bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhancement of visible photoluminescence in the SiNx films by SiO2 buffer and annealing
Authors: Xu M. , Xu S. , Chai J. W. , Long J. D. , Ee Y. C.
Published: December 2006

The authors report a simple method to significantly enhance the photoluminescence (PL) of SiNx films by incorporating a SiO2 buffer and annealing treatment under N2 protection. Strong visible PL is achieved with annealing temperature above 650°C. Optimal PL is obtained at 800°C. The composition and structure analysis reveal that strong PL is directly related to the content of the Si–O and Si–N bonds in the SiNx films. These bonds provide effective luminescent centers and passivate the interface between Si core and the surrounding oxide.
Use of a 9,10-Dihydrofulvalene Pincer Cycloadduct as a Cornerstone for Molecular Architecture
Authors: Golić Mirta , Johnston Martin R. , Margetić Davor , Schultz Austin C. , Warrener Ronald N.
Published: December 2006

Dimethyl-3,3a,3b,4,6a,7a-hexahydro-3,4,7-metheno-7H-cyclopenta[a]pentalene-7,8-dicarboxylate (3, a 9,10-dihydrofulvalene pincer cycloadduct) was found to be a versatile building block for the synthesis of polynorbornyl scaffolds containing various end functionalities such as porphyrins, pyrimidine, and the phenanthroline ligand in the free and complexed forms. The block is stable under various cycloaddition reaction conditions and has high π-bond reactivity. Molecular modelling using a semi-empirical based method (AM1) shows that incorporation of this diene block into polynorbornyl systems has an important influence on their overall architecture. In particular, incorporation of the block results in a straightening of the curvature normally observed in polynorbornyl molecules to form almost ideally linear polycyclic rigid spacers.
Deuterium-exchange Reactions with Substituted Aromatics. IV. The Poisoning Effect of Molecules Containing Nitrogen, Sulphur, or Arsenic
Authors: Ashby RA , Garnett JL
Published: December 2006

The catalytic exchange properties of a
number of organic compounds containing nitrogen, sulphur, or arsenic have been
studied in the presence of benzene and heavy water. The results confirm a
charge-transfer-no-bond adsorption mechanism previously proposed for the
deuteration of aromatic polycyclic hydrocarbons. For aromatic nitrogen
compounds an increase in ionization potential of substrate leads to an increase
in deuterium incorporation and a decrease in catalyst poisoning. Some aromatic
amines deuterate faster than expected by theory and this is attributed to rapid
exchange of the amino hydrogens in heavy water with a consequential increase in
D-H ratio at the catalyst; surface. Sulphur and arsenic, even in their
saturated valency states, extensively poison benzene exchange as does
triethylamine. p-Benzoquinone, 2,6-dichloroquinone, and NN-dimethyl benzylamine
exhibit catalytic side reactions which poison benzene exchange. With tritium
oxide, the technique is suitable for the synthesis of tritiated aromatic amines
and heterocycles to high specific activity.
Buffers of Low Ionic Strength for Spectrophotometric pK Determinations
Authors: Perrin DD
Published: December 2006

Buffers of low and constant
ionic strength (I = 0.01), covering
the pH range 2.2 to 11.6 at 20�C, are described. Their near-transparency in the
ultraviolet region makes these buffers suitable for spectrophotometric pK
determinations, and only small, constant corrections are needed to convert the
experimental values to thermodynamic quantities.
Organophosphorus Compounds. I. 2-Chloroalkylphosphonic Acids as Phosphorylating Agents
Authors: Maynard JA , Swan JM
Published: December 2006

Alcohols and phenols are phosphorylated in
high yield by reaction with various 2-chloroalkylphosphonic acids at 20-50�C in
the presence of three or more molar equivalents of cyclohexylamine or
triethylamine, the other products being the corresponding alk-1-ene and
chloride ion. The reaction probably proceeds by attack of an ROH molecule on
the phosphorus atom of a doubly-ionized phosphonate group.

2-Chlorodecyl-, 10-carboxy-2-chlorodecyl-,
and 2-chloro-octylphosphonic acid decompose rapidly in neutral solution giving
chloride ion, phosphate ion, and the corresponding alk-1-ene. In the absence of
hydroxylic compounds, 2-chlorodecylphosphonic acid is decomposed by
cyclohexylamine to dec-1-ene and a product which appears to be
N-cyclohexylphosphoramidate; t-amines and also aniline cause
dehydrohalogenation to dec-1-enylphosphonic acid.

The proton magnetic resonance spectra of
most of the phosphorus-containing substances described herein are recorded.
Linear Benzochromanones and Benzochromones. II. Synthesis of 6,7-Cyclohexenochromanone, 6,7-Benzochromanone, 6,7-Cyclohexenochromone, and 6,7-Benzochromone
Authors: Bell KH , Duewell H
Published: December 2006

��� 6,7-Cyolohexenochromanone,
6,7-benzochromanone, 6,7-cyclohexenochromone, and 6,7-benzochromone have been
synthesized from a common starting material, 6,6,7,8-tetrahydro-2-naphthol.
6,7-Benzochroman has been obtained as a reaction by-product.
The Structure of Tasmanone
Authors: Hellyer RO , Bick IRC , Nicholls RG , Rottendorf H
Published: December 2006

The original source of tasmanone appears
to have been Eucalyptus tasmanica rather than E. risdoni or E. linearis. A far
richer source has been found in E. camfieldii. Tasmanone has been shown to be a
tautomeric mixture of enols (IV) and (V). The major isomer forms approximately
70% of the mixture.
The Spectrophotometry of Sodium Nitrite Solutions in Aqueous Sulphuric and Perchloric Acids and the Equilibrium between Nitrosonium Ion and Nitrous Acid
Authors: Bayliss NS , Dingle R , Watts DW , Wilkie RJ
Published: December 2006

The spectra of solutions of sodium nitrite
in aqueous solutions of sulphuric and perchloric acids have been measured at a
number of temperatures, and from these spectra the concentrations of the
species HNO2 and NO+ have been calculated over the acid-concentration
ranges 0-100% sulphuric acid (by wt.) and 0-72% perchloric acid (by wt.). The
changes due to temperature were found to be less than the experimental error in
the determination of the concentrations of nitrous acid and nitrosonium ion.

