bluuebunny/crossref_metadata_2025 huggingface dataset:
The preparation and spectral properties of some monosubstituted 1,3,5,-Triphenyl-2-pyrazolines
Authors: Rivett DE , Rosevear J , Wilshire JFK
Published: September 2010

A large number of mono-para-substituted
1,3,5-triphenyl-2-pyrazolines and some related compounds has been synthesized,
and their absorption and fluorescence properties in cyclohexane and in methanol
measured. The effect of substituent on these properties and on the fluorescent
whitening ability of the 1,3,5-triphenyl-2-pyrazolines in general is discussed.
The presence of electron-withdrawing substituents, viz., cyano, methylsulfonyl
or methoxycarbonyl groups in the para-position
of the phenyl rings, has a dramatic effect on the absorption and the
fluorescence properties. Such substituents located (a) in the l-phenyl ring give pyrazolines exhibiting brilliant blue
fluorescence both in methanolic and cyclohexane solution, (b) in the 3-phenyl ring give highly fluorescent yellow compounds
which can be considered as dyes and (c)
in the 5-phenyl ring cause drastic quenching of the fluorescence.
Model Calculations on Base-Pair Interactions in DNA
Authors: Maclagan RGAR
Published: September 2010

Calculations are reported
using the potential field of Momany, Carruthers, McGuire and Scheraga of the
intra-pair interaction energy for all 29 base-pairing schemes proposed by
Donohue. Optimized relative orientations and separations of the DNA bases are given.
The observed base pairing would appear to be determined principally by the base
positions and orientations imposed by the fairly rigid sugar-phosphate
backbone. The inter-pair interaction energies for the various possible
combinations of the DNA bases in the double-helix models for the A and B forms
of DNA are reported. In the model for the B form, the inter-pair interaction
energy was found to be almost independent of the base-pair combination. The
importance of base overlap in determining the extent to which one base pair is rotated with respect to an adjacent pair was also investigated in a
preliminary manner.
Hydrogen Bonding and the n → π Blue Shift in α,β-Unsaturated Ketones
Authors: Beecham AF , Hurley AC
Published: September 2010

The c.d. spectra of α,β-unsaturated ketones through the n → π* absorption region are, in general, better resolved
than the corresponding ultraviolet spectra and are free of overlap from
neighbouring transitions. In consequence, the nature of the solvent-induced
blue shift is more clearly discernible in circular dichroism. That part of the
blue shift which is ascribable to hydrogen bonding is shown to result from a
redistribution of intensity between vibrational sub-bands rather than a change
in energy of the n → π* band as a whole.
On the Relationship Between Electronic Absorption and Molecular Geometry: Carbonyl Chromophore n-π. Transition Enhancement and Crystal Structures of Bicyclo[2,2,2]octenones and Bicyclo[2,2,2]octadienones
Authors: Becker H , Ruge B , Skelton BW , White AH
Published: September 2010

Spectroscopic studies on a
series of methoxycarbonyl-substituted β,γ-unsaturated bicyclic
ketones show a decrease in n-π* transition enhancement in the bicyclo[2,2,2]octadienone derivative relative to that observed in the
correspondingly substituted bicyclo [2,2,2] octenone.
Crystallographic studies on the related derivatives have been carried out in an
attempt to ascertain the influence of ground- state molecular geometry. The
results show the detectable difference in geometry to be small and suggest the
change in enhancement to be, more likely, a spectral repercussion of homodiene
conjugation.
Reactions of Methyl Radicals. III. Hydrogen Abstraction from Methyl Acetate and Methyl [2H3]Acetate
Authors: Arthur NL , Newitt PJ
Published: September 2010

A study of hydrogen abstraction by CH3 radicals from CH3COOCH3 in the temperature range
116-224°, and from CD3COOCH3 in the range 117-234°, has yielded data on the reactions:
CH3 + CH3COOCH3 → CH4 + [C3H5O2] (4)
CH3 + CH3COOCH3 → CH4 + CH2COOCH3 (5)
CH3 + CH3COOCH3 → CH4 + CH3COOCH2 (6)
CH3 + CD3COOCH3 → CH3D + CD2COOCH3 (7)
The corresponding rate constants, based dn the value of 1013.34 cm3 mol-1 s-1 for the recombination
of CH3 radicals, are given by (k in cm3 mol-1 s-1 and E in J mol-1):
logk4 = (11.56 ± 0.12) - (44430 ± 970)/19.145T (4)
logk5 = (11.17 ± 0.22) - (42900 ± 1760)/19.145T (5)
logk6 = (11.44 ± 0.16) - (46980 ± 1290)/19.145T (6)
logk7 = (11.39 ± 0.04) - (52110 ± 330)/19.145T (7)
At 400 K, 64% of abstraction occurs from the acetyl group, and 36% from the methoxy group.
The kinetic isotope effect at 400 K for attack on the acetyl group is 9.6; this is mainly due to a
difference in activation energies since the quotient of A factors is close to unity.
Nitrones and Oxaziridines, XXIII. Photorearrangement of 2-Cyano-1-pyrroline 1-Oxides
Authors: Black DSC , Blackman NA , Boscacci AB
Published: September 2010

2-Cyano-1-pyrroline
1-oxides undergo photorearrangement at 254 nm in benzene to afford cyanoformylazetidines
[(azetidinyl)oxoacetonitriles] via the related oxaziridines. The
cyanoformylazetidines can be hydrated by means of manganese(IV) oxide to the
crystalline oxamoyl azetidines. Several previously unreported 2-cyano nitrones
have been prepared by dehydration of the related 2-hydroxyimino nitrones with
2,4-dinitrofluorobenzene followed by triethylamine. Several of the intermediate
oxime ethers have been isolated and characterized.
Lecideoidin and 3'-Dechlorolecideoidin, New Depsidones from an Australian Lecidea (Lichen)
Authors: Chester DO , Elix JA , Jones AJ
Published: September 2010

