bluuebunny/crossref_metadata_2025 huggingface dataset:
13C Fourier-transform N.M.R. study of Trimethyl(penta-1,3-diynyl)silane
Authors: Hearn MTW
Published: September 2010

The natural-abundance
carbon-13 chemical shifts of trimethyl(penta-1,3-diynyl)silane and related
compounds have been measured. The effect on the shieldings
of the acetylenic carbons by the tri-methylsilyl substituent at C1 is discussed.
Correlation of 13C N.M.R. shifts with chemical reactivity in phenethyl systems
Authors: Blackwell LF , Buckley PD , Jolley KW
Published: September 2010

Correlations between 13C
substituent-induced chemical shifts (scs) for carbon atoms in substituted
phenethyl bromides, dimethylphenethylsulphonium bromides and ethylbenzenes have
been examined. C1 13C scs were found to correlate with Hammett D
values as expected from previous results with 1H scs. The β-carbons
showed no correlation while the α-carbons showed an inverse linear
relationship with the electron-withdrawing power of the substituents.
Tautomerism of Pyrazolidine-3,5-diones. I. N-Methylation and ultraviolet spectra
Authors: Woodruff M , Polya JB
Published: September 2010

Methylation of
3-phenyl-1H-1,2,4-triazol-5-ylpyrazolidine-3,5-diones attacks preferentially
the pyrazolidine ring. In these cases and those of mono- and di-phenyl analogues methylation by methyl iodide gives C-
and N-substitution only, while treatment with diazomethane affords O- methyl derivatives
as well. In cyclohexane the keto-iminol tautomer is favoured or, if this
tautomerization is blocked, the diketone form. In methanol again the
keto-iminol form is favoured but with the keto-enol form as an alternative or
main coexistent tautomer. Thus change from the more polar to the less polar
solvent is associated with tautomeric shifts from enol to iminol or enol to
ketone.
Root Inhibitors in Eucalyptus grandis. 2. Synthesis of the Inhibitors and Origin of the Peroxide Linkage
Authors: Crow W , Osawa T , Platz K , Sutherland D
Published: September 2010

Syntheses are described for
the three inhibitors G3 (1-hydroxy- 4,4,8,8,10,10-hexamethyl-2,3-dioxabicyclo[4,4,0]dec-5-ene-7,9-dione),
G1 and G2 (the diastereoisomers
4-ethyl-1-hydroxy-4,8,8,10,10-pentamethyl- 2,3-dioxabicyclo[4,4,0]dec-5-ene-7,9-dione).
Knoevenagel condensation of syncarpic acid with 2-methylpropanal or
2-methylbutanal respectively is followed by slow spontaneous uptake of
atmospheric oxygen and cyclization to give the products named. ��� Isolation of the naturally occurring
inhibitors from Eucalyptus grandis in an atmosphere
of 18O2 results in no incorporation of isotopic oxygen
into the peroxide linkage; this indicates that this structural feature was present
in the inhibitors in vivo.
Central nervous system active compounds. I. The synthesis of some caprolactam derivatives substituted at N1, C2 and C3
Authors: Duong T , Prager RH , Ward AD , Kerr DIB
Published: September 2010

The synthesis of a number
of caprolactam derivatives with alkyl, aryl and hetero atom substituents at N1,
C2 and C3 is described. Alkylation and arylation at C3 by a variety of methods
is discussed. Some of these compounds are powerful convulsing agents; a few are
depressants.
Conformational prediction for molecules containing vicinal lone pairs: Basis set studies for H2O2
Authors: Burton PG , Markey BR
Published: September 2010

The Dunning and Winter1
(DW) conformational study of H2O2 represents accepted
state-of-the-art methodology in accurate SCF computation of molecular
properties; nevertheless the prediction of a very short O-O bond length and a
very large O-O-H bond angle by DW indicates the difficulty in adequately
describing molecules with vicinal lone pairs. Consequently we have reexamined H2O2
with several standard Gaussian basis sets, and in addition have investigated
the properties of two further basis set prescriptions. While polarization
functions are confirmed to be necessary to attaining the correct H2O2
conformation, the situation of s (and p) Gaussian bond functions in mid-bond
positions is shown to be an economical and efficacious alternative to
traditional polarizing functions.
Substituent effects on the carbon-13 N.M.R. chemical shifts of side-chain carbons in aromatic systems
Authors: Bromilow J , Brownlee RTC , Craik DJ
Published: September 2010

Carbon-13 chemical shifts
have been measured for the side-chain carbon atoms of a number of meta- and para-disubstituted
benzenes. The side chains examined were CN, CF3, Ac, CO2Et,
Me, OMe and NMe2. The substituent-induced 13C
shifts of these side chains were related to Hammett substituent effects by the
Dual Substituent Parameter method and showed a widely varying dependence upon
the blend of inductive and resonance effects. The transmission of substituent
effects through aromatic systems and the factors that influence 13C
shifts are discussed.
The preparation and central pharmacological action of stereoisomeric bicyclic imides
Authors: Cameron DW , Down JG , Kissane PJ , Laycock GM , Shulman A
Published: September 2010

The stereochemistry of the
bicyclic imide, 4a-methyldecahydroisoquinoline-1,3-dione (1), has been
defined, as has that of intermediates in its synthesis. Epimers of (1) exhibit
dual stimulant-depressant central nervous system action in the mouse similar to
that shown by 3-methyl-3-propylglutarimide.
The reaction of carboxylic acids, esters and acid anhydrides with alkenylmagnesium bromide
Authors: Watanabe S , Suga K , Fujita T , Saito N
Published: September 2010

The reaction of carboxylic
acids, esters and acid anhydrides with alkenylmagnesium bromide yields mixtures
of alkenones and alkenols as the main products. The reaction of vinylmagnesium
bromide gives similar results to that of vinylmagnesium chloride. The reaction
of isopropenylmagnesium bromide and prop-1-enylmagnesium bromide with acids,
esters and anhydrides produces mainly isopropenyl ketones.
The reaction of thionyl chloride with methyl-substituted heteroaromatic compounds
Authors: Davis M , Scanlon DB
Published: September 2010

Some heteroaromatic
compounds with methyl substituents in the heterocyclic ring, such as
2-methylbenzothiazole, 2-methylbenzoxazole, and analogues, undergo rapid methyl
group chlorination when heated with thionyl chloride. A mechanism for such
reactions is proposed.
Mixed monolayers of simple saturated and unsaturated fatty acids
Authors: Feher AI , Collins FD , Healy TW
Published: September 2010

