bluuebunny/crossref_metadata_2025 huggingface dataset:
Noncritical phase-matched lithium triborate optical parametric oscillator for high resolution coherent anti-Stokes Raman scattering spectroscopy and microscopy
Authors: Jurna M. , Korterik J. P. , Offerhaus H. L. , Otto C.
Published: December 2006

An efficient, widely tunable, narrow-bandwidth, green-pumped, noncritical phase-matched lithium triborate based optical parametric oscillator (OPO) is applied to coherent anti-Stokes Raman scattering (CARS) spectroscopy and microscopy. The tunable signal beam (740–930nm) of the OPO is combined with the fundamental of a Nd:YVO4 pump laser (1064nm, 15ps) to obtain high resolution vibrational spectra of molecules around the CH vibrational stretch (2700–3100cm−1). The straightforward and convenient tunability of the OPO is demonstrated by CARS microscopy for the identification of different polymer microparticles on the same substrate.
Femtosecond time-resolved investigation of the vibrational modes of vitreous GeO2
Authors: Burgin J. , Guillon C. , Langot P. , Vallée F. , Hehlen B.
Published: December 2006

The vibrational response of vitreous GeO2 is investigated using an impulsive stimulated Raman scattering technique in the femtosecond regime. The results yield evidence for a weak vibrational mode ascribed to oxygen motion in three-membered planar ring structures. Its frequency and damping are determined and compared to theoretical predictions.
Nonequilibrium drift-diffusion transport in semiconductors in presence of strong inhomogeneous electric fields
Authors: Zakhleniuk N. A.
Published: December 2006

The self-consistent analysis of drift-diffusion transport in strong inhomogeneous electric fields shows that the local mobility is determined by the “field parameter” f(r)=∇rEc(r)∙∇rEF(r), rather than the electric field ∇rEc(r)∕e or the quasi-Fermi potential gradient ∇rEF(r)∕e, as is usually assumed. This takes place at both high and low carrier densities. The methods for derivation of μ(f) in both cases are presented. The analysis is applied to numerical simulation of a p-i-n photodiode, and it is shown that the use of μ(F) with F(r)=∣∇rEc(r)∕e∣ results in grossly exaggerated carrier drift velocities. The implications for drift-diffusion models used in commercial device simulators are discussed.
Terahertz oscillation in submicron sized intrinsic Josephson junctions
Authors: Wang H. B. , Urayama S. , Kim S. M. , Arisawa S. , Hatano T. , Zhu B. Y.
Published: December 2006

Intrinsic Josephson junctions (IJJs) with lateral sizes down to submicron have been fabricated in high temperature cuprate superconductor Bi2Sr2CaCu2O8+δ single crystals. With in-plane magnetic fields applied perpendicular to the short edges, equally spaced current steps with intervals up to millivolts have been observed in current-voltage characteristics, indicating that terahertz oscillation has been excited in the junctions. The one-by-one switching to the same resonance frequency will make possible to employ a submicron sized IJJs stack as a building block for solid state terahertz continuous wave sources.
Micromagnetic simulation of spin transfer torque switching combined with precessional motion from a hard axis magnetic field
Authors: Ito K. , Devolder T. , Chappert C. , Carey M. J. , Katine J. A.
Published: December 2006

The authors have performed micromagnetic simulations of spin transfer torque (STT) switching, combined with precessional motion induced by a pulsed or static hard axis field. They have found a significant reduction in the current required for STT switching in the presence of precessional motion. In particular, the switching current can be reduced below the zero-temperature threshold current at dc, when the hard axis field exceeds a fourth of the free layer coercivity. The simulations indicate that the critical current reduction arises from the strong STT present when the magnetization nearly passes through the hard axis during the initial few precessional turns.
Optical near-field ablation-induced plasma characteristics
Authors: Hwang David J. , Grigoropoulos Costas P. , Yoo Jong , Russo Richard E.
Published: December 2006

The physics of optical near-field based laser ablation plasmas is studied. A Cr thin metal film is ablated using visible nanosecond laser pulses coupled through an optical near-field fiber probe. The ablated plasma evolution is monitored via time-resolved emission imaging and spectral measurement. Intense plasma formed in the proximity of the near-field gap within the laser pulse duration and decayed after several nanoseconds. Highly directional jetlike material ejection was observed at later time scales. The measured spectra reveal that early stage plasma of short lifetime yields ablated material characteristic emission peaks, supporting possible application to laser-induced breakdown spectroscopy.
Test of Models of Achromatic Transparency
Authors: Masin Sergio Cesare
Published: December 2006

Consider an achromatic disk transparent on an achromatic background formed by two adjoining rectangles, with the common border of the rectangles dividing the disk in half. Current models of achromatic transparency contend that the perceived extent of transparency of the disk depends on the luminance contrast inside the disk and on the luminance contrast in the background outside the disk. Here, a model is proposed which contends that this perceived extent is determined only by the luminance contrasts inherent in the disk: inside the disk and between the disk and the background. Two experiments were designed to determine which luminance contrasts influence transparency. In the first experiment, subjects rated the perceived extent of transparency of the disk for different combinations of the luminances of the disk and of the background. The results strengthen the view that the perceived extent of transparency depends on the luminance contrasts inherent in the disk. In the second experiment, a test was made of the possibility that luminance contrasts between adjoining areas of the background outside the disk are nonessential for transparency. The results show that transparency occurred both when the areas of the background outside the transparent region adjoined one another and when they were separated, confirming that the perceived extent of transparency depended only on luminance contrasts between adjoining areas inherent in the disk.
The Effect of Spatial-Frequency Filtering on the Visual Processing of Global Structure
Authors: Sierra-Vázquez Vicente , Serrano-Pedraza Ignacio , Luna Dolores
Published: December 2006

