Synthesis of an asymmetric fullerene dimer via sequential cycloadditions

A single isomer of a monofunctionalised C₇₀ fullerene is isolated and characterised using variable temperature NMR spectroscopy. Pendant methylene bromide groups allow for further cycloaddition reactions and a C₆₀-C₇₀ asymmetric fullerene dimer is thus prepared.     

Nonlinear dynamics of charged particles interacting with combined ac-dc electromagnetic fields

A nonlinear Lorenz model describing interactions between charged particles and combined ac-dc electromagnetic fields is studied for various combinations of frequencies, field strengths and relative angle (θ) between the ac and dc magnetic fields. Strong directional effects on the magnitude and location of resonant particle motion are observed when θ is varied and the regular resonance windows in the aligned field (θ = 0) and linear version of the model studied previously by Durney etaal., break up to form irregular and less well pronounced regions of large and small particle displacements when nonlinearities are taken into account. The length of time takne to achieve resonant behaviour also becomes larger and more variable when nonlinearities are present. The possible relevance of these effects to interactions between electromagnetic fields and biological media is briefly discussed.     

The observation of a large gauche preference when 2-fluoroethylamine and 2-fluoroethanol become protonated

The energies of the gauche and anti conformers of 2-fluoroethylamine, 2-fluoroethanol and their protonated analogues are calculated using density functional theory. Unlike the non protonated systems, the protonated systems show a strong gauche effect where the C-F and the C-(+)NH(3) or C-F and C-(+)OH(2) bonds are gauche rather than anti to each other. Single crystal X-ray diffraction studies of 2-fluoroethylammonium compounds identify the same conformational preference.     

Structural and rate studies of the 1,2-additions of lithium phenylacetylide to lithiated quinazolinones: influence of mixed aggregates on the reaction mechanism

The 1,2-addition of lithium phenylacetylide (PhCCLi) to quinazolinones was investigated using a combination of structural and rate studies. (6)Li, (13)C, and (19)F NMR spectroscopies show that deprotonation of quinazolinones and phenylacetylene in THF/pentane solutions with lithium hexamethyldisilazide affords a mixture of lithium quinazolinide/PhCCLi mixed dimer and mixed tetramer along with PhCCLi dimer. Although the mixed tetramer dominates at high mixed aggregate concentrations and low temperatures used for the structural studies, the mixed dimer is the dominant form at the low total mixed aggregate concentrations, high THF concentrations, and ambient temperatures used to investigate the 1,2-addition. Monitoring the reaction rates using (19)F NMR spectroscopy revealed a first-order dependence on mixed dimer, a zeroth-order dependence on THF, and a half-order dependence on the PhCCLi concentration. The rate law is consistent with the addition of a disolvated PhCCLi monomer to the mixed dimer. Investigation of the 1,2-addition of PhCCLi to an O-protected quinazolinone implicates reaction via trisolvated PhCCLi monomers.     

Optical rotatory dispersion studies—CIV Low-temperature circular dichroism behavior of various chromophoric derivatives of alcohols and amines

The low-temperature circular dichroism behavior of various cyclic and alicyclic systems containing the methyl xanthato-, N,N-diethyl-N′-acylthioureyl-, N-phthalimido-, nitrito- and dithio-carbalkoxy- chromophores is discussed. Rotational strength (R₀^T) values are reported where possible and changes in this parameter upon variation of the temperature are interpreted, where relevant, in terms of the degree of steric inhibition to free rotation about the various bonds connected to the asymmetric center bearing (or nearest to) the chromophore moiety.     

Synthesis of a short-chain fullerene dimer

The synthesis of a short-chain fullerene dimer via bifunctional cycloaddition is demonstrated. A mono-functionalised C₆₀ species is isolated, and has the potential for further organic functionalisation.     

Application of tandem analyser to SIMS studies of hydrocarbon polymers

The fragmentation of ions sputtered from the surface of low-density poly(ethylene) (LDPE) has been investigated by studying their collisionally activated dissociation (CAD) when incident upon a variety of target gases in the collision cell of a triple quadrupole SIMS instrument. It was found that heavier targets resulted in more extensive CAD than was observed with lighter targets but that sulphur hexafluoride is inefficient target because of the amount opf energy that is transferred to its vibrational modes of motion (rather than being available to induce fragmentation in the parent ion.) The behaviour observed for an oxygen target was quite different to that observed for other targets (at higher pressures). In general oxygen induced markedly greater fragmentation for the small parent ions but xenon was the preferred target for the larger parent ions. Fragmentation patterns could readily be assembled for all of the parent ions observed in the SIMS spectrum of LDPE using the CAD data. There are good indications that the data obtained may assist in indentification of ion structures and in elucidation of general rules governing the fragmentation of organic materials during SIMS. For example, LDPE fragment ions were found to obey quite strictly the Even Electron Rule, a well-known rule in mass spectrometry.     

Chemistry of the podocarpaceae—IV Constituents of the heartwood of Podocarpus dacrydioides A. Rich

The extractives of the heartwood of Podocarpus dacrydioides A. Rich. contain the known diterpenoid constituents, podocarpic acid (I, R = H), methyl podocarpate (I, R = CH₃), ferruginol (II), Δ⁹-dehydro-ferruginol (III), sugiol (9-ketoferruginol, IV), xanthoperol (V) (in trace amount) and a new resin acid, C₂₀H₂₈O₅, for which the name pododacric acid is proposed. A saturated hydrocarbon also isolated is probably n-heptacosane.