Oxidative cyclization of 2-pyrrolidinyl-acetamide and 2-pyrrolidinyl-propionamide local anaesthetics

2 - Pyrrolidinyl - acetamide and -propionamide local anaesthetics (1a–d) on oxidation with mercuric acetate, potassium hexacyanoferrate(III) and potassium permanganate underwent oxidative cyclization to give new bicyclic compounds, hexahydro - 1H - pyrrolo[1,2 - a]imidazolin - 2 - ones (2a–d). The propionamides (1c–d) yielded mixtures of the two possible diastereoisomers of 2c and 2d. These were separated; in solution and above their melting points they epimerized via ring opening and reclosure between the 7a-carbon and 1-nitrogen atoms.     

Characterisation of River Po particles by sedimentation field-flow fractionation coupled to GFAAS and ICP-MS

A procedure for elemental composition determination of water-borne river particles (Po River) on both size-fractionated and unfractionated submicron particles (0.1–1 μm) by graphite furnace atomic absorption spectroscopy (GFAAS) and inductively coupled plasma-mass spectrometry (ICP-MS) is reported. Sample fractionation was performed using sedimentation field-flow fractionation (SdFFF). The distribution of relative mass vs. particle size was determined using UV detection. Fractions were collected over a narrow size range for scanning electron microscopy. With this combination of techniques the mass, elemental composition, and shape distributions can be obtained across the size spectrum of the sample.

The size distributions of the major elements (Al, Fe) were determined by coupling both GFAAS and ICP-MS techniques to the SdFFF. The procedure was validated using a reference clay sample. Satisfactory agreement was found between both the GFAAS and ICP-MS aluminium signal and the UV detector signal. Some discrepancies were observed in the Fe/Al ratios when comparing GFAAS and ICP-MS. Thus further investigation is in order to fully assess the role of SdFFF-ICP-MS and SdFFF-GFAAS techniques for elemental characterisation of aquatic colloids. Both GFAAS and ICP-MS signals unambiguously indicate a significantly higher Fe content in the lower size range, which is consistent with previous investigations.

Trace element levels in unfractionated Po River particles, determined by both GFAAS and ICP-MS, show good agreement. The high levels of Cu, Pb, Cr and Cd found associated with the colloidal particles underlines the significance of the environmental role played by the suspended matter in rivers in both highly industrialised and intensively cultivated areas.     

The Interaction of Benzyl Alcohol with Trimethoxyboroxine : Amine Adducts of Triarylboroxines as Model Compounds

The interaction of benzyl alcohol with trimethoxyboroxine has been investigated by hydrogen-1 and carbon-13 NMR and IR spectroscopy. These techniques indicate formation of a weak Lewis acid/base adduct, additionally stabilized by a hydrogen-bonding interaction, which undergoes rapid ligand exchange at room temperature. The system has been modelled by the synthesis and characterization of a series of amine-triarylboroxine adducts. These adducts rapidly undergo ligand dissociation-recombination in solution with ΔG⁺ of ca. 40-50 kJ/mol.     

Preparation,crystal and molecular structure of,and NMR parameters for,the exopolyhedral heterocyclic platinaundecaborane [μ-2,7-(SCSNEt2)-7-(PMe2Ph)-NIDO-7-PtB10H11]

The compound [μ-2,7-(SCSNEt₂)-7-(PMe₂Ph)-nido-7-PtB₁₀H₁₁] has been obtained in a yield of 52% from the reaction of [7,7-(PMe₂Ph)-nido-7-PtB₁₀H₁₂] and [AuBr₂(S₂CNEt₂)], and identified by single crystal X-ray diffraction analysis and multi-element single and double resonance NMR spectroscopy. The yellow-orange compound crystallizes in the monoclinic space group P2₁/n with a 1179.2(2), b = 1244.9(5), c = 1641.4(2) pm, β = 95.45(1)°, Z = 4, and the structure (R 0.0209, R_w = 0.0211 for 3719 observed reflections) is that of a nido-7-platinaundecaborane with an exopolyhedral N,N-diethyldithiocarbamate ligand bridging the Pt(7) and B(2) positions to give a $\text{-Pt-B-C-S-}$ five-membered ring. The tetrahapto platinum-to-borane bonding has a considerable twist distortion relative to other nido-7-platinaundecaboranes which do not possess this cyclic feature. The NMR parameters exhibit no anomalies and are consistent with the crystal molecular structure. A plot of δ(¹¹B) vs δ(¹H) for directly bound exo-terminal hydrogen atoms shows good correlation with the slope 16 : 1.     