The depsidones lecideoidin
(3',5-dichloro-2',4-dihydroxy-1'-methoxycarbonyl-6,6'-dimethyldepsidone) (3)
and 3'-dechlorolecideoidin (5-chloro-2',4-dihydroxy-1'-methoxycarbonyl-6,6'-dimethyldepsidone)(4) have been isolated from
an Australian Lecidea species. The
structure of these compounds followed from the spectroscopic properties and by
conversion of the former compound into the syntheticdepsidone, 3'-chloro-O-methylgangaleoidin (13).
An E.S.R. Study of Adducts of Organometallic Radicals with Some Quinones and Diketones
Authors: Bowmaker GA , Campbell GK
Published: September 2010

Radical species resulting
from the reaction of Mn2(CO)10 and [CO(CO)3P(OEt)3]2
with o-benzo- quinone have been
generated and their e.s.r. spectra recorded. The reactions of Mn2(CO)lo
with several other quinones and diketones have been similarly examined. In most
cases the radicals were produced after a short period of ultraviolet
irradiation. The radicals derived from Mn2(CO)10 and o-quinones or α-diketones are
formulated as six-coordinate complexes (CO)4MnA· in which the
manganese atom is chelated by the dicarbonyl compound A. The cobalt radical is
similarly formulated as a five-coordinate complex (CO)2P(OEt)3CoA·
(A = o-benzoquinone), The proton
coupling constants in these adducts are very similar to those of the
corresponding quinone or diketone radical anion; this indicates that the
unpaired electron resides mainly on the quinone or diketone molecule. The
radicals derived from the reaction of Mn2(CO)lo with p-quinones are much shorter lived than
those of the corresponding o-quinones,
but in the case of 2,3,5,6-tetrachlorobenzoquinone, a spectrum which might
belong to the Mn(CO)5 adduct of this molecule was recorded.
Ferricyanide Oxidation of Butanol Homogeneously Catalysed by Chlororuthenium Complexes
Authors: Godfrey AF , Beattie JK
Published: September 2010

The oxidation of butan-1-ol
by ferricyanide ion in alkaline aqueous solution is catalysed by solutions of
ruthenium trichloride hydrate. The kinetics of the reaction has been
reinvestigated and the data are consistent with the rate law -d[FeIII]/dt
= [Ru](2k1k2 [BuOH] [FeIII])/(2k1 [BuOH]+k2 [FeIII]) This
rate law is interpreted by a mechanism involving oxidation of butanol by the
catalyst (k1) followed by
reoxidation of the catalyst by ferricyanide (k2). The non-linear dependence of the rate on the butanol
concentration is ascribed to the rate-determining, butanol-independent
reoxidation of the catalyst, rather than to the saturation of complex formation
between butanol and the catalyst as previously claimed. Absolute values of the
rate constants could not be determined, because some of the ruthenium
precipitates from basic solution. With K3RuCl6 as the
source of a homogeneous catalyst solution, estimates were obtained at 30�0�C of
k1 = 191. mol-1 s-1 and k2 = 1�4 × 103 l. mol-1 s-1.
Interactions between Rhodamine B and wool. Analysis of luminescence quenching and energy transfer
Authors: Leaver IH
Published: September 2010

A reflectance technique is
described for quantitatively analysing the luminescence behaviour of wool in
the presence of a dye, rhodamine B. The bound dye exhibits delayed fluorescence
which is sensitized by one of the two naturally occurring phosphorescent groups
in wool. At low dye concentrations the phosphorescence of wool is quenched
mainly by simple optical screening and radiative transfer of energy from the
donor phosphorescent group to the dye, but radiationless dipole-dipole T →
S transfer becomes the predominant quenching process at high dye concentrations.
This process is characterized by a critical transfer distance ro of
5�0-5�3 nm. The fluorescence of wool is quenched only slightly by rhodamine B.
The results indicate that optical screening and radiative energy transfer are
the most important factors in the fluorescence quenching, and that
radiationless dipole-dipole S → S transfer has a negligible effect on the
fluorescence.
The structure of procumbide
Authors: Bendall MR , Ford CW , Thomas DM
Published: September 2010

A revised structure for
procumbide (2), an iridoid glucoside from Harpagophytum
procumbens, is proposed, based on 1H and 13C n.m.r,
spectral information and 1H homonuclear Overhauser enhancements. The
revised structure is an isomer of antirrhinoside, differing only in the
stereochemistry at C6.
Effect of alkyl chain length on the aqueous solubility and redox properties of symmetrical dixanthogens
Authors: Hamilton IC , Woods R
Published: September 2010

Aqueous solubilities of
methyl, ethyl and propyl dixanthogens have been determined spectrophoto-metrically.
The dependence of solubility on alkyl chain length is interpreted in terms of
the hydrophobic effect with dixanthogen molecules being 'folded' in aqueous
solution. The solubilities of butyl and pentyl dixanthogens were estimated by
extrapolation of the data for the lower homologues. Knowledge of dixanthogen
solubilities allows calculation of E�
values for dixanthogen/xanthate systems referred to 1 M solutions as standard
states from published values referred to saturated dixanthogen solutions. The
variation in E� values with chain
length is due to both an electronic effect and the conformation of dixanthogen
in solution. These conclusions are supported by E� values measured in an acetone/water solvent in which dixanthogen
as well as xanthate solutions of known concentration can be prepared.
Electron-Transfer Reactions in Non-Aqueous Media. VI. A Temperature-Dependence Study of the Reduction of cis-[CoCl2(en)2]+ by Iron(II) in Me2SO
Authors: Spiccia L , Watts DW
Published: September 2010

The kinetics of the
reduction of cis-[CoCl2(en)2]
� (en = ethylenediamine) by iron(II) in Me2SO
have been studied at four temperatures. The rate law has the form
d[CoIII]/dt = kK [COIII][FeII]/(1+K[FII])
The pseudo-first-order rate
constants determined at high [Fell] have been resolved into k and K, and their independent temperature dependence has been studied.
The results are totally consistent with an inner-sphere electron-transfer
process in which the precursor complex contains a double bridge using both the cis-chloro ligands and in which the iron
atom is octahedrally coordinated.
Halogenated Terpenoids. XVII The Structures of the Bromocamphorenic Acids, of α-Bromocampholide and of Dibromocampholide
Authors: Carman RM , Fielden R
Published: September 2010