The conventional surface
pressure-area per molecule isotherms of single and binary films in the acid
series, (Z)-octadec-9-enoic (?oleic?), its (E) isomer (?elaidic?),
octadecanoic (?stearic?) and eicosanoic (?arachidic?), have been obtained up to and including
collapse. While the films formed from binary mixtures of saturated fatty acids
were ideal at all mole fractions, the binary films formed with a saturated acid
and the (E) isomer of octadec-9-enoic acid produced negative deviations from
ideality; films of a saturated acid and the (Z) isomer produced positive
deviations from ideality. Mixed films of the two unsaturated acids showed
negative deviations at low mole fraction of (Z) isomer and positive deviations
at low mole fraction of the (E) isomer. The role of chain stereochemistry and
the effect of (Z) and (E) double bonds on hydrophobic interactions in mixed
monolayers is considered.
Aluminium corrosion studies. II. Corrosion rates in water
Authors: Berzins A , Evans JV , Lowson RT
Published: September 2010

The corrosion rate of
aluminium in flowing neutral waters at 50�C has been determined as a function
of pH, oxygen concentration and chloride concentration. The corrosion rate, At,
as total aluminium lost between the 4th and 80th day was observed to be logarithmic
according to At = B log t+C with a minimum
rate in the pH range 5-6, and with B c. 3 x 10-5g cm2, C c. 20 x 10-5 g cm-2 and t in days for
oxygen-saturated water. Saturating the water with nitrogen or adding up to 15
mg Cl- l-1 increased the
corrosion rate. It was concluded that this was due to competitive action on the
oxide surface, between dissolved oxygen and chloride ions.
The structural features of a tetrahedral 1,3-monothiolate complex: The crystal and molecular structure of Bis(ethyl 3-mercaptobut-2-enoato)zinc(II)
Authors: Hoskins BF , Pannan CD
Published: September 2010

The crystal and molecular
structure of bis(ethy 3-mercaptobut-2- enoato)zinc(II) has been determined by single-crystal X-ray
diffraction techniques. Solved by conventional Patterson and Fourier methods
the structure was refined by a least-squares method employing anisotropic
thermal parameters to all non-hydrogen atoms to R and Rw values of
0.040 and 0.046 respectively. The complex crystallizes in the monoclinic space
group P21/c with four molecules in a unit cell of dimensions a
11.107(1), b 18.239(2) and c 8.438(1) Ǻ and β 107.7(1)�. The
intensities of 2274 independent and statistically significant [I ≥
3σ(I)] reflections with θ values ≤ 70� were measured by counter
methods using nickel- filtered Cu Kα radiation.
The crystals comprise discrete monomeric molecules with the zinc atom bonded to
two sulphur atoms and two oxygen atoms giving a coordination arrangement which
is substantially distorted from an ideal tetrahedron. The mean values for the
Zn-S and Zn-O bond distances are 2.247(1) and 2.007(3) Ǻ respectively and
the average S-Zn-O intraligand bond angle is 99.25(8)�. The geometries of the
ligands differ in two ways. Firstly, the two ethyl groups adopt differing
conformations and secondly, while one ligand moiety is essentially planar with
the zinc atom displaced about 0.1 Ǻ from that plane, the displaced atom in
the other ligand is the carbon bonded to the sulphur atom and not the metal
which is, in this instance, coplanar with the other members of the ring. Bond
distances in each chelate ring indicate aromatic character with a lone pair of
electrons on the ethoxy-oxygen participating in the delocalization.
Organomercury compounds. XXII. Syntheses of polybromophenylmercurials by decarboxylation reactions
Authors: Deacon GB , Farquharson GJ , Miller JM
Published: September 2010

The mercuric polybromobenzoates, (C6Br2CO2)2Hg, (XC6Br4CO2)2Hg (X = p-F, p-Cl, p-Me,
o-Me, p-MeO or m-MeO) and (2,6-Me2C6Br3CO2)2Hg, and phenylmercuric pentabromobenzoate
have been prepared by reaction of mercuric acetate or phenylmercuric acetate with the appropriate
polybromobenzoic acids. Thermal decomposition of (C6Br5CO2)2Hg, (XC6Br4CO2)2Hg, (X = p-F,
p-Cl or p-MeO) and C6Br5C02HgPh in boiling pyridine gave the new polybromophenylmercurials
(C6Br&Hg, (XC6Br4)2Hg and C6Br5HgPh respectively, but similar treatment of (XC6Br4C02)2Hg
(X = p-Me, o-Me or m-MeO) and (2,6-Me2C6Br3C02)2Hg yielded pyridine complexes of the
mercuric carboxylates. Mercuric p-methyltetrabromobenzoate underwent decarboxylation in
boiling nitrobenzenelpyridine giving (p-MeC6Br4),Hg, but the method could not be extended to
(0-Mec~Br~C0~)o~r H(2g,6 -Me2C6Br,C02)2Hg. Decarboxylation of XC6Br4C02H (X = o-Me
or m-MeO) was effected in molten mercuric trifluoroacetate giving, after treatment of the products
with sodium chloride, the corresponding tetrabromophenylmercuric chlorides. All mercurials
underwent cleavage with iodine or triiodide ions in hot dimethylformamide to give the corresponding
iodopolybromobenzenes, and (C6Br5)2Hg was converted into C6Br5HgX (X = C1 or Br) by the
corresponding mercuric halides in hot xylene/nitrobenzene. Thermal symmetrization of C6Br5HgX
(X = C1, Br, or Ph) is detectable prior to melting, but (C6Br5),Hg is stable to at least 400'. The
mass spectra of the polybromophenylmercurials are discussed.
Vinylindenes and some heteroanalogues in the Diels-Alder reaction. I. Preparation of 3-vinylindene and some homologues
Authors: Bergamasco R , Porter QN
Published: September 2010

3-Vinylindene, 3-isopropenylindene
and 2-methyl-3-vinylindene have been prepared by dehydration of suitable
carbinols. In each case the vinylindene is in equilibrium with the isomeric alkylideneindene.
The Raman spectra of Bis(hexamethylenetetramine)-iodine(I) and -bromine(I) perchlorates
Authors: Bowmaker GA , Knappstein RJ
Published: September 2010

