bluuebunny/crossref_metadata_2025 huggingface dataset:
New nine-membered ring diterpenes from the brown alga Dictyota prolificans
Authors: Ravi BN , Wells RJ
Published: September 2010

Five new diterpenes,
related to 'dictyodial' (7), have been isolated from
the brown alga Dictyota prolificans.
The gross structures and, where possible, stereochemistry were solved by
spectral methods and comparison of 13C n.m.r. data with those of dictyodial.
The magnetic susceptibility and anisotropy for K3Fe(CN)6 and Fe(phen)3(ClO4)3,3H2O from very low to ambient temperatures
Authors: Baker J , Figgis BN
Published: September 2010

The magnetic
susceptibilities and anisotropies of K3Fe(CN)6 and of Fe(phen)3(ClO4)3,3H2O
have been measured between 1.6 and 300 K and between 4.2 and 300 K
respectively. The results yield parameter sets for the splitting of the 2T2g
ground term respectively: δ 130 cm-1, ε 67 to -10 cm-1, ζ 275
cm-1, k 0.73; δ 750 cm-1, ε 20 cm-1, ζ
280 cm-1,k 0.81. These
have reliability improved above the sets previously available for the compounds
and substantiate the earlier work. Unfortunately, they do not aid further in making
correlations between details of molecular geometry of the ions and their
electronic structures.
Constituents of Boesenbergia pandurata (syn. Kaempferia pandurata): Isolation, Crystal Structure and Synthesis of (±)-Boesenbergin A
Authors: Jaipetch T , Kanghae S , Pancharoen O , Patrick V , Reutrakul V , Tuntiwachwuttikul P , White A
Published: September 2010

Partly racemized
pinostrobin and pinocembrin, together with
2',6'-dihydroxy-4'-methoxychalcone, cardamonin and a
new chalcone (�) boesenbergin A, have been isolated from Boesenbergia pandurata Schl. (syn. Kaempferia pandurata Roxb., Zingiberaceae).
Spectroscopic studies and X-ray crystallographic analysis have established the
structure (�)-(E)-1-[7'-hydroxy-5'-methoxy-2'-methyl- 2'-(4''-methylpent-3''-enyl)-2'H-chromen-8'-yl]-3-phenylprop-2-enone
for boesenbergin A. A simple synthesis of boesenbergin A has been achieved and
its acid-catalysed cyclization has been studied.
Thienoisothiazoles. I. The synthesis of Thieno[2,3-c]isothiazole and some of its derivatives
Authors: James FC , Krebs HD
Published: September 2010

.Thieno[2,3-c]isothiazole-3-carboxylic acid was the compound
obtained by the reaction of ethyl-3-cyano-5,5-diethoxy-2-oxopentanoate
with phosphorus pentasulfide, previously assumed to yield thieno[3,4-d]isothiazole-4-carboxylic acid.
The parent thieno[2,3-c]isothiazole was
obtained by decarboxylation of thieno[2,3-c]isothiazole-3-carboxylic
acid and by deamination of thieno[2,3-c]-isothiazol-3-amine.
Condensation reactions of some α-aminodiazines with pyruvaldehyde dimethyl acetal
Authors: Barlin GB , Brown IL , Golic L , Kaucic V
Published: September 2010

The
condensation of 3-amino-4-methylaminopyridazine with pyruvaldehyde dimethyl
acetal in methanolic hydrogen chloride has been shown (by X-ray analysis) to
give 3-methoxy-2-methyl-8-methylaminoimidazo[1,2-b]pyridazine.
The crystals are triclinic, space group P1, with a 8.090(1),b 11.357(2),
c l1.618 (2) �, α 88.81(2), β
70.27(2), γ 89.47(2)�, Z 4. The structure was refined to an
R factor (on F) of 0.050 by full-matrix least-squares techniques. Similar
reactions were observed with other 3-aminopyridazines, 2-aminopyrazine and
2-aminopyrimidine.
The viscosity of dilute aqueous solutions of aliphatic alcohols
Authors: Alexander DM , Moy DC
Published: September 2010

Relative viscosities have
been measured of dilute aqueous solutions of aliphatic alcohols, including
methanol, ethanol, the propanols, the butanols and the pentanols, at
temperatures of 278, 293 and 313 K at concentrations in the range 10-4-10-2
mol dm-3. The Jones and Dole B
coefficients have been calculated and compared with literature data
extrapolated to low concentrations.
Photolysis of Di-t-butylnitroxide
Authors: Coxon JM , Patsalides E
Published: September 2010

Di-t-butylnitroxide (1) on photolysis in
methylcyclohexane gives in addition to t-butoxy(di-t-buty1)-amine (7) and
photolabile 2-methyl-2-nitrosopropane (2) a low yield of a white crystalline
solid identified as a mixture of di-t-butylhydroxylammonium nitrate (13) and
nitrite (14). Photolysis proceeds from the excited state produced by a π-π* transition, and in aerated solution is first order
both with respect to nitroxide and light intensity. More complex kinetics are
observed in deaerated solution.
The configuration of the Cr(ox)(trien)+ cation
Authors: House DA
Published: September 2010

On the basis of the
inversion reaction
Λ-(+)589-Cr(ox)(trien)+
+ HCl → Δ-(-)589cis-α-CrCl2(trien)+
the oxalato
complex is now believed to have the cis-β
configuration, rather than the previously suggested cis-α.
Chemistry of the Podocarpaceae. LXI. The rearrangement of aryl phosphates to ortho-hydroxyaryl phosphonates
Authors: Cambie RC , Palmer BD
Published: September 2010

Treatment of methyl 12-(diethoxyphosphoryloxy)podocarpa-8,11,13-trien-19-oate (14)
or its 13-bromo derivative (7) with butyllithium
effects a rearrangement of the phosphate group to give methyl
13-diethoxyphosphoryl-12-hydroxypodocarpa-8,11,13-trien-19-oate (11) in high
yield. Similar treatment of some simple aryl phosphates indicates that the
rearrangement is general. The reaction, which probably occurs by means of an ortho-metallation-nucleophilic
displacement sequence, is superior to existing methods for the preparation of o-hydroxyaryl phosphonates.
Gas-phase pyrolysis of isopropyl chloroformate
Authors: Johnson RL , Stimson VR
Published: September 2010

