bluuebunny/crossref_metadata_2025 huggingface dataset:
A convenient preparative method for tryptophan benzyl esters
Authors: Williams K , Halpern B
Published: September 2010

The utilization of amino
acid benzyl esters in synthetic peptide procedures offers advantages over the corresponding
methyl or ethyl derivatives. Whereas the latter groups must by cleaved by
alkaline saponification, the benzyl ester function
can be removed by acidolysis or by catalytic hydrogenation under conditions
which permit the simultaneous cleavage of N-acyl-protecting groups such as t-Boc or CBzl.*
Mass spectra of 1,2,4-triazoles: A novel skeletal rearrangement
Authors: Kallury RKMR , Nath TGS , Srinivasan VR
Published: September 2010

The mass spectra of
3-chloro-4,5-diphenyl-4H-1,2,4-triazole (1), 3- amino-4,5-diphenyl-4H-1,2,4-triazole
(2) and 3-chloro-5-(5?-chloro-2?- thienyl)-4-phenyl-4H-1,2,4-triazole
(3) revealed a novel skeletal rearrangement involving the migration of the
3-substituent to the C 5 carbon of the triazole ring followed by a concerted
loss of nitrogen and benzonitrile.
Birch reduction of 2-Methoxy-1-naphthoic acids
Authors: Oommen PK
Published: September 2010

The reduction of
2-methoxy-1-naphthoic acids (1) with 2.4 equiv. of sodium in liquid ammonia
leads to the formation of the 1,4-dihydro compounds (2). These reduction
products on esterification with diazomethane followed by hydrolysis with dilute
mineral acids yield methyl 2-oxotetralin-1-carboxylates (5). This constitutes a
satisfactory general method of synthesis of (5).
A physicochemical study of chromium(III) mononuclear, dinuclear and heteronuclear chelates of triethylenetetraaminehexaacetic acid
Authors: Smith TD , Lancashire RJ
Published: September 2010

The existence of mononuclear
and dinuclear chromium(III) chelates of triethylenetetraaminehexa-acetic acid
(ttha) in aqueous solution has been demonstrated by potentiometric pH titration
and electronic visible spectroscopy. The isolation of mononuclear, dinuclear
and heteronuclear chromium(III) chelates of ttha has been accomplished.
Magnetic susceptibility measurements on the isolated solids point to the
absence of magnetic exchange coupling in the dinuclear chromium(III) chelate
and in the heteronuclear chelate containing chromium(III) and copper(II).
However, the differences in the e.s.r. spectra of the mononuclear and dinuclear
ttha chelates observed in frozen aqueous solution may arise from some form of
magnetic dipolar coupling between the chromium(III) ions in the dinuclear
chelate.
A differential scanning calorimetric investigation of the solution properties of Poly(styrene : isoprene : styrene) block copolymers
Authors: Sothman RD , Urwin JR
Published: September 2010

D.s.c. heating curves have been obtained from solutions of
a series of well characterized poly-(styrene : isoprene : styrene) triblock copolymers. In the preferential solvent,
methylcyclohexane, endotherms and/or exotherms (depending on composition) were observed from all
polymers with composition in excess of 10% polystyrene. These phenomena were
not observed from solutions of the copolymers in good or poor solvents for both
kinds of segments. An explanation is given in terms of gel formation and
polymer aggregation.
The acetolysis of some ω-Cyclooctatetraenylalkyl p-Nitrobenzenesulphonates
Authors: Gream GE , Mular M
Published: September 2010

The synthesis and
solvolytic behaviour (in buffered acetic acid) of the p-nitrobenzenesulphonate
esters of 2-cyclooctatetraenylethanol, 3- cyclooctatetraenylpropan-1-ol and
4-cyclooctatetraenyl-butan-1-ol are described. For comparison with the
cyclooctatetraenylalkyl derivatives, kinetic data for the corresponding
ω-(cyclooct-1?-enyl)alkyl and ω- cyclooctyl p-nitrobenzenesulphonates
are reported. ��� Kinetic and product studies have shown that
π-bond participation occurs in the acetolysis of 2-cyclooctatetraenylethyl
p- nitrobenzenesulphonate. The nature of the cyclized products, which amount to
95 % when 1.1 equiv. of sodium acetate (the buffer) are used, depends markedly
on the concentration of buffer. ��� Acetolysis of 3-cyclooctatetraenylpropyl
p-nitrobenzenesulphonates gives at least 98% non-cyclized products. A probable
cyclized product (<2%) is tentatively identified as bicyclo[6,3,0]-undeca-1,3,5,7-
tetraene. ��� Cyclized products (44%) are formed in the
acetolysis of 4- cyclooctatetraenylbutyl p-nitrobenzene-sulphonate.
Electronic ground state structure and chemistry of nitroguanidine
Authors: Stals J , Pitt MG
Published: September 2010

VESCF(BJ)CI MO reactivity
indices were used to provide a consistent rationale for the ground state
structure, thermal decomposition and chemistry of nitroguanidine (1). Intra-
and inter-molecular NH...O and NH...N hydrogen bonds, attractive and repulsive
coulombic forces between nitrogen and oxygen atoms, appear to determine the
crystal structure of (1). An intramolecular hydrogen-abstraction reaction and
the cleavage of the molecule's weakest bond, viz. (H2N)2C-NNO2,
appear to be the main primary thermal decomposition pathways for (1). The
nitrimino nitrogen atom and the carbon atom were postulated to be the centres
of electrophilic and nucleophilic substitution reactions respectively.
Spin-saturation transfer in an exchanging system: 4-Hydroxycyclopent-2-en-1-ones
Authors: Effenberger R , Rickards RW
Published: September 2010

P.m.r. studies of the substituted 4-hydroxycyclopent-2-en-1-ones
(1a-d) in acetone solution show the presence of two slowly interconverting
species which correspond to free and hydrogen-bonded forms of these compounds.
Double resonance experiments show the transfer of spin saturation between
solute molecules in these different environments.
New Group IB chemistry. VI. Syntheses of some acetylenic derivatives of platinum
Authors: Salah OMA , Bruce MI
Published: September 2010

