A New Synthesis of Aromatic and Heteroaromatic Nitrogen Mustards Via 3-Pyrrolines

Reaction of aromatic and heteroaromatic halides with 3-pyrroline gives adducts which can be converted in a three-step process to nitrogen mustards.     

The relationship between nanobubbles and the hydrophobic force

The formation of nanobubbles on hydrophobic self-assembled monolayers has been examined in a binary ethanol/water titration using small angle X-ray scattering (SAXS) and atomic force microscopy (AFM). The AFM data demonstrates a localized force effect attributed to nanobubbles on an immersed hydrophobic surface. This evidence is arguably compromised by the possibility that the AFM tip actually nucleates nanobubbles. As a complementary noninvasive technique, SAXS has been used to investigate the interfacial region of the immersed hydrophobic surface. SAXS measurements reveal an electron density depletion layer at the hydrophobic interface, with changing air solubility in the immersing liquid, due to the formation of nanobubbles.     

Solubility Measurements of Crystalline Cu<Subscript>2</Subscript>O in Aqueous Solution as a Function of Temperature and pH

The equilibrium solubility of crystalline cuprous oxide, cuprite, was measured in liquid water and steam using two flow-through reactors and a conventional batch autoclave. These measurements were carried out from 20 to 400 °C. Different batches of pretreated cuprite were thoroughly characterized prior to and following each set of experiments. Metallic copper beads were added to the inlet end of the reactors and to the solid charge in the autoclave to preserve the Cu(I) oxidation state, although one series of experiments produced some results which were only compatible with CuO(cr) as the solubility limiting phase. Comparison of the solubility data for Cu₂O(cr) in aqueous solution with those from the only available high-temperature dataset (Var’yash, Geochem. Int. 26:80–90, 1989) showed that in near-neutral solutions the new data are lower by about four orders of magnitude at 350 °C. Moreover, the dominant species in solution at temperatures ≥100 °C were found to be only Cu⁺ and Cu(OH)₂^-\mathrm{Cu(OH)}_{2}^{-} with Cu(OH)⁰ occurring over a narrow pH range at ≤75 °C rather than the reverse trend reported previously. Solubility equations were developed as a function of temperature and pH, based on these new results, which showed increased solubility with temperature in acidic and basic solutions. The solubility of Cu₂O(cr) in steam decreased slightly with temperature and as expected increased with increasing pressure to supercritical conditions where limited, compatible data were available in the literature. The solubility at subcritical conditions was on the order of one to several parts per billion, ppb. A simple empirical fit was derived for the solubility in steam as a function of temperature and pressure.     

Retention behavior and selectivity of a latex nanoparticle pseudostationary phase for electrokinetic chromatography

The retention characteristics and separation selectivity of a novel latex nanoparticle (NP) pseudostationary phase (PSP) for electrokinetic chromatography have been characterized. The anionic NPs have very low or no affinity for cationic solutes, but show significant interactions and retention based on hydrophobic interactions. Retention factors of alkyl-phenyl ketones increase linearly with the concentration of the NPs and have zero or near zero y-intercepts as expected for electrokinetic chromatography with non-micellar PSPs. The retention factors of these solutes and representative pharmaceuticals decrease logarithmically with increases in the concentration of ACN in the background electrolyte, as expected for reversed-phase retention. Linear solvation energy relationship analysis indicates that the NPs are less cohesive than would be expected for polymeric PSPs with similar structure but that the overall separation selectivity can be expected to be similar to polymer PSPs with similar backbone chemistry. The results indicate that the hydrophobic core of the NPs is non-cohesive and is highly accessible to solutes, whereas the ionic head groups are not as accessible and do not contribute substantially to retention or selectivity.     

Nonlinearity and time-resolved studies of ion emission in ultrafast laser ablation of graphite

We have investigated the laser fluence dependence of the ion emission process in ultrafast laser ablation of graphite using a time-of-flight technique. Two regimes of ion emission have been identified: (1) a highly nonlinear laser absorption process accompanied by generation of a transient electrical field on the surface and collisionless emission of ions due to electrostatic repulsion; (2) a saturation regime for laser power absorption characterised by nearly equal kinetic energy of ejected carbon clusters. We also show the effect of the surface temperature on the emitted clusters’ stability and the influence of nonlinearity on the intensity autocorrelation traces.     

