individuals with periodontal inflammation
Authors: Forner Lone , Larsen Tove , Kilian Mogens , Holmstrup Palle
Published: May 2006

Scientific rationale for study: Bacteremia occurs with various frequency after oral procedures. Periodontal disease may affect the incidence, magnitude, duration and bacterial spectrum of bacteremia.

Principle findings: The incidence and magnitude of bacteremia after scaling was significantly higher in periodontitis than in gingivitis patients and healthy control individuals. In periodontitis patients, the magnitude of bacteremia was associated with gingival index, plaque index and number of sites with bleeding on probing, but not with probing pocket depth measurements.

Practical implications: The prevention and treatment of periodontal diseases appear to be crucial for the prevention of bacteremia associated with oral procedures.
A convenient synthesis of the flavor and scent material (±)-γ-(Z)-6-dodecenolactone and some analogs via N-chloroamide thermolysis
Authors: Benn Michael , Vohra Kanwal Nain
Published: May 2006

N-Chloro-N-propyl-threo-6,7-dibromododecanamide, prepared by the successive bromination and N-chlorination of N-propyl-(Z)-6-dodecenamide, was subjected to thermolytic homolysis in aqueous dioxane to yield a mixture of products from which, after zinc debromination, γ-6-(Z)-dodecenolactone was isolated. Some analogs of this lactone were similarly prepared.
2,3,12,13-Tetraselena[4,4]metacyclophane. A disparity with the literature
Authors: Mitchell Reginald H.
Published: May 2006

The synthesis of 2,3,12,13-tetraselena[4,4]metacyclophane (1) by alkaline hydrolysis of meta-xylylene selenocyanate (3a) in 8% yield is described and is shown to have different properties to those described for 1 by Günther and Salzmann. The variable temperature pmr spectra of 1 is described as is its conversion to 2,11-diselena[3,3]metacyclophane (4) by tris(diethylamino)phosphine.
Reactions of 4-hydroxy-6-methyl-2-pyridone with aldehydes
Authors: Findlay John A. , Krepinsky Jiri , Shum Foo Yu , Tam Wah Hung John
Published: May 2006

A novel condensation reaction of 4-hydroxy-6-methyl-2-pyridone with aldehydes giving 4 has been explored. A number of by-products are accounted for. The mass spectra of the major condensation products are discussed.
The shielding effect of heterosubstituents in 13C nuclear magnetic resonance
Authors: Beierbeck H. , Saunders J. K.
Published: May 2006

The effect of a heterosubstituent X on 13C chemical shifts, in conformations characterized by dihedral angles of 60°, is analyzed in terms of α-shifts, heteroatom–carbon (XC), hydrogen–heteroatom (HX) and carbon–heteroatom (CX) gauche interactions, and nonbonded γ(X) and δ(X) interactions. The more general parameters [Formula: see text] describe the β-heteroatom shifts in conformations in which the dihedral angles [Formula: see text] differ from 60°. The shielding effects of chlorine, exocyclic oxygen, and endocyclic nitrogen are analyzed.
A 13C nuclear magnetic resonance study of aliphatic ketone protonation in sulfuric acid solutions
Authors: McClelland Robert A. , Reynolds William F.
Published: May 2006

A 13C nmr investigation of the protonation in sulfuric acid of the aliphatic ketones MeCOR (R = Me, Et, i-Pr, tert-Bu), 3-pentanone, and the cyclic ketones from cyclobutanone through cyclooctanone is reported. With the exception of cyclobutanone which is considerably less basic, these ketones are all very similar in their basicity, with half-protonation in the region 73–78% H2SO4. The acidity dependence of the protonation is discussed; there appears to be a small dependence on molecular size. 13C nmr is shown to be a suitable alternative to 1H nmr in the study of the protonation of weak organic bases in strongly acidic solutions.
On the rigidity of planar tricoordinate carbon
Authors: Wolfe Saul , Schlegel H. Bernhard , Whangbo Myung-Hwan
Published: May 2006

A linear relationship has been found between the computed out-of-plane bending force constants of the methylene group and the total charge transfer from X to CH2 for the series XCH2+ (X = H, CH3, NH2, OH, F) and CH2=X (X = O, NH, CH2, S). As the electron-withdrawing power of X increases, out-of-plane bending becomes more difficult in all cases. Two complementary interpretations of this result are proposed.
13C kinetic isotope effects and reaction coordinate motions in transition states for SN2 displacement reactions
Authors: Buddenbaum Warren Edward , Shiner Jr. Vernon Jack
Published: May 2006

Reaction coordinate motions and 13C kinetic isotope effects at 25 °C have been calculated for the SN2 reactions of methyl iodide with iodide, cyanide, and chloride ions and for the SN2 reaction of benzyl bromide with hydroxide ion using transition state models characterized by single interaction force constant, F12, between the bond being formed and the bond being broken. The isotope effect calculations show that the dependence of calculated 13C isotope effects on transition state symmetry found by Willi and Sims etal. holds true for reaction barriers corresponding to small values of νL, while the symmetry dependence observed by Bron holds true for barriers corresponding to large values of νL.νL was also found to have a strong influence on the reaction coordinate motions of the transition states. In particular, for the methyl iodide reactions an increase in νL increases the distortion of the methyl group in the direction expected for a classical SN2 reaction. Finally, reaction coordinate motions were used to show that the model proposed by Bron for the borderline region between SN1 and SN2 reaction mechanisms predicts an increase in the 13C kinetic isotope effect with decreasing total bond order and not the decrease suggested by Bron.
Base-catalyzed intramolecular displacements on certain 1,2-epoxides
Authors: Srinivasan V. , Warnhoff E. W.
Published: May 2006