The structural assignments
of the 3- and 4-bromocamphorenic acids (3) and (7), of α-bromocampholide (10) and of dibromocampholide
(8) are corrected.
The Crystal Structure of 8β-Hydroxymethylpodocarpane-13β-carboxylic Acid Lactone: the Circular Dichroism of This and Some Related Lactones
Authors: Beecham AF , Cambie RC , Hayward RC , Poppleton BJ
Published: September 2010

The title compound
crystallizes in the orthorhombic space group P212121
with cell dimensions of a 7.313(1), b 9.093(1), c 24.514(2) �. The structure was solved by direct methods from
diffractometer data and refined by the method of least squares to an R of
0.050; bond lengths and angles are normal although the bridged lactone ring
exhibits an unexpected conformation. Circular dichroism spectra have been
obtained from the title compound and five related lactones, all of which are
similar in that the lactone group extended by an extra carbon atom (C-CO-O or CO-O-C) forms a 1,3 bridge across
a six-membered ring. For two of the compounds, the c.d. within the region of
the n → p* transition is bisignate. We conclude that
the correlations between structure and n → p* c.d. sign previously adduced for bridged-ring
lactones do not extend to lactones of this type.
The microwave spectrum of (Z)-Ethanimine
Authors: Brown RD , Godfry PD , Winkler DA
Published: September 2010

The microwave spectrum of ethanimine, CH3CH=NH, has been measured over the
range of 18-76 GHz. A series of lines have been attributed to the Z-isomer.
These have been fitted to an asymmetric rotor with inclusion of centrifugal
distortion parameters. An excited torsional state has
also been assigned and the barrier to internal rotation of the methyl group has
been determined. The dipole moment has been evaluated from the Stark effect as
2.42 D.
The quadrupole coupling constants of the
nitrogen atom have been obtained from high-resolution studies. In contrast to methanimine, we found no evidence of magnetic hyperfine
interaction in the structures of the multiplets.
Oxygen exchange and glycinate ring opening in [Co(en)2(gly)]2+
Authors: Boreham CJ , Buckingham DA
Published: September 2010

Over the pH range 0-2
chelated glycine in [Co(en)2(gly)2+ exchanges one of its oxygens according to
the rate law kobs = k(1),[H+] with k(1), (1.0+0.1) × 10-5
mol-1 dm3 s-1. The second oxygen exchanges
much more slowly with k(2) c. 7 × 10-8 s-1 in 0.1 mol dm-3 acid. In alkaline
solution, [OH-] being 1.0-10-3 mol dm-3, the two oxygen
atoms exchange according to the expression kobs = k(1),(2)[OH-] with
k(1) 3.0 × 10-3mol-1 dm3 s-1 and k(2) c. 1.7 × 10-6
mol-1 dm3 s-1 both at 25.0°C and ionic
strength, μ 1.0 (NaClO4). The latter process occurs with C-O bond fission
to form cis-[Co(en)2(gly)(OH)]+, with kd 1.8 × 10-5 mol-1
dm3 s-1, which subsequently undergoes a more rapid OH--catalysed
loss of glycine, with k'd, 6 × 10-4 mol-1 dm3 s-1,
to form cobalt(III) and cobalt(II) products.
The coordinating ability of the antibiotic cycloserine towards transition metal halides
Authors: Preti C , Tosi G
Published: September 2010

A series of cycloserine complexes of chromium(III), manganese(II),
rhodium(III) and iridium(III) halides has been prepared and characterized by
chemical analyses, conductivity measurements, room temperature magnetic moment
studies, electronic, i.r. and far-i.r.
spectra and isotope exchange (deuteration)
experiments. From the magnetic properties it was concluded that the above ligand forms high- spin complexes with chromium(III) and
manganese(II) and low-spin complexes with rhodium(III) and iridium(III). The
position and multiplicity of the metal-halogen stretching modes in the far-i.r. region have been extensively investigated, the results
being particularly useful in distinguishing between the mer
and fac isomers in the ML3X3-type octahedral
complexes. The ligand behaves as monodentate
O-bonded. The wavelengths of the principal electronic absorption peaks have
been accounted for quantitatively in terms of the crystal field theory and the
various parameters have been calculated. The calculated Dq
parameters are in accord with the presence of CrO6, CrN3X3,
RhO3X3 and IrO3X3 chromophores according to the infrared results. The values
of B and C obtained for the manganese complexes are significantly lower than
the corresponding values for the free gaseous ion. Under our experimental
conditions no metal-induced ring opening of the ligand
was observed.
Bisophenol Flukicides. II. The Crystal Structure of 2,2'-(2,2,2-Trichloroethylidene)bis(4-chloro-6-nitrophenol)
Authors: Hay D , Demunk P , Mackay M
Published: September 2010

Crystals of the title
compound, C14H7Cl5N2O6, belong to the monoclinic space group P21/c
with cell dimensions a 13.021(2), b 10.508(2), c 13.360(2)Ǻ, β
106.00(1)° and Z 4. The structure was solved by direct methods from
diffractometer data measured with Cu Kα
radiation, and refined to a conventional R index of 0.046 for 2465
non-equivalent terms. The phenyl rings are mutually inclined at 73.9ˌ, and the
equivalent substituents of each ring lie on the same side of the plane formed
by the bridging carbon atom and its two bonded aromatic carbon atoms.
The reactivity of the charge-transfer complex of butyl vinyl ether and maleic anhydride in the radical terpolymerization of butyl vinyl ether, maleic anhydride and acrylonitrile
Authors: Fujimori K , Wickramasinghe NA
Published: September 2010

The equilibrium constant of
the charge-transfer complexation of butyl vinyl ether (bve)
and maleic anhydride (manh) is measured in carbon
tetrachloride as 0.30�0.02 dm3 mol-1 at 37°C by n.m.r. spectroscopy.
The radical terpolymerization of the bve-manh-acrylonitrile
(acn) system is carried out in chloroform. The
participation of the complex is considered and the monomer reactivity ratios of
the bve-manh complex and acn
are obtained as rc 83 and racn 0.0090, respectively.
Flukicides. IV. Crystal and Molecular Structure of 3'-Chloro-4'(p-chlorophenoxy)-3,5-diiodo-salicylanilide (Rafoxanide)
Authors: Sindt A , Mackay M
Published: September 2010