Protein conformational flexibility prediction using machine learning

Using a data set of 16 proteins, a neural network has been trained to predict backbone 15N generalized order parameters from the three-dimensional structures of proteins. The final network parameterization contains six input features. The average prediction accuracy, as measured by the Pearson's correlation coefficient between experimental and predicted values of the square of the generalized order parameter is >0.70. Predicted order parameters for non-terminal amino acid residues depends most strongly on the local packing density and the probability that the residue is located in regular secondary structure.     

Raman spectroscopy of gallium‐based hydrotalcites of formula Mg6Ga2(CO3)(OH)16· 4H2O

Insight into the unique structure of hydrotalcites has been obtained using Raman spectroscopy. Gallium‐containing hydrotalcites of formula Mg₄Ga₂(CO₃)(OH)₁₂· 4H₂O (2:1 Ga‐HT) to Mg₈Ga₂(CO₃)(OH)₂₀· 4H₂O (4:1 Ga‐HT) have been successfully synthesized and characterized by X‐ray diffraction and Raman spectroscopy. The d(003) spacing varied from 7.83 Å for the 2:1 hydrotalcite to 8.15 Å for the 3:1 gallium‐containing hydrotalcite. Raman spectroscopy complemented with selected infrared data has been used to characterize the synthesized gallium‐containing hydrotalcites of formula Mg₆Ga₂(CO₃)(OH)₁₆· 4H₂O. Raman bands observed at around 1046, 1048 and 1058 cm⁻¹ are attributed to the symmetric stretching modes of the CO₃²⁻ units. Multiple ν₃ CO₃²⁻ antisymmetric stretching modes are found at around 1346, 1378, 1446, 1464 and 1494 cm⁻¹. The splitting of this mode indicates that the carbonate anion is in a perturbed state. Raman bands observed at 710 and 717 cm⁻¹ assigned to the ν₄ (CO₃²⁻) modes support the concept of multiple carbonate species in the interlayer. Copyright © 2009 John Wiley & Sons, Ltd.     

Vibrational spectroscopy and crystal structure analysis of two polymorphs of the di‐amino acid peptide cyclo(L‐Glu‐L‐Glu)

Cyclo(L ‐Glu‐L ‐Glu) has been crystallised in two different polymorphic forms. Both polymorphs are monoclinic, but form 1 is in space group P2₁ and form 2 is in space group C2. Raman scattering and FT‐IR spectroscopic studies have been conducted for the N,O‐protonated and deuterated derivatives. Raman spectra of orientated single crystals, solid‐state and aqueous solution samples have also been recorded. The different hydrogen‐bonding patterns for the two polymorphs have the greatest effect on vibrational modes with N H and CO stretching character. DFT (B3‐LYP/cc‐pVDZ) calculations of the isolated cyclo(L ‐Glu‐L ‐Glu) molecule predict that the minimum energy structure, assuming C₂ symmetry, has a boat conformation for the diketopiperazine ring with the two L ‐Glu side chains being folded above the ring. The calculated geometry is in good agreement with the X‐ray crystallographic structures for both polymorphs. Normal coordinate analysis has facilitated the band assignments for the experimental vibrational spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

ChemInform Abstract: Copper(I) and Copper(II) Coordination Structure under Hydrothermal Conditions at 325 °C: An X‐Ray Absorption Fine Structure and Molecular Dynamics Study.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Crystal structure of 4-(2-hydroxyethyl)-4-aza-5α-androstan-17β-ol “HS-478”

The crystal structure of HS-478 (aqueous solvate) has been determined by direct method and refined by block diagonal least squares to R₀ = 0.043. The intensity was measured in a four-circle diffractometer in the ω/2θ scanning mode, CuKα radiation. The crystals are triclinic P1, a = 6.721(3), b = 66.532(3), c = 12.188(5) Å, α = 96.86(2)°, β = 82.82(2)°, and γ = 114.68(2)°. Rings A, B, C are chair whereas ring D is envelope. Rings A/B and B/C are trans fused, whereas rings C/D are quasi trans. The hydroxyethyl side chain connected to N(4) has conformation of (−t, t).