Intramolecular displacement by hydroxyl on the 1,2-epoxide group under basic or neutral conditions has been studied for seven of the stereoisomeric 1,2-diols derived by oxidation of the exocyclic double bond of 1. In six of the examples (the seventh is ambiguous) the single or largely predominant product is that one of the less strained cis-fused isomers which has the fewer unfavourable steric interactions leading to it, without regard to whether the displacement occurs at the secondary or tertiary epoxide carbon.
Carbon-13 nuclear magnetic resonance spectra of organic sulfur compounds. Substituent chemical shift (s.c.s.) effects in the 4-thiazoline-2-thione series
Authors: Still I. W. J. , Plavac N. , McKinnon D. M. , Chauhan M. S.
Published: May 2006

13C nmr data have been obtained for a series of 4-thiazoline-2-thiones. Substituent chemical shift (s.c.s.) effects for methyl and phenyl substitution have been collated and are discussed in comparison with s.c.s. effects in other heterocyclic systems. Some attempt has also been made to compare our data with those reported previously for the thiazoles and for some thiones in the isothiazole series.
Influence de la nature des ions et sur l'évolution structurale des weberites A2B2O7: les weberites Cd 2−xSrxSb2O7
Authors: Desgardin G. , Robert C. , Raveau B.
Published: May 2006

A new series of solid solution Cd2−xSrxSb2O7 (0 ≤ x ≤ 2) of the weberite type has been prepared and characterized. Examination of the weberite structure has revealed the existence of three critical metal–oxygen distances. The proposed ordering of the A ions permits the structural features of these compounds to be explained.
On the extension of the Hückel rule to polycyclic non-alternant conjugated hydrocarbons
Authors: Gutman I. , Trinajstić N.
Published: May 2006

General rules for aromatic stability of non-alternant polycyclic conjugated hydrocarbons are obtained using graph–theoretical considerations. Every pair of odd-membered rings contained in the conjugated molecule has a stabilizing effect if one ring is of the size 4N + 1 and the other of the size 4N + 3. If both rings are of the size 4N + 1 or 4N + 3, a destabilizing effect occurs. This conclusion holds both for fused and disjointed rings. The π-electron System is said to be relatively more stable if the number of (4N + l)-membered rings is equal to the number of (4N + 3)-rings.
The nuclear Overhauser effect between phosphorus and hydrogen in selected organo phosphorus compounds
Authors: Beierbeck H. , Martino R. , Saunders John K. , Benezra Claude
Published: May 2006

The nuclear Overhauser effect (nOe) observed between phosphorus and hydrogen together with carbon and phosphorus spin lattice relaxation time (T1) data are presented for a number of phosphorus containing compounds. The dominant mechanism for phosphorus relaxation is shown to be the dipole-dipole interaction between phosphorus and hydrogen. From the nOe and T1 data the determination of phosphorus–hydrogen internuclear distances is demonstrated.
Basicité de solvants dipolaries aprotoniques
Authors: Domain Robert , Rinfret Marcel , Benoit Robert L.
Published: May 2006

The basicities of five dipolar aprotic solvents, sulfolane, propylene carbonate, acetonitrile, dimethylformamide, dimethyl sulfoxide, and of water have been characterized by using as parameter the solvation enthalpy of the gaseous proton. The corresponding values of ΔH(g → s)(H+) are deduced from experimental calorimetric data on the reaction HCl(g) → H+(s) + Cl−(s) and the known enthalpy changes for H+(g) → H+(aq) and Cl−(aq) → Cl−(s). The transfer enthalpies of Cl− from water to solvent are estimated on the basis of an extrathermodynamic assumption. The values obtained for ΔH(g → s)(H+) are (kcal mol−1): TMS(−252.6), AN(−256.6), PC(−259.5), H2O(−270.0), DMF(−276.7), DMSO(−276.1). These values are compared to other parameters currently used to define the basicity of these solvents whether as molecules or as media. Thus, proton affinities are such that in the gas phase, acetonitrile is more basic than water by 17 kcal mol−1, while in the liquid phase our results indicate that acetonitrile is less basic than water by 13 kcal mol−1. This variation of 30 kcal mol−1 is attributed to differences in the nature of the solvated proton H+(s) in both solvents: several indications suggest that H+(s) is present as H+(AN)2 in AN, an aprotic solvent, while it is stabilized as H+(H2O)n in water, a protic solvent because of the formation of hydrogen bonds of a cooperative nature. Solvent basicity orders as defined with respect to ΔH(g → s)(H+) and ΔH(g → s)(HA) are shown to differ and the consequences as to the solvent effect on the dissociation of acids HA are considered. Further, there is a nearly linear relationship for the five dipolar aprotic solvents between the values of ΔH(g → s)(H+) and the enthalpy of protonation in fluorosulfonic acid.
Spin–spin coupling between proximate protons on neighbouring aromatic rings and between hydroxyl protons in 2,2′-dihydroxy-4-methoxybenzophenone. Coupling through the hydrogen bond
Authors: Schaefer Ted , Chum Kalvin
Published: May 2006

The doubly hydrogen bonded conformation of 2,2′-dihydroxy-4-methoxybenzophenone ensures substantial nonbonded interactions between C—H bonds on neighbouring aromatic rings and gives rise to spin–spin coupling between the protons in those bonds. Because of the relative orientation of the C—H bonds containing the coupled protons, the coupling represents a direct mechanism which probably does not depend on the orbitals of the carbon atom. The observed coupling between the hydroxyl protons, formally over eight bonds, is small and indicative of an inappreciable covalent character of the hydrogen bond, in agreement with recent conclusions that a weak hydrogen bond is best represented by electrostatic and non-bonded forces only.
Synthesis of azacyclic compounds by an aminium radical route: orbital overlap requirements
Authors: Perry Richard A. , Chen Shi C. , Menon B. C. , Hanaya Kaoru , Chow. Yuan L.
Published: May 2006