The equilibria of importance in such
systems are discussed and equilibrium constants have been calculated for the
reactions

H2SO4
+ HNO2 <=> H2O + NO+ + HSO4-

and

HClO4 + HNO2 H2O + NO+ + ClO4-

Attempts have been made to
correlate the determined values for the concentration of nitrous acid and
nitrosonium ion with the acidity functions J0,
C0, and Hr for both solvent systems.

The nitroacidium ion (H2NO2+)
in these systems is found to be less important than previously thought.'
The Spectrophotometry of Nitrate Solutions in Aqueous Sulphuric Acid
Authors: Bayliss NS , Watts DW
Published: December 2006

The ultraviolet spectra of solutions of
potassium nitrate in aqueous sulphuric acid have been studied. Three
absorptions, those due to the species NO3-, HNO3,
and NO2+, have been found. From this study a
semiquantitative picture has been developed of the distribution of the total
nitrate between these three species. It was found that in the sulphuric acid
concentration range 0-15% by weight, the dissolved nitrate existed as nitrate
ion and that from 15-70% sulphuric acid, nitrate ion, and molecular nitric acid
were present in comparable amounts. In the sulphuric acid concentration range
72-82% nitric acid accounted for the total dissolved nitrate and as the
sulphuric acid concentration was increased from 82-90% nitric acid was
converted to nitronium ion.
Electronic Conduction in Polymers. II. The Electrochemical Reduction of Polypyrrole at Controlled Potential
Authors: Bolto BA , Weiss DE
Published: December 2006

Molecular iodine was removed from
polypyrrole by electrochemical reduction of slurries at a mercury cathode. This
method was found to be more effective than the treatment of rigid or packed
polymer electrodes.

Voltammetric plots indicated that two
reductions occurred, at potentials insensitive to pH. The current passage was
dependent on the iodine content, while partial reduction or solvent extraction
deleted the first current peak. Complete reduction or alkali treatment removed
both peaks, whereas iodide in solution increased the reduction potentials. From
this evidence it is postulated that the first peak is due to iodine in
solution, the second to iodine present as a charge-transfer complex of
polypyrrole. By estimating the amount of iodine and iodide present in the
electrolyte the reduction potential for dissolved iodine was calculated and
found to agree with that observed for the first peak in the slurry reduction.
Confirmation of this potential was obtained in the reduction of a blank containing
the found amounts of iodine and iodide.

Quantitative data were obtained for the
reduction of slurries in neutral electrolytes. There was reasonable agreement
between coulometric estimations and the iodine removed, after correction for
iodide already present, provided that the anode reaction did not supply
reducible material to the catholyte. Reduction of iodine by polypyrrole itself
did not appear significant in neutral suspensions.

Iodine was readily removed
electrochemically from the early polymers which contained only about 2.2
m-equiv/g. A later polymer contained almost a third more iodine and required
prolonged reduction times which were cut considerably by the use of a silver
anode to mop up iodide ion as it was formed. The reduction products were
compared for changes in acidity, resistivity, and oxygen content. I.
Electronic Conduction in Polymers. III. Electronic Properties of Polypyrrole
Authors: Bolto BA , McNeill R , Weiss DE
Published: December 2006

The electron spin resonance absorption and
electrical resistivity have been measured under rigorous conditions for a
series of polypyrroles prepared over the temperature range 120-500�. When
plotted as a function of pyrolysis temperature the resistivity shows a maximum
in the region 200-300�. Although the resistivity of the polymers prepared at
120� and 500� is roughly similar, their e.s.r. behaviour is quite different.
The low-temperature polymer, containing much complexed iodine, shows a very
broad signal arising from an excited state probably associated with a
polypyrrole-iodine charge-transfer complex; the high temperature polymer,
containing no iodine, shows a strong narrow signal arising from the ground
state of the polymer.

The changes in conductivity of the
polymers following the adsorption of electron acceptor or donor molecules have
been measured. It is concluded that, depending on the relative amounts of
electron donating or attracting chemisorbed species in relation to the
concentration of donor nitrogen atoms in the polypyrrole, the polymer may
behave as an intrinsic or extrinsic semiconductor with n- or p-type
characteristics. Charge-transfer complexes of strength sufficient to cause
partial ionization induce extrinsic behaviour by changing the ratio of the
number of electrons to the number of holes. Substituent groups such as the
hetero atoms which interact with the π-electron system inductively or
through resonance affect only the relative mobility of the charge carriers and
induce intrinsic behaviour.
The electronic structure of N2O4. I. σ-Electron delocalization study
Authors: Brown RD , Harcourt RD
Published: December 2006

A detailed molecular orbital study of the σ-
and π-electrons of N2O4 is described. Special
consideration is given to possible types of oxygen σ-electron
delocalization into antibonding NK and KO orbitals which are vacant in the
classical structure. Of these, only depopulation of oxygen 2pπ-orbitals
into the antibonding NN σ-orbital seems to be of overall importance for
interpreting the NN and NO bond properties. The other oxygen a-electron
delocalizations are small, and their contributions to the NO bond orders
(although sometimes significant), appear largely to cancel.

The possibility that our VESCF procedure
may yield an overestimate in the magnitude of the calculated NN σ-bond-order
is discussed.

A distinction is made between the nature of
molecular orbitals arising from combination of π-orbitals on oxygen with
the antibonding NN and the antibonding NO orbitals respectively.
Copper(II) catalysis of the hydrolysis of glycylglycine
Authors: Grant IJ , Hay RW
Published: December 2006

Copper(II) ions catalyse the hydrolysis of
glycylglycine in the pH range 3.5-6. The pH-rate profile has a maximum at pH
4.2, due to the formation of a complex CuGlyGly+. The decrease in
rate at higher pH values is associated with the production of catalytically
inactive CuGlyGly complexes produced by the ionization of the peptide hydrogen
atom. The mechanism of the reaction is discussed and its possible biological
significance considered.
The uncatalysed and nickel(II) catalysed decarboxylation of dihydroxyfumaric acid
Authors: Hay RW , Harvie SJ
Published: December 2006

The kinetics of decarboxylation of
dihydroxyfumaric acid have keen studied in aqueous solution at 25�, over a
range of pH. At 25�, the thermodynamic ionization constants are 2.7 x 10-2
= and 4.36 x 10-4, indicating the trans enol structure in aqueous solution.
The decarboxylation occurs in two consecutive steps to give glycolaldehyde as
the final product. The monoanion of dihydroxyfumaric acid with k = 2.69 x 10-2
min-1 is the active species in the reaction.