In three experiments we measured reaction times (RTs) and error rates in identifying the global structure of spatially filtered stimuli whose spatial-frequency content was selected by means of three types of 2-D isotropic filters (Butterworth of order 2, Butterworth of order 10, and a filters with total or partial Gaussian spectral profile). In each experiment, low-pass (LP), band-pass (BP), and high-pass (HP) filtered stimuli, with nine centre or cut-off spatial frequencies, were used. Irrespective of the type of filter, the experimental results showed that: (a) RTs to stimuli with low spatial frequencies were shorter than those to stimuli with medium or high spatial frequencies, (b) RTs to LP filtered stimuli were nearly constant, but they increased in a non-monotonic way with the filter centre spatial frequency in BP filtered stimuli and with the filter cut-off frequency in HP filtered stimuli, and (c) the identification of the global pattern occurred with all visible stimuli used, including BP and HP images without low spatial frequencies. To remove the possible influence of the energy, a fourth experiment was conducted with Gaussian filtered stimuli of equal contrast power ( crms = 0.065). Similar results to those described above were found for stimuli with spatial-frequency content higher than 2 cycles deg−1. A model of isotropic first-order visual channels collecting the stimulus spectral energy in all orientations explains the RT data. A subsequent second-order nonlinear amplitude demodulation process, applied to the output of the most energetic first-order channel, could explain the perception of global structure of each spatially filtered stimulus, including images lacking low spatial frequencies.
Are Olfactory Images Sensory in Nature?
Authors: Sugiyama Haruko , Ayabe-Kanamura Saho , Kikuchi Tadashi
Published: December 2006

We investigated the features of olfactory mental images by comparing odour images with perceptual and semantic representations. Participants who were assigned to three groups made similarity judgments about 17 common odours by smelling odours, imagining odours, or on the basis of the meaning of odour source names. In the smelling group, every pair of odours was compared. In the imagining group, imagined odours were compared twice, both before and after associative learning of the odour/name combinations. In the meaning group, the odour source names were compared in terms of general word meanings. Nonmetric multidimensional scaling analysis was applied to each group of similarity data and three-dimensional sensory, mental, and semantic spaces were composed. 17 elements in the mental and semantic spaces were super-imposed onto the sensory space by Procrustes rotation. We found that the averaged distances of the 17 elements between the sensory and the mental spaces (either before or after learning) were smaller than those between the sensory and semantic spaces. We suggest that odour images have sensory features, especially after associative learning between perceived odours and their names.
Face Recognition in Pictures is Affected by Perspective Transformation but Not by the Centre of Projection
Authors: Liu Chang Hong , Ward James
Published: December 2006

Recognition of unfamiliar faces is susceptible to image differences caused by angular sizes subtended from the face to the camera. Research on perception of cubes suggests that apparent distortions of a shape due to large camera angle are correctable by placing the observer at the centre of projection, especially when visibility of the picture surface is low (Yang and Kubovy, 1999 Perception & Psychophysics61 456 – 467). To explore the implication of this finding for face perception, observers performed recognition and matching tasks where face images with reduced visibility of picture surface were shown with observers either at the centre of projection or at other viewpoints. The results show that, unlike perception of cubes, the effect of perspective transformation on face recognition is largely unaffected by the centre of projection. Furthermore, the use of perspective cues is not affected by textured surfaces. The limitation of perspective in restoring 3-D information of faces suggests a stronger role for image-based, rather than model-based, processes in recognition of unfamiliar faces.
Color Onsets and Offsets, and Luminance Changes Can Cause Change Blindness
Authors: Arrington James G , Levin Daniel T , Varakin D Alexander
Published: December 2006

It has recently been demonstrated that people often fail to detect between-view changes in their visual environment. This phenomenon, called ‘change blindness’ (CB), occurs whenever the perceptual transient that usually accompanies a change is somehow blocked, or made less salient. In the well-known flicker paradigm, the transient is blocked by inserting a blank screen between the original and changed scenes. We tested whether transients that do not involve the appearance or disappearance of visual objects would also produce CB. Therefore we tested whether the appearance or disappearance of color information, and increments or decrements in luminance, could cause CB. In three experiments, subjects searched for changes in natural scenes. We found that both color transients and luminance transients significantly reduced change detection (by ∼30%) relative to a no-transient condition.
Classification of Self-Organization and Emergence in Chemical and Biological Systems
Authors: Halley Julianne D. , Winkler David A.
Published: December 2006

Most chemical and biological systems are complex, but the application of complex systems science to these fields is relatively new compared to the traditional reductionist approaches. Complexity can provide a new paradigm for understanding the behaviour of interesting chemical and biological systems, and new tools for studying, modelling, and simulating them. It is also likely that some very important, but very complicated systems may not be accessible by reductionist approaches. This paper provides a brief review of two important concepts in complexity, self-organization and emergence, and describes why they are relevant to chemical and biological systems
Reactions of 2,6-Dibenzylidenecyclohexanone and its Derivatives in High-Temperature Water
Authors: Bi Xian-Jun , Higham Luke T. , Scott Janet L. , Strauss Christopher R.
Published: December 2006

The reactivity of derivatives of 2,6-dibenzylidenecyclohexanone was investigated in water at 220–250°C under microwave conditions, without added catalyst. Retro-Claisen–Schmidt processes predominated. Hydrolytic attack at the benzylic position afforded a 2-benzylidenecyclohexanone derivative and liberated an aryl aldehyde. Dienones substituted with electron-withdrawing or -donating groups on the aryl rings were more susceptible to hydrolysis than was the parent 2,6-dibenzylidenecyclohexanone.
Glycosynthase-Assisted Synthesis of Some Glycosylated scyllo-Inositols
Authors: Scaffidi Adrian , Stick Robert V.
Published: December 2006

Three derivatives of scyllo-inositol, a 4-nitrophenyl ether, a benzyl ether, and an ester of 4-toluenesulfonic acid, have been treated with α-d-galactopyranosyl fluoride and a glycosynthase to give the corresponding mono-glycosylated inositols. In one instance, a similar treatment with α-d-glucopyranosyl fluoride gave a mono- and a di-glycosylated inositol.
Hydrogenolysis of Aryl p-Toluenesulphonates with Hydrazine in presence of Palladium
Authors: Rottondorf H , Sternhell S
Published: December 2006