Orthorhombic crystals of
rafoxanide, C19H11Cl2I2NO3,
belong to the space group Pca21 with a 23.234(2), b 8.980(2), c
9.582(2)Ǻ and Z 4. The structure was solved by the heavy-atom method from
diffractometer data measured with Mo Kα
radiation. Refinement with anisotropic temperature factors given to the
non-hydrogen atoms converged at R 0.059 for the 2025 observed terms. The two
aromatic rings of the salicylanilide moiety are almost coplanar with a dihedral
angle of 11.2°, whereas they are approximately perpendicular to the plane of
the phenoxy group. Weak inter-molecular hydrogen-bond-like interactions between
the nitrogen and carbonyl oxygen, which involve a glide motif, link the
molecules into ribbons extending along the c axis.
Hydrogen bonding and the n → p* blue shift in a,b-unsaturated ketones. II. Franck-Condon factors and estimates of the effects of hydrogen bonding on CO bond lengths
Authors: Beecham AF , Hurley AC , Johnson CHJ
Published: September 2010

Vibrational wave functions
and Franck-Condon factors are calculated for the n → π* transition
in α,β-unsaturated ketones by approximating
vibrations of the chromophore by those of a diatomic moiety (CO). Comparison of
the results with recent c.d. and u.v. absorption measurements indicates that
the principal effect of hydrogen bonding on the n → π* system of
these ketones arises from a differential lengthening of the CO bond in the
excited electronic state as compared with the ground electronic state. It is these
bond length changes which cause (through the Franck-Condon factors) the
redistribution of intensity between vibrational sub-bands which is such a
striking feature of recent highly resolved c.d. spectra.
Crystal and molecular structures of two aryldiazenato complexes of molybdenum of the type [Mo(N2Ar)(S2CNMe2)3]
Authors: Williams GA , Smith ARP
Published: September 2010

The crystal and molecular
structures of the aryldiazenato complexes of molybdenum, [Mo(N2C6H5)(S2CNMe2)3],CH2Cl2
(1), and the m-nitro derivative [Mo{N2C6H4(m-NO2)}-(S2CNMe2)3]2,�CH2Cl2,�H2O
(2), have been determined by single-crystal X-ray diffraction methods at 294 K.
Crystals of (1) are monoclinic, P21/n, a 13.056(1), b 13.366(1), c
15.350(1) Ǻ, β 93.80(1)°, Z 4. Crystals of (2) are monoclinic, C2/c,
a 32.442(8), b 17.670(4), c 17.867(3) Ǻ, β 99.03(1)°, Z 8. Automatic
diffractometry has provided significant Bragg intensities for 2849 (1) and 3898
(2) independent reflections and the structures have been refined by
least-squares methods to R 0.036 (1) and 0.053 (2). The two unique molybdenum
complexes in (2) are essentially chemically equivalent. The complexes in (1)
and (2) possess the expected seven-coordinate pentagonal bipyramidal structures
with the aryldiazenato ligands, singly bent, occupying axial positions. The
N=N-Mo units are linear, and the bonding can be represented by N=N→Mo with the aryldiazenato ligands three-electron
donors. The m-nitro substituent in (2) interacts with a dithiocarbamate
(dtc) nitrogen atom, thereby affecting the redox
behaviour of this compound. The possible significance of this O(nitro)...N(dtc) interaction to the mechanism, whereby included
nitrobenzene solvent in the crystal lattice lowers the magnetic moments of
ferric dithiocarbamates, is discussed.
Studies of Australian soft corals. XX. A new sesquiterpene furan from soft corals of the family Xeniidae and an examination of Clavularia inflata from north Queensland waters
Authors: Bowden BF , Braekman J , Mitchell SJ
Published: September 2010

Extraction of several soft
corals of the genera Cespitularia and Efflatounaria
have afforded, in addition to the reported epimeric diterpene alcohols (1a) and
(1b), varying amounts of three sesquiterpene furans,
'atractylon' (2), 'isofuranodiene' (3) and the new but related furan (4).
Concurrent examination of Clavularia inflata
indicated the presence of the same diterpene alcohol (1b), and a related tricyclic
diterpene diol (9) previously reported from the same organism. Evidence is
presented for a common biogenetic origin for (1a), (1b) and (9).
X-Ray structure analysis of methyl 2,3,4,5-Tetra-O-acetyl-α-D-galactoseptanoside
Authors: Choong W , McConnell JF , Stephenson NC , Stevens JD
Published: September 2010

The crystal structure of
the title compound was determined by X-ray diffraction and the use of the
multi-solution programs MULTAN 74. Crystals are monoclinic, space group C2
with Z = 4 in a unit cell of dimensions: a 21.140(6), b 9.394(3), c 9.765(3)
Ǻ, β 108.73(5)°. The structure was refined by full-matrix
least-squares methods to a final R of 0.036 for 1858 diffractometer
reflections. The seven-membered ring approximates to a twist-chair conformation
very similar to that found for the gluco analogue.
Chromium(III), manganese(II) and iron(III) O,O'-bonded complexes of the para- and meta-substituted benzeneseleninic acids
Authors: Preti C , Tosi G
Published: September 2010

A number of complexes of
chromium(III), manganese(II) and iron(III) with para- and meta-substituted
benzeneseleninic acids, XC6H4SeO2H (X = H, p-Cl, m-Cl, p-Br, m-Br, p-Me), are
reported. The newly prepared compounds are characterized on the basis of near-i.r. and far-i.r. spectroscopy,
electronic spectra and conductivity measurements, as well as by magnetochemical
evidence. The wavelengths of the principal absorption peaks have been accounted
for quantitatively in terms of the crystal field theory for chromium(III) and
manganese(II) derivatives. The nephelauxetic parameters are all indicative of
an appreciable metal-ligand covalency. The i.r.
spectral data suggest that the ligands act as bidentate in seleninato-O,O'
complexes and we can propose octahedral geometries with D3 symmetry
for the chromium(III) and iron(III) derivatives and octahedral geometries,
distorted towards D4h, for the manganese(II) complexes, in which the
water has been shown to be coordinated to the metal.
The alkaloids of Heliotropium curassavicum
Authors: Subramanian PS , Mohanraj S , Cockrum PA , Culvenor CCJ , Edgar JA , Frahn JL , Smith LW
Published: September 2010