Model compounds of Δ4,5-, Δ5,6-, and Δ6,7-alkenylnitrosamines were synthesized and photolyzed to generate the corresponding alkenylaminium radicals. The Δ5,6-alkenylaminium radicals underwent efficient intramolecular addition leading to the exclusive formation of pyrrolidine derivatives, the yield of which was lower if the steric strain and hindrance were severe in the cyclization transition state. The Δ6,7-alkenylaminium radical cyclized inefficiently to piperidine derivatives and the Δ4,5-alkenylaminium radicals did not appear to cyclize; in both cases other pathways having lower activation energies, such as elimination and hydrogen abstraction, predominated. Evidence that the direction of cyclization is controlled by the degree of p-orbital overlap, but not by stability of the developing products, in the transition state is presented. The stereochemical factors associated with the overlap determined the yields of the cyclization products. This is in excellent agreement with the fact that the transition state of cyclization is reached at an early stage in the reaction coordinate. Metal ion catalyzed or radical initiated decomposition of some alkenyl chloramines were found either to cyclize to a mixture of pyrrolidine and piperidine derivatives or to undergo no cyclization.
Organic sulfur mechanisms. 19. Sulfene–tertiary amine zwitterions and base size effects in sulfene condensations
Authors: King James Frederick , Harding David Roger Kay
Published: May 2006

The effect of changing the size of the tertiary alkylamine has been investigated in two systems: (a) the reaction of phenylmethanesulfonyl chloride with a tertiary amine, and (b) the formation of the β-sultone from the reaction of chloral, ethanesulfonyl chloride, and a tertiary amine. In the first reaction the yield of stilbene (3) or stilbene episulfone (4) increases and that of the thiobenzoyl chloride S-oxides (5) decreases as the size of the base decreases, as expected for a mechanism involving a tertiary amine – sulfene zwitterion in the formation of the stilbene products. In the second reaction the yield of the β-sultone is much enhanced by the use of a small amine; the latter observation precludes a simple sulfene–chloral cycloaddition mechanism and points to a zwitterionic intermediate derived from the amine and either the sulfene or chloral.
Excess volumes of binary mixtures of an alcohol + diethylketone
Authors: Reddy Kalluru S. , Rao Murari Venkata P. , Naidu Puligundla R.
Published: May 2006

Excess volumes of mixtures of 1-propanol +, 1-butanol +, 1-pentanol +, and 1-hexanol + diethylketone have been measured at 303.15 and 313.15 K. Of the four mixtures included here 1-propanol + diethylketone shows an inversion in sign in VE at 313.15 K. VE becomes more positive with increase in temperature.
Thermal pressure and energy–volume coefficients for the acetonitrile + water system
Authors: Grant-Taylor David F. , Macdonald Digby D.
Published: May 2006

Densities and thermal pressure coefficients for the acetonitrile + water system at temperatures from 298.15 to 328.15 K are reported. These data are used to derive expansivities, energy–volume coefficients, cohesive energy densities, isothermal compressibilities, and derivatives of entropy with respect to pressure. The variation of these parameters with composition and temperature is described.
Some thermodynamic properties of K3AlF6–KAlF4 melts
Authors: Thompson William T. , Goad David G. W.
Published: May 2006

The partial pressure of KAlF4 over K3AlF6–KAlF4 melts at temperatures as high as 815 °C was measured by thermogravimetry. Melt activities were calculated from the measurements. The results are discussed with reference to the use of this salt mixture as a flux for aluminum alloys.
Nuclear magnetic resonance study of electrolytes in 1,3-dimethylethyleneurea
Authors: Rosenfarb Joseph , Caruso Joseph A.
Published: May 2006

A series of lithium, sodium, potassium, and ammonium salts were investigated by proton magnetic resonance spectroscopy in 1,3-dimethylethyleneurea, a relatively new non-aqueous solvent of high polarity and moderately high dielectric constant. The salts were found to shift the solvent proton peaks linearly as a function of salt concentration. Thiosulfate, perchlorate, and iodide salts shifted the solvent peaks downfield while tetraphenylborate salts uniquely shifted the peaks upfield indicating an unusual type of solvation behavior for the tetraphenylborates in this solvent.
Surface and kinetic effects in gas chromatographic studies of polystyrene
Authors: Courval Gregory J. , Gray Derek G.
Published: May 2006

Considerable variation in the measurement of polymer–solvent interactions using gc retention data may occur due to kinetic factors, surface excess concentrations of probe vapour, and non-linear partition isotherms. The kinetic factors, which appear as a flow rate dependence of the retention volume, are analysed in terms of a previously reported theoretical model for retention on polymeric stationary phases passing through the glass transition. The predicted linear extrapolations to zero flow rate are obtained for the retention of n-tetradecane on polystyrene. The variation of this flow rate dependence with temperature and with the thickness of the stationary phase are also in qualitative agreement with the theory. A simplified model for the effect of loading on the retention diagram is presented. Non-linear absorption and bulk sorption isotherms result in a dependence of retention volume on sample size, necessitating an extrapolation of the measured retention volumes to zero peak height. The temperature variation of the flow rate dependence, the effect of loading, and the effect of sample size on retention volume are all further complicated by uneven distribution of polymer on support. From scanning electron micrographs of the beads it is evident that 'beading up' of the polystyrene on the glass surface may occur at low loadings, resulting in a non-uniform coating with large areas of the beads uncoated. It is concluded that in order to obtain reliable data on polymer–solvent interactions using gas chromatography, all of the above-mentioned factors must be considered.
The Raman spectra of tricoordinate CdX2Y− halogenocadmate(II) anions in the solid state
Authors: Contreras J. Guillermo , Tuck Dennis G.
Published: May 2006