The decarboxylation is catalysed by nickel(II)
ions at low metal ion concentrations, but at high metal ion concentrations
there is evidence for the formation of catalytically inactive metal complexes.
The application of computer techniques to consecutive first-order reactions is
discussed. The
enol + keto equilibrium of dihydroxyfumaric acid has been studied. In aqueous
solution the ultraviolet spectrum indicates that the acid is completely
enolized, but exists almost exclusively as the keto form in alkaline solution.
The rate constant for the process enol + OH- → keto + OH' is
2.9 l-1 mole sec-1 at 25�.
Proton magnetic resonance spectra of some 1,2-Dithiole-3-ones and 1,2-Dithiole-3-thiones
Authors: Brown RFC , Rae ID , Sternhell S
Published: December 2006

��� P.m.r. spectra of 31 derivatives in the
title series are tabulated. The chemical shifts of the heterocyclic ring
protons, the influence of substituents upon them, the differences between the
two systems, and allylic coupling in methyl derivatives are discussed. It was
not found possible to make any firm conclusion regarding aromaticity of these
systems, but there is some evidence that the bond order of C4 - C5 bond is less
than 2. ��� The p.m.r. spectra of a number of simple
aniline derivatives were examined as model compounds. Acetylation of the amino
groups causes a downfield shift (0.7-2.2 p.p.m.) in the ortho ring protons.
Synthesis of heterocyclics via enamines. II. Reactions of Cyclohex-1-enyl -aniline, -morpholine and -piperidine with 1,1-Dimethyl-3-oxobutyl isothiocyanate
Authors: Singh H , Singh S
Published: December 2006

The condensation of cyclohex-1-enylaniline
(8) with 1,1-dimethyl-3- oxobutyl isothiocyanate (5) gave
1,4,5,6,7,8,9,10-octahydro-2,4,4- trimethyl-1-phenyl-1,5-benzodiazocine-6(1H)-thione
(9) as the major product and 3-phenyl-4,6,6-trimethyl-1,2,3,6-tetrahydropyrimidine-2-
thione (7; R = Ph) as the minor product. The similar condensations of (5) with
cyclohex-1-enylmorpholine and cyclohex-1-enylpiperidine formed the 1-thiocarbamoyl
derivatives through β-elimination of the intermediate (15).
Preparation and N.M.R. spectra of 2,5-Diaryl-2,5-di-t-butyl-Δ3-1,3,4-thiadiazoline 1,1-Dioxides
Authors: Brophy GC , Collins DJ , Hobbs JJ , Sternhell S
Published: December 2006

The reaction of
1-(4-methoxyphenyl)-2,2-dimethyldiazopropane with sulphur dioxide in benzene at
5? gave a 54% yield of 2,5-di-t-butyl- 2,5-bis(4-methoxyphenyl)-Δ3-1,3,4-thiadiazoline
1,1-dioxide (4a). The n.m.r, spectra of this and the analogous compounds from
1-(4- chlorophenyl)-, and 1-(3,4,5-trimethoxyphenyl)-diazopropane,
showed temperature dependence due to restricted rotation of the aryl groups.
The energy barriers associated with this process were determined.��� Structural factors profoundly influence the
course of the reaction of 1-aryldiazoalkanes with sulphur dioxide. For example,
1-adamantyl-1- (4-methoxyphenyl)diazomethane gave no detectable amount of the
thiadiazoline derivative, but an almost quantitative yield of 1-(4- methoxybenzoyl)-adamantane.
Free radicals of coniferyl alcohol and isoeugenol
Authors: Smith GJ , Miller IJ
Published: December 2006

E.s.r, spectra have been
obtained from the free radicals formed by photolysis of coniferyl alcohol and
isoeugenol in low temperature ice matrices. Analysis of these spectra indicates
that the unpaired electrons are delocalized over the entire radicals and the
spin densities at the β carbon atoms are about a third of an electron.
Acetyl migration in Urs-12-ene-3α,24-diol
Authors: Khong PW , Lewis KG
Published: December 2006

A previous tentative
structural assignment of a monoacetate of urs-12- ene-3α,24-diol as the
3-mono-ester has been shown to require revision. Authentic urs-12-ene-3α,24-diol
3-monoacetate has been prepared as well as the 24-monoacetate and
interconversion of the two monoacetates has been demonstrated. The possibility
that this acetyl migration occurs through conversion of ring A to a boat form
is supported by the ready isolation of a 3α,24-O-isopropylidene
derivative.
The nature of some derivatives of leucodrin
Authors: McAlpine JB , Riggs NV
Published: December 2006

The structures of O-isopropylideneleucodrin
aryl methyl ether and leucodrin nor-aldehyde have been revised on the basis of
spectroscopic studies of these compounds and their acetyl derivatives.
The ZnO-rich area of the ternary system ZnO-TiO2-SiO2
Authors: Holland AE , Segnit ER
Published: December 2006

Equilibrium relationships
in the zinc-rich corner of the ternary system ZnO-TiO2-SiO2
have been studied. No ternary compounds were found. Three invariant points were
located, all eutectics. The minimum melting point in the system was 1315(�5)�C.
A large area of liquid immiscibility at high temperatures is postulated.
Sodium dichromate monohydrate
Authors: Hambly AN
Published: December 2006

When crystals of sodium
dichromate dihydrate are heated at 1 atm pressure,
the phase change