The low-wavenumber (<200
cm-1) Raman spectra of bis(hexamethylenetetramine)iodine(I)
perchlorate and bis(hexamethylenetetramine)bromine(I) perchlorate have been
measured, and the nitrogen-halogen symmetric stretching mode of the cation has
been assigned for each compound. The nitrogen-halogen bond stretching and
interaction force constants for the cations have been calculated, and these are
found to be very similar to those for the corresponding bis(pyridine)halogen(I)
cations.
Crystal structure of baylissite, K2Mg(CO3)2,4H2O
Authors: Bucat RB , Patrick JM , White AH , Willis AC
Published: September 2010

The crystal structure of
the title compound has been determined by X- ray diffraction at 295 K, and
refined by full-matrix least squares to a residual of 0.045 for 1153 ?observed?
reflections. ��� Crystal data: monoclinic, P21/n,
a = 11.404(4), b = 6.228(2), c = 6.826(2) Ǻ, β = 99.66(2)�, Z = 2. ��� The environment of the magnesium atom,
located on the inversion centre, is a compressed octahedron (Mg-O, 2.054(2),
2.093(2), 2.107(3) Ǻ). The environment of the potassium is abnormally
sparse, there being only five K...O contacts < 3.0 Ǻ. The carbonate
group is symmetrical (C-O, 1.282(4)-1.298(3); O-C-O,119.6(3)-120.4(2)�).
Reactions over metal catalysts. III. Hydrogenolysis of some 3-substituted nortricyclenes
Authors: Akhtar MN , Rooney JJ , Samman NG , Hugel HM , Jackson WR , Nicolson DM , Rash D
Published: September 2010

Hydrogenolysis of
3-methylnortricyclene over platinum in acetic acid solution leads to the
formation of almost equal amounts of 7-methylnorbornane and
exo-2-methylnorbornane with much smaller amounts of the endo-2-methyl compound.
In contrast, reactions over supported metal catalysts in the vapour phase lead
to a predominance of the 2-methyl compounds. Similar trends have been observed
in the hydrogenolyses of 3-cyclohexyl- and 3-acetoxy-nortricyclenes.
Permercurated arenes. III. Syntheses of periodoarenes and perchloroarenes by Iodo- and Chloro-demercuration of some permercurated arenes
Authors: Deacon GB , Farquharson GJ
Published: September 2010

The polyiodobenzenes C6I5X
(X = NO2, H, Br, Cl, F, MeO, Me, CO2H or CF3) and hexaiodo-benzene
have been prepared in good yield by reaction of triiodide ions with suitable
permercurated arenes in dimethylformamide at room temperature. Mass and/or p.m.r. spectra showed that singly recrystallized samples of
C6I5X (X = NO2, Br, Cl,
F or CF3) contained minor amounts of the corresponding
tetraiodobenzenes C6HI4X. In cases where further
recrystallization failed to remove the partially iodinated species, purer products
could be obtained from permercurated arenes prepared using increased Hg(O2CCF3)2/substrate
ratios. The polychlorobenzenes C6Cl5X (X = NO2,
H, Br, F, MeO, Me or CO2H) and
hexachlorobenzene have been prepared by reaction of chlorine with solutions or
suspensions of the appropriate permercurated benzenes in dimethylformamide at
room temperature. Attempted permercuration of naphthalene followed by chlorodemercuration
gave perchloronaphthalene containing a substantial
impurity of heptachloronaphthalene. Permercuration of sodium
p-toluenesulphinate was accompanied by complete desulphination giving
permercurated toluene.
The application of the Hammett equation to 13C N.M.R. spectrometry. II. Cβ resonances: a test of dual substituent parameter relationships
Authors: Happer DAR , McKerrow SM , Wilkinson AL
Published: September 2010

Previous studies (Part I)
have shown that the 13C resonance positions of the β-carbon of
both meta- and para-substituted β-nitrostyrenes are well correlated by means
of the Hammett equation if σ+ constants are used for para + R
substituents. These data have now been supplemented with measurements made on
five additional series: cinnamic acids, cinnamate ions, styrenes, β,β-dimethyl- and β,β-dicyano-styrenes.
��� The combined information has been analysed
by means of three ?dual substituent parameter? versions of the Hammett
equation. The results confirm that all three are only approximations, but that
the Yukawa- Tsuno and Ehrenson-Brownlee-Taft relationships are significantly
better than Swain's F/R treatment.
The formation of 5,6,7,8-Tetrahydronaphthalene-1,3-dicarbonitrile by thermal rearrangement of Cyclohex-1-enyl(prop-2-ynyl)malononitrile
Authors: Brown RFC , McAllan CG
Published: September 2010

Cyclohex-1-enyl(prop-2-ynyl)malononitrile
(1), heated neat at 200�, forms 5,6,7,8-tetrahydronaphthalene-1,3-dicarbonitrile
(2) and much polymer. Two probable intermediates (4) and (5) have been isolated
from rearrangements at lower temperatures and in hydrocarbon solvents. A
reaction pathway is proposed which includes Cope rearrangement, apparent [1,3]H
shift, electrocyclic reaction, [1,5]CN shift, and dehydrogenation. An
o-quinonoid imine (10) has been trapped with N- phenylmaleimide and other
dienophiles. Dehydrogenation of the adduct (11) with Pd/C in boiling Ph2O
proceeds with hydrogenolysis of a cyano group to a methyl group.
Methyleneketenes and methylenecarbenes. IX. Thermal rearrangements of Alkyl-and Aryl-acetylenes involving Alkyl- and Aryl-methylenecarbenes
Authors: Brown RFC , Eastwood FW , Jackman GP
Published: September 2010

Flash vacuum pyrolysis of
1-(1?-adamantyl)acetylene[2-14C] (780�) gives recovered alkyne which
contains 25% of the rearranged product, 1-(1?- adamantyl)acetylene[1-14C].
1-Ethynyl-1-methylcyclohexane(740�) is converted into toluene and benzene,
while evidence for rearrangement of 3,3-dimethylbut-1-yne[2-13C]
(790�) and 3-methyl-3-phenylbut-1-yne[2- 13C] (680�) was not
obtained before the onset of alternative reactions. These reactions of
alkyl-substituted alkynes are discussed in terms of possible methylene carbene
intermediates. Similar intermediates may possibly be involved in reactions of
arylalkynes. Thus, pyrolysis of 1- ethynylnaphthalene
(750�) yields acenaphthylene and of 1-ethynyl-8- methylnaphthalene (750�)
yields phenalene. The pathways for the formation of 2-phenyl- and
3-phenyl-indene from (2- methylphenyl)phenylethyne (790�) and of indene from
(2- methylphenyl)ethyne (740�) are obscured by facile thermal rearrangements.
The chemistry of pyrrolic compounds. XXXVIII. The synthesis of hexahydroporphyrin a and related compounds
Authors: Clezy PS , Fookes CJR
Published: September 2010