Hydrogenolysis of aryl tosylates with
hydrazine in presence of palladium catalyst involves a preliminary
decomposition of hydrazine to give inter alia hydrogen, which then accomplishes
the hydrogenolysis. The reaction can be carried out with molecular hydrogen in
the presence of the same catalyst but not under reaction conditions involving
the intervention of di-imide as the reactive species. Mono-nuclear aryl
tosylates cannot be successfully hydrogenolysed with hydrazine over palladium.
A novel method was established of generating di-imide from hydrazine and iodine
in presence of base or excess hydrazine.
Structure and Acid Strength of Opianic Acid and Its N-Methyl Oxime
Authors: Korsch BH , Riggs NV
Published: December 2006

In water, undissociated
opianic acid exists as an equilibrium mixture containing c. 30% of lactol form
(Ia) in equilibrium with open-chain form (IIa); the carboxyl group is therefore
a stronger acid by c. 0.5 pK units
than the measured value (pK 3.06 � 0.03)
indicates. Opianic acid N-methyl oxime exists largely as the classical nitrone
carboxylic acid (IIIa) in water, and is slightly weaker (pK 2.6-2.7) than opianic acid. Both compounds exist largely as
cyclic forms, (Ia) and (IV), respectively, in chloroform.
Photochemical Reactions of Azo Compounds. II. Photochemical Cyclodehydrogenations of Methyl- and Dimethylazobenzenes
Authors: Badger GM , Drewer RJ , Lewis GE
Published: December 2006

Substituted benzo[c]cinnolines have been prepared
from substituted azobenzenes by photochemical cyclodehydrogenation in 22N
sulphuric acid. The reaction seems to involve a photochemical
disproportionation as rearrangement products of the corresponding
hydrazobenzenes were also formed.

4-Methylazobenzene gave
2-methylbenzo[c]cinnoline. 3-Methylazobenzene gave a mixture of 1- and
3-methylbenzo[c]cinnolines: and 2-methylazobenzene gave
4-methylbenzo[c]cinnoline and benzo[c]cinnoline. The latter result is
noteworthy as it indicates that cyclization can proceed with elimination of a
methyl substituent. Similar elimination was observed with 2,2'-dimethylazobenzene,
which gave 4-methyl-benzo[c]cinnoline as well as the expected
4,7-dimethylbenzo[c]cinnoline. Photochemical cyclodehydrogenations of
4,4'-dimethylazobenzene and of 3,3'-dimethyl-azobenzene have also been studied.
Chorismic acid. A branch point intermediate in aromatic biosynthesis
Authors: Edwards JM , Jackman LM
Published: December 2006

The isolation and characterization of
chorismic acid are described. The structure of the acid has been elucidated by
spectroscopic methods and by chemical degradation as (IV). The relative and
absolute stereochemistries have been established as identical with the
corresponding centres in shikimic acid.

Chorismic acid has been shown to differ
from a compound for which Lingens and L�ck have claimed the structure (IV).
The formation of aromatic hydrocarbons at high temperatures. XXIV. The pyrolysis of some tobacco constituents
Authors: Badger GM , Donnelly JK , Spotswood TM
Published: December 2006

In an attempt to stud) the mode of
formation of polycyclic aromatic hydrocarbons in cigarette tar, pyrolyses of
dotriacontane (C32H66) and of stigmasterol at 700� have
been undertaken. Both compounds gave complex tars containing many aromatic
hydrocarbons. Mechanisms for the formation of some of these are discussed, and
the relative concentrations of some of the polynuclear hydrocarbons present 1n
both tars are compared with those in cigarette tar.
Synthesis of 6,7,8-Trimethoxy-1-naphthol
Authors: Bell KH , Weiss U
Published: December 2006

����� 6,5,8-Trimethoxy-1-naphthol was prepared
in a seven-step synthesis beginning with the Stobbe condensation of
3,4,5-trimethoxybenzaldehyde and dimethyl succinate. Each step gave yields
better than 80%.
Behaviour of disubstituted dithiocarbamates at the mercury electrode
Authors: Randle TH , Cardwell TJ , Magee RJ
Published: December 2006

The electrochemical
behaviour at the mercury electrode of a series of sodium dithiocarbamates in
aqueous solution has been investigated. Although the overall electrode reaction
mechanism is the same as that for sodium diethyldithiocarbamate in each case, the
current flowing in the main anodic wave is determined by the nature of the film
of the particular insoluble mercury(II) dithiocarbamate deposited on the
electrode and varies with the alkyl substituent group in the dithiocarbamate. A
porous, loosely bound film which periodically bursts, causing localized
stirring and large irregular currents, was indicated for large bulky alkyl
groups (e.g. butyl) while for small or planar alkyl groups (e.g. methyl,
tetramethylene) current inhibition was observed, suggesting a compact surface
film. The influence of the surfactant Triton X-100 on the product film has also
been examined. Linear sweep chronoamperometry is recommended as a general
method of analysis for dithiocarbamates as the electrolysis time (and therefore
the film thickness) can be selected to avoid the above interferences.
An N.M.R. study of the helix-coil transition in CNBr fragments of collagen
Authors: Batts BD , Brown RA , Mason P , Ward AR
Published: December 2006

Thermal transitions in solutions of collagen and two of its fragments α1CB3 (13600 molecular weight)
and α1CB2 (3600) have been examined by high-resolution proton n.m.r. spectroscopy and by optical
rotation.
The Dimroth rearrangement. XVII. The rearrangement of some 1,6-Dihydro-6-imino-1,2-polymethylenepyrimidines into 2,N6-polymethylene-bridged 6-aminopyrimidines
Authors: Brown DJ , Ienaga K
Published: December 2006

The cyclic imino ether,
2-ethoxy-3,4,5,6,7,8-hexahydroazocine (4; n = 6), condenses with amino-methylenemalononitrile
(3; R = CN) to give the bicyclic imine, 6,7,8,9,10,11-hexahydro-4-imino-4H-pyrimido[1,2-
alazocine-3-carbonitrile (5f), which undergoes Dimroth
rearrangement in boiling butanol to yield a β-bridged isomer, 2,10,13- triazabicyclo[7,3,1]trideca-1(13),9,11-triene-12-carbo-nitrile
(7a). Imino ethers (4) with fewer than six methylene groups give bicyclic
imines which are incapable of rearrangement; those with more than six methylene
groups give imines which cannot be isolated on account of their extremely
facile rearrangement into β-bridged isomers. Ionization constants and the
ultraviolet, infrared, proton magnetic resonance and mass spectra of the main
products are discussed.
New triterpenoid extractives from Lemaireocereus chichipe
Authors: Khong PW , Lewis KG
Published: December 2006