Anionic complexes of cadmium, of the type [CdX2Y]−, where X and Y are chlorine, bromine or iodine, have been prepared as the tetra-n-propylammonium salts. Raman spectra have been recorded, and serve to establish that these anions have C2v symmetry in the solid state. Force constants calculated on the Urey–Bradley approximation are correlated with previously reported results for CdX3− species.
A13C nuclear magnetic resonance study of thiolane sulfoxides. The configurations of neothiobinupharidine sulfoxides
Authors: LaLonde R. T. , Wong C. F. , Tsai A. I-M. , Wróbel J. T. , Ruszkowska J. , Kabzinska K. , Martin T. I. , MacLean D. B.
Published: May 2006

The sulfoxide configurations of neothiobinupharidine α- and β-sulfoxides have been determined through a 13C nmr investigation. The 13C nmr sulfoxidation increments (ΔδC-i = δC–iS–O − δC–iS) for all carbons in 2,2,4,4-tetramethylthiolane sulfoxide have been determined, Sulfoxidation increments for the C-2 methyl groups, the indicator carbons, were found to be similar in sign and magnitude to the increments reported for methyl groups in penicillin sulfoxides, wherein methyl groups cis to the sulfoxide oxygen show larger sulfoxidation increments than do the trans methyl groups. The sign and magnitude of the sulfoxidation increments for C-6 and C-8, the indicator carbons in the neothiobinupharidine sulfoxides, have been determined and compared with those of the model 2,2,4,4-tetramethylthiolane and those of the penicillins. The C-6 increments were −9.9 and −5.6 ppm respectively for the solid and liquid neothiobinupharidine sulfoxide. Therefore the solid sulfoxide is assigned the β-configuration and the liquid sulfoxide the α-configuration as a result of these studies.
A practical synthesis of cis-jasmone from levulinic acid
Authors: Bulat J. A. , Liu H. J.
Published: May 2006

A practical total synthesis of cis-jasmone (1) has been achieved in six steps and in an overall yield of 49% from levulinic acid.
Transition state enthalpies of transfer in aqueous dimethyl sulfoxide solutions. The hydroxide catalyzed ionization of chloroform
Authors: Jones John R. , Fuchs Richard
Published: May 2006

The accelerating effect of added dimethyl sulfoxide on the rate of hydroxide-catalyzed ionization of chloroform in water has been examined in terms of the solvation of reactants and transition state. Enthalpies of solution of chloroform in water, DMSO, and mixtures of the two have been measured. From these, together with enthalpies of activation for the detritiation of chloroform, and enthalpies of transfer of hydroxide ion from water to aqueous DMSO mixtures, transition state enthalpies of transfer have been calculated. The reaction is accelerated by small concentrations of DMSO because of increased transition state solvation, but by large DMSO concentrations due to reduced solvation of hydroxide ion. Transition state solvation is unlike that of the reactants, but resembles that expected for CCl3− ion.
N-Methylamino acids in peptide synthesis. VII. Studies on the enantiomeric purity of N-methylamino acids prepared by various procedures
Authors: Cheung S. T. , Benoiton N. Leo
Published: May 2006

The enantiomeric purity of N-methylamino acids and their derivatives obtained by various procedures has been examined by analysis with an amino-acid analyzer of the diastereomeric lysyl dipeptides formed by coupling them with a lysyl derivative. N-Benzyloxycarbonyl, and N-tert-butyloxycarbonyl,N-methylamino acids obtained by methylation of the parent derivative using sodium hydride and methyl iodide, and N-methylamino acids obtained by methylation of the p-toluenesulfonylamino acid followed by treatment with sodium in liquid ammonia, are optically pure. Compounds obtained by other procedures which include reductive alkylations or the use of silver oxide – methyl iodide are generally not optically pure.
Chemical constituents of the physodes of brown algae. Characterization by 1H and 13C nuclear magnetic resonance spectroscopy of oligomers of phloroglucinol from Fucus vesiculosus (L.)
Authors: Craigie James S. , McInnes A. Gavin , Ragan Mark A. , Walter John A.
Published: May 2006

Alcoholic extracts of Fucus vesiculosus contain small quantities of low molecular weight polyphenols derived from phloroglucinol and 2,2′,4,4′,6,6′-hexahydroxybiphenyl. 1H and 13C nmr were used to identify two of these as 4-(2′′,4′′,6′′-trihydroxyphenoxy)-2,2′,4′,6,6′-pentahydroxybiphenyl and 4-(2′′-(2′′′,4′′′,6′′′-trihydroxyphenoxy)-4′′,6′′-dihydroxyphenoxy)-2,2′,4′, 6,6′-pentanydroxybiphenyl.
Synthesis and structure of dichlorobis(thiosemicarbazide)mercury(II)
Authors: Chieh Chung
Published: May 2006

The reaction between mercury(II) chloride and thiosemicarbazide (1:2 molar ratio) in ethanol–water (1:1 by volume) gave, almost quantitatively, dichlorobis(thiosemicarbazide)-mercury(II), HgCl2(tsc)2. There was a trace of unidentified black material as a side product. The crystals of HgCl2(tsc)2 are orthorhombic with a = 8.675(7), b = 8.123(6), c = 15.786(11) Å, Z = 4, and space group Pbcn. The HgCl2(tsc)2 molecule in the crystal has a twofold axis and the mercury atom is bonded to two chlorine atoms at 2.841(3) Å, and two sulfur atoms at 2.417(3) Å, in a highly distorted tetrahedron. The bond angles are: S—Hg—S = 160.7(1)°; Cl—Hg—Cl = 96.6(1)°; S—Hg—Cl = 89.5(1)° (twice) and 103.4(1)° (twice). However, if the close contacts, [Formula: see text] were counted, the coordination around the Hg atom would be an approximate octahedron.
Entropy production in bulk isothermal relaxation
Authors: Yau Andrew W. , Pritchard Huw O.
Published: May 2006