������������������� Na2Cr2O7,2H2O
→ Na2Cr2O7,H2O + saturated
solution

occurs at 82.8�C with the
absorption of 17.6�0.95 kJ per mole of dihydrate. A second phase change

������������������� Na2Cr2O7,H2O
→ Na2Cr2O7 + saturated solution

occurs at 91.1�C with the
absorption of a further 12.4�1.5 kJ per mole of dihydrate.
Reactions of 1-substituted 2,4-dinitrobenzenes with diamines and anilines : the question of base catalysis by amines
Authors: Lee HH , Main L
Published: December 2006

Calculated second-order
rate constants for the reactions of ethane-1,2- diamine and propane-1,3-diamine
with 1-chloro-2,4-dinitrobenzene in methanol and with 2,4-dinitro-1-phenoxybenzene
in dioxan/water (3 : 2) are mildly dependent on amine concentration. The
catalysis is no weaker than that for monoamines and this is adduced as evidence
suggesting that it does not represent base catalysis in the second stage of the
intermediate-complex mechanism for activated aromatic nucleophilic
substitution. ��� The aromatic amines m-anisidine, aniline,
p-toluidine and p- anisidine mildly catalyse their own aminolysis reactions
with 1-fluoro- 2,4-dinitrobenzene in methanol; the catalytic effects are not
significantly smaller than that for the more strongly basic aliphatic amine
butylamine. Contrary to an earlier report, there is no kinetic evidence to
support charge-transfer complexing in the reaction of aniline with
1-fluoro-2,4-dinitrobenzene.
Oxidation of (738211;)-α-terpineol to some epoxy-alcohols
Authors: Wilson III CW , Shaw PE
Published: December 2006

α-Terpineol has been
converted by peracid oxidation into a 1,2-epoxy-8- ol(2a) and (2b), a 18-epoxy-2-ol
(3) and a 2,8-epoxy-1-ol(5). The mechanism for formation and stereochemical
assignments for these products are discussed.
Nucleophilic substitution of Bromo-p-benzoquinones by dimethylamine
Authors: Hewgill FR , Mullings LR
Published: December 2006

Product analysis shows that
dimethylamine, like methoxide anion, substitutes bromo-p-benzo-quinones by an
addition-elimination process, resulting in isomeric dimethylaminoquinones.
Bromo- dimethylaminoquinones were also formed, due to incomplete elimination of
hydrogen bromide. In contrast to the substitution by methoxide the product
distribution is largely unaffected by changing to a dipolar aprotic solvent. ��� The e.s.r. spectra of 2-t-butyl-5-(N,N-dimethylamino)-1,4-benzosemiquinone
and two related semiquinones have been analysed.
Assignment of configurations to adducts of 2-substituted anthracene with maleic anhydride by N.M.R. spectroscopy
Authors: Verma SM , Singh RM
Published: December 2006

Isomeric adducts of
2-methylanthracene and maleic anhydride and of
2-aminoanthracene and maleic anhydride were prepared
and their configurations determined by N.M.R. spectroscopy. The adducts were
transformed into their N-aminoimide derivatives. N'-Substituents
on the amino group were chosen so as to permit, because of their restricted
rotation and non-planarity about the N-N'
bond, an investigation into the magnetic effects of the cage moiety. When both
the dienyl parts of the Diels-Alder
adducts are almost identical, the N'-acetyl-N'-phenyl group has been found to be a
diagnostic probe for the configurational studies. In N-(N'-acetyl-N'-aroy1amino)imide
derivatives, the N'-aroyl group has been found to prefer an anti conformation
while in the N?-acetyl- N'-phenyl
group the N'-phenyl prefers the syn conformation.
Complexes of carbohydrates with metal cations. VIII. Lanthanide-induced shifts in the P.M.R. spectra of some methyl glycosides and 1,6-anhydrohexoses
Authors: Angyal SJ , Greeves D , Littlemore L , Pickles VA
Published: December 2006

Addition of lanthanide ions
to aqueous solutions of some methyl glycosides and 1,6-anhydrohexoses causes
shifts of the signals in their p.m.r. spectra. The
approximate location of the cation in the complexes was determined and an
attempt was made to explain the shifts in terms of contact and pseudocontact interactions.
Reactions of primulagenin A. III. Acetyl derivatives and acetyl migration
Authors: Baigent DR , Hensens OD , Lewis KG
Published: December 2006

Procedures have been
developed for the preparation of all of the possible acetylated derivatives of primulagenin A (olean-12-ene-3β,16α,28-triol).
Acetyl migration has been shown to occur between the oxygen atoms at the 16α-
and the 28-positions.
The chemistry of the metasternal gland secretion of the eucalypt longicorn Phoracantha synonyma (Coleoptera : Cerambycidae)
Authors: Moore BP , Brown WV
Published: December 2006

The metasternal
gland secretion of Phoracantha synonyma
contains a diversity of volatile components, one of which,
2-hydroxy-6-methylbenzaldehyde (1), is of widespread occurrence in the genus.
Threemajor components and
several minor components are macrocyclic lactones, of which the following have
been positively identified: decan-9-olide (2), (2)-dec-4-en-9-olide (3) and
11-hydroxytetradec-5-en-13-olide (4). The methyl and ethyl esters of
2-methylbutyric and related acids are also present and are responsible for the
characteristic odour of the fresh secretion.
Some reactions of 2'-benzyloxychalcone derivatives and preparation of trans-3-Hydroxy-7,4'-dimethoxyflavanone from a chalcone epoxide
Authors: Clark-Lewis JW , Tucker PG
Published: December 2006

Treating
2'-(4-methoxybenzyl)-4,4'-dimethoxychalcone epoxide with hydrochloric acid in
acetic acid gave trans-3-hydroxy-7,4'-dimethoxyflavanone
(18%), the first dihydroflavonol with a 4'-methoxylsubstituent obtained by
this route. This observation indicates the possibility that replacing the 2'-(4-methoxybenzyl)
protecting group in the chalcone by one with more
powerful electron-releasing substituents could lead to an acceptable synthesis
of dihydroflavonols.
The influence of pressure on the infrared spectra of hydrogen-bonded solids. V. The formation of Fermi resonance 'windows'
Authors: Hamann SD
Published: December 2006

