bluuebunny/crossref_metadata_2025 huggingface dataset:
Formolysis studies on some polysaccharides from red seaweeds
Authors: Brasch DJ , Chuah C , Melton LD
Published: September 2010

Formolysis of the
permethylated agaroses from marine algae of the Pterocladia species and Gracilaria
secundata, and of the permethylated porphyran from Porphyra columbina, resulted in a much higher recovery of
3,6-anhydro-2-O-methyl-L-galactosyl (relative to methylated D-galactosyl)
derivatives than was obtained from conventional methylation analyses. The
formolysis method, when followed by sulfuric acid hydrolyses, provided a novel
method for the estimation of 3,6-anhydro-L-galactose residues in these agar-type
polysaccharides. The 3,6-anhydro-2-O-methyl-L-galactose
was determined by gas chromatography of its alditol acetate, and identified by
g.l.c./m.s.
Applications of molybdenum-95 N.M.R. spectroscopy. X. Polyoxomolybdates
Authors: Gheller SF , Sidney M , Masters AF , Brownlee RTC , O'Conner MJ , Wedd AG
Published: September 2010

An initial survey of the 95Mo
n.m.r. properties of a range of 12 polyoxomolybdates
is presented. The species resonate in the range - 18 to + 140 ppm. The observed line widths generally exceed 100 Hz for
six-coordinate molybdenum sites of low symmetry, but can be narrow (< 20 Hz
at 20�) for four-coordinate sites. Aqueous solutions of [Mo7O24]6-
at pH 6.1 exhibit exchange between Mo- and Mo7-based species.
Solutions of α-[Mo8O26]4- in MeCN feature a single narrow resonance (δ16, Wh/2 23 Hz at 20�) assigned to the
tetrahedral capping sites, while two broad resonances (δ19, Wh/2 240 Hz; δ109, Wh/2 C. 270 HZ) are seen in
equivalent solutions of β-[Mo8O26]4-. In
the cases cited above, 17O n.m.r. is used to confirm the integrity
of sample solutions and assists in correction of the 95Mo n.m.r.
properties of β-[Mo8O26]4 reported in a
previous communication.
N.M.R. study of acid-base equilibria of aminoalkylphosphonic acids, +NH3(CH2)nPO3H- (n = 1,2,3): Evidence for cyclization in solution
Authors: Appleton TG , Hall JR , Harris AD , Kimlin HA , McMahon IJ
Published: September 2010

The variations with pD of 31P, 13C and lH n.m.r. chemical shifts for D2O
solution of MePO3H2 and NH2(CH2)nPO3H2
(n = 1, 2, 3) have been studied. In the aminoalkylphosphonic
acids, δp is profoundly affected by amine deprotonation.
'Cyclic' conformations in which the amine group is close to the phosphonate group are proposed, with the strength of the
amine-phosphonate interaction decreasing as n increases.
Synthesis and electrophilic substitution of some Hexa- and Penta-2,4-dienyl-silanes,-germanes and -stannanes
Authors: Jones M , Kitching W
Published: September 2010

Penta-2,4-dienyl and
hexa-2,4-dienyl derivatives of silicon, germanium and tin have been synthesized
(normally as E/Z mixtures) by metalation of the
corresponding pentadienyllithium reagents. The E/Z
isomeric mixtures have been fully characterized by 1H and 13C
nuclear magnetic resonance spectroscopy. Trifluoroacetolysis
of these compounds (CF3COOD) has been studied by direct 2H
n.m.r. spectroscopy, and ε-electrophilic attack is predominant. In
contrast, sulfur dioxide insertion (with the stannanes) is γ-regiospecific, but these kinetic γ-sulfinates
rearrange, by a presumed electrocyclic process, to the conjugated
dienylmethylsulfinates.
Synthesis of some thiosucrose derivatives
Authors: Jenkins ID , Thang S
Published: September 2010

Treatment of
3,3',4',6'-tetra-O-acetylsucrose in
dimethylformamide with thioacetic acid, triphenyl- phosphine and diethyl azodicarboxylate,
followed by acetylation, gave 6-thiosucrose octaacetate
in good yield. Similar treatment of 4,6:2,1'-di-O-isopropylidenesucrose followed by removal of the isopropylidene groups and acetylation gave 6'-thiosucrose octaacetate. Treatment of sucrose itself under these
conditions gave 6,6'-dithiosucrose octaacetate.
6,6'-Dithiosucrose octaacetate was readily converted
into 6,6'-dideoxysucrose by treatment with Raney nickel followed by deacetylation.
3-Nonyltetrahydrofuran from the reduction of alkenes with lithium and ethanol in ammonia
Authors: Massy-Westropp RA , Warren RFO
Published: September 2010

3-Nonylidenetetrahydrofuran
is readily reduced with lithium and ethanol in ammonia to yield mainly
3-nonyltetrahydrofuran together with 3-methyldodecan-1-ol. The reductions of a
mixture of 4-nonyl-4,5-dihydrofuran and 3-nonyl-2,Sdihydrofuran and of a mixture
of 3-nonyl-4,Sdihydrofuran, 3-nonyl-2,5-dihydrofuran and
3-nonylidenetetrahydrofuran are also reported.
Basic hydrolysis of some N-phenylcarbamates and basic methanolysis of some N-phenylacetamides containing an ortho nitro substituent
Authors: Broxton TJ
Published: September 2010

Kinetic studies of the
basic methanolysis of N-(2-nitropheny1)acetamides indicate that unlike the
4-nitro isomer, no change of mechanism occurs on inclusion of an N-methyl
group. Reaction occurs with rate-determining C-N bond breaking for both the N-H
and N-methyl compounds. Basic hydrolysis of some methyl
N-(2-nitropheny1)carbamates occurred by the BAC2 mechanism and the
tetrahedral intermediate formed during the hydrolysis decomposed with
preferential C-O bond breaking. This is in contrast to the basic hydrolysis of
methyl N-methyl-N-4-nitrophenyl- carbamate, which has previously been shown to
occur with preferential C-N bond breaking. For the hydrolysis of methyl
N-methyl-N-(2-nitrophenyl)carbamate, an induction period in amine production
was detected at 0.45 M hydroxide ion. This was interpreted to mean that the
tetrahedral intermediate breaks down by loss of methoxide
ion. At 0.93 M hydroxide ion, however, no induction period in amine production
was observed. The possibility of reaction through a dianionic
intermediate was raised to explain this observation. The amide ion (2-NO2C6H4NMe-)
is a poorer leaving group than its 4-nitro isomer. This is explained by steric
crowding in the 2-nitro compound, resulting in twisting of the nitro group out
of the plane of the benzene ring and a consequent reduction in the
electron-withdrawing resonance effect of the 2-nitro group compared to the
4-nitro group.
Pentakis(methoxycarbonyl)cyclopentadiene chemistry. VIII. Some onium salts X-ray structure of [Nme4][C5(CO2Me)5]
Authors: Bruce MI , Humphrey PASBW , White AH
Published: September 2010