Reactions between CuC2Ar(Ar = Ph, p-MeC6H4,
p-FC6H4 or C6F5)
and Pt(C2H4)(PPh3), afforded Pt(C2Ar)2(PPh3)2,
also obtained from PtCl2(PPh3)2 and CuC2Ar
(for Ar = C6F5). The acetylene HC2C6F5
reacts with Pt(C2H4)(PPh3)2 to give
Pt(η2-HC2C6F5)(PPh3)2
whereas Pt(PR3)4 (R = Phor Et) give the hydride-acetylide complexes trans-PtH(C2C6F5)(PR3)2
The behaviour of copper(II) dithiocarbamates at the mercury electrode
Authors: Randle TH , Cardwell TJ , Magee RJ
Published: September 2010

The reduction at the
mercury electrode of a series of copper(11) dithiocarbamates
[CU(S2CNR2)2] in propylene carbonate has been
investigated by a variety of electrochemical techniques. Thecomplexes undergo reduction
in two successive one-electron diffusion-controlled steps, with associated
adsorption of the complexes and the reduction products. Exhaustive reduction at
a mercury-pool electrode shows the completely reduced species [CU(S2CNR2)2]2-
to undergo slowdissociation. The alkyl
substituent influences the strength of adsorption of the reduction products, the
reduction potentials of the complexes and the reversibility of the first
reduction step, thesecond step being
quasi-reversible in all cases. The electroactive
centre appears to be the metal.
Specific β-Scission of 3β,5-Cyclocholestan-6-yl radical
Authors: Beckwith ALJ , Phillipou G
Published: September 2010

The 3β,5-cyclo-5β-cholestan-6-yl
radical (6), generated by interaction of triphenylstannane
with 6β-chloro-3β,5-cyclo-5β-cholestane (12), undergoes β-scission
by specific fission of the 4,5-bond to give the thermodynamically less stable
possible radical product (8). The results of these and earlier experiments
indicate that β-scission of cyclopropylcarbinyl
radicals is under stereoelectronic control, and involves a transition state
formed by primary interaction of the semi-occupied orbital with a βγ-σ* orbital.
Ammonia oxide. II. Bonding and calculated properties
Authors: Hart BT
Published: September 2010

An ab initio wavefunction
has been used to calculate the localized molecular orbitals,
Mulliken population analysis, one-electron properties
and e.s.c.a. chemical shifts for the hypothetical
molecule, ammonia oxide. Interpretation of these results, particularly when
compared with those for ammonia, has allowed some insight to be gained into the
electronic structure of the molecule. Calculated properties for the stable
tautomeric structure, hydroxylamine, are also reported. It is hoped that the
calculations reported in this paper will stimulate experimentalists in attempts
to isolate ammonia oxide.
Thio derivatives of β-diketones and their metal chelates. XXI. Mass spectra of 1,1,1-Trifluoro-4-mercapto-4-(2'-naphthyl)but-3-en-2-one and its metal chelates
Authors: Livingstone SE , Moore DS
Published: September 2010

The new monothio-β-diketone
l,l,l-trifluoro-4-mercapto-4-(2'-naphthyl)but-3-en-2-one, βC10H7-
C(SH)=CHCOCF3, and its chelates with iron(111), ruthenium(111),
cobalt(111), rhodium(111, nickel(11), palladium(11), platinum(11) and zinc(11)
have been prepared. The mass spectrum of the monothio-β-diketone
displays considerably more peaks than that of its parent β-diketone. Both
spectra give peaks for the ion CllH7+ (RC+
; R = β-C10H7). The mass spectra of the metal
chelates show some differences determined by the metal. All the metal chelates
except that of zinc show peaks due to the ion M'-MetS
and its daughter ions (M' = M for MetL2 and M - L for MetL3
; L = β-C10H7C(S)=CHCOCF3). It is
considered that the β-naphthyl group affects the fragmentation pattern,
since the mass spectra differ considerably from those of metal chelates of
other monothio-β-diketones.
The synthesis of 1,4-diketones
Authors: Nimgirawath S , Ritchie E , Taylor WC
Published: September 2010

Recent methods for the
synthesis of 1,4-diketones are briefly reviewed.Zinc and phenacyl bromide in dimethoxyethane
afforded 1,4-diphenylbutane-l,4-dione in moderate yield, but other solvents or
metals examined gave no or a lower yield. The route is unsatisfactoryfor aliphatic
1,4-diketones. Attempts to use 'levulinyl chloride' to acylate olefins or acetylenes were
fruitless. Routes involving aldol condensations of
hexane-2,5-dione or its monoacetal had very
restricted success, as did those depending on the halogenolysis
of acyl derivatives of phenacylmalonic ester. A fairly general route to 1,4-diketones was
found in the sequence: valine to N-acylvaline to oxazol-5-one to Michael addition
product with an α, β-unsaturated ketone followed by alkaline hydrolysis.The Michael addition is not
regiospecific and valine derivatives may also be
isolated. Yields of 1,4-diketones are only moderate but the synthesis is quick
and convenient.
The influence of pressure on the infrared spectra of hydrogen bonded solids. II. Bihalide salts
Authors: Hamann SD , Linton M
Published: September 2010

Infrared measurements have
been made of the influence of pressures between 0 and 40 kbar
on the asymmetrical stretching frequencies v3 and bending
frequencies v2 of the hydrogen-bonded ions FHF- and ClHCl- in the solid salts NaHF2, KHF2,
NH4HF2, (CH3)4NHCl2 and
(C2H5)4NHCl2 at 25�C. The behaviour
of the symmetrical stretching frequency v1 for FHF- in
KHF2 has been deduced indirectly from the shifts of combination
bands. Contrary to the behaviour of compounds with weaker, 'normal', hydrogen
bonds, the v3 bands shift to higher frequencies and the v2
bands shift to lower frequencies with increasing pressure. The vl band of KHF2 shifts to higher
frequencies. These trends are all in agreement with predictions made in Part I
for a simple model of hydrogen bonds. A new high-pressure phase transition has
been found to occur in NaHF2 at about 40 kbar.
Conformations of vinyl formate and vinyl acetate
Authors: Aroney MJ , Bruce EAW , John IG , Radom L , Ritchie GLD
Published: September 2010

Ab initio molecular
orbital theory has been used to deduce the preferred gas-phase conformations of
vinyl formate and vinyl acetate. In addition, experimental dipole moments (1030μ/Cm)
and molar Kerr constants (1027mK/m5 V-2 mol-1)
at 25�C are reported for both molecules as solutes in carbon tetrachloride:
vinyl formate (5.07, + 48.1) and vinyl acetate (5.70, + 3.8). The preferred
solution-state conformations indicated by the analysis of these results are
shown to be consistent with the theoretical predictions.
Comparative study of methods of computer-matching mass spectra. II
Authors: Mathews RJ , Morrison JD
Published: September 2010