Measurements have been made
of the influence of pressure to 40 kbar on the
infrared spectra of the normal and X-deuterated forms of seven solid compounds
which have strong X-H...Y hydrogen bonds and whose spectra show very broad and
intense X-H stretching bands at low frequencies. For two of the compounds,
isonicotinic acid and nicotinic acid, compression causes the smooth transformation
of superimposed absorption bands into Fermi resonance 'windows', or 'Evans
holes'. The effect probably arises from increased overlap of the wave functions
for in-plane ring-bending vibrations and X-H stretching vibrations.
Cyclic hydroxycarboxylic acids. II. Lactonization reactions on 2-Hydroxycyclopentanecarboxylic acids and 3-Hydroxyprolines
Authors: Philp RP , Robertson AV
Published: December 2006

The racemates of
cis-2-hydroxycyclopentanecarboxylic acid and of cis-3- hydroxy-N-tosylproline yield corresponding β-lactones upon
treatment with cold tosyl chloride-pyridine. Similar
treatment of trans-2- hydroxycyclopentanecarboxylic
acid gives cyclopent-1-enecarboxylic acid, but trans-3-hydroxy-N-tosylproline
is unchanged. Unlike in other 3-hydroxyprolines, the proline protons in the N-tosyl β-lactone have a completely first-order p.m.r.
spectrum which is analysed.
Crystal structure of Tetracarbonyl(2,3-η-1,4-dihydro-1,4-epoxynaphthalene)iron(0)
Authors: Raston CL , Wege D , White AH
Published: December 2006

The crystal structure of
the title compound, [Fe(CO)4(C10H8O)], has
been determined at 295 K from diffractometer data, and refined by least squares
to a residual of 0.073 for 2990 ?observed? reflections. Crystals are triclinic,
Pī, a 22.980(6), b 9.385(3), c 6.313(2) Ǻ,
α 85.22(3), β 87.67(3), γ 79.48(3)�, Z4. The two independent
molecules in the same cell differ only trivially in their geometries, the
coordination number about the metal being essentially five: four carbonyls and
the ethylene double bond in a pseudo-trigonal-bipyramidal arrangement. From
distortions observed within the molecular geometry as a result of steric
interactions between the epoxide oxygen and the nearby axial carbonyl, it
clearly emerges that the stability of the present derivative relative to that
of methylene bridged ligands is simply a consequence of the greatly increased
stereochemical interaction of the latter and not of any electronic effect.
The Beckmann rearrangement of 3β-Chloro-5α-cholestan-7-one oxime and related compounds and the Schmidt reaction of the corresponding ketones
Authors: Siddiqui AH , Baig MH , Lakshmi C
Published: December 2006

The chromic acid oxidation
of cholesteryl chloride gave 3β- chlorocholest-5-en-7-one, which on
hydrogenation gave 3β-chloro-5α- cholestan-7-one. The Schmidt
reaction of this ketone afforded a single lactam,
3β-chloro-7a-aza-B-homo-5α-cholestan-7-one. The Beckmann
rearrangement of its oxime by means of thionyl chloride or p- toluenesulphonyl
chloride and pyridine gave the same lactam. The structure of the lactam was
established by its conversion into a known lactam by reduction. 3β-Chlorocholest-5-en-7-one
oxime on treatment with thionyl chloride or the corresponding O-tosyloxime on passing through a column of alumina underwent
Beckmann rearrangement to give a single lactam, 3β-chloro-7α-aza-B-homocholest-5-en-7-one.
Tacticity of Poly(Methyl Methacrylate). Evidence for a Penpenultimate Group Effect in Free-Radical Polymerization
Authors: Moad G , Solomon DH , Spurling TH , Johns SR , Willing RI
Published: December 2006

The tacticity of poly(methyl methacrylate ) prepared by free-radical polymerization has been determined by analysing the carbonyl region of the 13C n.m.r . spectrum. This analysis demonstrates that the addition of poly(methyl methacrylyl ) radical to methyl methacrylate in benzene at 60°C is subject to a significant penpenultimate unit effect. The probability of forming a meso dyad is some 20% less if the preceding dyad in the chain is also meso . The polymerization (60°C, benzene) is described by the following parameters P(m) = 0.202, P(m|m) = 0.159, P(r | m) = 0.212.
The Nitration of Some 4-Alkylphenols; Acid-Catalyzed Rearrangements of Some Polysubstituted 4-Alkyl-4-Hydroxycyclohexa-2,5-Dienones
Authors: Gray MJ , Hartshorn MP , Vaughan J
Published: December 2006

The nitrations of 4-methyl (6a) and 4-ethyl (9a) tetrabromo phenols, and 4-methyl (6b) and 4-ethyl (9b) 2,3,5-tribromo-6-nitrophenols are described. The acid- catalysed rearrangements of 4-alkyl-4-hydroxycyclohexa-2,5-dienones (7a,b) and (8a,b) in concentrated sulfuric acid are described, and the effects of the nature of the C4- alkyl group and C6-substituent (Br or NO2) on the observed reactions are discussed.
Heterocyclic Amplifiers of Phleomycin .X. Derivatives of Diazine Mono-Thiol and Di-Thiol
Authors: Barlin GB , Brown DJ , Cronin BJ , Ngu M
Published: December 2006

A series of pyrazinethiols and pyrimidinethiols with phenyl substituents have been prepared and converted into their carbamoylmethylthio, 2-dimethylaminoethylthio and 2-aminoethylthio derivatives. Similar derivatives of pyrazine-2,3- and -2,6-dithiol were also prepared together with N,N-dimethyl-2-(1′- and 2′- naphthyloxy)ethylamine. As amplifiers of phleomycin these compounds showed moderate two-to- three-star activity.
Studies of Australian Soft Corals .XXXVII. The Structure Determination of 2 Cembranolide Diterpenes From Soft Corals of the Genus Efflatounaria (Coelenterata, Octocorallia, Alcyonacea)
Authors: Bowden BF , Coll JC , Engelhardt LM , Meehan GV , Pegg GG , Tapiolas DM , White AH , Willis RH
Published: December 2006