A procedure is described
which allows the synthesis of porphyrins substituted with an α-hydroxy
terpenoid side chain. Of particular significance is the preparation of the
hexahydro derivative of porphyrin a, the iron-free prosthetic group of
cytochrome oxidase.
Hydroxyisothiazoles. II. Preparation of isothiazolin-3-ones and their methylated derivatives from the oxidation of cyano-substituted dithioacetate salts
Authors: Davis M , Dereani MC , McVicars JL , Morris IJ
Published: September 2010

The hydrogen peroxide
oxidation of α-cyanoaryldithioacetate salts (3) affords substituted
isothiazol-3-ols (isothiazolin-3-ones) (4) in moderate yields. Methylation of
the products yields mainly N-methyl derivatives. 4-Arylisothiazol-3-ols can be
further oxidized to saccharin analogues (7).
Structural studies in the 1 : 1 copper(I) halide-pyridine base system
Authors: Campbell JA , Raston CL , White AH
Published: September 2010

The crystal structures of 1
: 1 adducts of cuprous iodide with collidine ICu(col) and 2,6-lutidine ICu(lut), and of cuprous chloride with pyridine ClCu(py), have been determined at
295 K and refined by full-matrix least squares to residuals of 0.052 [ICu(col)], 0.079 [ICu(lut)], 0.057 [ClCu(py)] for 465, 1761 and 720
?observed? reflections respectively. ��� Crystal data.-ICu(col), orthorhombic, P21mn, a 11.500(3), b
10.620(3), c 4.159(1) Ǻ, Z 2. ��� ICu(lut), monoclinic, P21/c, a 16.377(9), b
7.833(3), c 15.401(8) Ǻ, β 110.53(4)�, Z 8. ��� ClCu(py), monoclinic, P21, a 9.324(4), b 3.8484(7), c
8.663(4) Ǻ, β 107.08(3)�, Z 2. ��� The 1 : 1 cuprous bromide-pyridine adduct BrCu(py) is isomorphous with ClCu(py): a 9.423(2), b
3.9585(6), c 8.907(2) Ǻ, β 108.13(2)�. ��� In none of the three structures is the
tetrameric (CuXL)4 species found. The
structure of ICu(col) is an
infinite zig-zag I-Cu-I-Cu- polymer running parallel
to c; the copper is also coordinated by the collidine, Cu, I and N lying in the
mirror y = 0.5 which also bisects the collidine ring. The structure of ICu(lut) comprises dimeric
species, a pair of three-coordinated copper atoms being bridged by the two
associated iodines. ClCu(py)
has the ?ribbon? structure typified by CuCl,MeCN and CuBr,MeCN, an infinite polymer parallel to b. The inability
of ICu(col) and ICu(lut) to form tetramers is
attributed to steric hindrance of the methyl substituents of the base. The
Cu-Cu distance in ICu(lut)
is remarkably short (2.586 Ǻ).
The acid-catalysed dehydration of 13α-Substituted-13β-methylpodocarpan-8β-ols
Authors: Blunt JW , Boyd GS , Hartshorn MP , Munro MHG , Pannell LK
Published: September 2010

Acid-catalysed dehydration
of each of the 8β-hydroxy compounds (1a) and (1b) gives initially the
Δ7 (3), Δ8(14) (4) and Δ8 (5)
olefins. After extended reaction times the rearranged 8α-Δ5(16),
8α-Δ5(10) (14) and 8β- Δ5(10) (15)
olefins are major products; the 8β-Δ5(10) olefin (15) is
the only significant product of long-term acid treatment of the 8β-alcohol
(1b) or of the other olefins (3b), (4b), (5b), (14b) and (16b).
The flavanones of Agonis spathulata (Myrtaceae)
Authors: Cannon JR , Martin PF
Published: September 2010

The flavanones
(+)-pinostrobin (1), (-)-demethoxymatteucinol (2), and (-)-cryptostrobin (5) have
been isolated from Agonis spathulata
Schau.
The effect of pressure on the infrared spectrum of ammonium formate: HCO2NH4, DCO2NH4, HCO2ND4, DCO2ND4. An unusual intermolecular coupling of non-identical vibrations in phase II
Authors: Hamann SD , Spinner E
Published: September 2010

The infrared spectra of the
title compounds have been measured over the pressure range 0-42 kbar at 25�C.
The phase change at c. 12 kbar is accompanied by an increase in the NH
stretching frequencies and other well-defined spectral changes. Vibrational coupling
in phase II of HCO2NH4 between CH in-plane bending in HCO2-
and a bending motion in NH4+, and its counterpart for DCO2ND4,
account for some unusual frequency changes arising from isotopic substitution
in the counter ion. The spectral changes suggest that during the phase change I
→ II the NH...O hydrogen bonds are weakened and the cations move to
positions in close proximity beside the CH bonds.
The influence of pressure on the infrared spectra of hydrogen-bonded solids. VI. Ammonium salts
Authors: Hamann SD
Published: September 2010

The infrared spectra of 33
polycrystalline ammonium salts have been measured at 25°C, at pressures up to
45 kbar. The N-H stretching and bending bands of the
hydrogen-bonded NH4+ ions of most of the salts shift
anomalously to higher and to lower frequencies, respectively, as the pressure
is raised. In this sense, the salts behave as if they had very strong hydrogen
bonds, instead of quite weak ones. ��� A fairly good correlation exists between
the N-H stretching frequencies of salts with N+-H...O
bonds and their hydrogen bond strengths as measured by the minimum N+...O
distances in their crystals.
Studies of Australian soft corals. III. A novel furanoquinol from Sinularia lochmodes
Authors: Coll JC , Liyanage N , Stokie GJ , Altena IV , Nemorin JNE , Sternhell S , Kazlauskas R
Published: September 2010

A furanoquinol, C22H28O3,
extracted from a sinularian soft coral has been shown to have the structure (3)
based on spectroscopic evidence and the preparation of the related
furanoquinone (4).Tables of 1H and 13C N.M.R. values for
compounds (3) and (4) are given in two solvents. The compound (3) is best
regarded as a modified polyprenylated quinol, and has the systematic name:
2-[3',7'-dimethyl-8'-(4'-methyl-2'-furyl)octa-
2',6'-dienyl]-5-methylhydroquinone.
Reaction of 6-Oxocholest-4-en-3β-yl acetate with perbenzoic acid
Authors: Ahmad MS , Khan IA
Published: September 2010