Homogeneous, molecular
elimination of propene from isopropyl chloroformate takes place at 229-277�C with rate
ke = 1013.94exp(-174000/8.314T) s-1
Rate comparisons indicate
that a polar transition state is involved.
Adsorption of Tris(2,2'-bipyridine)ruthenium(II) cations at silica/aqueous solution interfaces
Authors: Furlong DN
Published: September 2010

The adsorption from aqueous
solution of tris(2,2'-bipyridine)ruthenium(II) cations onto colloidal silica at
25�C has been investigated. It has been shown that electrostatic attraction
between the ruthenium cations and negative silica surfaces provides the main
driving force for adsorption. Maximum adsorption densities are obtained at pH
above 9.5 and equilibrium ruthenium concentrations above 10-4 mol dm-3.
The maximum adsorption density appears to depend on the topography of the
silica surfaces.
Organolanthanoids. III. Preparations and properties of some Di(alkynyl)lanthanoids
Authors: Deacon GB , Koplick AJ , Tuong TD
Published: September 2010

From reactions between di(alkynyl)mercurials
and lanthanoid elements in tetrahydrofuran or
1,2-dimethoxyethane, the organolanthanoids (PhCC)2Yb and (PhCC)2Eu(thf)0.25 (thf = tetrahydrofuran) have been isolated, and (RCC)2M (R =
Ph or But, M = Yb; R = Ph, M = Eu) characterized in solution. Bis(phenylethynyl)ytterbium has also been obtained by ligand
exchange between (C6F5)2Yb or (ButCC)2Y and phenylacetylene.
The di(alkynyl)lanthanoids are considered to have associated structures
with bridging alkynyl groups. Hydrolysis of (RCC)2M
derivatives yields acetylenes RCCH, together with alkenes RCHCH2
(greater for M = Yb than M = Eu),
and, when M = Yb, R = Ph, a little ethylbenzene.
Reactions of aryldiazonium salts and alkyl arylazo ethers. VIII. General acid catalysis of the ionization of alkyl (E)-arylazo ethers in alcoholic solvents
Authors: Broxton TJ , Stray AC
Published: September 2010

Further studies of the
general acid-catalysed ionization of alkyl (E)-arylazo ethers in alcoholic solvents have been carried out.
The magnitude of catalysis and the degree of proton transfer as a function of
the substituent on the aromatic ring, the alkoxide
ion nucleofuge, the solvent and the ionic strength
have been studied. The results are consistent with a mechanism for the acid-catalysed ionization of alkyl (E)-arylazo ethers in which proton
transfer and N-O bond breaking are concerted. 1H and 13C
n.m.r. data for a number of alkyl p-nitrophenylazo ethers are reported.
Complexes of cobalt(II), nickel(II) and copper(II) with a pentadentate Bis(β-amino ketone); Crystal and molecular structure of Aqua(4,4,12,12-tetramethyl-5,8,11-triazapentadecane-2,14-dione)cobalt(II) perchlorate hydrate
Authors: Morgan KR , Gainsford GJ , Curtis NF
Published: September 2010

The diperchlorate
salts of the mono(β-amino ketone) 10-amino-4,4-dimethyl-5,8-diazadecan-2-one
and of the bis(β-amino ketone)
4,4,12,12-tetramethyl-5,8,11-triazapentadecane-2,14-dione, ttp,
have been prepared by reaction of the diperchlorate
of 3-azapentane-1,5-diamine with acetone. The salt [ttpH2] (ClO4)2
has been used to prepare the six-coordinate complexes [Cu(ttp)(H2O)]
(ClO4)2,1.5H2O and [Ni(ttp)(H2O)]
(ClO4)2,H2O, and the five-coordinate [Cu(ttp)] (CIO,),. The complex [Cu(ttp)] (ClO4), reacts with ammonia, methylamine
and ethylamine to form complexes of pentadentate β-amino
ketone β-amino imine ligands. The structure of
[Co(ttp)(H2O)] (ClO4)2,1.5H2O
has been determined by X-ray diffractometry [space
group P21/c, Z 4, a
797.5(2), b 1632.8(3), c 2236.4(3) pm, β 97.504(2)�, R
0.0749, Rw 0.0765 for 1678 reflections].
The complex cation has the bis(β-amino
ketone) ttp acting as a pentadentate
ligand, with the three nitrogen and one carbonyl oxygen atoms coplanar, and
with oxygen of a water molecule completing distorted octahedral coordination
about the cobalt(II) ion.
Branched cyclononane macrocycles with pentaamine and tetraamine-thioether donors. Preparation and base hydrolysis of chlorocobalt(III) complexes
Authors: Gahan LR , Lawrance GA , Sargeson AM
Published: September 2010

Synthetic routes to the
resolved unsymmetrical (u) isomers of
[Co(dats)Cl] (ClO4)2
[dats = 4,7-bis-(2-aminoethyl)-1-thia-4,7-diazacyclononane]
and [Co(datn)Cl] (ClO4)2
[datn = 1,4-bis(2-aminoethyl)-1,4,7-triazacyclononane]
are reported. The new macrocyclic ligand
1-thia-4,7-diazacyclononane (tasn) was synthesized
during the former preparation, and the cis-[Co(tasn)2]
(ClO4)3 complex prepared. Base hydrolysis of each chlorocobalt(III) complex proceeds with two consecutive
steps. The first reaction in each case is chloride hydrolysis, with kOH(dats) 3.6 × 104
dm3 mol-1 s-1 and kOH(datn) 2.85 × 103 dm3 mol-1
s-1 at 25�C and 10.1 M. The second reaction for the
dats complex is a base-catalysed
dissociation of the thioether to the cis-[Co(dats)(OH)2]+ complex, characterized
by 13C n.m.r. experiments, and occurring approximately 20 times
slower than chloride hydrolysis. However, the datn
complex undergoes a base-catalysed terminal ring
opening to the cis-[Co(datn)- (OH)2]+ complex at a rate
approximately 30 times slower than chloride hydrolysis.
Calculations on ionic solvation. VII. The free energy of solvation of ions calculated from various local solvent dielectric constant-distance functions
Authors: Abraham MH , Liszi J , Kristof E
Published: September 2010