The main alkaloids of Heliotropium curassavicum Linn.
have been identified. They are curassavine(4), an
ester of trachelanthamidine with a new acid, curassavic acid [2-hydroxy-2-(1-hydroxyethyl)-3- methylpentanoic acid] (3), coromandaline
(1), an ester of trachelanthamidine with (+)-viridifloric acid (previously unknown in nature), and heliovicine (2), an ester of trachelanthamidine
with the uncommon (-)-enantiomer of trachelanthic acid.
Reactions of trifluoromethyl radicals. V. Hydrogen abstraction from methyl acetate and methyl (2H3)Acetate
Authors: Arthur NL , Newitt PJ
Published: September 2010

Hydrogen abstraction by CF3
radicals from CH3COOCH3 and CD3COOCH3
has been studied in the temperature range 78-242°, and data have been obtained
for the reactions:
CF3 + CH3COOCH3
→ CF3H+[C3H5O2] �������������(3) CF3
+ CH3COOCH3 → CF3H+CH2COOCH3������������ (4)
CF3 + CD3COOCH3
→ CF3D+CD2COOCH3������������ (6)
CF3 + CD3COOCH3
→ CF3H+CD3COOCH2������������ (7)
The corresponding rate
constants, based on the value of 1013.36 cm3 mol-1
S-1 for the recombination of CF3 radicals, are given by
(k in cm3 mol-1 s-1 and E in J
mol-1): logk3 =
(11.52�0.05)-(35430�380)/19.145T ���� (3)logk4 =
(11.19�0.07)-(34680�550)/19.145T ���� (4)logk6 =
(11.34�0.06)-(46490�490)/19.145T ���� (6)logk7 =
(11.26�0.05)-(36440�400)/19.145T ���� (7)At 400 K, 59% of
abstraction occurs from the acetyl group, and 41 % from the methoxy group. The
kinetic isotope effect at 400 K for attack on the acetyl group is 25, due
mainly to a difference in activation energies.
Phosphorus-31, mercury-199 and selenium-77 n.m.r. studies of ligand exchange reactions in mercury(II) halide complexes
Authors: Colton R , Dakternieks D
Published: September 2010

Mercury(II) halide complexes
of tris(4-methoxyphenyl)phosphine have been investigated by 31P and 199Hg
n.m.r. spectroscopy of CH2Cl2 solutions. At room
temperature the phosphine exchanges at an appreciable rate and halogen exchange
is fast. At -50°C both phosphine and halogen exchange are slow on the n.m.r.
time scale and halogen redistribution reactions are observed. ��� Mercury(II) halide complexes with
tributylphosphine selenide have been investigated by 31P, 199Hg
and 77Se n.m.r. methods. This ligand is labile and exchanges rapidly
on the n.m.r. time scale at room temperature, although the exchange can be
slowed down at about -100°C. Halogen exchange is also fast at room temperature.
��� Ligand exchange reactions between
tributylphosphine and either tris(4-methoxyphenyl)phosphine or
tributylphosphine selenide were investigated and redistribution reactions to
give mixed ligand complexes were observed.
Kinetics and mechanism of substitution in trans-dichlorobis(ethylenediamine)-cobalt(III) chloride by organic bases in non-aqueous solvents
Authors: Janardan AS , Kesavan V , Mahadevappa DS
Published: September 2010

Kinetics of substitution of
a chloride in trans- dichlorobis(ethylenediamine)cobalt(III) cation by five
organic bases (piperidine, diethylamine, cyclohexylamine, butylamine and
benzylamine) in methanol, dimethylformamide and mixtures of the two solvents are
reported. Rates are high in methanol but appreciably smaller in
dimethylformamide and increase with the increase in methanol content in the
mixtures. A retardation was observed by the addition of amine hydrochloride to
the methanolic medium. These observations have been explained on the basis of
catalysis by methoxide ion and a mechanism (SN1CB) in terms of a
rapidly established acid-base equilibrium resulting in a conjugate base, which
dissociates in the rate- determining step, has been proposed. Activation
parameters have been evaluated on the basis of the rate data at four different
temperatures.
Coenzyme A: pKa and g values
Authors: Pitman IH , Morris IJ
Published: September 2010

The pKa
and γ values at 25°, I 0.1 M, of the mercapto group of coenzyme A were
calculated to be 10.35�0.15 and 0.70�0.02 respectively. The γ value was
calculated from differences in the partition coefficient of quinazoline between
cyclohexane and aqueous buffers and that between cyclohexane and aqueous
buffers which contained coenzyme A. The described procedure could be used to
obtain γ values of other nucleophilic reagents which, like coenzyme A,
absorb u.v, energy strongly.
Symmetry-based equivalence between the crystal-field and angular-overlap models
Authors: Steenkamp PJ , Gonsalves JW
Published: September 2010

Ratios between the cubic
ligand-field parameters Δ, as predicted by the crystal-field model, are
presented and compared with those obtained when utilizing the angular-overlap
model. The remarkable similarities revealed are attributed to symmetry by
introducing a symmetry- orientated reparameterization of the crystal-field
model. A new parametric equivalence between the two models, based on the
effects of symmetry, is established. Arguments suggesting a unified model are
outlined.
Nucleophilic alkenes. VII. 1 : 2-Addition of 1,1 -dimethoxyethene to 1,4-naphthoquinones substituted in the benzenoid ring
Authors: Cameron DW , Feutrill GI , Patti AF
Published: September 2010

Several 5-substituted
1,4-naphthoquinones have been treated with 1,1- dimethoxyethene to give isomeric
mixtures of 1,3,5- and 1,3,8- trisubstituted
anthraquinones. Similarly 6-substituted 1,4- naphthoquinonesgave
mixtures of the 1,3,6- and 1,3,7-series. The course of these reactions has been
correlated with substituent effects.
Crystal structure of trans-tetraamminebis(isothiocyanato)cobalt(III) acetate-acetic, acid (III)
Authors: Westcott TJ , White AH , Willis AC
Published: September 2010