Reactions between Tl[C5(CO2Me)5]
and [R]X [R = NMe4, NEt4, NPr4, NBu4,
AsPh4, N(PPh3)2; X = C1, Br] have given salts
[R][C5(CO2Me)5] as white, crystalline solids.
The X-ray structure of [NMe4][C5(CO2Me)5]
has been determined; the unit cell contains isolated cations and anions, with
no close interactions between them. The anion consists of a planar C5
ring [C-C 1.406(10) �] with five CO2Me substituents whose planes
have an essentially random orientation with respect to the C5 plane.
[NMe4][C5(CO2Me)5] is monoclinic,
space group P21/c, with a
9.267(4), b 16.249(5), c 14.687(6) ź, β 100.90(3)�, and Z
4; 1610 data with I >3σ
(I) were refined to R 0.066
and R' 0.053.
The reduction of some o-Nitrophenylazo dyes with thiourea S,S-Dioxide (Formamidinesulfinic acid): a general synthesis of 2-Aryl-2H-benzotriazoles and their 1-Oxides
Authors: Rosevear J , Wilshire JFK
Published: September 2010

Thiourea S,S-dioxide (formamidinesulfinic
acid) reacts with o-nitrophenylazo dyes in ethanolic alkali to give, depending
on the reaction conditions, either the corresponding 2-aryl-2H-benzo-triazoles
or their 1-oxides. The reagent is particularly effective for preparing in high
yield 2-(2'H- benzotriazol-2'-yl)phenols, which are important ultraviolet
absorbers. The corresponding reductions involving ammonium sulfide and sodium
dithionite were also examined. The former reagent was unsatisfactory; the latter
reagent behaved erratically and was a less effective reducing reagent than thiourea dioxide. Nevertheless, conditions were established
whereby sodium dithionite furnished the 2-(2'H-benzotriazol-2'-yl)phenols in
high yield and purity.
A phosphate-catalysed acyl transfer reaction. Hydrolysis of 4-nitrophenyl acetate in phosphate buffers
Authors: O'Conner CJ , Wallace RG
Published: September 2010

The pseudo-first-order rate
constants for the phosphate-catalysed hydrolysis of 4-nitrophenyl acetate have
been determined in water at 310.5 K. The reaction has been followed spectrophotometrically by the disappearance of the ester
and with n.m.r, spectroscopy by the appearance of both acetyl phosphate and the
acetate ion and by the disappearance of ester. A phosphate-catalysed acyl
transfer mechanism has been identified, in which the aryl ester is attacked by
phosphate to give acetyl phosphate which is subsequently hydrolysed
by water to acetate ion and regenerated catalyst. At concentrations of total
phosphate exceeding 1.0 mol dm-3 the presence of dimeric phosphate
species causes the appearance of a non-linear rate-concentration profile.
Catalysis has been also been observed in
2,2'-(propane-1,3-diyldiimino)bis(propane-1,3-diol) buffer solutions.
Crystal structure of 3-Oxo-2-phenyl-3H-pyrazolo[1,2-a]pyrazol-4-io-1-olate
Authors: Raston CL , White AH
Published: September 2010

The crystal structure of the title
compound, C12H8N2O2, has been
determined by single crystal X-ray diffraction methods at 295 K and refined by
least-squares methods to a conventional residual of 0.050 for 1208 independent
'observed' reflections. Crystals are monoclinic, P21/a, a 14.375(10), b 6.330(8), c 10.780(8) �,
β 102.52(6)�, Z = 4. The molecular skeleton is substantially planar (σ(non-hydrogen atoms), 0.07 �) with a delocalization
pattern representative of a betaine comprising a pyrazolinium cation and a delocalized ,β-diketone
rather than an 8 π-electron delocalized system.
Structural studies of Technetium Complexes. VIII. The Crystal Structure of Tetraphenylarsonium Tetrabromonitridotechnetate(VI)
Authors: Baldas J , Bonnyman J , Williams GA
Published: September 2010

The crystal structure of [AsPh4] [TcNBr4] has been determined by single- crystal X-ray diffraction methods at 20�1°C. Crystals are tetragonal, space group P4/n, with a 12.875(2), c 7.992(1)Ǻ, and Z 2. Full-matrix least-squares refinement gave a final R value of 0.039 for 1263 independent reflections. The compound is isostructural with the series [AsPh4] [MNBr4] (M = Mo, Ru , Re or Os) and [AsPh4] [MNCl4](M = Mo, Tc , Ru, Re or Os), and with [AsPh4] [OsNI4] and [AsPh4]- [MOCl4](M = Mo or Re). The [TcNBr4]- anion in
[AsPh4] [TcNBr4] possesses C4v symmetry with Br- Tc -Br bond angles of 87.08(1) and 153.91(4)°, and
N= Tc -Br bond angles of 103.04(2)°. The Tc≡N bond distance is 1.596(6)Ǻ, and the Tc - Br distances are 2.4816(5)Ǻ.
Malononitrile in Aromatic Solvents—Geometry of Solvation
Authors: Aroney MJ , Patsalides E , Pierens RK
Published: September 2010

Polarization and electric birefringence measurements are reported for malononitrile in dioxan , benzene and hexafluorobenzene solutions. These data, together with 1H n.m.r .shifts, are used to explore solute-solvent interactions. Changes in the proton shifts of CH2(CN)2 are studied with replacement of benzene solvent by fluorinated benzenes.
The Oxidation of Some Bisphenolic 1-Phenethyltetrahydroisoquinolines Studied by E.S.R. Spectroscopy
Authors: Hewgill FR , Pass MC
Published: September 2010