Oxidation of
6-oxocholest-4-en-3β-yl acetate (1) with 1 mol. equiv. of perbenzoic acid
(and p-toluene-sulphonic acid monohydrate as catalyst) gave 4-hydroxycholesta-2,4-dien-6-one
(2a), 7α-hydroxy-6-oxocholest-4-en-3β-yl acetate (3a), 3β-acetoxy-7-oxo-6,7-secocholest-4-en-6-oic
acid (4a) and 5-oxo-5,6-secocholest-3-en-6-oic acid (5). When treated with an
excess of perbenzoic acid (2.5 mol. equiv.), (1) provided (4a), (5) and 3β-acetoxy-6,7-secocholest-4-ene-5,8-dicarboxyic
acid (6). In each case, none of the expected ε-lactones (3c) and (3d) were
isolated. The products have been characterized on the basis of their spectral
properties, chemical transformations and comparison with authentic samples
where available.
Pyridone analogues of tetrahydroisoquinolines and protoberberines from mimosine and mimosinamine
Authors: Richards CM , Hofmann A
Published: September 2010

Several pyrido[1,2-a]piperazines
and their N-methyl derivatives have been prepared. These pyridine analogues of
the 1,2,3,4-tetrahydroisoquinolines were formed by
condensation of carbonyl compounds with mimosine and mimosinamine in the
absence of an acid catalyst. A Mannich reaction
converted one of these compounds, 1-(3,4-dimethoxybenzyl)-9-hydroxy-1,2,3,4-tetrahydro-8H-pyrido[1,2-a]-
pyrazin-8-one, into a pyridone analogue of the tetrahydroprotoberberine
caseadine.
Vibrational spectra of molecules on zeolites. IV. Raman spectra of cyclopropane on zeolites X
Authors: Tam NT , Tsai P , Cooney RP
Published: September 2010

Laser Raman spectra are
reported for cyclopropane adsorbed on cation- exchanged zeolites X. The results
have been interpreted in terms of an edge-on interaction of the cyclopropane
molecule with the zeolitic cation site. The symmetry of cyclopropane, when adsorbed
on LiX and NaX, appears to
be lowered from the free-molecule symmetry (D3h) to C2V
as evidenced by the splitting of the E' mode (v11) of cyclopropane.
In contrast to the previously reported case of the adsorption complexes, MX+C2H2
and MA+C2H2, the adsorption interaction appears to follow
a direct polarizing-power dependence on the zeolitic cation. Force- constant
calculations support an interpretation based on a cation- induced dipole
interaction.
Multiply charged aromatic cations : The heptalenium dication
Authors: Craig DP , Radom L , Schaefer III HF
Published: September 2010

A logical route to multiply
charged aromatic cations involves the successive fusion of monopositively
charged seven-membered rings, beginning with the tropylium cation C7H7+.
Ab initio molecular electronic structure theory has been applied to the second
member of the series, the heptalenium dication C12H102+,
which is predicted to be bound relative to selected possible fragmentation
partners. By suitable synthetic procedures, it should be possible to prepare
both the heptalenium dication and perhaps larger members of the series, such as
the cyclohepta[b]heptalenium trication C17H133+.
Photo-induced elimination in some aporphinium salts
Authors: Bremner JB , Winzenberg KN
Published: September 2010

Ultraviolet irradiation of
(+)-glaucine methiodide in methanol gave the elimination product 1-[2'-(N,N-dimethylaminoethyl)]-3,4,6,7-
tetramethoxyphenanthrene in good yield. Analogous
products were obtained from the ethiodide and benzylbromide salts of this
aporphine alkaloid, and from quaternary salts of (+)-boldine and (-)-O,O'-dimethylapomorphine.
This photoelimination reaction was also applied to the hydrochloride salts of
(+)-glaucine and (+)-boldine.
Methyleneketenes and methylenecarbenes. XI. Rearrangements of cycloalkylidenecarbenes
Authors: Baxter GJ , Brown RFC
Published: September 2010

The products of flash
vacuum pyrolysis of the cycloalkylidene derivatives (3) of Meldrum's
acid at 480-640° are rationalized in terms of formation of the
cycloalkylidenecarbenes (1; ring size n = 4-8)and their rearrangement to cycloalkynes, to bicyclic cyclopropenes (e.g. (7)), or to
further products derived from these. Pyrolysis of the 3,3-dimethylcyclobutylidene
derivative (3h) gave 3,5-dimethylphenol, probably formed by cyclization of the
(Z)-hexatrienone (22). ��� The tetrahydrofuran-3-ylidene derivative
(3i) gave butatriene and formaldehyde as major products of pyrolysis; these may
be formed by retro-Diels-Alder fission of the
heterocycloalkyne (27).
Quinones and quinone methides. III. A novel side-chain amination reaction of 2-(1-Phenylethyl)-1,4-benzoquinones
Authors: Jurd L
Published: September 2010

2-Benzyl-5-methoxy-1,4-benzoquinones
react as expected with morpholine to yield
2-phenylmorpholinomethylhydroquinones. However, 5-methoxy-2-(1-phenylethyl)-1,4-benzoquinones
undergo a novel amination reaction at the β-carbon atom of the alkyl group
with the formation of 2- morpholino-3-phenylbenzofurans.
Purine studies. XX. Approaches to the syntheses of 7,8- and 8,8-Dibenzyltheophylline
Authors: Lister JH , Bhushan K
Published: September 2010

Various routes for the
synthesis of 7,8-dibenzyltheophylline have been explored including inter alla
the attempted preparation of 8,8-dibenzyl(8H)theophylline as a possible
subject for rearrangement to the 7,8-dibenzyl isomer. The propensity of benzyl
groups to be eliminated from some of the intermediates encountered in this work
is illustrated by examples further to those already given in an earlier paper
of the series.
Formation of substituted 1-Benzazepine-2,5-diones from derivatives of kynurenine
Authors: Rivett DE , Stewart FHC
Published: September 2010

Several N-protected
DL-kynurenine derivatives have been converted into 3-substituted 3,4-dihydro-1H-1-benzazepine-2,5-diones
by thermal cyclization. This reaction was found to proceed less readily than
the analogous formation of 1,4-benzodiazepine-2,5-diones from o- aminobenzoylamino
acids. The incidence of specific peptide bond cleavage involving these
cyclizations was investigated with model compounds.
The photoelectron spectra of the propylbenzenes
Authors: Carnovale F , Nagy-Felsobuki E , Peel JB
Published: September 2010