Reinvestigation of the
glycosidic fraction of the extracts of the giant cactus Lemaireocereus
chichipe has resulted in the isolation of a new
triterpene triol to which is assigned the structure olean-12-ene-
3β,16β,22α-triol (5a). Two triterpene esters were also isolated,
hydrolysis of which gave the known isomeric 3β,16β,28-triol longispinogenin (1a) and a mixture of even-carbon content
fatty acids (C10-C18).
The structure of anadoline
Authors: Culvenor CCJ , Edgar JA , Frahn JL , Smith LW , Ulubelen A , Doganca S
Published: December 2006

The alkaloid previously
isolated from Symphytum orientale
and regarded as a diester of a new, doubly unsaturated pyrrolizidine diol with
tiglic and trachelanthic acids, is shown to be a monoester of retronecine
N-oxide. N.m.r. and mass spectral measurements and electrophoretic data show
that the tiglic acid esterifies not the C 7- hydroxyl of the pyrrolizidine
ring, but the secondary hydroxyl of the trachelanthate moiety. It is proposed
that the name anadoline be given in future to the corresponding tertiary base.
Quantum chemical studies in the design of organic metals. II. The equilibrium geometries and electronic structure of tetrathiofulvalene (ttf) andtetracyanoquinodimethane (tcnq) and their uni- and di-valent ions
Authors: Haddon RC
Published: December 2006

The MINDO/3 SCF MO method
has been used to investigate the equilibrium geometries, electronic structure
and ground state properties of ttf and tcnq and their uni- and di-valent ions. An analysis of the results indicates that
both ttf+ and tcnq-
have low energies of disproportionation and that electron addition or removal
leads to significant structural change. These considerations are discussed in
the light of recent suggestions that at low temperatures the charge- transfer
salt (ttf)(tcnq) gives rise
to superconducting fluctuations, superimposed on the general characteristics of
an organic metal.
Quantum chemical studies in the design of organic metals. III. Odd-alternant hydrocarbons - The phenalenyl (ply) system
Authors: Haddon RC
Published: December 2006

The MINDO/3 SCF MO method
has been used to investigate the equilibrium geometries, electronic structure
and ground state properties of ply and its univalent ions. The results indicate
that ply has a low energy of disproportionation and that electron addition or
removal leads to little structural change. From an analysis of the results it
is concluded that odd-alternant hydrocarbons, and systems based on the ply
nucleus in particular, have many of the characteristics which are considered to
be important in the design of organic metals and superconductors.
On the synthesis of 3,4-dihydroxyprolines. II. Synthesis, stereochemistry and reactivity of some 3,4-Epoxy-DL-proline derivatives
Authors: Hudson CB , Robertson AV , Simpson WRJ
Published: December 2006

N-Protected esters of
3,4-dehydro-DL-proline react with trifluoroperacetic acid to give, in high
yield, approximately equal amounts of the corresponding stereoisomeric
3,4-epoxy-DL-proline derivatives, direct separation of which proved difficult.
However individual members of the two families were obtained by discovery of
selective transformations and fractionations. Relative configurations of the
two 3,4-epoxy-N-tosylproline methyl esters were established by borohydride
reduction to authentic 4-hydroxy-N-tosylprolinols. Epoxide reduction is
regioselective. Extensive p.m.r. analyses then
permitted stereochemical assignment of other derivatives. These epoxides are
remarkably resistant to catalytic hydrogenolysis, and to hydration in acid or
alkali. N-Substituted 3,4-epoxyproline methyl esters undergo ready β-elimination
in alkali to yield the corresponding 4-hydroxy-2,3- dehydroproline esters and
ultimately the N-substituted pyrrole-2- carboxylic acid or ester. Prolonged
aqueous acid hydrolysis of 3,4- epoxy-N-tosylprolines, or of their methyl
esters, gives mixtures of 3,4-dihydroxy-N-tosyl-DL-prolines in the
2,3-cis-3,4-trans and 2,3- trans-3,4-trans families. Their stereochemistry was
allotted from p.m.r. of the diacetate methyl esters.
During acid hydrolysis of 3,4- epoxy-N-tosylproline
methyl esters, the ester of the trans stereoisomer hydrolyses selectively, and
some epimerization of the cis stereoisomer occurs. Ester hydrolysis is much
faster than epoxide hydration. Anhydrous acid cleavage of 3,4-epoxy-N-tosyl-DL-proline
t-butyl esters to the epoxy acids is unusually slow.
An electron spin resonance study of phosphorus-31-superhyperfine coupling in Bis(N,N-dimethylformamide)bis(diphenyl phosphato)copper(II)
Authors: Cookson DJ , Wakefield RF , Smith TD , Pilbrow JR
Published: December 2006

In contrast to the
copper(II) salts of dialkyl phosphates, the analogous aryl compound,
bis(diphenyl phosphato)copper(II), forms a dimethylformamide solvate which may
be doped into the corresponding cadmium compound. Under these circumstances,
the e.s.r. spectrum of the dimethylformamide solvate of bis(diphenyl
phosphato)copper(II) at -140�C shows signals
attributed to superhyperfine coupling between the 31P nucleus of the
ligand and the copper(II) ion. The magnetic parameters have been determined.
Lanthanide shifts in the 1H N.M.R. spectra of thioamides, selenoamides and 1,2-dithioles
Authors: Rae ID
Published: December 2006

The
effects of lanthanide shift reagents on the spectra of thioamides and related
amides and selenoamides are reported, and compared
with those in related sulphur compounds including 1,2-dithioles. The
thiocarbonyl group in a thioamide is less effective as a complexing site than
is the amide carbonyl, but more effective than the sulphur of a thioether.
Small but useful shifts are observed for selenoamides.
Thio derivatives of β-diketones and their metal chelates. XX. Magnetic moments of some ruthenium(III) chelates of fluorinated Monothio-β-diketones
Authors: Livingstone SE , Mayfield JH , Moore DS
Published: December 2006