Calculations
on the electrostatic free energy of solvation of Rb+ (and also Br-) in acetonitrile have been carried out by using various
functions that relate the local solvent dielectric constant to distance from
the centre of an ion immersed in the solvent. A simple one-step dielectric
constant-distance function yields a calculated value in good agreement with the
experimentally observed value; this agreement does not depend on any arbitrary
single-ion convention. The new dielectric constant profile suggested by Stiles
leads generally to too negative a calculated value, as does the Born equation, but
an amended profile of similar mathematical form to the function used by Stiles
also leads to good agreement between calculated and observed values. It is
suggested that although mathematical functions of dielectric constant-distance
may be selected on the basis of agreement between calculation and experiment
and of convenience of use, not too much physical significance should
necessarily be attributed to these functions.
Synthesis of azaanthraquinones: homolytic substitution of pyridines
Authors: Cameron DW , Deutscher KR , Feutrill GI , Hunt DE
Published: September 2010

Synthesis of specific di- and
tri-hydroxyazaanthraquinones by Friedel-Crafts procedures is limited by
orientational ambiguity and by the lack of reactivity of pyridine derivatives
in electrophilic acylation processes; however, suitable pyridines have been made
to undergo radical benzoylation and benzylation at unsubstituted positions 2, 4
and 6. In particular, derivatives of pyridine-3-carbo-nitrile have been
benzoylated at positions 2 and 4. Ring closure by intramolecular Houben-Hoesch
reaction has then led to specifically substituted 1-and 2-azaanthraquinones and
thence to the antibiotic bostrycoidin (1).
Reactions of benzyl compounds with synthesis gas in the presence of ruthenium carbonyl iodides
Authors: Hardin SG , Turney TW
Published: September 2010

Benzyl compounds, PhCH2X
(X = OH, OCH2Ph, OMe, OAc),
react with CO/H2 mixtures at 9-10 MPa and
220�C in the presence of aqueous HI and [RU(CO)3I2]2
to afford toluene, HX and polymers of the type H(C7H6)nH(n = 2-6). The mechanism
involves the initial dehydration of PhCH2OH to (PhCH2)2O
which disproportionates to toluene and benzaldehyde.
Ruthenium, present mainly as [Ru(CO)3I3]-
and cis-Ru(CO)4I2,
catalyses reduction of benzaldehyde back to benzyl alcohol or the production of
polymers. The significance of these results to toluene formation in benzyl
alcohol homologation reactions is discussed.
Nitration of 3,4,6-Tribromo-2,5-dimethylphenol and 3,4,5,6-Tetrabromo- 2-methylphenol; Towards a mechanism of formation of 6-Hydroxy-6-methyl- 2,5-dinitrocyclohex-3-enones
Authors: Hartshorn MP , Ing HT , Richards KE , Sutton KH , Vaughan J
Published: September 2010

The nitrations of the
2-methylphenols (1a) and (1b) give initially 4-nitrocyclohexa-2,5-dienones (6),
which undergo further reaction to yield 2,5-dinitrocyclohex-3-enones (4).
Reactions of these and other related compounds are reported which point towards
a mechanism of formation of substituted 2,5-dinitrocyclohex-3-enones from
2-methylphenols.
On the physical interpretation of through-bond interactions: A coupled-chromophore model for π-electron photoionization of non-conjugated dienes
Authors: Schipper PE , Paddon.-Row MN
Published: September 2010

A coupled-chromophore
model is presented to explain the splittings of the
photoelectron energies arising in the photoionization
of the π-electrons in non-conjugated dienes. The predictions of the model are consistent with
the experimental splittings for a range of dienes, and suggest that the σ framework plays no
physical role in coupling the two chromophores. The
implications for the physical interpretation in terms of through-bond
interactions are discussed.
New aspects of the nitration of some imidazo[1,2-a]pyridines. CNDO/2 calculations from X-ray structures
Authors: Teulade JC , Escale R , Rossi JC , Chapat JP , Grassy G , Payard M
Published: September 2010

The reactivity of the imidazo[l,2-a]pyridine system (1) was investigated, CNDO/2
calculations based on X-ray structure determinations of 5-ethoxyimidazo[l,2-a]pyridine
(2), ethyl 8-methylimidazo-[1,2-a]pyridine-2-carboxylate (5) and ethyl
6-methyl-3-nitroimidazo[l,2-a]pyridine-2-carboxylate (10c) are compared with
experimental results of the nitration of variously substituted imidazo[l,2-a]- pyridines, and are found compatible with
the individual reactivities.
The vapour pressure-composition diagram for halothane-methoxyflurane and its relevance to cross-contamination
Authors: Korman B , Ritchie IM
Published: September 2010

A cross-contaminated
anaesthetic agent forms a binary liquid mixture with its contaminant. Since it
was thought possible that the behaviour of contaminated vaporizers could be
predicted from a knowledge of the vapour pressure-composition diagram for the binary
liquid mixture, the diagram for a typical system was determined. The technique
used was to allow a suitable mixture of agents to equilibrate, measure their
combined vapour pressure, and determine the liquid and vapour compositions by
infrared analysis. A vacuum line suitable for the vapour pressure measurements
is described. The vapour pressure-composition diagram for
halothane-methoxyflurane was found to be ideal both at 20 and 25�C. This
finding is used to account for some results reported in the literature
concerning cross-contamination between halothane and methoxyflurane.
Kinetics and mechanism of the reaction of pyridinamine 1-oxides with acetylating agents in water and aprotic solvents
Authors: Deady LW , Stanborough MS
Published: September 2010

Pyridin-2-amine 1-oxides
react with acetic anhydride in dioxan and with p-nitrophenyl acetate in water by rate-determining O-acetylation followed by rapid
intramolecular rearrangement to give the amide. The rearrangement is so
favoured that no hydrolysis of the intermediate was detected in the aqueous
solvent. This behaviour in aprotic solvents contrasts with that of
pyridin-2-amine, previously shown to undergo acetylation directly at the amino
group. Acetylation of pyridin-4-amine 1-oxide, with acetic anhydride in
acetone, occurs by way of an analogous O-acetyl
intermediate which reacts slowly with a second molecule of amine 1-oxide.
Pyridin-Camine reacts in the same manner at a surprisingly similar rate. In
water, both compounds catalyse the hydrolysis of p-nitro-phenyl acetate, with the amine 1-oxide being very much less
efficient.
N.M.R. studies of myelin basic protein. VI. Proton spectra in aqueous solutions of proteins from mammalian and avian species
Authors: Mendz GL , Moore WJ , Carnegie PR
Published: September 2010