The performance of
different methods of computer-matching mass spectra has been examined for several
different classes of compounds that are frequently analysed in our
laboratories. We have chosen to retain systems employing the 'Big-6' and
'Big-8' peaks, and then examine doubtful identifications with a Conversational
Mass Spectral Retrieval System.
Basic halides and related species of molybdenum(III). I. The empirical formulae and unit cell dimensions of the basic halides
Authors: Stabb DJ
Published: September 2010

The basic halides MoOX(H2O), (X = F, Cl)
were examined by vacuogravimetric and evolved gas
analysis and by X-ray and electron diffraction techniques. The basic chloride
prepared by slow crystallization had y = 3.08, with an orthorhombic unit cell
0.723 by 0.820 by 1.805 nm. Basic chlorides produced by rapid precipitation
were less crystalline, of slightly larger unit cell dimensions and had 3.0 <
y < 4.3. The water in excess of y = 3 was loosely held, while three water
molecules per molybdenum were more strongly held. The fluoride, which could not
be obtained with the perfect MoOF(H2O)3
stoichiometry, was isomorphous (cell parameters 0.710 by 0.823 by 1.824 nm for
[MoOF0.96(OH)0.04(H2O)3] (H2O)0.28).
It is concluded that the only hydrate of MoOX
existing under normal conditions is MoOX(H2O)3,
not the previously reported tetrahydrate.
Solvent structure. III. The dependence of partial molal volumes on internal pressure and solvent compressibility
Authors: Dack MRJ
Published: September 2010

Partial molal
volumes, V�, at 25�C were measured for sucrose, ascorbic acid and aspirin in
the solvents water, formamide, N,N-dimethylformamide and methanol. The
dependence of V� on solvent compressibility enabled an estimate to be made of
the intrinsic volumes, Vint, of
the dissolved non-electrolytes. Effective pressures, Pe,
in aqueous electrolyte solutions were calculated from previously determined
internal pressure data. Substitution of Pe
into the Tait-Gibson equation yielded values of Ve, the volume contraction of water due to
electrostriction, which agree well with values obtained by other methods.
The carbanion mechanism of olefin-forming elimination. VIII. Theoretical analysis of substituent and isotope effects in proton transfers from 2,2-Diaryl-1,1,1-trichloroethanes
Authors: McLennan DJ , Wong RJ
Published: September 2010

Rate constants for the dehydrochlorination of the title compounds by anionic bases
in alcoholic solvents are those for simple proton transfer. Rate and estimated
equilibrium data for these reactions can be approximately analysed in terms of
the Marcus theory of proton transfer. In one reaction series comprising the
reactions of para-substituted Ar2CHCC13 compounds with NaOMe in MeOH, the work term (wr) and the intrinsic free energy of activation
(ΔG?) are comparable and large. The change in kH/kD
with variation in substituent can be quantitatively rationalized, and the fact
that kH/kD does not pass
through a maximum even though ΔpK = 0 within the
series can be understood. Although the required rate-equilibrium parabolic
relationship for a second series involving the reactions of (p-ClC6H4)2CHCCl3
with a series of bases is obtained, anomalous Marcus parameters are derived,
and reasons for the anomalies are given. A revised set of approximate pKa
values for Ar2CHCCl3 compounds is presented, and more
precise experimental values of rate constants for the reactions of (p-NO2C6H4)2CHCC13
and (p-NO2C6H4)2CDCCl3
with NaOMe in MeOH are
provided.
Purine studies. XVIII. The C- and N-alkylation of theophylline and derivatives
Authors: Bhushan K , Lister JH
Published: September 2010

Alkylation of theophylline in aqueous alkaline solution with benzyl
halides gives, in addition to the expected N7 benzylated derivative, both
8-benzyl- and 7,8-dibenzyl-theophylline. Synthetic routes to these derivatives
have been explored and unusual reactivity associated with benzyl groups in some
of the intermediates has been demonstrated. Results which do not preclude the
possibility that benzyl radicals could be responsible for the 8-benzylation
reaction have been obtained.
C.M.R. spectra and conformational dynamics of oxygenated cis-10-Methyldecalins
Authors: Blunt JW , Coxon JM , Lindley NB , Lane GA
Published: September 2010

The thermodynamic
parameters for equilibration of the chair-chair conformational enantiomorphs of cis-10-methyl-9-decalol
(1) and (2) have been determined as EA 69.8 � 0.9 kJ mol-1,
ΔH? 66.7 � 1.3 kJ mol-1 and ΔS? + 12 � 5 JK-1
mol-1. For cis-10-methyl-1-decalone,
conformer (3) is 1.25 kJ mol-1 more stable at 200 K than conformer
(4) with EA 42.9 � 0.7 kJ mol-1, ΔH? 41 .0 � 0.7 kJ
mol-1 and ΔS? -20 � 3J K-1 mol-1 for the
conversion of (3) + (4. The c.m.r. spectra of these
com- pounds, together with those for the coprostan-4-one and coprostan-6-one,
have been assigned.
An automated procedure for qualitative and quantitative analysis of mixtures by means of carbon magnetic resonance spectroscopy: Applications to carbohydrate analysis
Authors: Blunt JW , Munro MHG
Published: September 2010

A generalized, automated c.m.r. procedure is described for the rapid qualitative and
quantitative analysis of mixtures of related compounds. This technique has been
applied to the analysis of carbohydrates extracted from various tissues of Pinus radiata, giving
results comparable to those obtained by other techniques, but with many
advantages - in particular, the
availability of structural information on unknown components in the extract.
Reactions of propargyl alcohols. I. Lithium aluminium hydride reduction of 2,3,3-Trimethylhex-4-yn-3-ol
Authors: Damm LG , Hartshorn MP , Vaughan J
Published: September 2010

Lithium aluminium hydride
reduction of (R)-(+)-2,3,3-trimethylhex-4-yn-3-ol (3) in diglyme gave(S)-(-)-4,5,5-trimethylhexa-2,3-diene
(4) and (S)-(+)-(E)-2,3,3-trimethylhex-4-en-3-ol (5). The mechanism of the
allene-forming reaction is discussed.
Pyridines and pyridinium salts from cyanoacetamides
Authors: Cossey AL , Harris RLN , Huppatz JL , Phillips JN
Published: September 2010