Magnetic data have been
obtained for ruthenium(III) chelates of the fluorinated monothio-β-diketones
RC(SH)=CHCOCF3 (R = 2-thienyl, β- naphthyl,
Ph,p-MeC6H4, m-MeC6H4, m-ClC6H4,
m-BrC6H4).The compounds are low-spin (S = 1/2) with
moments in the range 1.68-1.84 B.M. at room temperature; the moments decrease
with decrease in temperature.
The sorption of copper species by clays. II. Illite and montmorillonite
Authors: Farrah H , Pickering WF
Published: December 2006

The effect of changes in pH
and the presence of ligands on the uptake of copper ions by an illite and a montmorillonite type
clay has been investigated. The observed adsorption behaviour on montmorillonite
can be interpreted in terms of an ion exchange model, i.e. all positively
charged solution species compete for available sites. For illite
(and kaolinite) the controlling process appears to be
the formation of polymeric hydroxy species attached to particular sites on the
clay. The solution pH controls the development of hydroxy bridges, and ligands
influence uptake through a masking action, i.e. prevention of hydroxy species
formation. Stable anionic complex ions are not adsorbed by either clay.
Thermodynamics of metal-ligand bond formation. XXI. Base adducts of nickel(II) glyoximato complexes
Authors: Graddon DP , Siddiqi IA
Published: December 2006

Bis(glyoximato)nicke1(11)
complexes and their BF2-bridged derivatives react with Lewis bases
in non-donor solvents forming low-spin 1 : 1 adducts. Thermodynamic data are
reported for formation of adducts of glyoximato
complexes with PBu3 and of BF2-bridged complexes with
pyridine (py), 4-methylpyridine (mpy), piperidine (pip), tributylphosphine, triphenylphosphine,
ethane-1,2-diyi- bis(diphenylphosphine) and tetrahydrothiophen. Adduct stability is increased by BF2-bridging;
in the Pbu3 adducts this is due to entropy factors. Variation of
alkyl groups in the glyoxinie has only a small
effect, but replacement of alkyl by Ph or H increases adduct stability while
lowering enthalpy of adduct formation. Average values of ΔH� and K (at 30�C)
for adducts of BF2-bridged complexes and for PBu3 adducts
of H-bridged complexes (last entry) are:

PY mpy pip PPh3 PBu3 Pbu3

-ΔH� (kJ mol-l) 29
31 35
23 43
42

K (1.mol-1) 3 5 80
4 800
60
Potential wool growth inhibitors. Synthesis of DL-α-Amino-β-(5-hydroxy-4-oxo-3,4-dihydropyrimidin-2-yl)propionic acid, a pyrimidine analogue of mimosine
Authors: Harris RLN
Published: December 2006

The synthesis of DL-α-amino-β-(5-hydroxy-4-oxo-3,4-dihydropyriidin-2-y)proponc
acid (3), a pyrimidine analogue of mimosine, is described. The overall yield in
four steps from aliphatic pre-cursors is 25%.
Methylmercury(II) derivatives of Pyridine-2(1H)-thione
Authors: Canty AJ , Marker A
Published: December 2006

Methylmercuric nitrate reacts with pyridine-2(lH)-thione (C5H5NS) in acetone to give
methyl-(pyridine-2(1H)-thione)mercury(11) nitrate, [MeHg(C5H5NS)] NO3. This
complex reacts with sodium bicarbonate in acetone to give
methyl(pyridine-2-thiolato)mercury(11), MeHg(C5H4NS).Infrared, Raman, and
nuclear magnetic resonance spectra indicate that MeHgH
is bonded to sulphur in both complexes, and that protonation of nitrogen occurs on reaction of MeHg(CsH,NS) with nitric acid to
give [MeHg(C5H5NS)] NO3.
Geminal interactions at the termini of polyenes
Authors: Haddon RC
Published: December 2006

The study describes a comprehensive investigation of the geminal union between the groups methylene,
ethylene, cyclopropane and the polyenes ethylene, butadiene, hexatriene, allyl, pentadienyl,
heptatrienyl (the latter three as cation and anion). The interactions are assessed with the frontier
molecular orbital method within the framework of simple perturbation theory. It is concluded that
geminal interactions with methylene fall in the groups: cyclohexadienyl cation (strong interaction),
cyclopentadiene (some interaction), cyclobutenyl anion, cyclooctatrienyl anion, cyclopropene,
cyclohexadienyl anion (little, if any, net interaction), cycloheptatriene, cyclobutenyl cation, cyclooctatrienyl
cation (deconjugated by way of a homoaromatic interaction). For ethylene the geminal
interaction groupings are found to be: benzyl cation and anion (strongly conjugated), trifulvene,
pentafulvene, heptafulvene (some interaction), methylenecyclobutenyl anion and methylenecyclooctatrienyl
anion (little, if any, net interaction), methylenecyclobutenyl cation, methylenecyclooctatrienyl
cation (deconjugated by way of a homoaromatic interaction). Whereas for cyclopropane the
geminal interactions are grouped as: spiro[2,5]octadienyl cation (strongly conjugated), spiro[2,4]-
heptadiene (some interaction), spiro[2,3]hexenyl anion, spiro[2,7]decatrienyl anion, spiro[2,2]pentene,
spiro[2,5]octadienyl anion (little, if any, net interaction), spiro[2,3]hexenyl cation, spiro[2,7]decatrienyl
cation, spiro[2,6]nonatriene (deconjugated by way of a homoaromatic interaction). Where possible,
analogies are drawn between homoaromatic (vicinal) union and the geminal interactions. Ringcurrent
effects are found to be quite important In cyclopentadiene (through methylene hyperconjugation)
and cycloheptatriene (through a 1-6 homoaromatic interaction), but much less so in the fulvenes.
It is concluded that little correlation may be expected between the resonance energies, ring
currents and other criteria of aromaticity in non-alternant hydrocarbons.
Properties of very dilute alcohol solutions
Authors: Smith F
Published: December 2006