Myelin basic proteins from
human, cow, pig, rabbit and chicken central nervous systems were studied in
aqueous solution by proton n.m.r. at 400 MHz. Species comparisons and other
techniques led to the assignment of resonances of 23 specific amino acid residues
in the primary structure. Resonances from side chains of polar amino acids
adjacent to aspartic residues could be assigned by anomalous effects of pH on
the chemical shifts. The pK values of histidine side chains all fall in the range
6.0-6.9, and four specific histidine residues were assigned. The conformation
of the protein in aqueous solution is that of an extended non-random
polypeptide chain with regions of localized structure. Nuclear Overhauser difference spectra showed that a reverse turn
similar to that previously suggested for an encephalitogenic
nonapeptide isolated from the protein (guinea pig
determinant) occurs also in the protein itself, thus supporting the concept of
special low-energy conformations responsible for biological activity. Upfield chemical shifts of some side chain methyl groups
from the central region of the primary structure suggest ring-current shifts
due to higher-order structuring.
Aspects of the mechanism of the Wittig reaction between cyclic anhydrides and stabilized phosphoranes
Authors: Abell AD , Massy-Westropp RA
Published: September 2010

It
has been established that the Wittig reaction between
cyclic anhydrides and methoxycarbonylmethylenetriphenylphosphorane,
a reaction used for the preparation of enol-lactones,
proceeds via an acyclic intermediate acylated
phosphorane for the three classes of anhydrides studied: succinic,
maleic and phthalic. The
formation of the acyclic intermediate can be irreversible or reversible, depending
on the structure of the anhydride. The stereochemistry of the enol-lactones produced is not controlled by the initial
reaction of the anhydride with the ylide but either
during or after cyclization of the acyclic intermediate. Product formation
appears to be under kinetic control with all the anhydrides studied. The
influence of substituents in substituted phthalic anhydrides
has been investigated.
Regiospecific synthesis of quinizarin and naphthazarin derivatives by cycloaddition
Authors: Cameron DW , Feutrill GI , Mckay PG
Published: September 2010

The diene
(E)-1,1,4-trimethoxybuta-1,3-diene underwent regiospecific cycloaddition to
derivatives of 2(3)-chloro-1,4-naphthoquinone. The resulting adducts were
aromatized to give 1,4-dioxygenated anthraquinones. The latter were obtained as
derivatives of quinizarin dimethyl ether or of quinizarin monomethyl ether
depending on the conditions of aromatization. Cycloaddition of the diene to
non-halogenated naphthoquinones proceeded similarly, orientation being
controlled by substituents in the benzenoid ring. Analogous reaction of the
diene with benzoquinones gave 5,8-dioxygenated naphthoquinones (naphthazarins),
generally in limited yield. The procedure has been applied to synthesis of the
mould metabolites helminthosporin and cynodontin.
Organotin(IV) monothio-β-diketonates
Authors: Saini SK , Gupta VD , Mehrotra RC
Published: September 2010

Triorgano-and monoorgano-tin(IV)
derivatives of monothio-β-diketones have been
prepared by different routes and characterized. Spectroscopic data suggest that
triorganotin(iV) complexes, in sharp contrast to monoorganotin(IV) analogues, contain monothio-β-diketone
moieties functioning as unidentate ligands bonded through the sulfur atoms.
Kinetics of the acid-catalysed hydration of prop-2-en-1-ol. Evidence for a free, ion-dipole intermediate in the heterolysis of propane-1,2-diol
Authors: Herlihy KP
Published: September 2010

Prop-2-en-1-ol in aqueous
acid solution gives propane-1,2-diol and propanal. At
100�C the amount of diol in this product ratio is
found to decrease from 65% in 1 M HClO4 to 50% in 4 M HClO4.
Pseudo-first-order kinetics are found to apply. The values obtained for the
activation parameters, Ea and ΔS‡ and for a Hammett acidity
plot, are similar to results reported for other alkenes. The relative rates of
partitioning between regeneration of the substrate and rearrangement for the pinacol rearrangement of optically active propane-1,2-diol
have been calculated previously. When these are compared with product ratios
obtained from the hydration of prop-2-en-1-ol, good agreement is found between
the respective values if it is assumed that the regenerated substrate has
undergone complete racemization of configuration.
This is interpreted to be evidence for a short-lived, but free ion-dipole as
the intermediate in the heterolysis of propane-1,2-diol.
The nitration of 3,4,5-tribromo-2,6-dimethylphenol; X-ray crystal structures of C 2-epimeric 3,4,5-tribromo-6-hydroxy-2,6-dimethyl-2,5-dinitrocyclohex-3-enones ;an unusual isomerization reaction
Authors: Chittenden AM , Hartshorn MP , Richards KE , Robinson WT , Sutton KH , Thompson RS , Vaughan J
Published: September 2010

Nitration of
3,4,5-tribromo-2,6-dimethylphenol (10) with fuming nitric acid in acetic acid
gives the C2-epimeric 2,5-dinitrocyclohex-3-enones (11) and (12), the
structures of which were determined by single-crystal X-ray analyses. Some
implications of these structural data are discussed.
The reaction of N-dichloromethylene-N,N-dimethylammonium chloride (Viehe's salt) with 1,2:5,6-di-O-isopropylidene-a-D-glucose
Authors: Copeland C , Stick RV
Published: September 2010

The
treatment of 1,2:5,6-di-O-isopropylidene-α-D-glucose with N-dichloromethylene-N,N-dimethyl ammonium chloride (Viehe's salt) (2: 1 or 1 : 1) gives two iminium salts. These are
readily hydrolysed to a carbonate and a carbamate. Treatment with sodium hydrogen
sulfide gave some thiocarbonate and thiocarbamate. One of the iminium salts
underwent a base-induced elimination to give 3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-ribo-hex-3-enofuranose.
The Wittig reaction with glutaric and succinic anhydrides
Authors: Abell AD , Doyle IR , Massy-Westropp RA
Published: September 2010

Six-membered
cyclic anhydrides, including glutaric and some of its
alkylated derivatives, have been shown to yield enol-lactones with ethoxycarbonylmethylenetriphenylphosphorane;
the (E)isomer is formed
preferentially. The reactions of methyl-substituted succinic
anhydrides with the same phosphorane give predominantly the (E) enol-lactone in all examples. The influence of alkyl substitutents on the rates of the reactions and the product
ratios in both the succinic and glutaric
anhydride series is discussed.
Dipole moment, Kerr constant, Cotton-Mouton constant and conformation of 1,4-dithiin
Authors: Mirarchi D , Phillips L , Ritchie GLD
Published: September 2010