Self-condensation of cyanoacetamides under the influence of phosphorus oxychloride leads to pyridines and pyridinium salts in high
yield. The mechanism of the reaction is discussed and evidence for the
structure of the products is described. The chemical activity of the new
pyridine derivatives has been briefly explored.
The oxidation of alkyl isothiocyanates by peroxomonosulphuric acid
Authors: Bridgart GJ , Wilson IR
Published: September 2010

Oxidation of methyl and
ethyl isothiocyanates by peroxomonosulphuric acid in
aqueous solution at 25�C has rate constants equal to 1.05 and 0.75 dm3
mol-1 s-1 respectively. The oxidation product was not
identified.
2-O-Acetyltenuiorin, a new tridepside from the lichen Pseudocyphellaria australiensis
Authors: Bryan AJ , Elix JA
Published: September 2010

The tridepside
2-O-acetyltenuiorin (4) has been
isolated from the lichen Pseudocyphellaria australiensis.� The structure of this compound followed from
spectroscopic data and was corroborated by permethylationwith diazomethane to give
methyl 2-0-acetyl-2',2"-di-O-methylgyrophorate
(5). Total synthesis of 2-O-acetyltenuiorin
confirmed the assigned structure. This new tridepside
was also shown to occur in several other Pseudocyphellaria species as well
as two Peltigera species.
Cobalt complexes of Bi- and Tetra-dentate N-substituted o-Mercaptobenzaldimines
Authors: Corrigan MF , West BO
Published: September 2010

The synthesis of a number
of cobalt(11) and cobalt(111) complexes of bi- and tetra-dentate N-substituted o-mercaptobenzaldimines is reported. The
Co11 bidentate complexes are spin-free and the tetra- dentate are
spin-paired. 2,2'-Ethylenebis(nitrilomethylidyne)]bis(benzenethiolato-S,N)cobalt(11) (Co-(mben)) does not behave as an oxygen carrier at room
temperature, in contradistinction to Co(salen). The
complex is easily oxidized in the presence of water to [Co(mben)(H2O)2]+
ions. A synthetic route to the complexes through the aldehydato
complex Co(mb)2 is described which avoids
condensation of the aldimines to cyclic nonanes.
A kinetic study of the chlorination of ketones by chloramine-T: Novel concentration dependences on the chlorinating agent and the ketones
Authors: Balasubramanian V , Thiagarajan V
Published: September 2010

The chlorination of acetone in aqueous acidic medium in the presence of acetic acid and dimethylformamide
was subjected to kinetic study. Although the kinetics follows the traditional mechanism
at high concentrations of chloramine-T (cat) and in aqueous acetic acid in the presence of sodium
acetate, a term in the rate law independent of ketone concentration is reported for the first time
in strongly acidic medium at low concentrations of chloramine-T. Generation of the chlorinating
species is considered as the rate-determining step (Scheme 1). The mechanistic changes which occur
on addition of chloride and on changing the structure of the ketone are reported. The effect of
acetate on the rate in aqueous acetic acid medium is rationalized by invoking a prior equilibrium
formation of enolate followed by a rate-controlling chlorination by chlorinium acetate. The
retardation in rate and the consequent changes in mechanism in the case of p-bromo- and p-nitroacetophenone
are accounted for by invoking a complex between the enol and the positive chlorine
species similar to that in the mechanism for the chlorination of phenols.
Cyclic hydroxycarboxylic acids. I. Synthesis, stereochemistry and reactivity of 2,3-trans-2,3-Dihydroxycyclopentanecarboxylic acids
Authors: Philp RP , Robertson AV
Published: September 2010

Cyclopent-2-enecarboxylic
acid and performic acid give a mixture of approximately equal amounts of the
corresponding c-2,t-3- and t-2,c-3-dihydroxycyclopentane-r-1-carboxylic acids.
The mixture was separated by chromatography of the methyl esters. Relative
configurations were assigned from the action of tosyl chloride-pyridine on the
separate acids. The c-2,t-3-dihydroxy acid yields a t-3-tosyloxy ,β-lactone
and the t-2,c-3-dihydroxy acid yields a r-2-tosyloxy γ-lactone. Structures
of the lactones were proved by correlating the products of acidic methanolysis
and of alkaline hydrolysis with various derivatives of the acids. Proton
magnetic resonance spectra are reported for 21 compounds from the two
stereochemical families, including acetate, trifluoroacetate, tosylate and
mesylate derivatives. Infrared data for relded lactones are tabulated.
Formation of β-lactones from β-hydroxy acids by tosyl chloride
appears to be unprecedented.
Chemistry of the Coccoidea. II. Condensed polycyclic pigments from two Australian pseudococcids (Hemiptera)
Authors: Banks HJ , Cameron DW , Raverty WD
Published: September 2010

The mealy bugs Nipaecoccus aurilanatus (Maskell) and Pseudococcus albizziae (Maskell) have
been found to contain the novel hypericin monocarboxylic acid (8). N. aurilanatus also contains hypericin(7) and the anthraquinones
(1), (2), (3) and (4) while P. albizziae
contains the protohypericins (13) and (14), skyrin (6) and the anthraquinones (1),
(2) and (3). A reinvestigation of the oxidation ofemodin bianthrone (17) has
provided useful syntheses of skyrin (6) and protohypericin (13), and provided
an unambiguous synthesis of the hypericin monocarboxylic acid (8). The
substance 'isohypericin' (21) could not be obtained by the literature
procedure, reaction affording protohypericin (13) as the only isolable product.
Internal rotation in N,N-dimethylcarbamoyl chloride: a 13C N.M.R. lineshape study
Authors: Trotter CM , Jolley KW
Published: September 2010

Activation parameters for
rotation about the C-N bond of N,N-dimethylcarbamoyl
chloride have been determined by a 13C N.M.R. total lineshape
method. The activation parameters agree within experimental error with those
obtained by other methods.
Reduction by dissolving metals. XXI. Some deuteroanisoles
Authors: Birch AJ , Johnson WMP
Published: September 2010

The reversibility of the protonation steps in the metal-ammonia reduction of anisole
has been investigated. Use of deuterated
substrates has indicated that the product, in this case, is determined by kinetic
protonation at both stages.
Dicarbenes. Dicarbenoid species from the reaction of 1,3-Bis(diazomethyl)benzene with zinc halides
Authors: Goh SH , Chan KC , Chong HL
Published: September 2010