1-(3,5-Dimethoxy-4-hydroxyphenylethyl)-6-methoxy-2-ethyl-1,2,3,4-tetrahydroisoquinolin-7-ol exhibits only a spectrum of the aryloxy radical of the phenethyl ring when oxidized in a flow system. This radical was characterized with the aid of a model compound. No radical could be obtained from (�)- homoorientaline.
Hydrometallurgical Thermodynamics. II. Solvent Effects on the Activity and Free Energies of Transfer of CN-, Ag(CN)2- and Au(CN)2- in Ethanol-Water and Acetonitrile-Water Mixtures
Authors: Muir DM , Singh P , Kenna CC , Tsuchida N , Benari MD
Published: September 2010

The free energies of transfer of CN-, Ag(CN)2- and Au(CN)2- ions from water to a range of acetonitrile -water and ethanol-water mixtures are reported. The values are based upon measurements of solubility products and formation constants of AgCN and Ag(CN)2-, and upon measurements of the Au(CN)2-/Au couple, by using known values of ΔGtr(Ag+) based on
the tetraphenylarsonium tetraphenylborate
( tatb ) assumption. Addition of acetonitrile
to water increases the activity of these ions in the order CN- > Ag(CN)2- ≥ Au(CN)2- much more than the addition of ethanol. Solvent effects on CN- and Ag(CN)2- are similar but slightly less than those on Cl - and AgCl2-, and show no special ion-solvent interactions between MeCN and CN-. The relative activity of CN- and Au(CN)2- in aqueous-organic mixtures rationalizes the ability of such mixtures to desorb gold from the activated carbon used in gold processing through an ion-exchange mechanism.
Rearrangement of Freelingyne with Base
Authors: Abell AD , Massy-Westropp RA , Reynolds GD
Published: September 2010

Treatment of freelingyne (1) with sodium hydroxide in aqueous methanol gives the rearranged acid (2a).
Lewis-Base Adducts of Group 1B Metal(I) Compounds. XXI The Crystal and Molecular Structures of the Unsolvated Forms of Dibromotris(triphenylphosphine)dicopper(I) and 'step' Tetrabromotetrakis(triphenyl-phosphine)tetracopper(I)
Authors: Dyason JC , Engelhardt LM , Pakawatchai C , Healy PC , White AH
Published: September 2010

The crystal structures of the title compounds have been determined by single-crystal X-ray diffraction methods at 295 K. Crystal data for (PPh3)2CuBr2Cu(PPh3) (1) show that the crystals are iso-morphous with the previously studied chloro analogue, being monoclinic, P21/c, a 19.390(8), b 9.912(5), c 26.979(9) Ǻ, β 112,33(3)°; R 0.043 for No 3444. Cu( trigonal )- P;Br respectively are 2.191(3); 2.409(2), 2.364(2) Ǻ. Cu(tetrahedral)- P;Br respectively are 2.241(3), 2.249(3); 2.550(2), 2.571(2) Ǻ. Crystals of 'step' [PPh3CuBr]4 (2) are isomorphous with the solvated bromo and unsolvated iodo analogues, being monoclinic, C2/c, a 25.687(10), b 16.084(7), c 17.815(9) Ǻ, β 110.92(3)°; R 0.072 for No 3055. Cu( trigonal )- P;Br respectively are 2.206(5); 2.371(3), 2.427(2) Ǻ. Cu(tetrahedral)- P;Br are 2.207(4); 2.446(2), 2.676(3), 2.515(3) Ǻ.
Studies in Bile Salt Solutions. XIV. Electronic, Charge and Steric Substrate-Effects on the Esterase Activity of Bile-Salt-Stimulated Human Milk Lipase. Hydrolysis of 4-Substituted Phenyl Propionates
Authors: Oconnor CJ , Mitha ASH
Published: September 2010

The rate constants of hydrolysis of a series of 4-substituted phenyl propionates, catalysed by bile-salt-stimulated human milk lipase in the absence and presence of cholate or taurocholate stimulation, have been measured at pH 7.3, 310.5 K. There is little evidence for an alkyl site electronic interaction in the rate-determining step of the esterolytic reaction. However, a negatively charged substrate or an amido-substituent caused an inhibition of unstimulated esterase activity. In the presence of the bile-salt cofactors, esterolytic activity against charged substrates may be stimulated or inhibited, depending on the proximity of the charge to the steroidal side chain and the subsequent substrate-interaction within the surrounding environment of the active site. It has been confirmed that bile-salt- stimulated lipase is not an amidase , but that an amide, of the correct geometry, may occupy the active site and restrict esterase activity.
Carvone- and Piperitone-Derived Allylic Stannanes and Aspects of Their Electrophilic Substitution
Authors: Young D , Jones M , Kitching W
Published: September 2010

cis - and trans- Carvotanacetols and - piperitols have been converted into the
corresponding allylic chlorides, which were made to react with both trimethyltinlithium and triphenyltinlithium . The resulting allylic stannanes were characterized by 1H, 13C and 119Sn n.m.r . spectroscopy, which permitted assignment of the relative configurations. Triphenyltinlithium appears to react in a (substantially) concerted fashion with the (optically active) chloride from the carvotanacetols yielding an optically active stannane . The corresponding trimethylstannane is optically inactive. Substitution reactions (SE′) with acid and sulfur dioxide (in chloroform) are preferentially γ-anti and specifically γ- syn respectively, in line with conclusions based on other cyclohex-2-enyl systems.
The Extraction of Cobalt(II) From Oxalate Solutions by Aliquat-336 Dissolved in Chloroform
Authors: Paimin R , Cattrall RW
Published: September 2010

A study is reported of the extraction of cobalt(II) from oxalate solutions by Aliquat 336 in chloroform. Equilibrium studies by two-phase titration show that the predominant organic-phase complex has the formula [(R3MeN)2Co(C2O4)2]. It is proposed that this species is formed by extraction of the anionic complex Co(C2O4)22- involving interfacial reactions. There is evidence for the formation of a small amount of the complex [(R3MeN)4Co(C2O4)3]. The extraction mechanism proposed is based on a study with the single-drop technique, and is supported by interfacial tension measurements and measurements with a stirred cell of constant interfacial area.
Olefin Oligomerization and Isomerization Catalysts. The Preparation, Properties and Catalytic Action of Dithio Nickel(II) Complexes With Chelating Phosphines
Authors: Cavell KJ , Masters AF
Published: September 2010