The crystal structure of
the title compound, trans-[Co(NH3)4(NCS)2] O2CCH3,HO2CCH3,
has been determined at 295(1) K by single-crystal X-ray diffraction and refined
by least squares to a residual of 0.11 for 300 'observed' reflections. Crystals
are orthorhombic, Pbam, a 14.851(9), b 7.068(4), c
7.031(4) Ǻ, Z 2. The cation is centred at the origin of the cell with
cobalt site symmetry 2/m, so that only one ammonia and one- half of the
N-bonded thiocyanate is crystallographically independent. Co-N(CS) is short (1.91(2)
Ǻ); Co-N(H3) being 1.96(2) Ǻ. Only one
crystallographically independent acetate species is found, lying close to a
coplanar, centrosymmetrically related image to which it is presumably bound by
a hydrogen bond (O...O 2.40(4) Ǻ).
The structure of some models for aqueous nickel chloride solutions in the high concentration range
Authors: Friedman HL , Dudowicz JB
Published: September 2010

The Monte Carlo method has
been applied to a charged soft-sphere model for the ions in aqueous NiCl2
to calculate the Ni-Ni partial structure factor. For some of the models
investigated, the wave vector location k0 of the first peak in the
partial structure factor is given closely by the equation ko =
2πp+1/3, where p+ is the particle number density of the Ni2+
ions. This is the behaviour that has been found experimentally by Enderby and
coworkers and that has been interpreted in terms of a 'quasilattice' structure
in the solutions. The present results indicate that rather general and non-specific
structural features are sufficient to account for the experimental data.
Use of binary diffusion and second virial coefficients to predict viscosities of gaseous systems
Authors: Arora PS , Robjohns HL , Bell TN , Dunlop PJ
Published: September 2010

Accurate binary diffusion
coefficients measured over the temperature range 275-323 K, together with some
excellent virial coefficients in the literature, have
been used to derive (m,6,8) potential parameters for the systems He-CH4,
He-CF4, He-O2, Ar-O2, CH4-C2H6,
CH4-C3H8 and CH4-C4H10.
These parameters predict quite well the viscosities reported for these systems
by Kestin and coworkers. The results indicate that
binary diffusion coefficients can be used to predict viscosities more
accurately than binary viscosities can be used to predict diffusion
coefficients.
An isothermal displacement calorimeter for the measurement of the enthalpy of solution of gases
Authors: Battino R , Marsh KN
Published: September 2010

The isothermal displacement
calorimeter initially described by Stokes, Marsh and Tomlins
has been modified to allow the measurement of the enthalpy of solution of
gases. This paper reports the enthalpy of solution of argon and nitrogen in
tetrachloromethane, cyclohexane, and benzene at 298.15 K and the enthalpy of
solution of carbon dioxide, methane, ethane, ethene, and propane in the above
three solvents at 298.15 and 318.15 K. Comparisons are made with other direct
measurements and with results derived from the variation of gas solubility with
temperature. The apparatus appears to have a higher precision than those
described previously. For carbon dioxide and the hydrocarbon gases the
precision is of the order of �0.2 kJ mol-1, while for argon and
nitrogen the precision is of the order of �0.5 kJ mol-1.
The triterpenes of Emmenospermum pancherianum
Authors: Baddeley GV , Simes JJH , Ai T
Published: September 2010

The free triterpenes
identified as constituents of Emmenospermum pancherianum Baill. are ceanothic acid
(wood), betulic acid (bark), and the new triterpene, 18α,24-dihydroxy-A(1)-norlupa-2,20(29)-diene-27,28-
dioic acid 28-methyl ester 27,18α-lactone (1a) (bark); the structure of
the last has been determined by spectroscopic analysis. Both wood and bark
contained saponin which in each case on acid hydrolysis gave ebelin lactone,
and two new sapogenins, 24,25-dihydroebelin lactone (9a)and the tetracarbocyclic
triterpenoid (10a) possessing an aromatic ring D; all three sapogenins are secondary
sapogenins. The primary sapogenins jujubogenin (11a) and dihydrojujubogenin
(12a)have been obtained by degradation of the wood saponin, and
dihydrojujubogenin has been shown to be the precursor of (9a) and (10a).
The isothermal displacement calorimeter: Design modifications for measuring exothermic enthalpies of mixing
Authors: Costigan MJ , Hodges LJ , Marsh KN , Stokes RH , Tuxford CW
Published: September 2010

The isothermal displacement
calorimeter described previously has been modified by the inclusion of a
thermoelectric cooling module to allow the study of both endothermic and
exothermic mixing. Other modifications are also described. Excess enthalpies
are reported for 1,4-dioxan+tetrachloro-methane, benzene+dichloromethane,
tetrahydrofuran+water, and ethanol+water at 298.15 K and 1,4- dioxan+dichloromethane
at 298.15 and 303.15 K. These mixtures have been suggested as possible
reference mixtures for either checking the operation of, or calibrating,
calorimeters to be used for making measurements on exothermic mixtures. The
performances of our calorimeters have been evaluated on the basis of the results
presented here and by comparison with previous results. Some advantages and
disadvantages of the proposed reference mixtures are discussed. Photochemical
effects from the tungsten thermostat lamp affect the results for mixtures of
tetra-chloromethane with 1,4-dioxan.
The hydrolysis of coordinated amidines in the sexadentate complex u-fac-2,3-Bis[(2-aminoethyl)(methyl)aminoethylimino]-1- methylpiperazinecobalt(III) perchlorate
Authors: Searle GH
Published: September 2010

