Naphtho[1,2-c:5,6-c]difuran: a reactive linker and cyclophane precursor

Naphtho[1,2-c:5,6-c]difuran has been isolated in a 9-step synthesis from 2,6-dimethylnaphthalene. It is a highly reactive diene similar in nature to the related isobenzofuran. In Diels-Alder reactions, its intermediate monoadducts are actually less reactive that the parent difuran making possible sequential Diels-Alder reactions with different dienophiles. Reaction with a tethered bis(dienophile) leads to the production of a naphthalenic cyclophane.     

Use of S-pentafluorophenyl tris(2,4,6-trimethoxyphenyl)phosphonium acetate bromide and (4-hydrazino-4-oxobutyl) [tris(2,4,6-trimethoxyphenyl)phosphonium bromide for the derivatization of alcohols,aldehydes and ketones for detection by liquid chromatography/electrospray mass spectrometry

The synthesis of S-pentafluorophenyl tris(2,4,6-trimethoxyphenyl)phosphonium acetate bromide (TMPP-AcPFP) and the novel compound (4-hydrazino-4-oxobutyl) [tris(2,4,6-trimethoxyphenyl)phosphonium bromide (TMPP-PrG) is described and the use of these compounds as derivatizing reagents for alcohols, aldehydes and ketones evaluated. Methods have been developed for the pre-column derivatization of alcohols using TMPP-AcPFP and for aldehydes and ketones using TMPP-PrG. The reactions were investigated by the use of a variety of individual test compounds containing the target functional groups. The TMPP acetyl ester and TMPP propyl hydrazone derivatives formed with their respective target analytes produced an enhanced response in electrospray ionization mass spectrometry (ESI-MS), and reproducible chromatography. The use of these two reagents to derivatize and facilitate detection of alcohols (including sugars and steroids), aldehydes and ketones (including steroids) by LC/ESI-MS was investigated.     

Biotreatment of produced water for removal of sulfides,organics, and toxicity

Applied Biochemistry and Biotechnology - Water coproduced with petroleum may contain sulfides and organic constituents that give the water an aquatic toxicity preventing surface discharge. A...     

The hydrolysis of bromodifluoromethyltriphenylphosphonium bromide [1]

Hydrolysis of [Ph₃$\text{P}\text{+}$CF₂Br]Br^? afforded a high yield of bromodifluoromethane and triphenylphosphine oxide. Hydrolysis in the presence of a radioactive isotope of bromine or sodium iodide gave unequivocal evidence that the mechanism for this reaction proceeds through a difluorocarbene intermediate.     

Factors influencing the atomization of vanadium in graphite furnace AAS

We have made the determination of V conform to the requirements of the modern (stabilized temperature) furnace technology where the integrated absorbance (A·s) signals are used to quantitate analyte volatilized into a chamber whose temperature is relatively constant during the period when the analyte peak is measured. Graphite tubes with good pyrolytic coating and fast (maximum power) heating are required. We explored the advantages of specially designed tubes, of a cool-down procedure between the char and atomization steps and of very thin platforms. We found that Mg(NO₃)₂ was advantageous as a matrix modifier. With these conditions we found no problems with several matrices reported by earlier workers to be troublesome, for example HNO₃, phosphate, Fe, Mg and Ca. However metals that form very refractory carbides, such as La, Mo, W and Zr may remain troublesome for V, probably because mixed carbides result which include VC. A group of geological samples was analysed for V. Our recommendation is the use of wall atomization from tubes with good pyrolytic coatings, Mg(NO₃)₂ as a matrix modifier and the cool-down procedure to establish a nearly constant temperature along the tube.     

Regiochemistry of the metal-halogen exchange induced cyclization of ω-iodoepoxides

The regiochemistry of the cyclization reations of some ω-lithioepoxides as a function of chain length and substitution pattern has been examined. Striking changes in regiochemistry have been observed in the presence of certain Lewis acids and metal halides.     

A Short Existence Proof for Correlation Dimension

The Grassberger–Hentschel–Procaccia correlation dimension has been put on a rigorous basis by Pesin and Tempelman. We simplify their proof that this dimension is given in terms of the measure of neighborhoods of the diagonal.     

Graphite-tube effects on perchloric acid interferences on aluminum and thallium in the stabilized-temperature platform furnace

The determination of aluminum in the presence of perchloric acid is shown to depend upon the quality of the pyrolytic coating of furnace tubes. With new pyrolytically coated tubes, no interference was found from 0.5 M HClO₄ on 0.5 ng Al and no decrease in signal or deterioration of the pyrolytic coating was found after more than 150 firings. Very little interference was found in the determination of thallium in perchloric acid. In both cases the literature reported severe interferences. The determination of thallium and aluminum in perchloric acid appears to be more sensitive to the quality of the pyrolytic graphite coating than any of the materials studied previously here.     

The reactions of [Fe2(η-Cp)2(CNAr)4] complexes with halogens and tin(II) halides

Summary [Fe₂(-Cp)₂(CNAr)₄] (2) (540-01, C₆H₄Me-2, C₆H₄Et-2, C₆H₃Me₂-2,4, C₆H₃Me₂-2,6, C₆H₃(Me)Et-2,6, C₆H₃Et₂-2,6 or C₆H₃ i-Pr₂-2,6) react with I₂ to give [Fe(-Cp)(CNAr)₂I], but with Br₂[Fe(-Cp) (CNAr)₃]⁺ salts are the only products; IBr gives a mixture of the two. With SnX₂ (X = F, Cl, Br or I) in refluxing n-butanol, (2) gives isolable [{Fe(-Cp)(CNAr)₂}₂SnX₂] only when the CNAr ligands have two ortho substituents, otherwise decomposition occurred. When X = F, [Fe(-Cp) (CNAr)₂SnF₃] was also obtained from this reaction. Attempts to prepare [Fe(-Cp)(CNAr)₂X] (X = Cl or Br) by reaction of (2) with HX in the presence of air gave rather unstable products which with SnX₂ formed [Fe(-C₅H₅)-(CNAr)₂SnX₃]. Similar compounds, [Fe(-Cp) (CNAr)₂ SnX₂I], were obtained from [Fe(-Cp)-(CNAr)₂I] and SnX₂ (X = Cl or Br but not I). All of these complexes are much less stable than their Fe(-Cp)(CO)₂ counterparts; all decompose in solution to [Fe(-Cp)(CNAr)₃]⁺ which then break down to unidentified species. X-ray diffraction studies show that in [Fe(-Cp)(CNC₆H₃-i-Pr₂-2,6)₂I] and [{Fe(-Cp)(CNC₆H₃Me₂-2,6)₂}₂SnBr₂] there is pseudo-octahedral coordination about Fe. In the latter there is also distorted tetrahedral coordination about Sn so that its structure is very similar to that of [{Fe(-Cp)(CO)₂}₂SnCl₂]. Spectroscopic studies show that in all complexes rotation of the aryl rings of the CNAr ligands cannot be slowed in solution, and that there is free rotation about all 540-02 bonds.