Favorskii rearrangement of α,β-epoxy ketones

Reactions of α,β-epoxy ketones with nucleophilic bases generally take one of two courses: (1) α-displacement followed by β-elimination of water or (2) Favorskii rearrangement via a cyclopropanone or zwitterion intermediate. Among the factors that appear to control these reactions, it is suspected that an α′-substituent effect may operate. Such an effect has been confirmed by observing the conversion of 3,5,5,6 - tetramethyl - 2,3 - epoxycyclohexanone (1) to the ring-contracted γ-lactone 3, together with other Favorskii rearrangement products, on treatment with refluxing methanolic potassium hydroxide. The α′-methyl substituted steroid 2 under similar reaction conditions was transformed into roughly equal amounts of 4, 5 and 4 (all rationalized by a Favorskii-like mechanism). In each case the analogous epoxy ketone lacking an α′-Me substituent failed to give any Favorskii products.     

Emulsion copolymerization behavior of α-methylstyrene with methacrylonitrile

The emulsion copolymerization behavior of α-methylstyrene with methacrylonitrile is described. The effects of polymerization temperature, potassium persulfate initiator concentration, sodium lauryl sulfate emulsifier concentration on copolymer yield, molecular weight, and rate of copolymerization are described. The copolymer was found to have an azeotropic composition at 43 mole-% AMS. Reactivity ratios were determined to be 0.06 and 0.28 for AMS and MAN, respectively.     

Mass spectrometric methods for the analysis of chlorinated and nitrated isoflavonoids: a novel class of biological metabolites

Electrospray ionization combined with tandem mass spectrometry was applied to a study of some representative chlorinated and nitrated isoflavones-potential metabolites of isoflavones in inflammatory cells. Upon collision-induced dissociation of deprotonated [M - H](-) ions of these compounds, a number of structurally characteristic product ions were produced. The product ion analysis of 3'- and 8-chlorodaidzein in the tandom mass spectra led to ready differentiation of these isomers. 3-Nitro derivatives of both genistein and daidzein have product ions due to the losses of HNO(2) and two OH groups. Chlorinated derivatives of isoflavones were detected in cell-based experiments and their structures were proposed by comparing the tandem mass spectra of their product ions with those of standards. This work provides a suitable analytical basis to aid the characterization of chlorinated and nitrated metabolites in studies in vivo and in vitro.     

Graphite rod atomization and atomic fluorescence for the simultaneous determination of silver and copper in jet engine oils

S-Methyldithizone(5-methylmercapto-1,5-diphenylformazan) reacts with the chlorides of copper(II), mercury(II) and phenylmercury(II) to give the 1:1 chelates [CuCl(MeDz), HgCl(MeDz) and C₆H₅Hg(MeDz)] and with nickel(II) and palladium(II) to give the 1:2 chelates, M(MeDz)₂. All these complexes are intensely coloured in chloroform solution. No complexes are formed from cobalt(II), manganese(II) or zinc(II) or from the nitrates or acetates of copper and mercury. Coordination increases the reactivity of the sulphur atom in dithizone. Whereas dithizone is unaffected by methyl iodide, nickel dithizonate, Ni(HDz)₂, gives Ni-(MeDz)₂ when heated with methyl iodide in ethanol in the presence of sodium acetate; palladium dithizonate behaves similarly. The 1:1 adduct of nickel dithizonate with 2,2'-bipyridyl gave only Ni(MeDz)₂ on treatment with methyl iodide, and this complex would not form an adduct with bipyridyl. On standing in the light, Ni(MeDz)₂ reacted photochemically to give the yellow isomer of S-methyl-dithizone.     