Four theorems relating to complete monotonicity of entropy production in isothermal bulk relaxation have been proved, and in another two cases, it is shown by numerical experiment that the entropy production is probably monotonic also. The total entropy and the total energy do not in general relax with the same rate constant, and under many conditions the time constant for entropy relaxation approaches twice the time constant for energy relaxation. We speculate that the maximum entropy principle used in the information-theoretic approach to bulk relaxation may be synonymous with the principle of complete monotonicity of entropy production.
Chelating agents in high temperature aqueous chemistry. 2. The thermal decomposition of some transition metal complexes of nitrilotriacetate (NTA)
Authors: Booy Meindert , Swaddle Thomas Wilson
Published: May 2006

The kinetics and mechanism of decomposition of NTA complexes of FeIII, FeII, CoII, NiII, and CuII under hydrothermal conditions (425–573 K) have been examined. The relative rates at 573 K are CoIINTA− < NTA3−[Formula: see text] < NiIINTA− < FeIIINTA0 < H3NTA0 < CuIINTA− < H4NTA+. Aqueous CoIINTA− and FeIINTA−, like NTA3−, decomposed at 573 K by decarboxylation, precipitating Co(OH)2 and Fe3O4 respectively; NiIINTA− precipitated Ni(OH)2 initially but subsequently Ni metal. At 530 K, FeIIINTA0 solutions precipitated FeII3(NTA)2•H2O, but at higher temperatures Fe3O4 formed, the NTA ligand being reduced to HCHO and iminodiacetate (IDA) rather than decarboxylated. Similarly, CuIINTA−gave IDA and HCHO at temperatures as low as 425 K, forming first CuI (which precipitated as CuCl in the presence of Cl−) and then metallic Cu. The applicability of NTA to corrosion control in boilers and to 60Co removal from water-cooled nuclear reactors is briefly considered. The half-life of FeIIINTA in the hydrosphere is estimated at 80 years (cf. 8 × 106 years for free NTA), in the absence of photolysis or biodégradation.
Nonhomogeneous charge neutralization kinetics in nonpolar organic solids (Extended Abstract)
Authors: Ametov K. K. , Frankevich E. L. , Novikov G. F. , Yakovlev B. S.
Published: May 2006

not available
Electron states in liquid metals: especially optical and magnetic properties
Authors: March N. H.
Published: May 2006

The theory of optical absorption of the simple liquid metals (e.g. the alkalis) is outlined. At not too large frequencies, the Drude theory is regained. The relaxation time is that given by the weak scattering (Ziman) theory of electrical resistivity. For high frequencies, the relaxation time, however, becomes frequency dependent. Appreciable structure enters the theory, arising from collective excitations. The relation to recent ellipsometric measurements on liquid Na is briefly discussed. The optical conductivity and density of states in the divalent metals Hg and Be is then discussed, followed by the relation between photoemission and soft X-ray experiments and current electron theory. Specific attention is given to the evidence for a pseudo-gap in the divalent metals and to changes in the electron states which occur on melting the noble metals.The second major area treated is concerned with the magnetic properties of liquid metals. The theory of orbital and spin magnetism in simple liquid metals is reviewed and confronted with experiment. It is clear that the electron–electron enhancement effects have a dominant influence on the trend of the spin susceptibility of simple liquid metals as a function of density. However, electron–ion interactions must be introduced as corrections to the interacting electron gas values and in a metal like Li the nearly free electron theory fails to do this adequately. Knight shift results are summarized, and some attention is given to a recent experiment on the Knight shift of expanded fluid Hg. Difficulties for the theory in relation to transport and the pseudo-gap are pointed out. Finally, new theoretical calculations are reported on the relation between the magnetic properties of the liquid rare earth metals and their electrical conductivity. Mathiessen's rule is shown to break down because of very strong potential scattering. A recent theory of this by Parrinello et al. shows that in the strong scattering limit the magnitude of the localized spin carried by the rare earth ion drops out of the transport theory, as required by the experiments of Güntherodt et al.
Metal complex catalyzed reactions of anils. III. Kinetic and mechanistic studies
Authors: Boate A. R. , Eaton D. R.
Published: May 2006

The kinetics of the homogeneously catalyzed formation and hydrolysis of anils in non-aqueous solution have been studied. The catalysts used are zinc complexes of thiourea. It is shown that all the evidence obtained, kinetic and otherwise, is consistent with a model in which the rate determining step for anil formation is nucleophilic attack by an aniline held in the second coordination sphere of the metal complex on an acetone molecule directly bound to the metal atom. Analogous mechanisms are suggested for anil hydrolysis and for transimination.
Kinetics and mechanism of the decarboxylation of pyrimidine-2-carboxylic acid in aqueous solution
Authors: Dunn Gerald E. , Lawler Edward A. , Yamashita A. Brian
Published: May 2006

Pseudo-first-order rate constants for the decarboxylation of pyrimidine-2-carboxylic acid have been determined at 65 °C in aqueous solution over the acidity range pH = 2 to H0 = −9.5. Rate constants increase rapidly from pH = 2 to H0 = −3, then remain constant. This behaviour can be accounted for by a Hammick-type mechanism in which monoprotonated pyrimidine-2-carboxylic acid loses carbon dioxide to form an ylide (stabilized by the adjacent positively charged nitrogens) which rapidly converts to pyrimidine.
Intermolecular interactions in nuclear magnetic resonance. XI. The 13C and proton medium shifts of CH4 in the gas phase and in solution
Authors: Rummens Frans H. A. , Mourits Frank M.
Published: May 2006