The reaction of
1,3-bis(diazomethy1)benzene with zinc halides in diethyl ether and
tetrahydrofuran gave dicarbenoid intermediates which could be trapped by
olefins to give moderate yields of dicyclopropylderivatives. Insertion into
a-C-H bonds of the ethereal solvents occurs in the absence of olefins. The
dicarbenoid species m-C6H4(CHIZnI)2 in
tetrahydrofuran was found to have a half-life of about 4h at 0�C.
Steric effects in quaternizations. Alkylation of pyridine, thiazole, isothiazole and some benzologues with methyl, ethyl and isopropyl iodides
Authors: Deady LW , Stillman DC
Published: September 2010

Results of quaternization reactions in sulpholane
at 65� are reported. A large steric hindrance is noted for quinoline
relative to pyridine. A much smaller variation in rate with change in alkyl
halide is seen in the benzothiazole/thiazole pair.
Steric effects are very small and the rate retardation resulting from benzofusion is ascribed largely to an electronic effect.
2,l-Benzisothiazole reacts at essentially the same rate as isothiazole
under these conditions.
Reactions of N-acetoxyphenacetin: an in vitro model for the metabolism of phenacetin
Authors: Calder IC , Creek MJ
Published: September 2010

The solvolysis reactions of N-acetoxy-4'-ethoxyacetanilide in the presence of nucleophiles under
neutral conditions and at low pH yield p-benzoquinone, 3'-substituted 4'-hydroxyacetanilides and
2'-substituted 4'-ethoxyacetanilides. The product ratio is dependent on the nature of the nucleophile
and the pH. This type of reaction accounts for many of the minor metabolites of phenacetin.
Association of Trichlorotris(tetrahydrofuran)molybdenum(III) in solution
Authors: Boyd IW , Wedd AG
Published: September 2010

Evidence is provided in
support of the following equilibrium in tetrahydrofuran (thf)
and dichloromethane solutions of [MoCl3(thf)3]:

2[MoCl3(thf)3] ↔
[Mo2CI6(thf)3] +
3thf (1)
Proton transfer as a first step in ion-molecule reactions of diethyl ether and tetrahydrofuran
Authors: McAllister T
Published: September 2010

Mechanisms may be written
for several of the ion-molecule reactions in tetrahydrofuran and diethyl ether
for which the first step is protonation to give the
ion (M+l)+. This hypothesis was tested inan ion cyclotron resonance
mass spectrometer by double-resonance experiments on mixtures of each of the
ethers with methane. It was shown that CH5+ is a precursor for the
tetrahydrofuran reactions,but not, with one
exception, for the diethyl ether reactions.
Frequency dependence of nuclear spin relaxation in paramagnetic transition-metal complexes
Authors: Pegg DT , Doddrell DM
Published: September 2010

Proton spin-lattice
relaxation times have been determined as a function of magnetic field strength
(H0) for a series of paramagnetic transition-metal complexes chosen
so that, for some, the electron spin relaxation times (te)
fall in the Redfield limit (te � tr) while for others te
<< tr being the rotational
correlation time. When te � tr dominates the nuclear relaxation and the
experimental results can be readily explained by Redfield theory. When te << tr
current theory predicts the nuclear T1 values to get longer as H0
decreases. This is not observed experimentally. This can only be explained by
using non-Redfield relaxation theory and by assuming the spacings of the
electron-nuclear spin energy levels are not dominated by H0. It is
shown that, although the trace of the zero-field splitting tensor is zero

TrD = 0

because TrD
is averaged by tr when te
< tr the value of Dzz
is important in determining the energy-level spacings. By this approach the
frequency dependence can be explained. Experimentally, it is shown that a Phase
Alternating Pulse Sequence (PAPS) is required to measure T1. The
problem originates from interference from transverse magnetization. A density
matrix theory of the PAPS sequence is presented.
The cyclopolymerization of N-Allyl-N-methyl(2-substituted allyl)amines. The structure of the polymers and low molecular weight products
Authors: Hawthorne DG , Johns SR , Solomon DH , Willing RI
Published: September 2010

Mass and 13C
nuclear magnetic resonance spectroscopy are used to determine the structures of
the poly(N-methylpyrrolidines), poly(N-methylpiperidines) and low molecular weight products
obtained from N-allyl-N-methyl(2-substituted allyl)amines by cyanoisopropyl radical induced cyclizations.
The structures are used to determine the preferred site of initial radical
addition to the diallylamine and the subsequent
direction of cyclization of the intermediate azaheptenyl
radicals. Steric interactions induced by the β-substituents tend to favour
attack at the unsubstituted allyl group whereas conjugated substituents favour
attack at the substituted group with the consequent formation of
conjugation-stabilized radicals. Kinetically controlled cyclization to the pyrrolidines occurs in all cases except that of the t-butyl
derivative in which steric interactions induce cyclization to both piperidine and pyrrolidine
products.
Activities of PbCl2 in the K+, Pb2+/Cl-,SO42- reciprocal molten salt system
Authors: Anthony RG , Bloom H
Published: September 2010

Activities of PbCl2
in the molten system K2SO4+PbCl2 have been
measured at 1012 K by a transpiration vapour pressure method. Values of PbCl2
activities are calculated from the conformal ionic solution model (CIS), the
result being in reasonable agreement with experimentally measured values.
Results obtained may therefore be summarized by the CIS equation

APbCl2 = xpb(xcl)2exp[0.2405/T)(X?k)2{-3285-X?pb(11564+2032(3X?k-1))}]

where Xi, X?t are ion fractions and equivalent ion
fractions respectively.
Synthesis of Methyl 2-oxo-2,3,4,4a,9,10-hexahydrophenanthrene-4a-carboxylates
Authors: Oommen PK
Published: September 2010

The reaction of methyl
7-methoxy-2-oxotetralin-1-carboxylate (2a) with methyl vinyl ketone in the
presence of benzyltrimethylammonium methoxide
catalyst yielded the expected tricyclic keto alcohol
(3a) and the latter on dehydration with p-toluenesulphonic acid gave the unsaturated ketone (la).
This constitutes a general method of synthesis of the title compounds. When
sodium methoxide was used as the catalyst in the above reaction, (la) was not
obtained.
A comparison of the fundamental vibrations of the anions: O-methylmonothiocarbonate and O-methyldithiocarbonate
Authors: McNaught IJ , Murphy CN
Published: September 2010