The syntheses and properties of cationic nickel complexes containing dithio-β-diketonate and chelating bisphosphine ligands of general formula [Ni{R1C(S)CR2C(S)R3}{(PL1L2)R(PL3L4)}]X(Rj,Lj = alkyl or aryl, R = (CH2)n, n = 1-4, X = halide, BPh4, PF6, etc.) are described. The compounds are shown to be effective catalysts for the oligomerization and double bond shift isomerization of olefins with a high specificity for dimeric products rich in desirable linear and near linear isomers.
The Rate-Constant for the Recombination of Methyl Radicals
Authors: Arthur NL , Biordi JC
Published: September 2010

Rate constants for the recombination of CH3 radicals have been measured by means of the rotating sector technique in the temperature range 373- 463 K, and at a pressure of 30 Torr . CH3 radicals were produced by the photolysis of acetone, and the experimental data were fitted to sector curves generated from Shepp's theory. The results give kb = (2.81�0.22)×1013 cm3 mol-1 s-1, which, under the chosen experimental conditions, is close to its high-pressure limiting value. A comparison is made with the other values of the rate constant reported in the literature, and a best value is suggested.
Critical-Points (Azeotropic Compositions) in Multicomponent Copolymerization
Authors: Moad G , Solomon DH , Spurling TH , Vearing DJ
Published: September 2010

The necessary and sufficient conditions for the existence of critical points ( azeotropic compositions) in multicomponent copolymerization are defined, and the preferred method for calculating critical points for a given set of reactivity ratios is provided. This method offers considerable advantages in both simplicity and computation speed over methods already in the literature. A computer program for performing the calculation on systems with up to 10 components is briefly described. Approximate probabilities for the existence of critical points in ternary and quaternary systems have been evaluated as a function of whether binary critical points exist for pairs of the monomers involved. These data show that, contrary to the widely held view, in systems of three or more components all rij > 1 or all rij < 1is neither a necessary nor a sufficient condition for the existence of a critical point. Those systems which always and those systems which never give rise to critical points are indicated.
Thermal-Degradation of Polymers. I. Integrity of Monomer Derived From Thermal-Degradation of Poly(Methyl Methacrylate) and Poly(Methacrylonitrile)
Authors: Hodder AN , Holland KA , Rae ID
Published: September 2010

A random copolymer of methyl methacrylate and its (D5)analogue has been used to show that thermal degradation of the polymer regenerates the original monomer units. A similar result has been obtained for poly( methacrylonitrile ). In each case, thermal degradation at 200° produced mainly the (D0)- and (D5)-species, while at higher temperatures some (D2)- and (D3)-ions were observed in the mass spectrum of the recovered monomer.
Synthesis and Analgesic Activity of C-3-Allyl( and 3-Propyl)-1,3-Dimethyl-4-Phenylpiperidin-R-4-Yl Propanoates
Authors: Bell KH , Hyne RV
Published: September 2010

c-3-Allyl-1,3-dimethyl-4-phenylpiperidin-r-4-yl propanoate ( li ) and the corresponding propyl derivative (1j) have been prepared and evaluated for analgetic activity. Compound (1i) shows very high potency which resides mostly in the (3R,4R)- enantiomer.
Activity-Coefficients of Some Quaternary Ammonium Salts in Chloroform
Authors: Paimin R , Cattrall RW
Published: September 2010

Activity coefficients for dioctyl-, di (1-ethyl-3-methylpentyl), dinonyl -, methyltridecyl - and methyltrioctyl -ammonium chlorides and for methyltridecylammonium oxalate in chloroform have been studied by vapour phase osmometry. The results show that, below c. 0.001 mol dm-3, activity coefficients can be assumed to be unity and can be assumed to be constant at concentrations greater than c. 0.04 mol dm-3. Conductance measurements show negligible dissociation of the salts in chloroform.
The Isomers of the Bis(Diethylenetriamine)Chromium(III) and Bis[Di(3-Aminopropyl)Amine]Chromium(III) Cations, [Cr(Dien)2]3+ and [Cr(Dpt)2]3+: Preparation and Characterization
Authors: Searle GH , House DA
Published: September 2010

Addition of dien in slight excess to CrCl3.6H2O
in Me2SO (which has been dehydrated at 190�C, then cooled to 170�) produces an isomeric mixture of orange-yellow [Cr( dien )2] Cl3.Me2SO of � approximate composition mer 70%; s- fac 30%; u- fac <2%. The isomers are partially separated by dissolving the mixture in 3M HCl and adding ZnCl2; pure lemon-yellow s- fac -[Cr( dien )2] (ZnCl5) then deposits. Addition of NaClO4 to the mother liquor results in the crystallizationof an orange-yellow mer/u-fac -[Cr( dien )2] (ClO4)3 (>98% mer ) mixture. All three isomers can be obtained as (Hg2Cl7)3- salts, suitable for single-crystal X-ray analysis, and the cation geometries have been established from these X-ray data. The mer and s- fac isomers are distinguished by their different labilities in acidic solution ( mer is relatively inert, s- fac decomposes rapidly), their different infrared and visible absorption spectra, and their different chromatographic behaviour on SP- Sephadex C-25. However, this latter technique failed to detect the u- fac form and was complicated by the facile decomposition of the s- fac isomer. The mer and s- fac forms isomerize rapidly in Me2SO and the equilibrium is largely towards the mer. [Cr( dpt )2]Cl3 [ dpt = di(3- aminopropyl )amine]
could be obtained only by direct reaction between anhydrous CrCl3 and dpt , and was subsequently precipitated as the iodide and perchlorate salts. These consisted entirely of the mer isomer, from their isomorphism with the corresponding mer -[Cr( dpt )2
]3+ salts. The six-membered rings in -[Cr( dien )2 ]3+ are considerably more resistant to hydrolytic decomposition than the rings in mer -[ cr ( dien )2]3+ and mer -[Co( dpt )2]3+.
Dimethylplatinum(IV) Complexes With Cyanide: Thermal and Photoassisted Substitution Reactions, and Characterization of Products by N.M.R.
Authors: Appleton TG , Hall JR , Williams MA
Published: September 2010