A detailed study is
reported of the association behaviour of normal alcohols in very dilute
solution (c < 0.2 mol/dm3) in benzene, carbon tetrachloride and
alkane solvents using experimental i.r., N.M.R., dielectric constant, enthalpy
and free energy of mixing data. The concentration dependence of the degree of
association F(c) has been derived from these data and the results compared and
critically assessed. The derived F(c) data have been found to be independent of
the property used, while the hydrogen-bonding propensities of the OH groups are
found to be independent of the alcohol chain length. The implications of the
form of F(c) for association models is discussed and used together with
dipole-dipole correlation data g(c) to obtain information on imer structure. An
indication has been obtained of the cause of the distinctive forms of the F(c)
and g(c) functions found for alcohol solutions in the different types of
solvent.
Properties of n-alcohol + n-alkane mixtures
Authors: Smith F
Published: December 2006

The total polar contributions (AP) to three properties [infrared absorbance, mixing enthalpies (HM)
and excess free energies (GE)] of alcohol + alkane (alp) systems are separated into a direct hydrogenbond
contribution ( AB) from the formation of isolated imers and a dipole-dipole contribution (AD)
resulting from dipolar correlation between these transient imers.
Dilute concentration range data giving the AB contributions to these properties were found
dependent only on OH group concentration (c) and are used to show the serious inadequacies of
previous theories. A new proposed association model having only two parameters, that are fixed
for all systems, does give good results for the AB contributions and further is quite compatible with
the effect of temperature change and with the n.m.r. chemical shift (ε) and apparent mean square
dipole moment (p2) data that are also studied. Thus association theory has been made quantitative
for the AB contributions to three properties of a/p systems and the approach given for deriving
models appears capable of wider application.
The model was used to extrapolate the AB contributions into the concentrated alcohol range to
thus give the AD contributions by difference. The latter are then shown to be the origin of the distinctive
behaviour shown by lower alcohols in their pure and binary mixture properties either with
alkanes or with other alcohols where for the latter the principle of congruence is shown to be completely
misleading.
Two contributions (Ag and AD) explain the different c dependence shown by the i.r., HM and
the δ data for a/p systems and, qualitatively, the HM data for alcohol+alcohol systems while the
existence of a significant dipole term is strongly supported by the remarkable similarities found
between the p2(c) data and the derived dipole-dipole contribution to the entropy of a/p systems.
A method is given for predicting latent heats and partial molar enthalpies of higher alcohols
from the HM data for one a/p system and a refined estimate is made of the enthalpy of formation
of a hydrogen bond. Polar structure and non-linear dielectric effects are also discussed.
On the reaction of epoxides with diborane
Authors: Marshall PA , Prager RH
Published: December 2006

The reaction of some sterically crowded styrene epoxides (phenyloxirans) with diborane has been
investigated. (Z)-1-Phenylpropene oxide (cis-2-methyl-3-phenyloxiran) reacts with diborane in
tetrahydrofuran at 20° to give, after oxidation, 1-phenylpropan-2-ol(53 %), 1-phenylpropanol (23 %)
and 1-phenylpropane-1,3-diol(2%4 ). 2-Methyl-1-phenylpropene oxide (2,2-dimethyl-3-phenyloxiran)
under similar conditions affords 2-methyl-1-phenylpropanol (7%) and 2-methyl-1-phenylpropane-
1,3-diol(84%), the major isomer of which was the threo. The epoxide of 2-methyl-3-phenylpropene
gives a diol mixture (81%) consisting of the above diols plus 2-benzylpropane-1,3-diol, and 2-methyl-
3-phenylpropanol (3%). The reaction of 1-methyl-2-phenylcyclohexene oxide with diborane gave
a complex mixture af products, three of which have been identified. The mechanism of the reaction
is discussed with supporting evidence from the use of deuterated diborane.
Base decomposition of dichromate
Authors: Clare BW , Druskovich DM , Kepert DL , Kyle JH
Published: December 2006

The rate of decomposition
of dichromate, Cr2O72-, to form chromate, CrO42-,
is very dependent upon the choice of cation, and its concentration. At a total
ionic strength of 1.0 mol l-1 and at 25.0°C, the second-order rate
constant decreases in the order Ca2+ (2600 mol-1 l. s-1)
>> K+ + (960) > Na+ (920) >Li+ (700)>>
bistet2+ (410) >> Me4N+ (125) >>
Et4N+ (35) where bistet2+ is the
N,N,N,N',N',N'-hexamethylethylene-1,2-diammonium ion. In the presence of sodium
chloride the second-order rate constant increases as the ionic strength
increases (200 and 1900 mol-1 l. s-1 at ionic strengths
of 0 and 2.7 mol l-1 respectively), whereas in tetramethylammonium
chloride a maximum is reached at intermediate ionic strengths. The equilibrium
between dichromate and hydrogen chromate is shifted towards the dichromate side
in the presence of tetraalkylammonium ions, and towards the hydrogen chromate
side in the presence of calcium ion.
The chemistry of pyrrolic compounds. XXXIV. Vinylporphyrins from derivatives of 2'-hydroxyethylporphyrins
Authors: Clezy PS , Fookes CJR
Published: December 2006

The bromo, chloro and methanesulphonate
derivatives of 2'-hydroxyethylporphyrins are readily converted in high yield
into the corresponding vinylporphyrins by treatment with sodium hydroxide in
refluxing aqueous pyridine.
Ring contraction of 4-substituted 2,6-dichlorophenols. The crystal structure of 2,2,4α,5α-Tetrachloro-1α,3α-dihydroxycyclopentane-1,4-carbolactone
Authors: Christie RM , Rickards RW , Schmalzl KJ , Taylor D
Published: December 2006