Twelve of the bands
observed in the infrared and Raman spectra of the anions, O-methylmonothiocarbonate and 0-methyldithiocarbonate, have been
assigned to in-plane vibrations, on the basis of normal coordinate analyses. It
is shown that, because of the large number of parameters, vibrational studies
of this type cannot be used to determine, unambiguously, the relative
contribution of the canonical forms -S(-O)C=O+-CH3
and 2-S2C=0+-CH3 to the structures
of the corresponding anions.
The exchange of dimethyl methylphosphonate on Pentakis(dimethyl methylphosphonate)dioxouranium(VI) ion
Authors: Crea J , Lincoln SF , Williams EH
Published: September 2010

The greatly predominant
dioxouranium(V1) species existing in the presence of perchlorate anions in
dilute dimethyl methylphosphonate (dmmp) solutions in CH2Cl2 diluent is
shown from 1H N.M.R. studies to be [U02(dmmp)5]2+. Lineshape
analyses of exchange-modified 1H N.M.R. lineshapes
show the rate of dmmp exchange to be consistent with
the rate law: kex5[U02(dmmp)52+]
over a 9.7-fold variation of [dmmp]. A typical set of rate
parameters is kex(268 K) = 82 � 5 s-1, ΔH? = 57.3 �
1.0 kJ mol-1 and ΔS? = 6.3 � 3.6 J k-1 mol-1
for a solution in which [U02(dmmp)52+],
[dmmp] and [CH2Cl2] are
respectively 0.104, 0.515 and 13.59 mol dm-3. The mechanism of the
exchange process, which is considered to be predominantly dissociative in
nature, is discussed.
1,1',3,3'-Tetramethyl-5-(4-methylamino-3-nitrobenzyl)-5,5'-methylenebisbarbituric acid
Authors: Clark-Lewis JW , Aldous GL , Thompson MJ
Published: September 2010

The previously proposed
structure (2) for the compound named in the title is confirmed by spectroscopic
methods and by synthesis of related compounds. The barbituric acid undergoes a
very facile thermal fragmentation in the mass spectrometer into 1,3-dimethyl-5-(4-ethylamino-3-nitrobenzy1)-barbituric
acid (3) (which was also prepared by unambiguous synthesis) and
1,3-dimethyl-5-methylenebarbituric acid (4). The electron-impact,
chemical-ionization, and negative-ion mass spectrometric behaviour of the
barbituric acid (2) was examined.
Chemistry of the Coccoidea. III. Isolation of a bianthrone glucoside from Callococcus acaciae and of ceroalbolinic acid from Cryptes baccatum (Hemiptera: Insecta)
Authors: Banks HJ , Cameron DW , Edmonds JS , Raverty WD
Published: September 2010

The major polycyclic
constituent of an asterolecaniid Callococcus
acaciae (Maskell) is shown to be the 10,l0'-dimer of acetylemodin anthrone glucoside.
This follows from hydrolytic, reductive andoxidative reactions. The
coccid Cryptes baccatum
Maskell is shown to contain ceroalbolinic acid as its
principal colouring matter. On decarboxylation it gave isoerythrolaccin,
identical with a syntheticspecimen
Volatility studies of metal chelates. I. Thermal studies of vanadium β-diketonates
Authors: Dilli S , Patsalides E
Published: September 2010

The complexes of
vanadium(111) and oxovanadium(1V) with pentane-2,4-dione;
l,l,l-trifluoropentane-2,4-dione; 1,1,1,5,5,5-hexafluoropentane-2,4-dione;
l,l,l-trifluoro-5-methylhexane-2,4-dione; l,l,l-trifluoro-5,5-dimethylhexane-2,4-dine
1,1,1,2,2-pentafluoro-6,6-dimethylheptane-3,5-dione and
1,1,1,2,2,3,3-heptafluoro-7,7-dimethyloctane-4,6-dione have been prepared. The
volatility, thermal and chemical stability of the chelates have been examined
by simultaneous differential thermal and thermogravimetric analysis in dynamic
atmospheres of nitrogen, air and water-saturated nitrogen and air, in addition
to heating under vacuum to temperatures approaching 360�C. The vanadium(111)
chelates of the fluorinated β-diketones volatilized with little evidence
of decomposition even in air and were stable in the absence of air to
280-320�C. In contrast, the oxovanadium(1V)chelates partly decomposed during
volatilization at temperatures as low as 150�C, and completelydecomposed over the
temperature range 180-240�C.
Thermodynamics of metal-ligand bond formation. XXIV. Reaction of mercury(II) halides with tertiary arsines and phosphine and arsine sulphides
Authors: Gallagher MJ , Graddon DP , Sheikh AR
Published: September 2010

Thermodynamic data have
been obtained by calorimetric titration for the formation of 1 : 1 adducts of
mercury(11) halides with tertiary arsines in benzene solution. In contrast to phosphines, only one molecule of arsine adds to HgX2
in dilute solution. Enthalpies of adduct formation, in the range - ΔH� =
50-80 kJ mol-1, are not much changed by replacement of phenyl by
methyl, but adduct stabilities increase in the order

Ph3As < Ph2AsMe < PhAsMe2 <
AsMe3

HgI2AsMe3
is dimeric in solution. The diarsines Ph2As(CH2),AsPh2
are unidentate, but Ph2P- (CH2),AsPh2
is bidentate. Data are also reported for addition to HgX2 of Ph3PS,Ph2PSCH2PSPh2
and corresponding arsine sulphides; the disulphides are bidentate. Factors affecting chelation in
these compounds are discussed.
Asymmetric reductinon of carbonyl compounds by yeast. II. Preparation of optically active α- and β-hydroxy carboxylic acid derivatives
Authors: Deol BS , Ridley DD , Simpson GW
Published: September 2010

α- and β-Keto
esters and amides are readily reduced by an actively fermenting mutant of Saccharomyces cerevisiae and
produce optically active α- and β-hydroxy esters and amides in moderate
yields. Typically, methyl 2-oxo-2-phenylacetate gave methyl (R)-(-)-2-hydroxy-
2-phenyl- acetate; 2-oxo-2-phenylacetamide gave (R)-(-)-2-hydroxy-2- phenylacetamide; ethyl benzoylacetate gave ethyl
(S)-(-)-3-hydroxy-3- phenylpropionate, and ethyl
2-oxocyclohexanecarboxylate gave ethyl (1R,2S)-(+)-2-hydroxycyclohexanecarboxylate.
In each case, the product obtained was optically pure. However, the reduction
of ethyl pyruvate to ethyl lactate produced partially racemized products.
Nitrones and oxaziridines. XV. Approaches to 3-Oxo-1-pyrroline 1-Oxides by oxidation of 1-Pyrroline 1-Oxides
Authors: Black DSC , Boscacci AB
Published: September 2010