The 1H and 13C resonances of methane have been measured at 298 K, both as pure CH4 in the gas phase as function of the density as well as at low concentration in solution, using polar, non polar, isotropic, as well as magnetically anisotropic solvents. It is found that both the gas and the solution proton shift data can be readily understood in terms of the Van der Waals shielding σw and the mean-square field due to the dispersive interactions: [Formula: see text]. Either a macroscopic reaction field model or a binary collision statistical mechanical model for [Formula: see text] can be used with an approximately equal degree of success. Whereas the 13C gas phase shifts of CH4 are also proportional to the density, the 13C gas-to-solution shifts indicate that, apart from σw, there exists even in non-polar isotropic solvents another effect which is not proportional to [Formula: see text]. The present study also includes a new proposal regarding [Formula: see text], a discussion of anisotropy shielding σa in magnetically anisotropic solvents and a discussion of the effective B parameters (1H and 13C) of CH4 in the gas and the solution state.
A template synthesis of nickel 6,8,15,17-tetramethyldibenzo[b,i][1,4,8,11]-tetraazacyclotetradeca-2,4,7,9,12,14-hexaene
Authors: Cutler A. R. , Dolphin D.
Published: May 2006

The title macrocyclic nickel complex has been conveniently prepared in moderate yield using 2,5-dimethyl-3H-1,5-benzodiazepine, or a mixture of o-phenylenediamine and pentane-2,4-dione in a template synthesis using nickel salts. The previous low yield synthesis of this macro-cycle required condensation of nickel bisacetylacetonate in molten o-phenylenediamine.
Radiation chemistry of acetylene at high intensity: the initial product distributions
Authors: Willis C. , Back R. A. , Morris R. H.
Published: May 2006

The distribution of products observed in the radiation chemistry of acetylene at high dose rate is dramatically different from that observed at low dose rate. The dominant products observed at high dose rate are vinyl acetylene and diacetylene with C3 to C9 compounds having smaller but significant yields. At low dose rate benzene and cuprene are the exclusive products. The difference in product distribution is attributed to the suppression of secondary attack on products at high dose rate so that the observed distribution approximates more closely the 'zero dose' or 'initial' distribution.
Competitive adsorption of urea and Et4NBr at the electrode/electrolyte interface
Authors: Kimmerle Frank M. , Ménard Hugues
Published: May 2006

The simultaneous adsorption of urea and tetraethylammonium bromide has been investigated in ternary solutions varying in composition from 10−3 to 1 mol ℓ−l. The adsorption of urea at the electrode/electrolyte interface can be described at low surface coverage by a Langmuir isotherm taking into account the surface unoccupied by the ionic components of the Et4NBr salt. At high surface coverage, perturbation of Гurea by the simultaneous adsorption of the electrolyte is explained in terms of the lateral attractive forces previously observed in concentrated bulk solutions.
Volumes and heat capacities of some amino acids in water at 25 °C
Authors: Ahluwalia JagDish C. , Ostiguy Claude , Perron Gerald , Desnoyers Jacques E.
Published: May 2006

The apparent molal volumes and heat capacities of nine amino acids were measured in water at 25 °C with a flow densimeter and a flow microcalorimeter. It is shown that the poor additivity of the standard partial molal quantities of amino acids in water are attributable to the ionization of the two groups NH2 and COOH. The hydration of these ionic groups interfere with each other when they are separated by less than three carbon atoms.
Preparation and Mössbauer spectra of organotin(IV) compounds containing the CH3(C6H5)Sn(IV) moiety
Authors: Sham T. K. , Tse J. S. , Wellington V. , Bancroft G. M.
Published: May 2006

The synthesis and Mössbauer spectra of 16 organotin compounds of the type MePhSnX2 (X = F, Cl), [Et4N]MePhSnCl3, MePhSnCl2L2 (L = oxygen and nitrogen neutral donor ligands), and MePhSnL2′ (L′ = acetylacetonates and 8-hydroxyquinolate) are reported. The Mössbauer quadrupole splittings (qs) are used to assign the structures of the complexes. The MePhSnX2 (X = F, Cl) compounds have similar structures to their Me2Sn analogues, while the six-coordinate complexes show a greater structural similarity to their Ph2Sn analogues. Thus MePhSnF2 is a highly associated structure like Me2SnF2 with a six-coordinate Sn atom; while the MePhSnL2′ complexes have the cis structure like their Ph2Sn analogues. The structures of the six-coordinate organotin complexes are rationalized using steric calculations and the known bonding properties of the ligands. The quadrupole splittings and centre shifts (cs) are also used to suggest variations in ligand bonding properties, and to discuss variations in C—Sn—C angles from the MePhSn complexes to their Ph2Sn analogues.
Thermochemical measurement of the ligand field splitting energies for hexaammine complexes of Mn(II), Fe(II), and Zn(II)
Authors: Badri M. , Jamieson J. W. S.
Published: May 2006

Various lower ammines and high-energy modifications of lower ammines of the sulphates of Mn(II), Fe(II), and Zn(II) have been prepared and their heats of solution have been measured. For each of these ammine systems, the maximum difference in heat of solution, expressed in kcal/mol of heptaammine, has been found to be of the right order of magnitude to be regarded as the ligand field splitting energy for the hexaammine complex of the metal ion.
Kinetics of ligand exchange between a uranium(IV) β-diketonate and free β-diketone
Authors: Folcher G. , Keller N. , Kiener C. , Paris J.
Published: May 2006