The title complex u-fac-[Co(amam)]3+ (1)
has a sexadentate ligand which involves a novel diamidine arrangement of an
N,N'-disubstituted amidine and a trisubstituted amidine, each amidine group
being coordinated through one nitrogen. It is inert in acid but it hydrolyses
in base in two clean sequential stages through an amidine imide complex (2) to
the diimide complex u-fac-[1,14-diamino-3,12-dimethyl-3,6,9,12-
tetraazatetradeca-6,8-diene-7,8-diolato(2-)]cobalt(III) ion (3). The structures
of complexes (2) and (3) isolated as perchlorates have been characterized by 13C
and 1H n.mr.r spectra, electronic and infrared spectra, and by their
unusual ion-exchange chromatographic behaviour. Complexes (2) and (3) exist as
the deprotonated forms of the amides, and become partially protonated only at
[H+] ≥ 1 M. The structures of (2) and (3) demonstrate that
coordinated amidines base-hydrolyse specifically to retain the Co-N-C bond, and
that the less highly substituted amidine group hydrolyses the more readily.
The crystal and molecular structure of metachloral, 2(e),4(e),6(e),8(e)-Tetrakis-(trichloromethy1)-1,3,5,7-tetraoxocan
Authors: Hay DG , Mackay MF
Published: September 2010

The molecular conformation
of the title compound has been defined by an X-ray crystallographic analysis
from diffractometer data measured with Cu Kα
radiation. The monoclinic crystals belong to the space group P21/n
with a 16.256(6), b 6.130(1), c 9.812(2) Ǻ, β 96.42(2)°, and Z 2. The
structure was solved by direct methods and refinement converged to give an R of
0.071 for the 1221 observed terms. Unlike other 1,3,5,7- substituted
eight-membered heterocyclic compounds, the molecule adopts a chair conformation
and has exact C1 symmetry. All the trichloromethyl substituents are
equatorial.
Reactions over supported metal catalysts. V. The effects of halogen-containing compounds on transition metal catalysts supported on silica or pumice. Reactions of 1-Methylbicyclo[4,1,0]heptane
Authors: Jackson WR , Nicolson DM
Published: September 2010

Reactions of
1-methylbicyclo[4,1,0]heptane with hydrogen over palladium and platinum
catalysts supported on pumice are described. Pretreatment of these catalysts
with halogen-containing compounds greatly changes the product distribution, and
the mechanism of halogen influence is discussed.
Glutamate and aspartate complexes of copper(II): equilibrium and E.P.R. measurements
Authors: Claridge RFC , Kilpatrick JJ , Powell HKJ
Published: September 2010

Complexes [CuHL]+ containing protonated ligand have been
characterized for the ligands L-glutamate and L-aspartate:
��������������� logK3(M+H+L↔MHL)
= 12.62�0.05 and 12.70�0.03
respectively, at 25°C, I
0.10 M KNO3. Equilibrium constants have been redetermined for the
complexes [CuL] and [CuL2]2-.
Visible absorption and e.p.r. parameters are reported
for the complexes; these data establish that the complexes [CuHL]+
have the α-amino carboxylate group coordinated to copper(II).
The crystal structure of a dithiophosphate-bridged binuclear cobalt(II) complex of a macrocyclic ligand
Authors: Williams GA , Robson R
Published: September 2010

The crystal and molecular
structure of LCO2 [S2P(OEt)2]2
(where L is a binucleating ligand derived from the
macrocycle LH2 formed by condensation of two molecules each of
propane-1,3-diamine and 2-hydroxy-5-methylisophthalaldehyde) has been
determined by single-crystal X-ray diffraction techniques at 295 K. The
compound crystallizes in the triclinic space group Pī with two molecules in a
cell of dimensions a 18.644(6), b 11.694(4), c 9.487(4) �, α 84.99(3), β 82.61(3), γ 73.48(2)�.
Automatic diffractometry has provided significant Bragg intensities for 2799
independent reflections and the structure has been refined by least-squares
methods to R 0.054. The structure is molecular, consisting of discrete
binuclear units LCo2[S2P(OEt)2]2.
The two centrosymmetric molecules in the unit cell are crystallographically
unique but essentially chemically similar. The two cobalt(11) atoms in each
molecule are separated by 3.075(2) and 3.072(2) �. Each cobalt atom is in an
octahedral environment, with an N2O2 equatorial plane and
two sulfur atoms of bridging dithiophosphate ligands
in the axial positions. The Co-S bonds are the longest yet observed [2,680(3),
2.652(3), 2.642(3), 2.623(3) �]. The cobalt(11) centres
are high spin, with �eff 4.53 BM per cobalt atom. The macrocyclic
ligand deviates slightly from planarity. The forces exerted both by the ligand
L on associated metal atoms, and by axial ligands on the macrocycle, are
discussed.
An E.S.R. study of the oxidation of some malonic and other acids by hydroxyl radicals
Authors: Hewgill FR , Proudfoot GM
Published: September 2010

A series of terminal
dicarboxylic acids, malonic acids and branched-chain aliphatic acids on
oxidation with TiC13/H2O2 in a flow system
give rise to e.s.r. spectra arising from mixtures of
radicals. In most cases the dominant radical is that formed by abstraction of
hydrogen from the β-carbon.
Malonic acids complex with titanium(III) ions sufficiently strongly to be
examined at elevated pH values without the need for added ethylenediaminetetraacetic
acid.
The thermal decompositions of 2-methyl-2-phenoxypropane
Authors: Daly NJ , Robertson SA , Steele LP
Published: September 2010

The thermal reactions of
2-methyl-2-phenoxypropane have been studied in gas phase over the range 600-670
K by quadrupole mass spectrometry and pressure
studies. The reaction is shown to be a homogeneous first-order elimination of
phenol and 2-methylpropene which is described by the Arrhenius
equation k = 1014.10�0.12exp[(-210.46�1.36)/RT] s-1
Possible reaction mechanisms are considered and the reaction is found to be a unimolecular elimination rather than a radical chain
process initiated by homolysis to phenoxy
and 1,1-dimethylethyl radicals. Evidence for the rearrangement to
4-t-butylphenol previously proposed has been carefully sought and it is
concluded that the process does not occur in the gas phase. The A-factor observed for the reaction is in
good agreement with that calculated for the four-centred transition state
proposed for elimination of 2-methylpropene from alkoxypropanes.
Derivatives of isatin in aqueous solution. II. Z-E isomerism in isatin β-thiosemicarbazones
Authors: Stunzi H
Published: September 2010