The HeI
photoelectron spectra of propyl- and isopropyl-benzene have been measured and
compared. The two isomers have the same first ionization potential, but show
variations in the higher ionization energy range. Comparison with the benzene
and propane spectra, aided by the results of SPINDO calculations, indicates
that the propylbenzene spectra can be interpreted according to a composite-molecule
model.
Mössbauer studies in transition metal chemistry. IV. Iron(II) complexes of 2-(2'-Pyridyl)benzimidazole
Authors: Martin RL , Roos IAG , Goodgame DML , Machado AASC
Published: September 2010

Mossbauer spectra of a
number of compounds containing the [Fe(pyb)3]2+ complex
cation [pyb, 2-(2'-pyridyl)benzimidazole] confirm that these compounds undergo
a change of spin state with temperature consistent with a 5T2-1A1
spin crossover. The nature of the Mossbauer spectra and their
temperature-dependence are sensitive to the associated anion and the method of
preparation. ��� The temperature-dependence of the Mossbauer
parameters has been used to derive information about the distortions from
octahedral symmetry and it is concluded that the dimensions of the crystal-line
lattice are changing slightly with temperature.
Structural studies in the phenylmercury/oxinate system
Authors: Raston CL , Skelton BW , White AH
Published: September 2010

The crystal structures of
PhHgL [L = quinaldinate, C10H8NO- (1);
oxinate, C9H6NO-, two phases, (2) and (3)]
have been determined at 295 K and refined by least squares to residuals of
0.068 (2148 'observed' reflections) for (1), 0.107 (1165) for (2) and 0.046 (1146)
for (3). Crystals of (1) are mono-clinic, C2/c, a 22.961(8), b 9.142(2), c
16.412(6) Ǻ, β 127.75(2)°, Z 8; those of (2) are orthorhombic, Pnam,
a 23.12(3), b 16.59(2), c 6.62(1) Ǻ, Z 8; those of (3) are orthorhombic,
P212121, a 5.584(2), b 9.902(3), c 22.073(9)
Ǻ, Z 4. ��� In (1) the molecules are grouped as loose
dimeric associations about a twofold axis with Hg...O bridges. In (2) the
molecules lie stacked in a loose infinite array along c, while in (3) the
disposition is an infinite helical array; in both (2) and (3), the Hg...O
contacts are very long.
Methyleneketenes and methylenecarbenes. XII. Thermal rearrangement of acetylene
Authors: Brown RFC , Eastwood FW , Jackman GP
Published: September 2010

Flash vacuum pyrolysis of
1,2,3,4-tetrafluoro-9-methoxy-9,10-dihydro- 9,10-ethenoanthracene[12-13C;10,12-D2],
(600°) gives doubly labelled acetylene HC≡13CD. At
temperatures of 700° and greater, the ethenoanthracene gives a mixture of
HC≡13CD and DC≡13CH. Formation of the
acetylene at 600° followed by pyrolysis at 850° confirmed that it is the free
acetylene that undergoes intramolecular rearrangement: ����������������������������������� >700.����������������������������� HC≡13CD
↔ DC≡13CH
The pattern of labelling in
the acetylene was determined by allowing it to react with bromine and examining
the resulting 1,1,2,2- tetrabromoethane by p.m.r. and
infrared spectroscopy. Mass spectral studies on the tetrabromoethane showed
that no significant intermolecular hydrogen exchange takes place up to 1050°.
Crystal structure of 5,9-Dimethoxy-3,3,8-trimethy1-7,10-dihydro-3H-naphtho[ 2,1-b]pyran-7,10-dione
Authors: Hall SR , Raston CL , White AH
Published: September 2010

The crystal structure of
the title compound, C18H18O5, has been
determined by single-crystal X-ray diffraction methods at 295 K and refined by
least squares to a residual of 0.058 for 1502 'observed' reflections. Crystals
are monoclinic, P 21/n, a 22.048(6), b 7.075(2), c 10.443(3) Ǻ, β
100.40(3)°, Z 4. ��� The structure was solved by a combination
of special direct phasing procedures and translation functions, after
conventional direct methods had failed.
A synthesis of 3-O-(2-Acetamido-2-deoxy-α-D-galactopyranosyl)-D-galactopyranose and 3-O-α-D-Galactopyranosyl-D-galactopyranose
Authors: Lemieux RU , Stick RV
Published: September 2010

The condensation of
1,2:5,6-di-O-isopropylidene-α-D-galactose with dimeric tri-O-acetyl-2-deoxy-2-nitroso-α-D-galactopyranosyl
chloride gives 3-O-(tri-O-acetyl-2-hydroxyimino-α-D-lyxo-hexopyranosyl)-1,2:5,6-
di-O-isopropylidene-α-D-galactose. This hydroxyimino glycoside may then be
converted, by an established reductive sequence, into the title 2- acetamido-2-deoxydisaccharide
and its talo epimer. Alternatively, hydrolysis of the hydroxyimino glycoside
yields a ketone which, again by an established reductive sequence, may be
converted into the title disaccharide and its talo epimer.
Gas-liquid critical temperatures of mixtures containing an organosilicon compound
Authors: Waterson SD , Young CL
Published: September 2010

The gas-liquid critical
temperatures of 16 binary mixtures containing an organosilicon compound have
been measured by the sealed-tube method, together with the gas-liquid critical
temperature and pressure of tetramethoxysilane,
tetraethoxysilane and tetrapropoxysilane.��� The results for the mixtures have been used
to calculate a parameter characterizing the interactions between unlike
molecules. An iterative solution to the criticality condition was used together
with the one-fluid model and a 'hard sphere+attractive
term' equation of state. ��� The interaction parameters are discussed
briefly. The one-fluid model in the form used here, at least, appears to be
unsatisfactory for predicting the composition dependence of the gas-liquid
critical temperatures within 5 K for mixtures of molecules of widely differing
sizes (i.e. size ratios as estimated from molar volumes of greater than 1 : 4).
Structure, absolute configuration and electrochemical properties of Tris(N-methylformothiohydroxamato)iron(III), an antibacterial metal chelate and potential iron siderochrome
Authors: Murray KS , Newman PJ , Gatehouse BM , Taylor D
Published: September 2010