Two isomeric 7,8-epoxycembra-3,11,15-trien-16,2-olides have been isolated from different species of the soft coral genus Efflatounaria. The structure of each was deduced spectroscopically , and the relative stereochemistry of one was determined by X-ray crystallography. The absolute stereochemistry of each cembranolide was obtained by chemical correlation with known compounds.
Pentakis(Methoxycarbonyl)-Cyclopentadiene Chemistry .X. Crystal-Structure of the Charge-Transfer Complex Tropylium Pentakis(Methoxycarbonyl)Cyclopentadienide
Authors: Bruce MI , Humphrey PA , Skelton BW , White AH
Published: December 2006

The compound [C7H7][C5(CO2Me)5] forms very long but thin orange-red needles, which, in contrast to a previous report, form orange-red to deep red solutions in polar solvents. Decolorization of an acetone solution occurs on standing, but the white compound so obtained has not been identified. Single-crystal X-ray structure determination at 295 K (R = 0.078 for 1030 'observed' reflections) shows the presence of an infinite sandwich structure comprising columns of interleaved anion and cation planes normal to b. Crystals are rthorhombic, Pbcn , a 18.206(6), b 13.954(12), c 17.243(5)Ǻ, Z 8.
Thermal Β-Elimination of Benzenesulfenic Acid From a Terminal Sulfoxide and Its Re-Addition exo to a Strained C=C Bond in the Same Bicyclo[2.2.1]Hept-5-Ene System
Authors: Brown RFC , Coulston KJ , Eastwood FW , Fallon GD
Published: December 2006

A product from the thermolysis of 2,2-dimethyl-5-(endo-3′- phenylsulfinylmethylbicyclo [2.2.1]-hept-5′-en-2′-ylidene)-1,3-dioxan-4,6-dione (1) in carbon tetrachloride is 2,2-dimethyl-5-(3′-methylene-exo-5′-phenylsulfinylbicyclo[2.2.1]heptan-2′-ylidene)-1,3-dioxan-4,6- dione (3).
Electron-Spin-Resonance Study of Tetracyclopentanaphthalene Radical Ions
Authors: Bakker MG , Claridge RFC
Published: December 2006

From an e.s.r. investigation of tetracyclopentanaphthalene cation and anion radicals it was found that the oscillation of the alkyl cyclopentyl rings is sufficiently rapid to average the splitting constants observed. The averaged splitting constants found were 0.5891, 0.1983 and 0.0207 mT in the anion, and 1.1637, 0.4387 and 0.0062 mT in the cation.
The Synthesis of Optically Pure Epoxy-alkyl β-D-Glucosides and β-Cellobiosides as Active-Site Directed Inhibitors of Some β-Glucan Hydrolases
Authors: Rodriguez EB , Scally GD , Stick RV
Published: December 2006

(2R)- and (2S)-2,3-Epoxypropyl, (3R)- and (3S)-3,4-epoxybutyl and (4S)- 4,s-epoxypentyl B- Dglucopyranoside , together with the (3R)- and (3s)-3,4-epoxybutyl β- cellobiosides , have been prepared by condensation of a glycosyl bromide with the appropriate enantiomer of a chiral alcohol containing a diol protected as an isopropylidene acetal, and subsequent manipulation of the unmasked diol into the epoxide function. As well, in an improvement to the whole process, both diastereoisomers of the various epoxypropyl and epoxybutyl glycosides were available from just the one enantiomer of the alcohol by an alternative manipulation of the diol. Finally, precursors to 2,3-epoxy-4-hydroxybutyl β-D-glucosides and β- cellobiosides were prepared in high optical purity by Sharpless asymmetric epoxidation of the appropriate 4-hydroxybut-2-enyl glycosides.
3-Methyl-8-(substituted phenyl)-pteridine-2,4(3H,8H)-diones as Potential Antimalarials
Authors: Halladay PK , Cowden WB
Published: December 2006

A series of 6,7,8-substituted 3-methylpteridine-2,4(3H,8H)- diones was synthesized by condensation of 5-amino-6-(substituted anilino )-3-methylpyrimidine-2,4(1H,3H)- dione with α- dicarbonyl reagents. These compounds were tested for antimalarial activity against the human parasite Plasmodium falciparum in culture, and lethal Plasmodium vinckei vinckei in mice. The 6,7-unsubstituted pteridinediones were active against cultured P. Falciparum ; however, none of the series was active against P. vinckei vinckei in mice.
Monosubstitution of Symmetrical Piperazine-2,5-dione Derivatives
Authors: Badran TW , Easton CJ
Published: December 2006

Bromination and methanolysis of derivatives of glycine anhydride affords the corresponding 3-bromo- and 3-methoxy-substituted piperazine-2,5-dione derivatives in a simple one-pot procedure.
Synthesis of Casein-Related Peptides and Phosphopeptides. III. The Unexpected Dephosphorylative Rearrangement of the Simple Model Phosphopeptides Ac-Ser(PO3Bzl2)-NHMe and Ac-Ser(Po3H2)-NHMe
Authors: Perich JW , Johns RB
Published: December 2006

The simple phosphopeptide, Ac-Ser(PO3Bzl2)-NHMe , was found to be subject to a dephosphorylative rearrangement and gave H-Ser-NHMe .( BzlO )2PO2H after 12 months at 20°C. This dephosphorylative rearrangement process is proposed to proceed by an O to N phosphorus shift followed by acid hydrolysis of the N-acetyl group. Alternatively, the simple phospho-peptide, Ac-Ser(PO3H2)-NHMe, was found to undergo conversion into H-Ser- NHMe.H3PO4 over a period of four years, this process being established by a 13C n.m.r. spectroscopy study to proceed through initial acid hydrolysis of the N-acetyl group followed by phosphate loss.
N-Benzylidene-2-nitrobenzenesulfenamide and 1-Nitro-2-(phenylthio)benzene: Comparison of Their Behavior on Flash Vacuum Pyrolysis and Under Electron Impact
Authors: Gillis RG , Porter QN , Yeoh LL
Published: December 2006