Alkaline chlorination of
the 4-alkyl-2,6-dichlorophenols (2b) and (2c) proceeds through ring contraction
and halolactonization to form the 4α-
alkyl-2,2,5α-trichloro-1α,3α-dihydroxycyclopentane-1,4-carbolactones
(4b) and (4c). Under similar conditions, 2,4,6-trichlorophenol affords the
analogous 2,2,4α,5α-tetrachloro-1α,3α-dihydroxycyclopentane-1,4-
carbolactone (4a) in low yield, in addition to the Hantzsch acid (3a) as the
major product. The acid (3a) upon further treatment undergoes chloro-lactonization
to give the lactone (4a). The structures of the lactones (4b) and (4c) follow
from spectroscopic comparison with (4a), the structure of which has been
established by X-ray diffraction (C6H4Cl4O4
orthorhombic a 13.485(1), b 12.348(1), c 11.371(1) Ǻ, space group Pccn, Z
8, solved by direct methods and refined by block-diagonal and full-matrix least
squares to R 0.031, Rw 0.043 for 1313 unique counter data with
I/σ(I) ≥ 3.0).
Cyano esters and malononitriles. IV. Cyano(fluorenyl)acetohydrazides and fluorenylpyrazolones
Authors: Latif N , Mishriky N , Hammad M
Published: December 2006

Cyano(fluoren-9-yl)acetohydrazides
cyclize readily under acid or basic conditions to give 3-amino-4-(9-substituted
fluoren-9-yl)pyrazol-5(4H)- ones (3). Upon thermolysis of the hydrazides the pyrazolones
and/or dimeric products are produced.��� The cyanoacetohydrazides condense with
phthalic anhydride to give the 2-(fluoren-9-yl)-N-phthalimidoacetamides(7),
whereas, with succinic anhydride, the open-chain compounds (10) are obtained which
upon thermolysis afford the dimeric compounds (6). The acetamides (7) undergo
unusual reductive cleavage with sodium borohydride affording the
fluorenylpyrazolones (3). Electronic, infrared and N.M.R. spectra of the
products are discussed.
Reduced 2-Methyl-4-Oxo, 2-Methylamino-4-Oxo, 2-Methylthio-4-Oxo and 2-Amino-4-Thioxo 6,7-Dimethylpteridines, and 6,8-Dimethylpterin as Substrates for Dihydropteridine Reductase
Authors: Armarego WLF , Ohnishi A , Taguchi H
Published: December 2006

The syntheses of unsubstituted (4), 6-methyl- (6), cis-6,7-dimethyl- (8), cis-2,6,7-trimethyl- (10), cis-6,7-dimethyl-2-thioxo-(1H)- (12) and cis-6,7-dimethyl-2-methylthio- (13) 5,6,7,8- tetrahydropteridin -4(3H)-one and the deuterated derivatives (5), (7), (9) and (14), and a cis and trans mixture of 2-amino-6,7-dimethyl-5,6,7,8- tetrahydropteridin-4(3H)- thione (11) are described. The existence of the transient quinonoid species (15)-(17) had been previously demonstrated by showing that they are substrates for the enzyme dihydropteridine reductase from human brain. We report that the transient quinonoid species cis-2,6,7-trimethyl-(18), cis-2-methylthio-6,7-dimethyl-(25), cis-2-methylamino-6,7-dimethyl-(26), and 2-amino-6,8-dimethyl-(29)7,8-dihydropteridin-4(6H)-one, and 2-amino- 6,7-dimethyl-7,8-dihydropteridin-4(6H)- thione (28), but not cis-6,7- dimethyl-2-thio-7,8-dihydropteridin-4(6H)-one (27) are substrates for this enzyme showing that a variety of substituents in position 2 of the pteridine ring can be tolerated, and confirming that the predominant tautomer (1) of the quinonoid species in aqueous solution is also the reactive tautomer at the active site of this enzyme.
Crystal-Structures of (Nh4)2(AgI3)∞/ ∞.H2O And (Nme4)(Ag2I3)∞/∞
Authors: Kildea JD , Skelton BW , White AH
Published: December 2006

Single-crystal X-ray structure determinations of the title compounds at 295 K are reported. For (1), (NH4)2(AgI3)∞/∞.H2O, the structure is isomorphous with that reported previously for K2AgI3, being orthorhombic, Pbnm , a 21.20(2), b 10.84(1), c 4.629(3)Ǻ, Z 4, R 0.032 for 1211 'observed' independent reflections. Locations and refinement of an artefact modelled as a water molecule raises the possibility that other members of the isomorphous series may be monohydrates rather than anhydrous. (NMe4)(Ag2I3)∞/∞, (2), is orthorhombic, Pnam , a 17.760(7), b 10.077(4), c 7.431(2)Ǻ, Z 4, R 0.043 for 977 'observed' independent reflections; the structure is a redetermination of better precision confirming the essential features of an earlier study and treating the cation in terms of an ordered rather than a disordered model.
Synthesis of Casein-Related Peptides and Phosphopeptides. V. The Efficient Global 'Phosphite-Triester' Phosphorylation of Protected Serine Derivatives and Peptides by Using Dibenzyl or Di-t-butyl N,N-Diethylphosphoramidite
Authors: Perich JW , Johns RB
Published: December 2006

Both dibenzyl N,N- diethylphosphoramidite and di -t-butyl N,N- diethylphosphoramidite are shown to be suitable reagents for the efficient 1H-tetrazole-catalysed 'phosphite-triester' phosphorylation of the protected serine derivative Boc-Ser-OCH2C6H4NO2-p. Both these reagents were also used for the phosphorylation of the protected serine derivative Boc-Glu ( OBut )-Ser- Leu-OBut, and subsequent hydrogenolytic treatment of Boc-Glu ( OBut )-Ser(PO3Bzl2)- Leu-OBut or acidolytic treatment of Boc-Glu ( OBut )-Ser(PO3But2)- Leu-OBut gave the O- phosphoseryl tripeptide Glu -Ser(PO3H2)- Leu in near-quantitive yield.
Approaches to the Synthesis of Lincosamine, a Derived Portion of the Antibiotic Lincomycin
Authors: Engelhardt LM , Skelton BW , Stick RV , Tilbrook DMG , White AH
Published: December 2006