Reactions of cyanide with the dimethylplatinum (IV) complexes, [PtMe2(OH) (H20)1.5 n, [PtMe2Br2]n and fac-PtMe2Br(H2O)3+, have been studied, principally by 1H, 13C and 195Pt n.m.r. Cyanide rapidly displaces the ligands trans to the methyl groups. Subsequent reactions cis to the methyl groups occur more slowly with heating, or, for bromo complexes, on ultraviolet irradiation. These substitution reactions compete with reductive elimination of groups from the platinum(IV) compounds to produce platinum(II) products. All attempts to prepare solutions of fac-PtMe2(CN)(H2O)3+ were unsuccessful. Oxidative addition of ICN to cis-PtMe2( py )2 ( py = pyridine) gave PtMe2I(CN)( py )2, from which a solution of fac-PtMe2(CN)( MeOH )3+ in methanol could be obtained. Addition of water or aqueous acid to this solution gave a very insoluble precipitate of [PtMe2(CN)(OH)n. The cis and trans influences on Jpt -C and δC of the cyanide ligands have been evaluated.
A 13C N.M.R. Study of Some Oxygenated Hopane Triterpenes
Authors: Wilkins AL , Ronaldson KJ , Jager PM , Bird PW
Published: September 2010

Chemical shift assignments are reported for some hopane triterpenoids variously oxygenated at C3, C6, C7, C15, C22 and/or C24. Substituent group effects are compared and correlated with a local symmetry axis. Revisions to a recently reported interpretation of the 13C n.m.r. spectrum of 7β-acetoxyhopan-22-ol (1c) are described.
Steric and Stereoelectronic Effects in the Hydrogenolysis and Birch Reduction of Some Hindered Tertiary-Benzylic Carbinols
Authors: Collins DJ , Jacobs HA
Published: September 2010

3-(4'-Methoxyphenyllpentan-3-ol (3a) and 3-(4'-methoxypheny1)-2,4-dimethylpentan-3-ol (3b) underwent catalytic hydrogenolysis over 10% palladium/charcoal at moderate temperatures and pressures. The more hindered tertiary-benzylic carbinols 3-(4'-methoxypheny1)-2,2,4-trimethylpentan-3-ol (6), 3-(4'-methoxyphenyl)-2,2,4,4-tetramethylpentan-3-ol (3c), 1-(4'- methoxyphenyl )-2,2,6,6-tetramethylcyclohexan-l-ol (8) and 1-(1',1'-dimethylethy1)-6-methoxy- 2,2-dimethyl-l,2,3,4-tetrahydronaphthalen-1-ol (10) were completely resistant to hydrogenolysis, even under vigorous conditions. While the hindered tertiary-benzylic carbinols (6),(8) and (10) readily underwent Birch reduction, the analogous di-t-butyl anisyl carbinol (3c) was unchanged. The failure of (3c) to undergo Birch reduction is probably due to a hitherto unrecognized stereoelectronic effect: the C-OH bond of (3c) is constrained to lie more or less in the plane of the benzene ring, and addition of an electron to the benzene ring of the derived oxyanion (31) is inhibited in this conformation.
Lewis-Base Adducts of Main Group 1 Metal Compounds. IV. Synthesis and Structure of the XLiL3 System (X = Cl, Br, I, L = 4-t-Butylpyridine, and X = I, L = Quinoline)
Authors: Raston CL , Skelton BW , Whitaker CR , White AH
Published: September 2010

Complexes [XLiL3], X = Cl , Br, I; L = 4-t-butylpyridine, (1)-(3) have been synthesized by recrystallization of the anhydrous lithium halide from the parent base, and characterized structurally by single-crystal X-ray structure determination. (1) and (2) are isomorphous (monoclinic, P21), a ≈ 11.8, b ≈ 12.1, c ≈ 11.8 Ǻ, β 120°, Z 2 (R 0.051, 0.040 for No 1491, 1499 'observed' reflections); (3) is orthorhombic, Pbca, a 22.119(10), b 21.108(10), c 12.845(10) Ǻ, Z 8, R 0.067 for No 967. (1)- (3) are all pseudo- trigonal and contain four-coordinate XLiN3 arrays [Li-X, 2.33(1); 2.53(1); 2.76(4) Ǻ; Li-N, 2.03(1)-2.11(1); 2.04(1)-2.09(2); 2.03(4)-2.07(4)Ǻ]. Similar data are also recorded for X = I, L = quinoline (4)[monoclinic, P21/c, a 15.684(6), b 7.693(4), c 26.758(12) Ǻ,β 107.71(3)°, Z 4; R 0.072, No 3096; Li-I, 2.78(2); Li-N, 2.08(2)- 2.13(2)Ǻ]. While a close parallel may be drawn between the similarity of the chemistry of lithium(I) and copper(I) in respect of (1)-(3), (4) is unusual being the first XML3 derivative for a quinoline -type ligand; it is a monoquinoline solvate.
Preparation of 2-Isopropyloestradiol
Authors: Pert DJ , Ridley DD
Published: September 2010

A simple route to 2-alkyloestradiols is demonstrated by the conversion of oestradiol into its 2-isopropyl derivative.
Accessibility of Formally Six-Coordinate Ruthenium(IV) Complexes Generated by Electrochemical Oxidation of Ruthenium(II) Dimethylglyoxime and Related Complexes Containing Phosphorus, Nitrogen or Oxygen Donor Axial Ligands
Authors: Bond AM , Khalifa M
Published: September 2010

The chemistry of higher valent ruthenium(IV) complexes has attracted considerable attention because of its possible relevance in catalytic processes and the fact that analogous iron complexes may be biologically important. In this work a range of RuII (N4)(X)(Y) complexes (N4 = nitrogen-based macrocycle or related ligand ; X, Y = axial ligands) has been prepared. It is shown that the presence of macrocyclic type ligands and suitable axial ligands leads to readily accessible six coordinate formally ruthenium(IV) complexes on the voltammetric time scale as ascertained by studies at platinum, gold, glassy carbon and mercury electrodes. Thus, dimethylgloxime complexes RuII ( dmgH )2(PPh3)2 and other complexes containing non- oxidizable macrocyclic type ligands readily undergo two chemically and electrochemically reversible one-electron oxidation processes to produce six coordinate ruthenium(III) and ruthenium(IV) complexes. The ruthenium(III) species are moderately stable on the synthetic time scale at ordinary temperature, whereas -78°C is required to generate low concentrations of the formally ruthenium(IV) complexes with a
limited range of complexes. When the axial phosphine ligands are replaced by nitrogen and oxygen donors (N-methylimidazole , dimethyl sulfoxide , pyridine, etc.), the stability of the six-coordinate ruthenium(IV) complexes are significantly lowered as evidenced by the more complex voltammetry for the ruthenium(III)/(IV) oxidation process. Similarly, replacement of the (N4) macrocyclic type system by (N-O)2 (e.g. quinolin-8-ol as ligand ) lowers the stability of the ruthenium(IV) complexes. When the macrocyclic type ligand can itself be oxidized (e.g. benzoquinone dioxime as a ligand) four electrons can be transferred reversibly. In this case the oxidation processes are not readily assigned in terms of formal oxidation states although ruthenium(IV) still appears to be an accessible oxidation state. Electrochemical oxidation of the iron complexes, Fe( dmgH)2(P(Obu)3)2 and Fe(Pc)(P( OBu ),3)2 (Pc = phthalocyanine ), also produces two reversible one-electron oxidation processes, confirming that information derived from the more kinetically inert ruthenium systems may be applied to related iron systems on the voltammetric time scale and that macrocyclic type ligands
stabilize both high oxidation state formally ruthenium(IV) and iron(IV) oxidation states.
Applications of 95Mo N.M.R. Spectroscopy. XVIII. Relaxation Times, Quadrupole Coupling Constants and Partial Field Gradients in [Mo(CO)5L] Complexes
Authors: Brownlee RTC , Shehan BP , Wedd AG
Published: September 2010