Tetraphenylboroxinate(1-) salts of monoborate cations: Synthesis and single-crystal X-ray structures of [Ph2B{OCH2CH2N(Me)(CH2)n}2][Ph4B3O3] (n = 4, 5)

The salts, [Ph₂B{OCH₂CH₂N(Me)(CH₂)_n}₂][Ph₄B₃O₃] (n = 4, 5), were prepared in moderate yields in MeOH solution from reaction of Ph₂BOBPh₂ with [N(CH₂)_n(Me)(CH₂CH₂OH)][OH] and PhB(OH)₂ in a 1:2:4 ratio. The reactions also lead to Ph₃B₃O₃. Both salts were characterized by NMR (¹H, ¹³C, ¹¹B) IR, and single-crystal XRD studies. The salts are comprised of cationic monoborates (zwitterionic, 2N⁺ and 1B⁻) and tetraphenylboroxinate anions.     

An NMR thermometer for cryogenic magic-angle spinning NMR: the spin-lattice relaxation of (127)I in cesium iodide

The accurate temperature measurement of solid samples under magic-angle spinning (MAS) is difficult in the cryogenic regime. It has been demonstrated by Thurber et al. (J. Magn. Reson., 196 (2009) 84-87) [10] that the temperature dependent spin-lattice relaxation time constant of ⁷⁹Br in KBr powder can be useful for measuring sample temperature under MAS over a wide temperature range (20–296 K). However the value of T₁ exceeds 3 min at temperatures below 20 K, which is inconveniently long. In this communication, we show that the spin-lattice relaxation time constant of ¹²⁷I in CsI powder can be used to accurately measure sample temperature under MAS within a reasonable experimental time down to 10 K.     

A low-cost light-scattering detector for the flow-injection nephelometric determination of sulfate.

A simple low-cost flow-through light-scattering detector was developed for determining the particle mass concentration in colloidal suspensions. Employing a laser pointer as a light source and a photodiode IC as a light sensor, the detector was shown to have good sensitivity, yet was small and battery operated. The detector was demonstrated to be effective for the flow-injection nephelometric determination of sulfate by precipitation as barium sulfate.     

Templated heptaborate and pentaborate salts of cyclo-alkylammonium cations: structural and thermal properties

The synthesis and characterization of a series of cyclo-alkylammonium pentaborate salts {[cyclo-C(n)H(2n-1)NR(3)][B(5)O(6)(OH)(4)] (R = H, n = 3, 5-7 (1-4); R = Me, n = 6 (5))} are reported. Compounds 1, 2 and 5 have been further characterized by single-crystal XRD studies. Attempted recrystallization of 3 and 4 yielded small crops of the unexpected heptaborate salts, [cyclo-C(6)H(11)NH(3)](2)[B(7)O(9)(OH)(5)]·3H(2)O·B(OH)(3) (6) and [cyclo-C(7)H(13)NH(3)](2)[B(7)O(9)(OH)(5)]·2H(2)O·2B(OH)(3) (7) which were also characterized crystallographically. All compounds show extensive supramolecular H-bonded anionic lattices templated by the cations. H-bond interactions are described in detail. TGA-DSC analysis of the pentaborates 1-5 showed that they thermally decomposed in air at 800 °C to 2.5B(2)O(3), in a 2 step process involving dehydration (<250 °C) and oxidative decomposition (250-600 °C). BET analysis of materials derived from the pentaborates had internal porosities of <1 m(2) g(-1).