The molecular ion of N-benzylidene-2-nitrobenzenesulfenamide (1) loses SO2 and N2 and gives a base peak at m/z 165, C13H9, and another abundant peak at m/z 166, C13H10. Analysis, by gas chromatography/mass spectrometry and by preparative thin-layer chromatography, of the products of flash vacuum pyrolysis at 500-800°C of (1) showed no detectable hydrocarbon, but dibenzothiophen (mol. wt 184) was isolated and identified. The abundance of m/z 184 in the positive-ion mass spectrum of (1) is about 1%. In the mass spectrum of 1-nitro-2-( phenylthio )benzene (2a) the base peak is at m/z 167, C12H9N, and there is a fragment ion at m/z 184, C12H8S (35%). However, carbazole (3) could not be isolated from the flash vacuum pyrolysis products, but dibenzothiophen (4) was obtained in increasing yield as the pyrolysis temperature was raised from 500 to 800°C. It is clear from these results that drawing analogies between electron impact mass spectra and flash vacuum pyrolysis results is somewhat hazardous.
The X-Ray Crystal-Structure of 5-C-Methyl-α-L-idopyranose
Authors: Craig DC , Stevens JD
Published: December 2006

The crystal structure of 5-C-methyl-α-L-idopyranose (1) has been determined by X-ray diffraction. Crystals of (1), prepared as the hemihydrate, are tetragonal, space group P41212 with a 7.4931(3), c 32.645(2)Ǻ, Z 8, Refinement on 1043 observed reflections measured with Cu Kα radiation converged at R 0.031.
Oxidative Cyclizations. VIII. Mechanisms of Oxidation of ortho-Substituted Benzenamines and Improved Cyclizations by Bis(acetato-O)Phenyliodine
Authors: Dyall LK , Harvey JJ , Jarman TB
Published: December 2006

Published reports describe the oxidative cyclization of suitable ortho-substituted arenamines to form such products as 2,1-benzisoxazoles, benzofurazan 1-oxides and benzotriazoles, by using bis(acetato-O)phenyliodine at room temperature. However, the reactions are often inconveniently slow. We now report attempts to achieve short reaction times with more powerful iodine(III) oxidants. These often failed to give cyclic products, but the results enable us to argue that the reaction competing with cyclization involves the arenaminyl, cation ArN+H. When such cations are predicted to be relatively unstable, the parent arenamine can be rapidly cyclized in high yield by oxidation with bis(acetato-O)phenyliodine in boiling benzene.
Investigation of the Range of a Plastic pH Sensor Based on a Dibasic Ionophore
Authors: Cardwell TJ , Cattrall RW , Deady LW , Murphy KA
Published: December 2006

A study is reported of the use of a neutral carrier reagent containing two nitrogen atoms with very different basicities in a pH-sensitive membrane electrode with a view to obtaining a broad response range. This electrode responds well in the pH region of 6-12 but suffers anion interference in the region of pH 2-6. A study is included of the effect of adding various amounts of potassium tetrakis(4-chloropheny1)borate as an anion suppressing reagent to the membrane in order to reduce the anion interference at low pH values. The conclusion is drawn that an extension to the working pH range is not possible with this approach unless controlled amounts of anion suppressing reagent can be provided to approximately balance the positive charge of the carrier in each region of the pH scale.
Structural Studies of Two Bioactive Furanosesquiterpenes From Cryptocarya densiflora (Lauraceae)
Authors: Achmad SA , Azmina h , Effend y , Ghisalberti EL , Hakim EH , Makmur L , White AH
Published: December 2006

The structures of two bioactive germacranolide furanosesquiterpenes from Cryptocarya densiflora B1. ( Lauraceae ) have been determined by X-ray crystallogaphic methods and have been shown to correspond to linderane and pseudolinderadine. The ambiguity regarding the stereochemistry of the C1-C2 epoxide in pseudolinderadine is clarified. This compound has not been reported previously as a natural product.
Vase treatments containing gibberellic acid do not increase longevity of cut Grevillea 'Sylvia' inflorescences
Authors: Setyadjit  , Irving D. E. , Joyce D. C. , Simons D. H.
Published: December 2006

The longevity of Grevillea ‘Sylvia’ inflorescences can be very short and is influenced by exposure to ethylene. Gibberellic acid has the potential to delay senescence in some cut flowers by acting as an anti-ethylene treatment. Gibberellic acid was therefore applied to Grevillea ‘Sylvia’ inflorescences in vase solutions to determine its effects on longevity. Treatments with gibberellic acid did not prolong the longevity of inflorescences or influence 1-aminocyclopropane-1-carboxylic acid concentrations. Treatments at high gibberellic acid concentrations enhanced flower abscission and we therefore conclude that vase-applied gibberellic acid treatments are not suitable for extending the longevity of cut Grevillea ‘Sylvia’ inflorescences.
Dual energy X-ray absorptiometry predicts the effects of dietary protein on body composition of pigs
Authors: Suster D. , Leury B. J. , Kerton D. J. , Dunshea F. R.
Published: December 2006