A study of ,95Mo spin-lattice relaxation times (T1) and linewidths of [Mo(CO)5L] complexes, where L = PPh3, AsPh3, SbPh3, pyridine and Cl-, has shown that the relaxation times are due entirely to the quadrupolar mechanism, with no scalar coupling contribution to linewidth where molybdenum is bonded to a quadrupolar nucleus. Based on the literature value of the quadrupole coupling constant obtained by n.q.r . for the PPh3 complex (1.972 MHz), the quadrupole coupling constants of the arsine and stibine complexes are determined to be 3.36 and 3.75 MHz respectively. These values, and that of the pyridine complex (2.80 MHz), are found to correlate with ligand partial field gradient parameters obtained from Mossbauer spectra of FeII complexes, and are rationalized in terms of metal- ligand bonding interactions. For Et4N [Mo(CO)5Cl], the correlation is very poor; this result is attributed to the effects of ion in solution.
Molecular Topology of 1,2-Substituted (E) and (Z)-1,2-Di(9-anthryl)ethenes
Authors: Becker HD , Hansen L , Skelton BW , White AH
Published: September 2010

Single-crystal X-ray structure determinations have been carried out on six derivatives of (E)- and (Z)-1,2-di(9-anthryl) ethenes in which the central carbon-carbon double bond is additionally substituted, establishing the molecular topology in terms of the angles between the planes of the anthryl moieties and the plane of the central ethene bond. In general terms, substitution increases the torsion angle about the anthryl-ethene single bond by up to approximately 30°, so that the anthryl and ethene planes lie virtually orthogonal.
The Entry of Free Radicals Into Polystyrene Latex Particles
Authors: Adams ME , Trau M , Gilbert RG , Napper DH , Sangster DF
Published: September 2010

Mechanistic understanding of the processes governing the kinetics of emulsion polymerization has both scientific and technical interest. One component of this process that is poorly understood at present is that of free radical entry into latex particles. Measurements were made of the entry rate coefficient as a function of temperature for free radicals entering polystyrene latex particles in seeded emulsion polymerizations initiated by γ-rays. The activation energy for entry was found to be less than 24�3 kJ mol-1, consistent with entry being controlled by a physical (e.g., diffusional ) rather than a chemical process. Measurement of the entry rate coefficient as a function of the γ-ray dose rate suggested that the factors that determine the entry rate when the primary free radicals are uncharged are similar to those that determine the entry rate for charged free radicals derived from chemical initiation by peroxydisulfate. This result was consistent with measurements of the entry rate coefficient of charged free radicals derived from peroxydisulfate; these data were found to be virtually independent of both the extent of the latex surface coverage by the anionic surfactant sodium dodecyl sulfate and the ionic strength of the continuous phase. The data refute several proposals given in the literature for the rate-determining step for entry, being inconsistent with control by (1) collision of free radicals with the latex particles, (2) surfactant desorption , and (3) an electrostatic barrier arising from the colloidal nature of the entering free radical. The origin of the activation energy for entry remains obscure.
Solvation of Fluoride Ions. II. Enthalpies and Entropies of Transfer From Water to Aqueous Methanol
Authors: Hefter GT , Mclay PJ
Published: September 2010

Enthalpies of transfer of potassium fluoride from water to water-methanol mixtures over the whole composition range have been determined by calorimetry. Combination of these values with literature data has enabled calculation of the enthalpies and entropies of transfer for the individual ions through the tetraphenylarsonium tetrapbenylborate ( tatb ) assumption. The values of ΔtH°(F-) and ΔtS°(F-) show a complex dependence on solvent composition which closely parallels the dependence of the other halide ions. These effects are discussed in terms of ion-solvent and solvent-solvent interactions. The halide ions appear to be (weakly) preferentially solvated by H2O, and the alkali metal ions by MeOH.
Transoid Homoallylic Proton-Proton Coupling Constants
Authors: Barfield M , Spear RJ , Sternhell S
Published: September 2010

Transoid homoallylic coupling constants (5JH,H) for six compounds (5,10-dihydroindeno[2,1-alindene and confertifolin derivatives) of fixed stereochemistry were determined and compared with calculated values. Magnetic equivalence limited discrete determination of 5Jtrans and 5Jcis to three of these compounds. The single compound where unequivocal assignment could be made revealed 5Jtrans > 5Jcis; this was supported in two other compounds by tentative assignment. Changes in the magnitude of the couplings suggested that substantial substituent effects may be operative. INDO-MO calculations correctly predicted the angular dependence but incorrectly predicted 5Jcis > 5Jtrans.
Micellar Catalysis of Organic Reactions. XXVI. SNAr Reactions of Azide Ions
Authors: Broxton TJ , Christie JR , Chung RPT
Published: September 2010

The azidodehalogenation of a number of aromatic compounds has been studied in the presence of micelles of cetyltrimethylammonium bromide (ctab). The variation of the observed rate of reaction with ctab concentration has been treated by using the model of Rodenas and Vera to determine the rate constant for reaction in the micellar pseudo-phase, k2m, the binding constant of the substrate to the micelle, Ks, and the nucleophile-micellar counter ion exchange constant KAzBr :. The ratio of the rate constants in the micellar pseudo-phase and in water varied between 0.9 and 52. For reactions involving the production of a dianionic intermediate the largest catalysis was found for compounds containing two nitro groups to stabilize the double negative charge. In addition significant differences in the catalysis were found between compounds having the reaction centre at the micelle-water interface and those for which the reaction centre was more buried inside the micelle. As previously reported the resulting aryl azides undergo cyclization to form a benzofuroxan if a nitro group is located ortho to the azide group. Furthermore, a reversible photochemical reaction was detected for two compounds having a carboxylate group ortho to the azide group.
Photooxidation of m-Phenoxytoluene at Colloidal Titanium Dioxide/Non-Aqueous Solution Interfaces
Authors: Blatt E , Furlong DN , Mau AWH , Sasse WHF , Wells D
Published: September 2010