The intermolecular ligand exchange kinetics between a uranium(IV) β-diketonate and free β-diketone were studied by 1H nmr as a function of temperature and concentration. The reaction was found to be of first order in both chelate and free ligand. The results suggest that the exchange mechanism involves a ninth coordination site in the uranium(IV) chelate.
Additivity schemes permitting the estimation of partial molar heat capacities of organic compounds in aqueous solution
Authors: Guthrie J. Peter
Published: May 2006

The available [Formula: see text] values for neutral organic compounds in aqueous solution can be fitted with useful precision by additivity schemes based on atomic, bond, or group contributions. For the set of 132 compounds these schemes require 11, 14, or 49 parameters and give weighted average deviations of 14, 9, or 6 J K−1 mol−1. For acyclic molecules the atomic contributions scheme permits chemically useful estimates of [Formula: see text] to be made for compounds of C, H, O, and N.
Pyridine-catalyzed halogenation of aromatic compounds. III. Chlorination and the relative stabilities of trichloride and tribromide in chloroform
Authors: Dunn Gerald E. , Pincock James A.
Published: May 2006

The mechanism of catalysis of aromatic chlorination by pyridine was investigated by measuring the rates of chlorination of toluene in acetic acid with and without added pyridine, pyridinium nitrate, or lithium chloride. All three increase the rate of chlorination slightly and to about the same extent. The effect on the second-order rate constant for chlorination of p-chloranisole in chloroform was determined for pyridine, pyridinium chloride, N-ethylpiperidinium chloride, tetra-n-butylammonium chloride, and tetra-n-butylammonium perchlorate. Again, all additives increase the rate constant, with the increase being least for pyridine. It is concluded that, for chlorination in dilute solution, pyridine has no specific catalytic effect, but probably increases the rate by increasing the polarity of the medium. Tetra-n-butylammonium chloride was observed to have a decreasing accelerating effect on chlorination in chloroform as its concentration is increased. This was thought to be the result of complexation of chlorine as trichloride. The formation constant for tetra-n-butylammonium trichloride in chloroform was found by the Benesi–Hildebrand spectrophotometric method to be 17 ± 3 M−1. This, together with the previously determined value of 9 × 104 M−1 for the corresponding tribromide, shows that the order of stability of trihalides in nonaqueous solvents is [Formula: see text] contrary to an earlier report.
Polyol–Water interactions. Apparent molal heat capacities and volumes of aqueous polyol solutions
Authors: DiPaola Giuseppa , Belleau Bernard
Published: May 2006

Volumetric specific heats (25 °C) and densities (24 °C) were measured with a flow microcalorimeter and flow densimeter for 12 polyols in water (0.05 to 2 m), and for NaCl and n-Bu4NBr in 1 m aqueous alditol solutions. The infinite dilution properties [Formula: see text] of the polyols show specificities in polyol−water interactions which are discussed in terms of the compatibility of the polyol stereochemistry and the existing water environment. The derived heat; capacities and volumes of transfer of hydrophobic and hydrophilic probes to aqueous solutions of homologous polyols suggest that structural interactions are reduced in these systems as compared to pure water.
Synthesis and crystal structure of thiosemicarbazidedichloromercury(II)
Authors: Chieh Chung , Cowell Dianna H.
Published: May 2006

Thiosemicarbazidedichloromercury(II) was synthesized in an ethanol–water solution by keeping the molar ratio of HgCl2 and thiosemicarbazide (tsc) at 1:1. The crystal is monoclinic: a = 8.966(11), b = 6.817(9), c = 12.092(14) Å, β = 100.3(1)°, and space group P21/c with four molecules per unit cell. The tsc is a bidentate ligand in this complex with Hg—S = 2.417(6) Å, Hg—N = 2.51(2) Å. The mercury atom is trigonal pyramidally four-coordinated, with two Hg—Cl distances of 2.366(6) and 2.770(5) Å. When the tsc is coordinated to the mercury(II) ions, the chemical shift of the 1H atoms on the NH2 and NH groups shift to a lower field.
The mechanism of the thermal decarbonylation of 2,2-dimethyl-3-butenal
Authors: Crawford Robert J. , Lutener Stuart , Tokunaga Hirokazu
Published: May 2006

The thermal decarbonylation of 2,2-dimethyl-3-butenal is shown to be an intramolecular extrusion of carbon monoxide concerted with the transfer of hydrogen (deuterium) to the γ-position. The reaction displays a kinetic isotope effect of 2.8 (at 296.9 °C) and follows first order kinetics (Ea = 44.2 ± 0.2 kcal mol−1, log A = 13.4 ± 0.3).
Salt effects on adsorbed nonelectrolytes
Authors: Aveyard Robert , Saleem Syed M.
Published: May 2006

An approach to the study of the influence of electrolytes on adsorbed nonelectrolytes at liquid surfaces is described. The adsorption of tetrabutylammonium bromide (Bu4NBr) from aqueous solution to the interfaces with octane, decanol, and air has been determined. Results are presented for the effects of some inorganic salts (NaCl, NH4Br, and Na2CO3), and of Bu4NBr on monolayers of butanol at the air – aqueous solution interface, and of Bu4NBr on dodecanol adsorbed at the octane – aqueous solution interface. The interfacial salt effects differ from the bulk effects in the cases studied. The inorganic salts, which salt-out butanol (and alkanols generally) in aqueous solution, have little or no effect on adsorbed butanol. On the other hand, Bu4NBr which salts-in alkanols in bulk aqueous solution has a strong salting-out effect on dodecanol at the liquid–liquid interface; a similar but less marked effect is observed for butanol at the liquid–vapour surface. Salting-in of alkanols by Bu4NBr in bulk has previously been ascribed to hydrophobic interactions between cations and alkyl groups of the alkanol, whereas the surface effect is assumed to result from interactions between alcoholic OH groups and cations.
Metal complexation by α-mercapto- β-aryl acrylic acids
Authors: Wagner Joseph , Vitali Pierre , Schoun Josiane , Giroux Eugene
Published: May 2006