The title compound, which
previously had been isolated from bacteria and shown to possess anti-bacterial
activity, has been chemically synthesized. The molecular structure has a cis
(facial) arrangement of the asymmetric {S,O} bidentate ligands (Fe-S 2.441(1)
Ǻ, Fe-O 2.010(1) Ǻ) as required by the crystallographic C3
molecular symmetry. (Crystal data: C6H12N3O3S3Fe,
rhombohedral, space group R3, a 7.094(2)Ǻ, α 102.00(1)°, Z 1.) The
complex was spontaneously resolved into enantiomers on crystallization and the
absolute configuration in the crystal studied was established as Λ by the
anomalous dispersion technique. Magnetic, e.s.r. and Mossbauer studies are
compatible with a distorted octahedral complex of high-spin iron(III). Cyclic
voltammetric studies in acetone of the title compound and some related iron(III)
thiohydroxamates were carried out. A reversible FeIII/FeII
reduction wave was observed for the N-methylformothiohydroxamato chelate, in
contrast to the irreversible reduction of tris(benzohydroxamato)iron(III),
a related complex containing an {O,O} chelate. The tris(benzothiohydroxamato)
chelate, Fe(PhC(S)NHO)3, which possesses a
non-alkylated nitrogen, also showed an irreversible reduction wave.
Structural and kinetic trans effects in cobalt(III) complexes with cobalt-sulfur bonds. The crystal structure of trans-Bis(ethylenediamine)imidazolesulfitocobalt(III) perchlorate dihydrate
Authors: Raston CL , White AH , Yandell JK
Published: September 2010

The crystal structure of
the title compound, [Co(C2N2H8)2(C3N2H4)(SO3)]
ClO4,2H2O has been determined by X-ray diffraction, using
diffractometer data, at 295 K, and refined by full-matrix least squares to a
residual of 0.071 for 3425 ?observed? reflections. Crystals are orthorhombic, Pcmn, a 15.822(9), b 11.924(6), c 9.261(2) Ǻ, Z 4. The
imidazole and sulfite ligands are trans in the cation, which has m symmetry
(Co-S 2.223(2); Co-N 2.008(4) Ǻ).  is 1.964Ǻ.
The apparent thermal motion of the sulfite about the Co-S axis is very high.
The internal internuclear distances are compared to
the data reported for series of similar complexes in which trans effects are
observed.
Methylthiomethyl ethers: Their use in the protection and methylation of hydroxyl groups
Authors: Pojer PM , Angyal SJ
Published: September 2010

Methylthiomethyl ethers are
obtained in good yield from primary, secondary and tertiary alcohols by
treating them with a mixture of dimethyl sulfoxide, acetic anhydride and acetic
acid. The methyl- thiomethyl groups are readily removed on heating the compounds
with methyl iodide in moist acetone. The methylthiomethyl ethers are converted
into methyl ethers by the action of 'nickel boride'.
The stereochemistry of organometallic compounds. XVII. Reactions of π-allylpalladium compounds with acetylacetone
Authors: Jackson WR , Strauss JU
Published: September 2010

Reactions of π-allylpalladium
compounds with sodium acetylacetonate, sodium malononitrile, and sodium
ethylacetoacetate in dimethyl sulfoxide solution give diallyl substitution
products. Reaction of the acetylacetonate complexes with carbon monoxide in benzene
give mono- allyl substitution products. Application of these reactions to the
π- allyl complexes from 1-acetyl-4-t-butylcyclohex-1-ene and from 3-oxo 4-
ene steroids in an attempt to examine the stereochemistry of ligand transfer
gave no substitution products.
Pterins. III. Methylation of 6-Methyl-5,6,7,8-tetrahydropterin, N-5-Demethylation of 1,3,5,6-Tetramethyl-5,6,7,8-tetrahydropterinium chloride hydrochloride and exchange of the 5-Methyl group in 5,6-Dimethyl-5,6,7,8-tetrahydropterin
Authors: Armarego WLF , Schou H
Published: September 2010

Methylation of
6-methyl-5,6,7,8-tetrahydropterin (1) in the presence of sodium hydroxide
furnishes 1,3,6-trimethyl-5,6,7,8-tetrahydropterinium chloride (3) which can be
methylated further to yield 1,3,5,6- tetramethyl-5,6,7,8-tetrahydropterinium
chloride (4). Demethylation of the latter salt occurred on a Dowex 50W/3 N-aqueous ammonia column with loss of the
5-methyl group to give the salt (3). The structures of these salts were deduced
by a study of similar alkylations of authentic 1,6-dimethyl-,3,6-dimethyl-
(6), 5,6-dimethyl-(15), 6,8-dimethyl-, 1,5,6-trimethyl-, and 3,5,6-trimethyl-5,6,7,8-tetrahydropterin
(7), and of 6-methyl-2-methylamino-5,6,7,8-tetrahydropteridin- 4(3H)-one (10).
Methylation of 5,6-dimethyl-5,6,7,8-tetrahydropterin (15), with trideuteromethyl
iodide in the presence of alkali, was shown to give the tetramethylpterinium
salt (4) in which considerable exchange of the 5-methyl group by a
trideuteromethyl group had taken place. ��� The pterinium salts (3) and (4) were
considerably more stable to aerial oxidation than 6-methyl-, 1,6-, 3,6-, 5,6-,
6,7-, 6,8-dimethyl-, and 1,5,6-trimethyl-5,6,7,8-tetrahydropterin. Loss of the
5-methyl group from the salt (4), and exchange of the 5-methyl group in the
5,6- dimethylpterin (15), allowed a mechanism for the enzymic transfer of the
5-methyl group in 5-methyl-5,6,7,8-tetrahydrofolic acid in biological
methylations to be proposed.
Raman spectrum of cadmium nitrate
Authors: James DW , Carrick MT , Leong WH
Published: September 2010

The Raman spectra of Cd(NO3)2,4H2O and
anhydrous Cd(NO3)2 are
reported. The spectrum of Cd(NO3)2,4H2O
is compatible with the known crystal structure Fdd2. The spectrum of the
anhydrous salt is complex and indicates that the 16 NO3-
ions are on four sites with different potential energy environments and each
site is occupied by four NO3- ions. The centrosymmetric
space group Pbcm is favoured to the non-
centrosymmetric space group Pca21. Multiple-site splitting, site- symmetry
splitting and correlation-field splitting are used to explain the complex band
structures.
Crystal structures of the simple monoclinic and orthorhombic polytypes of tripotassium hexacyanoferrate(III)
Authors: Figgis BN , Skelton BW , White AH
Published: September 2010