The present study investigated the potential of dual energy X-ray absorptiometry to determine the effect of dietary protein on live pig body composition compared with the standard methods. The experiment utilised 48 Large White × Landrace gilts, stratified on liveweight at 17 weeks of age (initial liveweight about 60 kg), and allocated within strata to diets containing either 85 or 100% of dietary protein requirements. The diets were fed ad libitum and contained 14.6 or 16.7% protein, respectively. Pigs were housed individually to allow weekly measurement of feed intake and liveweight. A Hologic QDR4500A dual energy X-ray absorptiometer was used to determine lean, fat and ash composition of pigs initially and 4 weeks later at the end of the experiment. Daily gain was increased by about 200 g in pigs fed the protein-adequate diet, but feed intake was not affected. Therefore, pigs fed adequate protein had a lower feed conversion ratio (2.92 v. 3.52 g/g, P<0.001). Feeding the protein-adequate diet increased lean deposition by about 150 g/day (577 v. 429 g/day, P<0.001) and ash deposition by about 4 g/day (28.7 v. 25.0 g/day, P<0.001), but did not affect fat accretion. This resulted in carcasses with a higher lean content (54.0 v. 50.7 kg, P<0.001) and ash content (2.35 v. 2.28 kg, P<0.05) but unaltered fat content. Therefore, an inadequate level of dietary protein leads to suboptimal growth in lean tissue and bone mineral, with no pronounced effect on fat. These observations were substantiated by chemical analysis and available corrective equations were useful in correcting differences between dual energy X-ray absorptiometry outputs and chemical values. After correction, dual energy X-ray absorptiometry estimates differed less than 5% from the chemical values for lean, protein, water and ash and 10% for lipid. In addition, reduced standard error of the differences around most dual energy X-ray absorptiometry measurements, relative to chemical analysis, allowed small changes in body composition to be detected with increased confidence. These data support the efficacy of using dual energy X-ray absorptiometry in nutritional studies of pigs.
Head area measurements of dead, live, X- and Y-bearing bovine spermatozoa
Authors: Révay T. , Nagy S. , Kovács A. , Edvi M. E. , Hidas A. , Rens W. , Gustavsson I.
Published: December 2006

The head area of bull spermatozoa was measured after viability and acrosome staining using trypan blue and Giemsa stains, followed by X- and Y-chromosome-specific fluorescence in situ hybridisation (FISH). The former staining made possible the categorisation of cells according to morphology and membrane integrity, whereas the latter allowed distinction of spermatozoa bearing X- and Y-chromosomes. Individual spermatozoa could be followed during the consecutive steps of staining, measurement and FISH. Using a high-resolution digital imaging system and measurement software, the head area of more than 3000 cells of five bulls was determined precisely. In all bulls, morphologically normal, viable cells with intact acrosomes were significantly smaller than dead cells with damaged acrosomes. No significant difference in the head area between X- and Y-chromosome-bearing viable, acrosome-intact spermatozoa was found in individual bulls. However, significant between-bull differences were detected in all cell categories.
Effect of the oxidative phosphorylation uncoupler 2,4-dinitrophenol on hypoxia-inducible factor-regulated gene expression in bovine blastocysts
Authors: Harvey A. J. , Kind K. L. , Thompson J. G.
Published: December 2006

In cattle embryos, development to the blastocyst stage is improved in the presence of 10 μm 2,4-dinitrophenol (DNP), an uncoupler of oxidative phosphorylation, coincident with an increase in glycolytic activity following embryonic genome activation. The present study examined redox-sensitive gene expression and embryo development in response to the addition of DNP post-compaction. 2,4-Dinitrophenol increased the expression of hypoxia-inducible factor 1α and 2α (HIF1α, HIF2α) mRNA. Although HIF1α protein remained undetectable in bovine blastocysts, HIF2α protein was localised within the nucleus of trophectoderm and inner cell mass (ICM) cells of blastocysts cultured in the presence or absence of DNP, with a slight increase in staining evident within the ICM in blastocysts cultured in the presence of DNP. However, the expression of GLUT1 and VEGF mRNA, genes known to be regulated by HIFs, was unaffected by the addition of DNP to the culture. Although the development of Grade 1 and 2 blastocysts was unaltered by the addition of DNP post compaction in the present study, a significant increase in the proportion of ICM cells was observed. Results indicate that 10 μm DNP improves the quality of bovine embryos, coincident with increased HIF2α protein localisation within ICM cells and increased HIFα mRNA levels. Therefore, the results demonstrate redox-regulated expression of HIF2.
Influence of hormone environment and donor age on cryopreserved common wombat (Vombatus ursinus) ovarian tissue xenografted into nude mice
Authors: Cleary M. , Shaw J. M. , Jenkin G. , Trounson A. O.
Published: December 2006

Developmentally competent oocytes can be collected from xenografted ovarian tissues; however, optimal xenograft conditions need to be established for this technique to be of use in assisted reproduction. In the present study, common wombat ovarian tissue was xenografted under the kidney capsule of nude mice to clarify the role of recipient gonadal status and donor tissue age on graft establishment, follicle development and oocyte recovery. Eighty-nine per cent of all grafts were recovered; of these, 78% contained growing follicles. In female graft recipients, follicle development to the antral stage occurred earlier in ovariectomised recipients compared with intact graft recipients. Similarly, follicle development occurred earlier in recipients of pouch young ovarian tissue grafts when compared with subadult xenografts. Follicle development proceeded to the antral stage in subadult grafts placed under the kidney capsule of male recipient mice, albeit at a slower rate than subadult grafts placed in female recipients. Oocytes were collected from grafts placed in female and male recipients, but no mature oocytes were observed at the time of collection, nor could these oocytes be matured in vitro. The present study demonstrated that common wombat pouch young tissue xenografted to female recipient mice, and subadult ovarian tissue xenografted to male recipient mice, can develop to the antral stage and can therefore facilitate oocyte collection. However, mature oocytes were not obtained using the current protocol.
Founders' Lecture. Human spermatozoa: fruits of creation, seeds of doubt
Authors: Aitken R. John
Published: December 2006

Deoxyribonucleic acid damage in the male germline is associated with defective fertilisation, impaired embryonic development, reduced implantation, abortion and childhood disease. Oxidative stress and the retention of excess residual cytoplasm by the spermatozoa are frequently associated with the induction of such damage. The redox cycling of xenobiotics by oxido-reductases in the germline, the patient’s age, the incidence of genital tract infections and Sertoli cell dysfunction are all possible contributors to DNA damage in germ cells. Collateral peroxidation of unsaturated fatty acids in the sperm plasma membrane generally ensures that spermatozoa experiencing severe oxidative DNA damage cannot participate in the process of fertilisation. The adaptive termination of pregnancy through the selective vulnerability of genes involved in placentation may also help prevent the vertical transmission of damaged DNA. However, the ultimate safeguard against this form of damage will be to understand the biochemical basis of oxidative stress in human spermatozoa, so that the underlying causative mechanisms can be addressed in a logical manner.