The species and reactions
of β-thiosemicarbazonoisatin-5-sulfonate
(2) which cause hysteresis in pH titrations in
aqueous solution [I 0.15 M
(KNO3) at 37�] were studied by pH-metric and kinetic examination,
and u.v. and n.m.r. (1H and 13C) spectroscopy. In
acidic-to-neutral solutions, this compound is stable in the Z configuration (HLZ. Rapid
deprotonation gives the species LZ which slowly isomerizes to the E configuration (LE). On fast
protonation, the species HLE is obtained with a smaller pKa value than its isomer HLZ--the
cause for the observed hysteresis. The pKa values of the species HLZ
and HLE (9.92 and 7.41, respectively) were obtained from fast pH titrations.
The rate law for the Z-E isomerization was obtained by examination of the variation
of pH with time, when addition of base was discontinued. The equilibrium
constants for the isomerizations are [HLZ]/[HLE]
= 14 and [LE]/[Lz] = 23.
Similar results were found for the 1-methyl derivative (3) and for β-semicarbazonoisatin-5-sulfonate
(4).
Kinetic study of the thermal isomerization of fulvene
Authors: Gaynor BJ , Gilbert RG , King KD , Harman PJ
Published: September 2010

The thermal unimolecular
isomerization of fulvene to benzene was studied by the technique of very
low-pressure pyrolysis. The observed fall-off regime rate coefficients
(obtained over the temperature range of c.
1050-1150 K) were fitted by using RRKM (Rice-Ramsperger-Kassel-Marcus) theory
(assuming a concerted reaction mechanism) to give high-pressure Arrhenius
parameters in the range E∞ = 268-285 kJ mol-1, log(A/s-1) = 13-14.
The characterization of copper 4,4',4'',4'''-Tetrasulfonated phthalocyanine ([29H, 31H-phthalocyanine-2,9,16,23-tetrasulfonato(2-)-N29, N30, N31,N32]copper) and the α-form of copper phthalocyanine ([29H,31H-phthalocyaninato(2-)-N29, N30, N31, N32]copper)
Authors: Moxon NT , Fielding PE , Gregson AK
Published: September 2010

Powder X-ray diffraction,
e.p.r, and magnetic susceptibility studies on copper 4,4',4'',4'''-tetrasulfonated
phthalocyanine, Cu(tspc), and α-copper phthalocyanine, αCu(pc), are
reported. Cu(tspc) was found, by analogy with the previously reported structures
of the α, β and γ forms of Cu(pc), to have a triclinic unit cell
of dimensions a 26.9, b 3.8, c 25.6 �, α 89.9, β
90.0 and γ 95.5�. The e.p.r. and magnetic susceptibility data for both
Cu(tspc) and αCu(pc) suggest the presence of exchange interaction. The
magnetic susceptibility data are best explained by using an S = � Heisenberg chain model with J -0.84 and -0.71 cm-1
respectively.
The 1H N.M.R. five-spin system of phenyl
Authors: Duewell H
Published: September 2010

Chemical shifts and coupling
constants for the [AX]2M system of phenyl group protons in benzoyl
and N-phenyl were determined for
seven compounds by 270-MHz n.m.r.
Heterocyclic ambident nucleophiles. II. The alkylation of adenine
Authors: Beasley AE , Rasmussen M
Published: September 2010

The alkylation of
un-ionized adenine by a variety of primary alkyl halides under standardized,
common conditions (HCONMe2, 100�) was investigated. The alkylation
pattern (N 1 : N 3 : N 7 : N 9) was found to be relatively insensitive to
changes in the nature of the alkylating agent, except for cases involving
benzyl chloromethyl ether and chloromethyl pivalate. An interpretation of these
patterns in terms of modern ambient nucleophile reactivity concepts and
variable SN2 transition state structures is presented.
Isolation of 3β-Hydroxyolean-18-en-28-oic acid (morolic acid) from Eucalyptus grossa and the crystal structure of methyl morolate acetate
Authors: Cannon JR , Metcalf BW , Raston CL , White AH
Published: September 2010

3β-Hydroxyolean-18-en-28-oic acid (morolic acid) has been
isolated from the leaves of Eucalyptus
grossa Benth. The crystal structure of methyl morolate acetate has been
determined and some distortions of the angular geometry in the A/B trans-decalin moiety have been noted.
The tritium kinetic isotope effect for the iodination of L-(5-3H)-3-Iodotyrosine
Authors: Baldas J , Colmanet S , Porter QN
Published: September 2010

The kinetic tritium isotope
effect (kH/kT) for the iodination of L-(5-3H)-3-iodotyrosine
at pH 7·5 was found to be 4·29�0.25 with molecular iodine and 4·50�0.26
with chloramine-T/potassium iodide. This effect establishes that the
rate-limiting step is proton removal by the general base. A novel method for
measuring the fraction of tritiated water by high performance liquid chromatography
is described.
The electrical double-layer properties of the mica (muscovite)-aqueous electrolyte interface
Authors: Lyons JS , Furlong DN , Healy TW
Published: September 2010

Electrophoresis and
streaming potential data are reported for crushed and sheet muscovite mica
respectively. For streaming potential measurements a newly designed radial flow
apparatus was used. Measurements on crushed mica show that both aluminium and silicon
leach out of the mica. Leached aluminium and silicon may readsorb
to confer increased positive and negative charge respectively on the mica.
Electrophoresis data indicate that leaching of aluminium occurs more rapidly
than of silicon. Aging experiments on sheet mica show leaching effects to be
much slower than on crushed mica. Streaming potential measurements on freshly
cleaved mica sheets showed that (i) the zeta-
potential depended strongly on electrolyte (KCl) concentration; (ii) the
zeta-potential was relatively independent of pH and (iii) monovalent
cations were adsorbed in the sequence H+ > Cs+ > K+
> Na+ > Li+, whilst Ca2+ adsorbed more
strongly than K+. It is proposed that the structure of the electrical
double layer at the mica/electrolyte interface results from the distribution of
all ions between the diffuse layer,
the Stern plane (hydrated) and more critically the lattice holes of the
silica-alumina basal plane.