A variety of approaches towards the synthesis of lincosamine, a derived portion of the antibiotic lincomycin , are reported. Initial approaches involved the intramolecular delivery of a nitrogen atom ( trichloroacetimidate , trichloroacetylcarbamate , carbamate, 2-amino-2- phenylacetate ) attached to O4 onto C6 of a 6,7-anhydrooctoside. Later approaches, albeit more direct but again largely unsuccessful, involved the Sharpless titanium(IV)-mediated nucleophilic opening of a suitable 6,7-anhydrooctose, and the Sharpless oxyamination and the aziridination of suitable octenoses . As an aid to the structure elucidation of several compounds encountered in this work, single-crystal X-ray structure determinations are reported for methyl 6,7-anhydro-2,3-di-O-benzyl-8-deoxy-α-D-threo-D-galacto-octopyranoside , methyl 6,7-anhydro-2,3-di-O-benzyl-8-deoxy-α-D-threo-D-gluco-octopyranoside and 7-azido-7-deoxy-1,2:3,4-di-O-isopropylidene-β-L-erythro-Dgalacto-octose.
The Constituents of Marine Sponges. IV. The Isolation of Degraded Spongian Diterpenoids From Aplysilla tango (sp. nov.) (Dendroceratida)
Authors: Poiner A , Taylor WC
Published: December 2006

From the orange encrusting marine sponge Aplysilla tango (sp. nov .) five degraded spongian diterpenes were isolated: gracilin A, aplytandiene-1, aplytandiene-2, aplytangene-1 and aplytangene-2. Gracilin A was confirmed by spectroscopic methods to be (4Z, 1R*, 1′S*, 3S*, 3aR*, 7aR*)-4-ethylidene-5-(1′,3′,3′-trimethylcyclohexyl)-1,3,3a,4,7,7a- hexahydroisobenzofuran-1,3-diyl diacetate (31, and related diterpenes aplytandiene-1 and -2 were confirmed to be (4) and (5) respectively. Aplytangene-1 was shown to be (1′Z, 1R*, 1″S*, 5S*,6R*, 8R*)-8-[1′-ethenyl-2′-(1′,3″,3″-trimethoxycyclohexyl) ethenyl ]-3-oxo-2,7-dioxabicyclo [3.2.1]oct-6-yl acetate (6) and aplytangene-2 to be methyl (4E, 1′S*, 3R*, 3aR*, 5R*,6aS*)-5-methyl-2-oxo-4-(1′,3′,3′-trimethylcyclohexylmethylene ) hexahydrofuro [2,3-b]furan-3-acetate (7). A steroid fraction was also isolated.
The Structure of Cadmium Bis(isopropylxanthate)-4,4'-Bipyridine
Authors: Abrahams BF , Hoskins BF , Winter G
Published: December 2006

The crystal structure of cadmium bis(isopropylxanthate)-4,4?-bipyridine [Cd(ipxa)2(4,4?bipy)] has been determined. Crystals of the title compound are orthorhombic, P21212 (D3/2, No. 18), a 14.812(3), b 12.993(2), c 12.028(2) A, Z 4. The structure consists of Cd(ipxa)2 units linked by 4,4′-bipyridine ligands to form linear polymeric chains which extend in the c-direction.
Synthesis of 9-Methoxymethyl-18-methyl-2,11-dithia[3.3]metacyclophane: a Dithia[3.3]metacyclophane With a Protected Internal Benzylic Functional Group
Authors: Lai YH , Tan QM
Published: December 2006

A synthetic route to a dithia [3.3] metacyclophane with a benzylic functional ( methoxymethyl ) group at C9 is described. The benzylic function however had to be introduced at a later stage in the synthetic scheme to optimize the overall yield. Only the anti isomer of the desired dithiacyclophane (7) was isolated. The entire methoxymethyl group lies within the shielding zone of the opposite benzene ring as indicated in the 1H n.m.r. spectrum. Attempts to convert anti-(7) into the novel aromatic system (5b) by a rearrangement-elimination sequence however failed.
Applications of Optically Active Aryl Cyanohydrins in the Synthesis of α-Hydroxy Aldehydes, α-Hydroxy Ketones and β-Hydroxy Amines
Authors: Jackson WR , Jacobs HA , Jayatilake GS , Matthews BR , Watson KG
Published: December 2006

Cyanohydrins, prepared in high optical purity from aryl aldehydes, have been converted into α- hydroxy aldehydes, β- hydroxy ketones and β- hydroxy amines without any racemization and frequently with good stereoselectivity for the erythro-diastereoisomer (>90%) at the newly introduced stereogenic centre.
Synthesis of Casein-Related Peptides and Phosphopeptides. XVI. The Efficient Synthesis of the Casein-Related O-Phosphoseryl-Containing Peptide Ac-Glu-Ser(P)-Leu-Ser(P)-Ser(P)-Ser(P)-Glu-Glu-NHMe
Authors: Perich JW , Johns RB , Reynolds EC
Published: December 2006

The multiple-O-phosphoseryl-containing peptide, Ac-Glu-Ser (P)-Leu-Ser (P)-Ser (P)-Ser (P)-Glu-Glu-NHMe, was prepared in high yield by the use of Boc-Ser(PO3Ph2)-OH in the Boc mode of peptide synthesis for the preparation of the protected Ser(PO3Ph2)-octapeptide followed by its one-step hydrogenolytic deprotection with platinum oxide. Peptide synthesis was performed by the repetitive excess mixed-anhydride coupling procedure and 40% CF3CO2H/CH2Cl2 for removal of the Boc group from intermediate peptides. The phosphopeptide was found to be greater than 99% pure by C8 r.p.-h.p.1.c. analysis, and was readily characterized by amino acid analysis, 13C n.m.r. spectroscopy and f.a.b. mass spectrometry.
Structural Chemistry of the Platinum Group-Metals: MCl2(bpy) (M = Pd, Pt, bpy = 2,2′-Bipyridine)
Authors: Canty AJ , Skelton BW , Traill PR , White AH
Published: December 2006

A singlecrystal X-ray structure determination of (2,2′-bipyridine)dichloropalladium(II), iso-
morphous with the 'yellow' form of the platinum(II) analogue, has been carried out. Crystals are orthorhombic, Pbca, a 18.144(5), b 15.952(5), c 7.494(2) A, Z 8, 1113 diffractometer reflections being refined by full matrix least squares to a residual of 0.052. The planar molecules of PdCl2(bpy) are stacked into columns along the c direction, at a separation of c/2, neighbouring molecules in the stacks being related by glide planes with Pd…Pd separations of 4.587(2) A.