Measurements of the
infinite-dilution dipole moment, molar Kerr constant and molar Cotton-Mouton
constant of 1,4-dithiin dissolved in cyclohexane and carbon tetrachloride at 25�C
are reported and analysed to provide information concerning the solution-state
conformation, the polarizability anisotropy and the magnetic anisotropy of this
molecule.
Equatorial ligand effects on the visible spectra of dioxouranium(VI) complexes in solution
Authors: Lincoln SF , Ekstrom A , Honan GJ
Published: September 2010

The visible spectra of [UO2L5]2+,
where L = OCMe(NMe2), OCMe(NHMe), OCH(NMe2), OCH(NHMe),
OP(OMe)3 and OPMe(OMe)2 ; and [UO2 {OP(NMe2)3}]2+,
in CH2Cl2 solution are reported. The spectra have been
resolved into 13, 14 or 15 bands depending on the complex. These bands exhibit
variations in both frequency and molar absorptivity
which are consistent with the nature of the equatorial ligands in the
equatorial plane about the UO22+ axis being of major
importance in determining the nature of the spectra. The overall influence of
the equatorial ligands on the dioxouranium(VI)
spectra appears to be determined by the combined effects of stereochemistry and
ligand electron-donating ability.
Preparation and characterization of the isomers of (Diethylenetriamine)[di(3-aminopropyl)amine]cobalt(III) ion and the crystal structure of the mer isomer
Authors: Searle GH , Hambley TW
Published: September 2010

The reaction [Co(dpt)Cl3]+ dien in
propan-2-ol [dpt=di(3-aminopropyl)amine,
dien = diethylene-triamine]
gives mer-[Co(dpt)2]3+ and the three geometric
isomers of [Co(dien)2]3+,
almost quantitatively. The reaction [Co(dien)Cl3]
+ dpt in propan-2-ol, catalysed by water, yields the three
isomers of [Co(dien)(dpt)]3+
as the main products, in the approximate ratio u-fac : mer : s-fac 4 : 2 : 1. Preparation of mixed amine complexes by
substitution therefore requires that the amine (dien)
forming the more stable complexes be incorporated in the reactant complex. The
geometric structures of the isolated [Co(dien)(dpt)] (ClO4)3 isomers are assigned by
13C n.m.r. spectra. They each hydrolyse in
water or base, the mer
isomer rapidly, and no isomerization has been detected. X-ray crystallographic
analysis of mer-[Co(dien)(dpt)]2 (S2O6)3,H2O,EtOH
(from the isolated perchlorate by metathesis)
confirms the assigned mer
geometry. The two independent complex molecules in the asymmetric unit have
different conformational geometries. The crystals are monoclinic, space group
P21/c, with a 15.548(4), b 9.178(3), c 31.664(8) �,β 89,04(2)�. The
structure was refined by blocked-matrix least-squares techniques to an R-factor
(on 2752 F) of 0.058.
Reactions of aryl diazonium salts and alkyl arylazo ethers. X. General acid and intramolecular electrostatic catalysis in the ionization of methyl (E)-2-Organyl-5-nitrophenylazo ethers in alcoholic solvents
Authors: Broxton TJ , Mcleish MJ
Published: September 2010

The ionization of the (E)-methyl ethers derived from 2-carboxy-5-nitrobenzenediazonium salt and
some related compounds have been studied in alcoholic solvents. In the presence of buffers
prepared from aliphatic carboxylic acids and their salts, intermolecular general acid catalysis is
observed. The observed rate of ionization in buffered solution depends on the pH of the solution.
The carboxy group of 2-carboxy-5-nitrophenylazo methyl ethers is ionized to a different extent in
each of the carboxylic acid buffers depending on the pH of each solution. Furthermore, it has
been found that the carboxylate (COO-) form of this compound ionizes more rapidly than the
protonated (COOH) form.
For these reasons, the calculated catalytic rate constants cannot be used to determine a Bronsted
α-value for the reaction and the uncatalysed rates determined in buffer solutions of each carboxylic
acid are different.
Buffers of cyanoacetic acid are found to behave anomalously when compared to all the other
carboxylic acid buffers used.
The greater rate of ionization of the carboxylate form is shown to be the result of different
electronic effects of the COO- and CO2H substituents. By comparisons of estimated electronic
and steric effects it is possible to show that the COO- form also exerts intramolecular electrostatic
catalysis in the ionization of the azo ether group.
For the ionization of the 2-carboxy-5-nitrophenylazo methyl ether in the more acidic buffer
solutions, the plots of absorbance against time are linear for up to 20% of reaction. This effect
is explained by the small amount of reactive COO- form of the substrate in these buffer solutions.
As the reaction proceeds the reactive form is replenished by the equilibrium between the COOH
and COO- forms of the substrate. Thus, the linear portion of the absorbance-time plot is greater
than normal.
Ionization of the 2-methoxycarbonyl-5-nitrophenylazo methyl ether in both basic methanol and
in the presence of buffers of dichloroacetic acid occurs by two concurrent reactions. The slower
of these reactions is believed to be the normal ionization of the arylazo ether. A number of
possibilities for mechanism of the faster reaction have been eliminated and a possible mechanism
is suggested.
Nucleophilic substitution reactions in m-nitrobenzylic substrates
Authors: Barker SD , Norris RK
Published: September 2010

The reaction of m-nitrobenzyl 2,4,6-trimethylbenzoate
(11) with the salt (2) of 2-nitropropane, or the thiolate
(16), gives moderate yields of substitution products [e.g.(3) or (17)].
However, the mechanism of formation of these products could not be definitively
assigned. The m-nitrobenzyl
chloride (12), on the other hand, was clearly demonstrated to undergo SRN1
substitution reactions with a variety of anions including the anion from the
salt (2), thiolate ion from (16), azide
from (22), the malononitrile anion from (20), and the
malonic ester anion from (21). Inhibition and entrainment effects clearly rule
out an alternative radical anion-radical process involving cage collapse. The
occurrence of SRNl reactions in m-nitrobenzylic
substrates adds support to a mechanism involving association of radicals with
anions, and for dissociation of radical anions, which involves σ* and π* radical anions.
On the formation of ethoxy alcohols from reaction of trans-1,2-Epoxy-3-methyl-1,3-diphenylbutane and 1,2-Epoxyoctane with boron trifluoride etherate
Authors: Blunt JW , Coxon JM , Lim C , Schuyt HA
Published: September 2010