Protonation constants of several α-mercapto-β-aryl acrylic acids and constants for formation of complexes between these ligands and bivalent metal cations were determined by computer-assisted analysis of pH-titration data. Ligand–metal ion mixtures in 50% (v/v) dioxane–water and in water, I = 0.1 M (NaClO4) were titrated at 25 °C with sodium hydroxide. Initial estimates of complex formation constants were refined with the SCOGS program. The ligands were shown to complex zinc(II) and nickel(II) metal ions avidly. These ligands potently inhibited the metal-dependent enzymes alkaline phosphatase, carboxypeptidase A, coeruloplasmin, and thermolysin. Partition of zinc(II) between aqueous and n-butanol or n-octanol phases was enhanced in favor of the organic phase by several of these complexants.
Déplacements chimiques de la résonance magnétique nucléaire 13C dans les complexes carbonylés octaédriques des métaux de transition du groupe VIB. Effet écran produit par les électrons d non-liants du métal
Authors: Cozak Daniel , Butler Ian S.
Published: May 2006

The 13C nmr shielding effect at the carbonyl ligands due to the paramagnetic current in the non-bonding d orbitals of the metal in the group VIB M(CO)6 complexes has been evaluated. For these complexes, the only contribution of significant importance to the chemical shielding calculated for the carbonyl ligands is opposite to that observed experimentally. The carbonyl chemical shift produced by substitution of one of the carbonyl ligands is discussed in terms of electronic structure of the metal and the metal–carbonyl bond lengths in the M(CO)5L complexes.
Pyrrole chemistry. XVII. Alkylation of the pyrrolyl ambident anion
Authors: Wang Nam-Chiang , Teo Kang-Er , Anderson Hugh J.
Published: May 2006

A series of experiments were carried out to find optimum conditions for C- and N-alkylation of the pyrrolyl ambident anion. While almost total C-alkylation could be obtained, isolation of a single alkylation product was not feasible. However, N-alkylation of pyrrole and several 2-substituted pyrroles was readily achieved by phase transfer catalysis with primary alkyl halides.
An acidity function based on thiocarbonyl indicators
Authors: Edward John T. , Lantos Ivan , Derdall Gary D. , Wong Sin Cheong
Published: May 2006

not available
Terpenoids. Part 44. Oxidative rearrangement of 17-nor-13β-kauran-16-one with thallium(III) nitrate
Authors: Fujita Eiichi , Ochiai Masahito
Published: May 2006

17-Nor-13β-kauran-16-one (1) on treatment with thallium(III) nitrate in acetic acid gives an oxidatively rearranged product, 9,10-friedo-17-norkaur-5(10)-en-12-one (2). On heating in the presence of acid, compound 2 undergoes rearrangement to give an αβ-unsaturated ketone, 17-norkaur-9(11)-en-12-one (8). The structure and stereochemistry of the compound 8 were established by the total synthesis of its racemate.
Studies related to antitumor antibiotics. Part XIII. Reactivity of 2- and 3-indolylcarbinyl compounds as models for mitosane action
Authors: Lown J. William , Weir Gordon L.
Published: May 2006

The base-catalyzed methanolyses of 1-methylgramine methiodide 2, 1-methylisogramine methiodide 3, and l-methylindol-2-ylmethyl N-tert-butylcarbamate 4 were studied in the temperature range 50–90 °C in order to gain information about the relative reactivity of 2- and 3-indolylcarbinyl Systems, analogous to the proposed reactive sites of the mitosane antitumor antibiotics when enzymatically reduced. The leaving groups were also analogous to those found in the mitosanes. The methanolysis of 2 proceeds with strict first-order kinetics in accord with indole nitrogen lone pair assistance of the displacement. The comparable reactions of 3 and 4 proceed with second-order kinetics in accord with a direct SN2 process and the carbamate moiety is the better leaving group by a factor of 10. Gramine methiodide 5 undergoes a very rapid elimination of the elements of [Formula: see text] followed by addition of a nucleophile such as methanol at a rate which is too rapid to follow kinetically even at −78 °C. In accord with the model for the mode of action of the mitosanes, 2.2 mM5 alkylates and cross-links DNA to the extent of 71% at pH 7 and 37 °C. The extent of cross-linking is proportional to the (G + C) content of DNA's as was found for the mitosanes and occurs at a position other than N-7 on guanine. The results suggest that in the reaction of the mitosane antibiotics with DNA the inherent greater reactivity of the 10-carbamate moiety towards nucleophilic displacement is more than offset by the rate enhancement of the 1 position due to relief of aziridine ring strain.
Hydrothermal reaction kinetics. The decomposition of nickel(II) hydroxide
Authors: Swaddle Thomas W. , Wong Tony C. T.
Published: May 2006

The fractional extent α of decomposition of ripened Ni(OH)2 into green NiO in alkaline hydrothermal conditions under nitrogen is given by the rate law α1/3 = kc[OH−]t, where kc = 2.4 × 10−5 kg mol−1 s−1 at 561 K. The Arrhenius activation energy is 220 + 25 kJ mol−1. The reaction is accelerated moderately by O2 (giving black NiO1+δ) and strongly by added NiO. A reaction mechanism involving dissolution of Ni(OH)2 as Ni(OH)3− (aq) and rate-determining, surface-controlled reprecipitation of this as NiO is proposed.