The selective photooxidation of m- phenoxytoluene to m-phenoxybenzaldehyde has been investigated in the system m-phenoxytoluene/O2/titanium dioxide/non-aqueous solvent/light. In acetonitrile the conversion was found to be c. 20% with starting concentrations of m-phenoxytoluene in the range 0.05-0.5 mol dm-3. Adsorption of m-phenoxytoluene, m-phenoxybenzaldehyde or the intermediate product m-phenoxybenzyl alcohol from acetonitrile on titanium dioxide was not detectable by an equilibration/centrifugation/supernatant analysis technique. Photoemission and photoexcitation measurements, however, showed that m- phenoxytoluene and m-phenoxybenzyl alcohol, but not m-phenoxybenzaldehyde , formed charge-transfer complexes with titanium dioxide surfaces. The selectivity of the photooxidation is explained in terms of pathways involving these charge-transfer complexes.
Early Stages of the Hydrolysis of Chromium(III) in Aqueous Solution. V. Measurement of the Equilibrium Between Singly and Doubly Bridged Dimer
Authors: Merakis T , Spiccia L
Published: September 2010

Ion-exchange chromatography has been used to measure the equilibrium between singly bridged (SBD) and doubly bridged (DBD) forms of the hydrolytic dimer of chromium(III), at variable [H+] (0.008-0.97 M) and T (288.2-318.2 K) and constant I (1.0 M). From these measurements, the acid dissociation constant, Kal , for SBD, and the equilibrium constant, K, for interconversion between monodeprotonated SBD and DBD have been determined together with their corresponding thermodynamic constants. The results at 298.2K were as follows: K = 10.1( �0.6) [ΔH� = -10( �3) kJ mol-1 and ΔS�=-15( �9) J K-1 mol-1]; KKal = 1 .83(�0.04) mol dm-3 [ΔS� = 30(�1) kJ mol-1 and ΔS�= 104(�4) J K-1 mol-1]; Kal = 0.18( �0.2) mol dm-3 [ΔS�= 43(�4) kJ mol-l and ΔS�= 128(�13) J K-1 mol-1]. The high Kalis attributed to the participation of monodeprotonated SBD in hydrogen bonding. As the temperature increases, the overall equilibrium (given by KKal ) is driven towards DBD by a dramatic increase in the acidity ( Kal ) of SBD, an increase which more than offsets a concurrent decrease in K.
A New Furanosesterpene From the Marine Sponge Psammocinia rugosa
Authors: Liokas V , Garson MJ , Carver JA
Published: September 2010

A tetronic acid (5), 5-[13-(furan-3-yl)-2,6,10-trimethyltrideca-2,6,8-trienyl]-4-hydroxy 3-methylfuran-2(5H)-one,* with weak antimicrobial activity has been isolated from the sponge Psammocinia sp. and characterized by analysis of 1H and 13C n.m.r. data including 'H-1H correlation (COSY) experiments. The compound may be identical to a tetronic acid isolated by the Roche group, previously assigned structure (3).
Ritter Reactions. I. Combined Intramolecular Cyclization and Amide Formation
Authors: Amin i , Bishop R , Burgess G , Craig DC , Dance IG , Scudder ML
Published: September 2010

1,5-Dimethylenecyclooctane (5) and 7,11-dimethylene-6,7,8,9-tetrahydro-5,9-propano-5H-benzocycloheptene (7) undergo efficient intramolecular cyclization and Ritter reaction in a one-flask procedure. Similarly,11-methylene-5,6,8,9-tetrahydro-5,9-propano-7H-benzocyclohepten-7-one (10) may be converted into cyclic hydroxy amide products. Alternatively, a combined intramolecular cyclization and double Ritter reaction with acetonitrile can be carried out to produce 7,9-bis( acetamido )-6,7,8,9,10,11-hexahydro-5,9:7,11-dimethano-5H-benzocyclononene monohydrate (12) whose crystal structure (C19 H24 N2 O2 H2O,P21/ca = 10.477(l), b = 14.595(1), c = 14.493(l) �, β =127.900(3)�, Z= 4) was determined with a final R = 0.039. Hydrogen-bonded dimeric units of the bis(amide) are surrounded by six water molecules which are involved in three different hydrogen-bonded arrangements. Mixed bis(amide) products may also be produced from (10) via the hydroxy amide, demonstrating that the bis(amide)(12) results from sequential Ritter reactions.
Some Chemistry of Pentakis(methoxycarbonyl)cyclopentadiene, HC5(CO2Me)5, and Related Molecules
Authors: Bruce MI , White AH
Published: September 2010

This article summarizes the results of investigations into the chemistry of HC5(CO2Me)5 and, in particular, of metal complexes containing the C5(CO2Me)5 ligand . As an anion, the ligand is very stable, forming air-stable, water-soluble salts with many cations with coordination to the metal atom in the solid state generally occurring through the ester carbonyl groups. Second- and third-row transition metals form complexes which retain the covalent ligand-metal bond in solution, 'harder' metals coordinating by the ester carbonyl groups, while 'softer' metals are bound to the ring carbons; a variety of behaviour is shown by the Group 11 metals. Even when the ligand is η5-bonded to the metal, ready displacement by other ligands may occur, as found with Ru (η-C5H5){η5-C5(CO2Me)5}, for example. In the rhodium system, formal replacement of CO2Me groups by hydrogen is found, as with the formation of [ Rh {η5-C5H2(CO2Me)3}2][C5(CO2Me)5]. Brief mention is made of other polysubstituted cyclopentadienyls with electron-withdrawing ligands and some related compounds, and their metal derivatives where known.
Alkyl Substituent Effects in Diamagnetic Dithiocarbamate Cobalt(III) and Nickel(II) Complexes
Authors: Healy PC , Connor JW , Skelton BW , White AH
Published: September 2010