Reaction of trans-1,2-epoxy-3-methyl-1,3-diphenylbutane
(1) with boron trifluoride etherate
in benzene gave 3-methyl-2,3-diphenylbutanal (3), shown by deuterium labelling
experiments to be formed by C1-O cleavage and alkyl migration, and (1RS,2RS)-l-ethoxy-3-methyl-1,3-diphenyl-
butan-2-ol (16) in a process involving retention of configuration at Cl. In
ether as solvent the epoxide gave, in addition to aldehyde (3) and ethoxy alcohol
(16), 3-methyl-1,3-diphenylbutan-2-one (11) and vinyl ethers (19) and (20).
Reaction of 1,2-epoxyoctane (17a) with boron trifluoride
etherate in ether gave 1-ethoxyoctan-2-ol (18a) shown
by deuterium labelling experiments to be formed by inversion of configuration
at C1. The mechanistic implications of these results are discussed.
Studies of Australian soft corals. XXX. A novel trisnorsesquiterpene from a Cespitularia species and the isolation of guaiazulene from a small blue Alcyonium species
Authors: Bowden BF , Coll JC , Tapiolas DM
Published: September 2010

A novel trisnorsesquiterpene
(1,4-dimethyl-2,3,3a,4,5,6-hexahydroazulene) and an optical antipode of the
known sesquiterpene cubebol have been isolated from
the soft coral Cespitularia
species. The pigment in a small blue Alcyonium species has been identified as guaiazulene.
Structural studies in the ruthenium(II)/(±)-ortho-Phenylenebis{methyl(phenyl)-phosphine/arsine} system. I. Crystal structure of trans-Carbonylhydridobis-[(±)-ortho-phenylenebis {methyl(phenyl)phosphine)]ruthenium(II)hexafluorophosphate(V)-acetone (1/2)
Authors: Grocott SC , Skelton BW , White AH
Published: September 2010

The crystal and molecular
structure of the title complex, trans-[RuH(CO)(opmpp)2]+
(PF6)-.2(CH3)2- CO [opmpp ≡ (�)-ortho-phenylenebis
{methyl(phenyl)phosphine) , o-C6H4(PMePh)2], has been established by a
single-crystal X-ray diffraction study at 295(1) K, being refined to a residual
of 0.066 for 2293 independent 'observed' reflections. Crystals are monoclinic,
C2/c, a 11.943(4), b 26.151(9), c 15.974(6) �, β 90.97(7)�, Z 4. In the model adopted, the
ruthenium atom is located on a crystallographic twofold axis; the carbonyl and hydrido ligands lie trans
to each other and are disordered about the ruthenium atom. The
ruthenium-phosphorus distances are 2.320(2) and 2.317(2)�.
Studies of Australian soft corals. XXXI. Novel furanosesquiterpenes from several sinularian soft corals (Coelenterata, Octocorallia, Alcyonacea)
Authors: Bowden BF , Coll JC , de Silva ED , de Costa MSL
Published: September 2010

Fifteen structurally
related furanosesquiterpenes have been isolated from
two different species of sinularian soft corals. The
structures were assigned on the basis of 1H and 13C
n.m.r. spectroscopy.Complete 13C
n.m.r. assignments are reported for all compounds.
Neutral and anionic derivatives of the diphenylgallium halides Ph2GaX (X = Cl or Br)
Authors: Helliwell BN
Published: September 2010

Derivatives Ph2GaX.L
and Ph2GaX2-, where X = Cl or Br, and L = pyridine or
triphenylphosphine, are prepared from Ph2GaX and characterized, the
anions as salts with (Ph3P)2 N+. Vibrational spectra are reported and assigned.
Paramagnetic organometallic molecules. XIV. Ion-pair and steric effects in dissociative electron transfer reactions of metal cluster carbonyl radical anions
Authors: Kirk CM , Peake BM , Robinson BH , Simpson J
Published: September 2010

An investigation of
electron attachment reactions of cluster metal carbonyls is presented. In
general, alkyl and organometallic halides react rapidly with metal carbonyl
cluster radical anions at ambient temperatures to give the neutral cluster
molecule. Halide ion and alkyl or organometallic radicals are also produced,
which indicate that these are dissociative electron attachment reactions
analogous to those of organic radical anions. The rate of dissociative electron
attachment in reactions of PhCCo3(CO)9- was found to
depend on the R-X bond energy, the size of the alkyl group and the nature of
the counter-ion. In particular, (Ph3P)2N+ retarded
some electron transfer reactions to the extent that the bimolecular decay of
PhCCo3(CO)9- effectively competed with the
electron transfer process in determining the reaction path.
Crystal Structure of Soybean Ferric Leghaemoglobin a Nicotinate at a Resolution of 3.3Ǻ
Authors: Ollis D , Appleby C , Colman P , Cutten A , Guss J , Venkatappa M , Freeman H
Published: September 2010

The crystal structure of
soybean ferric leghaemoglobin a
nicotinate has been solved at 3.3 � resolution by the multiple isomorphous
replacement method. The molecular structure resembles those of other monomeric
haemoglobins but is distinguished by the absence of a D helix, an enlargement
of the haem pocket, and the possible presence of an additional pathway from the
solvent region into the haem pocket.
Structure and stereochemistry in 'f-block' complexes of high coordination number. VIII. The [M(unidentate)9] system. Crystal structures of [M(OH2)9] [CF3SO3]3, M = La, Gd, Lu, Y
Authors: Harrowfield JM , Kepert DL , Patrick JM , White AH
Published: September 2010

The crystal structures of
the nonahydrates of the rare earth trifluoromethanesulfonates, [M(OH2)9]
[CF3SO3]3 have been determined at 295 K for
the configurations fO, f7, f14,
i.e. M = La, Gd, Lu, together with that of the
yttrium analogue. The structures are similar to those of the rare earth ethyl
sulfate nonahydrates, belonging to space group P6,/m (hexagonal) with cell dimensions a ≈
13.7, c ≈ 7.5 �, Z 2, with the coordination about the rare earth atom
being a tricapped trigonal prism. The structure is
compared with that found from repulsion energy calculations.
Radical and ionic nucleophilic substitution reactions on α-Alkyl-γ-(p-nitrophenyl)allyl derivatives
Authors: Barker SD , Norris RK
Published: September 2010

