Ab initio Structure Determination of [(Dimethylamino)methylene]bis[phosphonic Acid] Dihydrate from X-Ray Powder Diffraction Data: Comparison with the Corresponding Monohydrate and Unhydrated Form

The structure of [(dimethylamino)methylene]bis[phosphonic acid] dihydrate (C₃H₁₁NO₆P₂⋅2 H₂O; 1 ) was solved ab initio from synchrotron powder X-ray diffraction data. The structure determination was based on direct methods combined with difference Fourier techniques, and the refinement was carried out using the Rietveld method. Using this high-quality diffraction pattern, it was possible to index a second phase which corresponds to the structure of the known [(dimethylamino)methylene]bis[phosphonic acid] monohydrate ( 2 ). [(Dimethylamino)methylene]bis[phosphonic acid] dihydrate ( 1 ) is monoclinic, space group P2₁/c, Z=4, with a=10.6644(1), b=9.1599(1), c=10.5213(1) Å, and β=98.353(1)°. The structure analysis indicates two non-equivalent P-atoms in the molecule of 1 which are also observed in the corresponding monohydrate 2 and unhydrated form 3 . All three compounds exhibit extended H-bonding networks which result in remarkably different ³¹P-NMR spectra. The [(dimethylamino)methylene]bis[phosphonic acids] 1 – 3 crystallize in the betaine-type structure which, therefore, contains two nonequivalent P-atoms. The −P(=O)(OH)₂ and −P(=O)(OH)O⁻ groups of 1 – 3 are involved in a number of strong H-bonds which can be characterized by the different ³¹P-NMR chemical shifts of the two P-atoms of 1 – 3 .     

Synthesis of Tricyclic Ketones with Sesquiterpene Skeletons by Acid-Catalyzed Rearrangement of β-Monocyclofarnesol

Starting from dihydro-β-ionone ( 6 ) a mixture of three tricyclic ketones with sesquiterpene skeletons 14 , 15 , and 16 was prepared by Wittig-Horner reaction with triethyl phosphonoacetate, Red-Al^® reduction, acid-catalyzed rearrangement of the resulting β-monocyclofarnesol ( 7 ), alkaline hydrolysis of the formates 8 – 10 , and subsequent molybdenium-catalyzed oxidation. The mechanistic background of the acid-catalyzed rearrangement of β-monocyclofarnesol ( 7 ) is discussed in detail. The resulting tricyclic ketones 14 – 16 exhibit intense woody odor notes with peppery vetiver or camphoraceous cedarwood aspects.     

High-rate and high-density gas separation adsorbents and manufacturing method

High-rate and high-density gas separation adsorbents used in vacuum pressure swing adsorption (VPSA) processes are described. Agglomerated zeolite Li–LSX compositions made using colloidal silica binding agents and having improved nitrogen pore diffusivity compared to like compositions prepared with traditional clay binders, are also described. Preparation methods for the colloidal silica-bound adsorbents are described together with their characterization by mercury (Hg) porosimetry, scanning electron microscopy (SEM) and low dead-volume breakthrough testing, from which the pore diffusivity is obtained. In this article, we show how the location and dispersion of the colloidal silica binding agent within the agglomerated zeolite particle yields pore-architectures that resemble “state-of-the-art” binderless adsorbents. In addition, we use VPSA process simulations to show that the best process performance is achieved by the combination of high-rate and high-density adsorbent properties.     

Conversions between ordered and disordered cellulose. Effects of mechanical treatment followed by cyclic wetting and drying

An investigation into the effects of mechanical treatment and hydration on the order of cellulose substrates (microcrystalline cellulose and Cladophora cellulose) was performed by the use of ball milling followed by cyclic wetting and drying. The results, monitored by¹³C-CP/MAS NMR-spectroscopy, were evaluated by calculation of the crystallinity indices and principal component analysis of the NMR data acquired. The results showed that a large part of the disorder induced by the mechanical treatment of cellulose by ball milling is reversible and reordering upon hydration leads to the cellulose I form initially present. The C4 signals corresponding to the reversibly disordered cellulose chains are observed in the amorphous region between 79 and 86 ppm in the¹³C-CP/MAS NMR-spectra together with signals from cellulose chains on the surface of ordered regions. The peak cluster which contains the C2, C3 and C5 ring carbons can be divided into two specific spectral regions; one between 74 and 77 ppm largely originates from ring carbons within disordered cellulose structures, and one between 70 and 74 ppm contains larger contributions from ordered cellulose. The behaviour of the celluloses upon milling is in accordance with a concept of ordered cellulose fibrils containing amorphous cellulose mainly as surface layers and induced reversible lattice distortions.     

Synthesis of the Deuterium Labeled Isoflavone-<Emphasis Type="Italic">O</Emphasis>-glucoside 8,3′,5′-D<Subscript>3</Subscript>-Daidzin

The regio- and stereospecific glycosylation of 8,3′,5′-trideuterodaidzein 1 with α-acetobromoglucose to provide 8,3′,5′-trideuterodaidzein-7-O-β-glucopyranoside 2 is presented.     

Infrared and Raman spectral interpretations of the ferroelectric phases of NaH3(SeO3)2 and NaD3(SeO3)2

The infrared and Raman spectra of NaH₃(SeO₃)₂ and NaD₃(SeO₃)₂ have been recorded from 24 to 300°K. The interpretation, assignments, and analysis of the spectral studies are presented on the paraelectric α phase (proton disordered), ferroelectric β phase (proton ordered) and ferroelectric γ phase (proton ordered). A discussion of a newly proposed proton-triggered phase transition mechanism and a possible origin of the hydrogen-bonded OH stretching region of KH₂PO₄-type ferroelectrics is given.     

Synthesis of [4.2]cyclophanes

Vinyl $\text{p}$-xylylene cross-dimerizes with other xylylene-type intermediates to yield cycloadducts of the [8+6] and [6+6] type. This reaction provides a simple entry to the [4.2]paracyclophane system as well as the analogous [4.2]cyclophanes containing furan and pyrrole moieties.     

Sesquiterpenoids—27: X-ray crystallographic analysis of istanbulin-B,A 1-oxo-eremophilenolide

The stereochemistry of istanbulin-B has been defined by X-ray crystal-structure analysis. Rings A and B are transfused, with the Me groups at C(4) and C(5) cis. The α,β-unsaturated,γ -lactone ring is essentially planar. Crystals of istanbulin-B are orthorhombic, space group P2₁2₁,2₁, with a = 6.729(2), b = 13.447(3), c = 14.721(3)Â,and Z = 4. The crystal structure was determined by direct phasing and the atomic parameters were subsequently adjusted by least-squares calculations that converged at R 38% over 1179 diffractometer |F_a| values     

Determination of avermectins in plasma at nanogram levels using high-performance liquid chromatography with flourescence detection

An analytical method is described for the determination of the avermectins in plasma based upon high-performance liquid chromatography of flourescent derivatives of these compounds. The analyte is isolated by adsorption chromatography on Florisil, dehydrated in an acetic anhydride-pyridine mixture, and the fluorophore is further separated by chromatorgraphy on silica gel in advance of introduction into a reversed-phase system. This method, which can be applied to samples containing as little as 0.2 ng drug per ml, has an accuracy of 5% mean relative error and a precision of 8% relative standard deviation. A study and discussion of several factors which affect the analytical reaction are included.     

A direct method for the substitution of imidazo[1,5-a]pyridines at position 5

3-Ethylthioimidazo[1,5-a]pyridine lithiates at carbon 5. Quenching of the anion with an electrophile followed by desulphurisation gives 5-substituted imidazo[1,5-a]pyridines.