5,5-Dimethyl-1-pyrroline
1-oxide can be converted either by selenium dioxide or 3-methylbutylnitrite
into the related 3-oxo compound, but the reaction is not general for other
nitrones. Three 3-ethoxycarbonyl- 1-pyrroline 1-oxides have been prepared by
base-catalysed acylation of simple pyrroline oxides, and nitrosation of one of
these compounds results in the formation of a 3-oxo-pyrroline. The peracid
oxidation of this oxopyrroline affords an oxazinone, the product of ring expansion.
New laurene derivatives from Laurencia filiformis
Authors: Kazlauskas R , Murphy PT , Quinn RJ , Wells RJ
Published: September 2010

Three new compounds
containing the laurene skeleton are reported from the red alga Laurencia filiformis f. heteroclada.
Lithium-ammonia reduction of 3-furoic acid
Authors: Slobbe J
Published: September 2010

Reduction of 3-furoic acid
by lithium in ammonia at -33� proceeds with β-elimination and ring opening
and consumption of four equivalents of metal to give (3) and (4). Other
products (1) and(2) have been observed from reduction in the presence of a
proton source.
The radiation-induced grafting of vinylpyridines to cellulose. I. The effect of solvent structure
Authors: Garnett JL , Martin EC
Published: September 2010

A wide range of solvents
have been examined for the radiation-induced grafting to cellulose of 2- and
4-vinylpyridines and 2-methyl-5- vinylpyridine by the mutual irradiation
technique. The presence of a functional group containing a nitrogen and/or
oxygen atom in the solvent is important for high grafting efficiency. The two
most favourable groups are NH2 and OH, the former being the more
effective. Inclusion of both groups in suitable positions in the one molecule,
the aminoalkanols in particular (e.g. 2-aminoethanol), leads to maximum effect
in grafting. Heterocyclic solvents such as pyridine and 3- picoline are also
useful. Other variables affecting grafting and studied in these experiments
were the effect of pK, as well as swelling, wetting
and dielectric strength of solvents. The effect of surface area of cellulose on
copolymerization was also examined. A novel ionic mechanism for the grafting
reaction involving association between solvent and monomer is proposed.
Colouring matters of the Aphidoidea. XL. The external wax of the woolly apple aphid Eriosoma lanigerum (Hemiptera : Insecta)
Authors: Cameron DW , Drake CB
Published: September 2010

Apart from hydrocarbon and
ester fractions the major components of the wax of the pemphigid Eriosoma
lanigerum were found to be homologous diketo esters. On hydrolysis, keto
alcohol and keto acid fractions were obtained. Their major constituents,
1-hydroxytetratriacontan-15-one and 13-oxodotriacontanoic acid have been
synthesized. The wax of another pemphigid, Pemphigus spirothecae, was of
similar composition, differing from that of the aphid Brevicoryne brassicae.
A 19F nuclear magnetic resonance study of the exchange of the fluoro ligands of the tetrafluoroberyllium(II) ion
Authors: Lincoln SF , Sandercock AC , Stranks DR
Published: September 2010

A 19F N.M.R.
study is reported of the exchange of the fluoro ligands of [BeF4]2-.
The exchange rate law is: ����������� rate = kobs4[BeF42-]
= k'4[BeF42-]+ k''4[BeF42-][BeF3H2O-]
where k'(298 K) = 69�3 s-1,
ΔH‡ = 30�3 kJ mol-1, ΔS‡ = -110�10 J
mol-1 K-1 and k''(298 K) = (1.6�0.5)×103 dm3
mol-1 s-1, ΔH‡ = 26�3 kJ mol-1,
ΔS‡ = - 96�9 J mol-1 K-1. The k' exchange
process appears to be predominantly dissociative in nature, and the k'' exchange
process apparently proceeds through a fluoro bridged species [Be2F7]2-.
Electron impact studies. CIX. The detection of doubly charged negative ions by ion cyclotron resonance spectroscopy
Authors: Stapleton BJ , Bowie JH
Published: September 2010

Ion cyclotron resonance
allows the sensitive measurement of doubly charged anions at low cell pressures.
Evidence is presented which suggests the formation of X-- (X = halogen) ions
from alkyl halides.
The synthesis of 3-Oxatetracyclo[5,3,1,12,6,04,9]dodecane (oxaiceane) and 12-Oxatetracyclo[5,3,1,12,5,04,9]dodecane (abeo-oxaiceane) and the reduction of intermediate mercury compounds
Authors: Hamon DPG , Taylor GF , Young RN
Published: September 2010

Tricyclo[5,3,1,04,9]undec-5-en-2-one
(2) was reduced by sodium borohydride to the endo alcohol (3).
Oxymercuration-reduction gave a mixture of oxaiceane (4) and abeo-oxaiceane (5)
and these were separated and characterized. The intermediate mercury compound,
which leads on reduction to oxaiceane, was obtained pure and it was shown that
the mercury group is in the hindered prow (flagpole) position. The reaction
which allowed this determination was the sodium amalgam- deuterium oxide
reduction of the mercury compound which proceeds with retention of
configuration. This is probably the most demanding test to which the
stereospecificity of this reaction has yet been put.
Mutarotation of α-D-glucose catalysed by pyridine-phenols and pyridine-water catalyst pairs in dimethylformamide
Authors: Fujimori K
Published: September 2010

The rate of mutarotation of
α-D-glucose is at a maximum for close to 1 : 1 molar composition of acid and
base catalysts when pyridine-phenol, pyridine-p-cresol and
pyridine-p-chlorophenol catalyst pairs are used in dimethylformamide solutions
at 34.6�C. The evidence favours a termolecular bi-functional catalytic
mechanism. No rate maximum is detectable for the pyridine-water catalyst pair under
the same conditions. Two water molecules appear to be operative at the rate- determining
step in dilute dimethylformamide solution.
A new approach to space-charge-limited conduction theory
Authors: Bonham JS , Jarvis DH
Published: September 2010