The nature of the reaction
between α-alkyl-γ-(p-nitrophenyl)allyl
chlorides (1)-(3), which have the general form p-O2NC6H4CH=CHCH(Cl)R, and a
variety of nucleophiles depends on the alkyl group R and the nucleophile. The
chloride (1) (R = Me) undergoes ionic (SN2
and subsequent Michael addition) processes with the salt (7) of 2-nitropropane
to give products (15) and (16) whereas the chloride (2) (R = Pr1)
gives a mixture of products (17) and (18) which are shown to arise by a
radical-chain nucleophilic substitution process, with allylic rearrangement-an SRNl' reaction-and ionic processes respectively.
The chloride (3) (R = But) gives the SRN1' product (25)
with the salt (7). Other nucleophiles with (2) and (3) appear to react by ionic
(SN2 and SN2') and/or SRNl' processes; e.g. (3) gives an excellent
yield of the malononitrile (32) by an SN2'
process when treated with the sodium salt (9).
Reactions of methyl-substituted Hex-5-enyl and Pent-4-enyl radicals
Authors: Beckwith ALJ , Easton CJ , Lawrence T , Serelis AK
Published: September 2010

Relative and absolute
kinetic data have been determined for ring closure of methyl-substituted
hex-5-enyl radicals: 2-methyl- (10a), 3-methyl-(4a), 4-methyl-(5a),
2,2-dimethyl-(10c), 3,3-dimethyl-(4c) and 4,4-dimethyl-hex-5-enyl (5c)
radicals, generated by interaction of tributylstannane
with the corresponding bromides (1a)-(3a) and (1c)-(3c). Each radical undergoes
regiospecific or highly regioselective
1,5-cyclization more rapidly than does the unsubstituted radical (4d). The rate
enhancements, which arise mainly from lowering of the activation energy, can be
rationalized in terms of the gem-dimethyl
effect. 1,5-Ring closures of monosubstituted species
are stereoselective: 2-methyl- and
4-methyl-hex-5-enyl radicals (10a) and (5a) give mainly trans products, whereas
3-methylhex-4- enyl radical gives mainly the cis. This behaviour reflects the effect
of the substituent on the stabilities of cyclic transition complexes in
chair-like conformations. Ring closure of 2,2-dimethylpent-4-enyl radical or of
3,3-dimethylpent-4-enyl radical (19) could not be detected.
Constituents of Endiandra species. V. 2-[3',5'-Dioxo-4'-phenyl-10'-{(E,E)-5''-phenyl-penta-2'',4''-dien-1''-yl}-2',4',6'-triazatetracyclo[5,4,2,02,6,08,11]tridec12'-en-9'-yl]-acetic acid derived from Endiandra introrsa (Lauraceae)
Authors: Banfield JE , Black DSC , Fallon GD , Gatehouse BM
Published: September 2010

The structure (9) of the
title compound, obtained by treatment of the mother liquor from recrystallization of the naturally occurring acid (6a) with
4-phenyl-1,2,4-triazoline-3,5-dione, has been elucidated by X-ray
crystallographic analysis.
Bond order-bond length relationships in conjugated hydrocarbons - the microwave spectrum and structure of 3,4-dimethylenecyclobutene
Authors: Brown RD , Godfry PD , Hart BT , Ottrey AL , Onda M , Woodruff M
Published: September 2010

The microwave spectrum of
the benzene isomer 3,4-dimethylenecyclobutene including spectra of all possible
single 13C-substituted and sufficient singly and doubly
D-substituted species to give a complete r5 geometry, have been
measured and analysed. An estimate of the re geometry has also been
derived. The additional precise CC bond lengths obtained for an unsubstituted, conjugated
hydrocarbon enable us to examine bond order-bond length relationships more thoroughly
than has previously been possible. The CC bond lengths exhibit a noticeably
better correlation with SCFMO bond orders than with simple H�ckel
bond orders. Further confirmatory measurements of the dipole moment of dimethylenecyclobutene have been made. Ab initio molecular orbital calculations
using a 6-31G basis set give an optimized geometry with CC bond lengths within
2 pm of the r5 values. The computed dipole moment agrees almost exactly
with experiment but a corresponding calculation on fulvene
is discrepant with experiment by 0.16 D, which is probably a more typical
error.
Micellar catalysis of organic reactions. X. Further evidence for the partial failure of the pseudophase kinetic model of micellar catalysis for reactions of hydroxide ions
Authors: Broxton TJ , Sango DB
Published: September 2010

Rates of hydrolysis for a
number of amides and hydroxydehalogenation of some activated aryl halides have
been determined in the presence of micelles of cetyltrimethylammonium bromide
(ctab) and cetyltrimethylammonium fluoride (ctaf). The rates of reaction in
micelles of ctaf are greater than in micelles of ctab in each case but the
ctaflctab rate ratios are smaller than predicted by the pseudophase model of
micellar catalysis. The results are discussed in terms of reactions in ctaf
occurring within the micelle but reactions in ctab occurring both within the
micelle and across the micellar interface. The extent of reaction across the
micellar interface is shown to be dependent on the structure of the substrate.
Substrates chosen were those bearing hydrophobic or hydrophilic substituents,
designed to orient the substrate molecules in predictable ways within the
micelles.
Synthesis of 1,2,3,4-Tetrahydro-β-carbolines
Authors: Kirkpatrick A , Maclaren JA
Published: September 2010

1,1-Disubstituted
1,2,3,4-tetrahydro-β-carbolines are formed by the action of trifluoroacetic
acid on enamines derived from tryptamine or tryptophan. With methanolic
hydrogen chloride, either cyclization to the corresponding β-carboline
derivative, or acidolysis to regenerate the parent amine, occurs. The course of
this reaction depends on the substitution pattern. Mixtures of products are not
formed. Authentic phenacyl L-tryptophanate hydrochloride has been synthesized.
Cyclopentadienyl-ruthenium and -osmium chemistry. XXI. Synthesis and X-ray structure of OsCl(PPh3)2(η-C5H5).CH2Cl2. Some structural comparisons of ruthenium-osmium pairs
Authors: Bruce MI , Williams ML , Patrick JM , White AH
Published: September 2010