The room-temperature (295
K) crystal structures of potassium ferricyanide, K3[Fe(CN)6],
have been determined for the simplest monoclinic (a reinvestigation) and
orthorhombic polytypes by single- crystal X-ray diffraction. The monoclinic
form is P21/c, a 7.047(3), b 10.400(3), c 8.384(3) Ǻ, β
107.29(3)°, Z 2. The iron atoms lie on special positions with symmetry 1. In
the orthorhombic form, Pnca, a 13.422(6), b
10.396(4), 8.381(4) Ǻ, Z4, the iron atoms now lie on special positions
with symmetry 2 (parallel to c). Residuals are 0.036 and 0.048 for 1232 and 855
'observed' reflections respectively.
Reactions of aryl diazonium salts and arylazo alkyl ethers. III. Substituent effects in the ionization of anti-arylazo ethyl ethers in ethanol
Authors: Broxton TJ
Published: September 2010

A dual substituent
parameter analysis of substituent effects on the ionization of anti-arylazo
ethyl ethers in ethanol shows that the reaction is affected primarily by
inductive effects. The reaction is insensitive to resonance effects and an
explanation for this behaviour is offered.
Synthesis of benzofuranoid systems. V. Alternative total synthesis of cyperaquinones
Authors: Macleod JK , Worth BR , Wells RJ
Published: September 2010

An alternative route to
unsymmetrically substituted benzo[1,2-b:5,4-b']difuranquinones
starting from pyrogallol and proceeding via the linear furocoumarin nucleus has
been used to synthesize the three naturally occurring compounds cyperaquinone
(1), conicaquinone (2) and demethylcyperaquinone (3).
Tropone (cyclohepta-2,4,6-trienone) derivatives related to biphenylene. 5H-Benzo[3,4]cyclobuta[1,2]cyclohepten-5-one, 6H-Benzo[3,4]cyclobuta[1,2]cyclohepten-6-one and 7H-Benzo[3,4]cyclobuta[1,2]cyclohepten-7-one
Authors: Lombardo L , McCulloch RK , Wege D
Published: September 2010

Synthetic routes to
5H-benzo[3,4]cyclobuta[1,2]cyclohepten-5-one (6), 6H-benzo[3,4]cyclobuta-[1,2]cyclohepten-6-one
(5) and 7H- benzo[3,4]cyclobuta[1,2]cyclohepten-7-one (7), which are analogues
of biphenylene in which one benzenoid ring has been replaced by the
cyclohepta-2,4,6-trienone (tropone) ring, have been investigated. The tropone
(5) was obtained as a stable, crystalline solid and 1H n.m.r, evidence suggests
that (5) has a more localized π-bond system in the seven-membered ring
than tropone itself. The reactive tropone derivative (7) was generated in
solution, and trapped as a 6πs+4πs cycloadduct
with cyclopentadiene.
Photovoltaic effect and conduction mechanism in metal-insulator-metal cells containing metal-free phthalocyanine
Authors: Hall KJ , Bonham JS , Lyons LE
Published: September 2010

Metal-insulator-metal cells
containing metal-free phthalocyanine sandwiched between two metals (six
different combinations of gold, lead and aluminium) have been prepared, and
their photoelectrical properties studied in ultra-high vacuum. With irradiation
incident on the non- substrate electrode the spectral response and sign of the
photovoltage are consistent with conduction by injected holes. At low voltages,
the photocurrent-voltage curves can be quantitatively explained by a space- charge-free
theory of conduction. Energy barriers to hole injection, and hence the built-in
field, are not determined by the work function of the metal, but in each case
the higher barrier occurs on the non-substrate side of the phthalocyanine. This
fact, together with the observed variation of the built-in field with
irradiance and the failure of the space-charge-free conduction model at high
voltages, is explained by assuming that the metals make ohmic contact to the
phthalocyanine and that the effective barriers to injection are determined by
space-charge effects of holes trapped near the metal-insulator interface. The
trap density is highest at the non-substrate side of the film and is
approximately uniform with energy. The dark current exceeds the saturation
photocurrent at high voltages, which suggests that the mechanism of
photoinjection into the bulk is probably exciton dissociation at defects near
the illuminated electrode rather than exciton-induced photoinjection directly
from the metal. ��� Reasons for the low photovoltaic
power-conversion efficiencies in these cells, and theoretical limitations on
more-ideal cells of this type, are discussed.
Mechanism of thermal degradation of sucrose. A preliminary study
Authors: Richards GN , Shafizadeh F
Published: September 2010

Evidence is presented which
indicates that the initiating reaction in the thermal decomposition of sucrose
is a first-order intramolecular displacement yielding D-glucose and a fructose
derivative(F*) (anhydride?). The latter product has not yet been identified,
but is postulated as reacting rapidly with sucrose to yield trisaccharides of
the type F2G. When another alcohol (erythritol) is present in the
melt, F* reacts with it to produce fructoside(s).
Semi-empirical calculation of rates of SN2 Finkelstein reactions in solution by a quasi-thermodynamic cycle
Authors: McLennan DJ
Published: September 2010

Free energies of activation
for the reactions:
������������� Nu-+MeX
→ MeNu+X- (Nu
= nucleophile, X = halogen)
are calculated by a
quasi-thermodynamic cycle. The six steps involved are: (i)
desolvation and escape into the gas phase of MeX;
(ii) desolvation and escape of Nu- ; (iii)
loss of an electron from Nu-; (iv)
combination of Nu.(g) with MeX(g) to form a methyl radical transfer 'transition state';
(v) placement of an electron on the 'transition state'; (vi) transfer of the
anionic transition state from the gas phase to the solvent. The BEBO method is
used to calculate the energetics of step (iv), and the BEBO exponents for
various Nu and X are calculated from the measured or
estimated rates of the symmetrical halide exchanges X-+MeX and Nu-+ MeNu. The energy of the system is plotted as a function of
the fractional bond orders of the Nu...C and C...X
partial bonds, and ΔG‡ is identified with the maximum value of
this energy. An excellent correlation of calculated against experimental
results is found for reactions in water and methanol, whilst interactions
between polarizable HCONMe2 and polarizable SN2
transition states lead to small but regular discrepancies in HCONMe2.
Observed nucleophilic and leaving group orders of reactivity are reproduced, as
is the lack of a correlation between reactivity and selectivity. The computed
transition state bond orders do not concur with predictions based on the
Hammond postulate.