Reversed-phase ion-pair liquid chromatography of the angiotensins

The isocratic reversed-phase liquid chromatography of the angiotensins and a number of their synthetic analogues is described. Complete separation of 10 out of 12 peptides was achieved through a solvent optimization strategy with a total analysis time of about 20 min. The retention behavior of the angiotensins studied was described in terms of the hydrophobic contribution of their amino acid residues; there was good correlation between predicted and experimental retention for those peptides that were retained by a common mechanism. However, because ion-pair chromatography was required for good peak symmetry, retention was substantially modulated by the presence of acidic and basic residues. The limit of detection of these peptides was 3-5 pmol by UV absorbance at 214 nm. For those peptides containing a primary amino group the detection limit was improved by two orders of magnitude by fluorogenic derivatization with naphthalene-2,3-dicarboxaldehyde/cyanide to the corresponding N-substituted 1-cyanobenz[f]isoindole (CBI) derivatives. The contribution of the CBI ring system to retention was also investigated.     

Formation of fluorinated nonionic surfactant microemulsions in hydrofluorocarbon 134a (HFC 134a)

A structurally related series of fluorinated nonionic oxyethylene glycol surfactants of the type C(m)F(2m+1)(CH(2))(n)O[(CH(2)CH(2)O)(p)H], denoted C(m.n)E(p) (where m=4, 6, or 7, m=1 or 2, and p=4 or 6) were synthesized and their surface behavior in aqueous solution was characterized. The ability of these surfactants to form water-in-hydrofluorocarbon (HFC) propellant 134a microemulsions suitable for use in the aerosolized delivery of water-soluble drugs has been investigated. Phase studies showed that, regardless of the composition used, clear one-phase systems could not be prepared if a fluorinated nonionic surfactant was used alone, or in combination with a short or medium fluorocarbon alcohol cosurfactant. Clear one-phase systems could, however, be prepared if a short-chain hydrocarbon alcohol, such as ethanol, n-propanol, or n-pentanol, was used as cosurfactant, with the extent of the one-phase region increasing with decreased chain length of the alcohol cosurfactant. Light-scattering studies on a number of the hydrocarbon-alcoholcontaining systems in the propellant-rich part of the phase diagram showed that only systems prepared with C(4.2)E(6) and propanol contained microemulsion droplets (all other systems investigated were considered to be cosolvent systems).     

Determination of antimony in rain water at the nanogram level with surfactant and brilliant green

A new, simple, selective and sensitive method for the spectrophotometric determination of antimony in rain water is described. It includes preconcentrating Sb with surfactants (i.e. cetylpyridinium chloride (CPC) and Triton X-100 (TX-100)) into toluene and allowing the extract to react with a dye, i.e. brilliant green (BG). The value of apparent molar absorptivity is 5.55 × 10⁵ L-mol^–1· cm^–1 at λ_max = 620 nm; the detection limit is 3 ng/mL Sb in rain water at 3-fold preconcentration.     

The synthesis and conformational analysis of tetrahydro-1,2,4-oxadiazines

The synthesis and variable temperature ¹H and ¹³C NMR spectra of three tetrahydro-1,2,4-oxadiazines are reported. The N(4)-Me inversion barriers are 6.8–7.0 (ax→ts) and 7.4–7.9 kcal mol^?1 (eq→ts) with ΔG° 0.6–0.9 kcal mol^?1. The N(2)-Me inversion barriers are 10.4–11.4 (ax→ts) and 11.6–13.1 kcal mol^?1 (eq→ts) with ΔGδ 1.2–1.7 kcal mol^?1. The barrier to ring inversion is ca. 12.7 kcal mol^?1. “R value” analysis shows the ring to have a 56.5±2δ dihedral angle about the C(5)-(6) bond, indicative of the expected chair conformation.     

Quantitative Determination of Eugenol from Cinnamomum tamala Nees and Eberm. Leaf Powder and Polyherbal Formulation Using Reverse Phase Liquid Chromatography

A simple, rapid and precise reverse-phase high performance liquid chromatographic method has been developed for the quantitative determination of eugenol from the extract of dried powder of Cinnamomum tamala leaves and its polyherbal formulation. Chromatographic analysis was carried out on Zorbax C₁₈ column (150 mm × 4.6 mm, 5 μm) with a mobile phase of mixture of water, acetonitrile and methanol in the volume ratio of 50:40:10, at a flow rate of 1.0 mL min^-1. Quantitation was performed using a UV-visible detector at 210 nm. Good linearity was obtained over the ranges of 0.20–3.0 μg mL^-1 for eugenol.