The X-ray structure of the
CH2Cl2-solvate of OsCl(PPh3)2(η-C5H5)
has been determined, and compared with that of the non-solvated ruthenium
analogue. Crystal are triclinic, space group P1, with a 14.490(3), b 14.110(3),
c 9.937(3) �, α 99.84(2), β
106.57(2), γ 100.08(2)� and Z 2. Refinement of 5297 data with I > 3σ(I)
converged with R 0.033, R' 0.038. The Os-C and Os-Cl distances are c.0.007 �
longer than corresponding Ru-C and Ru-Cl distances, while the Os-P separations are 0.017 � shorter than the Ru-P
separations.
Crystal structure of Bis(2,2':6',2''-terpyridyl)cobalt(III) chloride
Authors: Figgis BN , Kucharski ES , White AH
Published: September 2010

The crystal structure of
the title compound [CO(C15H11N3)2]Cl3
has been determined by single crystal X-ray diffraction methods at 295 K and refined
by least-squares methods to a residual of 0.069 for 2953 'observed' reflections.
Crystals are triclinic, PI, a 9.018(4),
b 11.751(4), c 18.085(6)�, α 9O.82(6), β 9O.66(7), γ 90.79(7)�, Z
2. The determination establishes for the first time metal-nitrogen distances in
the bis(terpyridyl)cobalt(III) species; (Co-N)(central,
distal) are 1.86, 1.93 �. The precision of the determination is adversely affected
by widespread solvent/anion disorder.
Oxidation of alkoxyphenols. XXIX. Phototautomerism and dinierization of 4,6-Di-t-butyl-4a-hydroxy-8-methoxydibenzofuran-2(4aH)-one
Authors: Hewgill FR , Raston CL , Skelton BW , Webb RJ , White AH
Published: September 2010

In solution in non-polar
solvents the title compound undergoes photochemical ring opening to its hydroxyphenylquinone tautomer.
Oxidation of 3,3'-di-t-butyl-5,5'-dimethoxybiphenyl-2,2'-diol withvanadium oxytrifluoride in the presence of trifluoroacetic acid
yields bisdibenzofurans. The crystal structures of
4,4',6,6'-tetra-t-butyl-2',8-dimethoxy-1,1'-bisdibenzofuran-2,8'-diol and of
4,6-di-t-butyl-4a-hydroxy-8-methoxydibenzofuran-2(4aH)-one have been determined.
The E2C mechanism in elimination reactions. IX. Re-examination of the olefin-like transition-state
Authors: Muir DM , Parker AJ
Published: September 2010

The kinetics and product
olefins arising from E2C-like elimination reactions of secondary
bromides and tosylates having various alkyl and
conjugating substituents at Cα and Cβ are re-examined in the light of the
theoretical Pross-Shaik valence-bond model and the
apparent lack of a β-phenyl effect. Comparison of the effect of
substituents at Cα and Cβ
shows that whilst there are differences in reactivity and products of E2C
reactions there is also a large degree of double-bond character in the
transition state. There is a good correlation between the kinetics of E2C
reactions and the double-bond stabilization energy arising from both alkyl and
conjugating substituents. Contributing valence-bond structures, giving
asymmetry and partial charge at Cα and Cβ appear to vary in importance according to
leaving group and substituent type.
Hydrometallurgical thermodynamics. I. Effect of sulfate ion-pairing and ion-solvation on the copper-iron redox equilibrium in aqueous acetonitrile
Authors: Clare BW , Singh P , Mangano P , Parker AJ , Muir DM
Published: September 2010

The copper-iron redox
equilibrium is shifted to the right
CuII+FeII↔CuI+FeIII
by strong ion-pairing of
sulfate ion with FeIII and by specific solvation
of CuI with acetonitrile. The equilibrium
constant has been measured by direct e.m.f. and
spectroscopic methods between pH 0-2 and found to be about 107
higher for practical solutions of sulfates in acetonitrile/water
than that calculated for perchlorates in pure water.
Enthalpies and free energies of transfer of these ions from water to acetonitrile/water show that the shift in equilibrium to Cul+FeIII
in acetonitrile/water solution is strongly favoured
by enthalpy changes associated with copper(I)-acetonitrile
ion-solvation. Ion-pairing of sulfate ion with
iron(III) results in an increase in entropy and a small shift of the
equilibrium to the right.
Elimination reactions of stilbene dibromides. Dehydrobromination by acetate, cyanide or chloride ions in dimethylformamide
Authors: Avraamides J , Parker AJ
Published: September 2010

Rates of dehydrobromination of a series of 4-nitro-and methoxystilbene dibromides by
means of acetate, cyanide or chloride ions in dimethylformamide have been
measured. A product analysis was performed which indicated a strong preference
for anti elimination. Probable transition state structures utilized by each of
the three nucleophiles are described. Attack by the base may be at either β-hydrogen
(E2H) or Cα (E2C). The slowest reaction is
with chloride ion, which also gives the highest anti/syn elimination product ratio.
Estimation of transfer activity coefficients for single ions between dipolar aprotic solvents from the E.M.F. of cells with liquid junction
Authors: Goldberg SS , Popovych O
Published: September 2010

Transfer activity
coefficients for the sodium ion, logmγNa,
between pairs of dipolar aprotic solvents were
estimated from the e.m.f. of cells consisting of two
sodium-selective electrodes in different solvents connected by a salt-bridge of
triisoamylbutylammonium tetraphenylborate
[(tab+)BPh4-], or tetraethylammonium
picrate (Et4NPic), or tetraethylammonium
perchlorate (Et4NclO4). The solvents were:
acetonitrile (MeCN), N,N-dimethylformamide (HCONMe2),
dimethyl sulfoxide (Me2SO), propylene carbonate (pcar),
and N-methylformamide
(HCONHMe). Values of logmγNA
were estimated first by neglecting the liquid-junction potential E, and then,
for some systems, by applying an Ej
correction from theory. A novel method of estimating transfer activity
coefficients for single ions, based on the Ej
equation, was demonstrated on the (tab+) and Pic-ions.
Transfer activity coefficients for the hydrogen ion between MeCN
and HCONMe2 as well as MeCN and Me2SO
were similarly estimated from the e.m.f. of two pH
(glass) electrodes immersed in buffer media in the above pairs of solvents.