Single-crystal X-ray structure determinations have been recorded at 295 K for the tris(dithiocarbamato)cobalt(III) compounds: [Co(S2CN(CH2)4)3], [Co(S2CNEt2)3] (redeterminations), [Co(S2CN(CH2Ph)2)3], and [Co(S2CNPri2)3] at 120 and 295 K. [Co(S2CN(CH2)4)3] crystallizes in the space group C2/c with a 28.984(15), b 14.416(2), c 16.206(15)Ǻ, β 104.20(5)°, Z 12; [Co(S2CNEt2)3] also crystallizes in space group C2/c with a 14.097(3), b 10.305(2), c 17.070(7)Ǻ, β 110.19(3)°, Z 4; [Co(S2CN(CH2Ph)2)3] crystallizes in space group P21 with a 11.851(6), b 29.920(8), c 12.395(3)Ǻ, β 97.74(4)°; [Co(S2CNPri2)3] crystallizes in space group R3c with a 13.367(6)Ǻ, α 58.04(2)° (295 K); a 13.155(6)Ǻ, α 58.59(3)° (120 K), Z 2. The structure of [Ni(S2CNPri2)2] has been redetermined, the complex crystallizing in the space group P21/c with a 8.147(2), b 17.820(3), c 15.630(3)Ǻ, β 110.32(2)°, Z 4. The results obtained from this study support the hypothesis, put forward by Ymen and Stahl, that the influence of aliphatic hydrocarbon substituents on the ligand-field strength at the sulfur atoms of the dithiocarbamate ligand is not through the π bonding network of the conjugated S2CN moiety, but, rather, intraligand S…H-C interactions which increase with increasing bulk of the substituent atoms. Unlike the free anion systems, or the iron(III) complexes, however, the changes in the S-C-S angles with increasing field strength, while observable, are very small.
C-Terminal Sequencing of Peptides: An Investigation of the Iminohydantoin Method
Authors: Bentley JD , Maclaren JA
Published: September 2010

A method for the C-terminal sequencing of peptides was briefly outlined at a conference in 1975, but no further results have been reported since. This method converts the carboxy group into an acyl-S-alkylisothioureide, which on treatment with base reportedly gives the acylcyanamide. Following cyclization and hydrolysis, the iminohydantoin corresponding to the C-terminal residue is formed. Thus the peptide chain is shortened by one residue at each cycle. Using model peptides, we have prepared authentic samples of the supposed products at each step, and have shown that the acylcyanamide is not an intermediate in this reaction. With glycine as the C-terminal residue, the iminohydantoin is obtained in near-quantitative yield.
Synthesis and Molecular Structure of Stable Derivatives of (E)- and (Z)-Dehydrophenylalanine
Authors: Easton CJ , Hutton CA , Roselt PD , Tiekink ERT
Published: September 2010

Bromination of the phenylalanine derivative (1) affords the bromides (2) and (3), which react by stereospecific anti-elimination to give the isomeric pair of stable dehydrophenylalanine derivatives (4) and (5). The molecular structures of (4)and (5), which have been determined by X-ray crystallographic analysis, correlate with their lack of interconversion and the unusual stability of (5).
The Two-Step Hydrolysis of Dimethoxo(tetraphenylporphyrinato)tin(IV)
Authors: Lin HJ , Lin HJ , Chen JH , Chen JH , Hwang LP , Hwang LP
Published: September 2010

The hydrolysis of dimethoxo ( tetraphenylporphyrinato )tin(IV), Sn ( tpp )( OMe )2 was studied by n.m.r. spectroscopy. The use of specially dehydrated CDCl3 allowed the hydrolysis intermediate hydroxomethoxo (tetraphenylporphyrinato )tin(IV) Sn ( tpp )( OMe )(OH), to be identified. The results show that the second step, of the two-step hydrolysis, is rate limiting.
Molecular Cocrystals of Carboxylic-Acids. V. The Crystal-Structures of (2-Carboxy-phenoxy)acetic Acid and Its 1 : 1 Adduct With 4-Aminobenzoic Acid
Authors: Byriel KA , Lynch DE , Smith G , Kennard CHL
Published: September 2010

The crystal structures of (2-carboxyphenoxy)acetic acid (cpaa) (1) and its 1 : 1 adduct [( cpaa )(4-aba)] (2) with 4-aminobenzoic acid have been determined by X-ray diffraction and refined to residuals R 0.077, (1), and 0.051, (2), for 783 and 1062 observed reflections, respectively. The dicarboxylic acid (1) is extended into a one-dimensional zig-zag polymer by hydrogen bonding through the two acid groups [O…O, 2.67(1)Ǻ]. The adduct (2) represents the first example of a phenoxyalkanoic involved in a hetero-dimer association through the conventional cyclic hydrogen-bonding system [O…O, 2.54, 2.68(1)Ǻ]. The 2-carboxy group is also weakly hydrogen bonded to the 4-amino group of (4-aba) [O…N, 2.99(1)Ǻ], and in both (1) and (2) it has an intramolecular hydrogen bond to the ether oxygen of the oxyacetic acid side chain.
Dna-Binding Compounds. IV. Synthesis and Solution Conformation of a Novel Macrocyle Formed by Coupling of the Side-Chains of Adjacent L-Lysine Residues
Authors: Bray AM , Kelly DP , Lim TK
Published: September 2010

The novel macrocyclic dilysine derivatives (8S,11S)-11-t-butoxycarbonylamino-2,10-dioxo-1,3,9-triazacyclopentadecane-8-carboxylic acid methyl (5) and t-butyl (6) esters were prepared by coupling of the є-amino groups of adjacent lysine residues of the esters of Boc-Lys-Lys-OR with 1,1′-carbonyldiimidazole under mild conditions. The conformation of (6) in dimethyl sulfoxide solution was determined by the use of a variety of one- and two-dimensional n.m.r. techniques.
Influence of Protonation Exothermicity on Gas-Phase Concurrent Dealkylation and Isomerization of p-Cymene
Authors: Perez G , Possagno E , Lilla E
Published: September 2010

The gas-phase protonation is reported of p-cymene (p- isopropyltoluene ) by different radiolytically formed protonating agents (O2H+, N2H+, CH5+, COH+). The characteristics of the reactions vary with the protonation exothermicity . Both dealkylation and isomerization are observed with O2H+ or N2H+ ions. Only dealkylation occurs when the protonating agent is the CH5+ ion. Formation of products is not observed when the less energetic COH+ ions are employed. The results show that in the competition between isomerization and dealkylation the dealkylation reaction becomes favoured as the protonation exothermicity decreases.