We describe a new method for obtaining numerical solutions to the single-carrier conduction problem
(including diffusion) in insulators. The method is illustrated by treating the space-charge-limited
current problem in the case where both electrodes are ohmic, and traps in the insulator are assumed to
be absent, or shallow, or exponentially distributed in energy. Transformation of the conduction
equation to express charge density as a function of field, followed by straightforward numerical
solution, gives the current and voltage parametrically as functions of the field at the charge density
minimum. For voltages less than a few tenths of a volt the current is given by j ∝ U/d2l+1, and at
rather high voltages the standard result j ∝ Ul+1/d2l+1 is valid. Simple formulae, valid except at
very low voltages, are derived for the position and height of the potential maximum.
The isomerization of ammonium cyanates. I. The kinetics of ammonium cyanate and alkylammonium cyanate isomerization in dimethyl sulphoxide
Authors: Hall KJ , Watts DW
Published: September 2010

The isomerization of
ammonium cyanate in dimethyl sulphoxide leads to urea with a substantial side
reaction yielding biuret (c. 25 % at 60�). Biuret is formed in a process that
is competitive with urea formation and not in a subsequent reaction involving urea.
The production of urea, as in water, is by the reaction of ammonia and cyanic
acid molecules and it is postulated that biuret is formed through an
intermediate of dimerized cyanic acid. Temperature and ionic strength
dependence have been studied. Kinetic
studies of the isomerization of methylammonium and ethylammonium cyanates are
also described.
Reactions of propargyl alcohols. II. Solvent effects in the reduction of 1,1-Diphenylbut-2-yn-1-ol with lithium aluminium hydride
Authors: Hartshorn MP , Thompson RS , Vaughan J
Published: September 2010

Lithium aluminium hydride
reduction of 1,1-diphenylbut-2-yn-1-ol in diethyl or diisopropyl ether gave
1,1-diphenylbuta-1,2-diene (4) and the (Z)- and (E)-1,1-diphenylbut-2-en-1-ols
(5) and (6), but reaction in tetrahydrofuran solution gave only the (E)-alkenol
(6).
Chemistry of pyrrolic compounds. XXXVI. Some aspects of the chemistry of 2'-hydroxypropionate porphyrins: new syntheses of harderoporphyrin trimethyl ester, 'S-411 porphyrin' trimethyl ester and related compounds
Authors: Chaudhry IA , Clezy PS , Diakiw V
Published: September 2010

The 2?-hydroxypropionate
porphyrins (1h) and (2g) were obtained by sodium borohydride reduction of the
corresponding keto esters. Dehydration of (1h) and (2g) led to the acrylate
esters (1b) and (2b) respectively; fragmentation of both the hydroxyl and carboxyl
functions in (1h) and (2g), by way of a cyclic intermediate, furnished the
vinylporphyrins (1a) and (2a) respectively. The synthesis of the 2?- hydroxypropionate
porphyrin (9a), a possible biogenetic precursor of protoporphyrin-IX, was
achieved.
Insecticides. XI. Crystal structure of endosulfan, β-6,7,8,9,10,10-Hexachloro-1,5,5a,6,9,9a-hexahydro-endo-6,9-methano-2,4,3-benzodioxathiepin 3-Oxide
Authors: Smith G , Kennard CHL , Shields KG
Published: September 2010

The crystal structure of
hexagonal β-endosulfan (β1) was determined by direct
methods. On a four-circle diffractometer, 2350 reflections were collected. The
crystals were hexagonal, (P63/m), with Z = 6, in a cell of
dimensions a = 1492.0(2), c = 1150.6(2) pm. The structure was refined by least
squares to R 0.068 from 573 unique reflections having F > 2.5σ(F). The
methylene sulphite ring showed an ?endo-endo-endo? configuration with respect
to its attachment to the methano- bridged hexachlorocyclohexane and exo to the oxide portion of the
sulphite group. Space group requirements for P63/m resulted in the
molecules lying along the mirror planes at Z = 1/4 and 3/4.
The isomerization, catalysed by boron trichloride, of 2-Methylbut-1-ene
Authors: Cameron GS , Stimson VR
Published: September 2010

Boron trichloride (2% in
carbon dioxide) catalyses the isomerization of 2-methylbut-1-ene to 2-methylbut-2-ene
at 368-467� with

���������������������� k2 = 109.71exp(-91460/8.314T)
s-1 ml mol-1

Gas-phase isomerization
catalysed by Lewis acids is thus extended to olefins.
Reactions of Mono- and Di-substituted acetylenes with planar iridium(I) complexes and carbonylation of the resulting adducts
Authors: Bennett MA , Charles R , Fraser PJ
Published: September 2010

Alk-1-ynes (RC2H;
R = H, Pr, Bu, CH2CH2OH, Ph, CO2Me) undergo
irreversible oxidative addition to the iridium(I) complex IrCl(PPh3)3
to give six-coordinate hydrido acetylides of iridium(III), IrHCl(C2R)(PPh3)3,
the stereochemistry of which is deduced from 1H N.M.R. and infrared
data. Isomers of the corresponding adduct of phenylacetylene with IrCl(PMePh2)3 can be isolated.
Carbonylation of IrHCl(C2R)(PPh3)3
gives IrHCl(C2R)(CO)(PPh3)2,
which can be isolated only when R = H, Ph or CO2Me; when R = Pr, Bu
or CH2CH2OH, the complexes immediately decompose to IrCl(CO)(PPh3)2 and the alkyne. This
reductive elimination also occurs to some extent for R = Ph. Diphenylacetylene
and dimethyl acetylenedicarboxylate react with IrCl(PPh3)3
to give the known alkyne complex IrCl(PhC2Ph)(PPh3)2
and the known iridiacyclopentadiene complex IrCl-(MeO2CC2CO2Me)2(PPh3)2
respectively. The additions of alk-1-ynes to IrClL3 and to other
lowvalent metal complexes are compared, and the relevance of the oxidative
addition to catalysis of linear polymerization of alk-1-ynes is noted.
Lanthanide shifts in the 1H N.M.R. spectra of peri-Alkoxy- and -Alkylamino-quinones
Authors: Cameron DW , Feutrill GI , Patti AF
Published: September 2010

Unusually large
lanthanide-induced shifts are observed for proton resonances of methoxy, ethoxy
and dimethylamino substituents peri to carbonyl
groups of anthraquinones and naphthoquinones. Such an arrangement allows the
substrate to act as a bidentate ligand and is evidently the favoured site of
coordination.