A deuterium nuclear quadrupole double resonance study of the ferroelectric phase transition in potassium dihydrogen phosphate

A study has been made of the nuclear quadrupole double resonance (NQDR) spectrum of deuterium in a powdered sample of potassium dihydrogen phosphate, KH₂PO₄ or KDP for short, both as a function of temperature and of percentage deuteration. Double transitions have also been observed and these enable the orientation of the ferroelectric electric field gradient (EFG) tensor to be determined.     

Immobilization of amyloglucosidase onto granular chicken bone

Amyloglucosidase was immobilized onto granular chicken bone (BIOBONE?) by noncovalent interactions. The amount of activity bound relative to an equal amount of free enzyme was 13.6 ?0.4%. The estimated specific activity for amyloglucosidase decreased from 75.3?0.8 to 43.5 ?9.6 U/mg protein upon immobilization. TheKm value of the bone-immobilized enzyme using glycogen as substrate increased from 3.04?0.38 mg/mL (free) to 9.04? 1.51 mg/mL (immobilized), butKm showed no change upon immobilization when starches were used as substrates. A decrease in V_max values occurred upon enzyme immobilization for all substrates, but this largely reflected the percentage of enzyme initially bound to the bone. Immobilization also improved enzyme stability in the presence of various additives (e.g., detergent, KC1, and ethanol) or under low or high pH reaction conditions. Bound amyloglucosidase maintained high activity (>90%) following five cycles of continuous use at moderate (23 ?C) and high (55?C) temperatures. Data derived from Lineweaver-Burk and Arrhenius plots indicated that substrate and product diffusion limitation were minimal.     

Influence of a silyl group on an allylic position. A theoretical approach

Allylsilanes show in certain cases a behaviour towards electrophiles which is opposite to that of its carbon homologues. Theoretical calculations using Dewar's MINDO/3 method performed on 3-methyl 3-butenyl trimethylsilane and 2-methyl 2-butene show that geometrical optimization leads to a silicon-allylic carbon bond nearly parallel to the double bond π cloud, and both net atomic charges and HOMO coefficients indicate an inversion between these two substrates.     

Assignments for vibrational spectra of 700 benzene derivatives,volumes 1 and 2 : G. Varsanyi,Adam Hilger,London, 1974, pp. 668, price £25.00 (volumes 1 and 2 as a set)

Force constants and normal coordinates are reported for the spiropentane molecule. These data are based on the recently determined fundamental vibration frequencies of spiropentane-H₈.The results have been used to predict the fundamentals of spiropentane-D₈, to calculate the centrifugal distortion parameters, in particular the parameter r₆, which is non-zero for molecules with a four-fold axis of rotation and to calculate thermodynamic parameters. Good agreement is observed between the calorimetric vapour heat capacity of spiropentane and the value based on our assignments for the fundamental vibrations of spiropentane.The transferability of the cyclopropane force field has been tested and shown to be valid for predicting the deformations of the methylene groups of spiropentane.     

Utilisation des mélanges H2O+H2SO4+SO3 en tant que solvants: I. Étude du ferrocène et de quelques hydrocarbures polynucléaires dans les mélanges H2O+H2SO4. Comparaison des domaines d'électroactivité

The variation of the electroactivity range with composition of water+ sulphuric acid mixtures has been studied. It is shown that ferrocene provides a reference potential independent of solvent at low H₂SO₄ contents while polynuclear hydrocarbons fulfill the same function at high H₂SO₄ contents. Water+H₂SO₄ mixtures become more oxidizing (reduction limit) and less reducing (oxidation limit) when the H₂SO₄ concentration increases.     

The pyrolysis of trimethylgermane and trimethylsilane

The number of products and the H₂/CH₄ ratio obtained from the flow pyrolyses of (CH₃)₃GeH and (CH₃)₃SiH were very different. The (CH₃)₃GeH decomposition is consistent with the following mechanism:

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The pyrolysis of (CH₃)₃SiH was found to be much more complex, presumably due to the formation of silicon-carbon double bonded intermediates and the (CH₃)₂Si(H)CH₂ radical. We also present data which supports the presence of a H atom chain sequence during this pyrolysis.     

Preparation and oxidation of 3-methylene-, 3-Oxo- and 3-hydroxy-bicyclo[2,2,1]heptane-2, 6-carbolactones

3-methylenebicyclo[2,2,1]heptane-2,6-carbolactone (previously incorrectly claimed) has now been prepared and converted to the 3-oxo-lactone. Some 3-hydroxy-bicyclo-[2,2,1]heptane-2,6-carbolactones have been prepared and their rates of oxidation with chromic acid determined. The results do not support a theory about the mechanism of oxidation, involving a dipolar interaction from the lactone.     

Zusammenh?nge zwischen Koordination und polarographischem Verhalten unterschiedlicher Alizarin S-Chelate

Zusammenfassung Alizarin S und seine 11-Metallchelate lassen sich an der Quecksilbertropfelektrode reduzieren. Aus der Beeinflussung der diffusionskontrollierten und der Adsorptionsstufe durch die Chelatbildung lassen sich Aussagen über die Konstitution und Ladung der adsorbierten Chelate machen: Beryllium wird in peri-, Aluminium und Gallium werden in ortho-Stellung des Alizarinmoleküls gebunden. Die 11-Chelate des Be und Al sind ungeladen. Das Ga-Chelat ist negativ geladen und enthält offensichtlich zusätzliche anionische Liganden.Wir danken der Deutschen Forschungsgemeinschaft, Bonn-Bad Godesberg, dem Minister für Wissenschaft und Forschung des Landes Nordrhein-Westfalen, Landesamt für Forschung, sowie dem Verband der Chemischen Industrie, Fonds der Chemie, für Sachbeihilfen.     

Etude structurale de combinaisons sulfurees et seleniees du molybdene. II. Structure cristalline de Ni0,33Mo3Se4

The crystals of Ni_0,33Mo₃Se₄, are triclinic, space group $\text{P}\text{1}$, with two formula units in a cell: a = 6,727 (9) Å, b = 6,582 (11) Å, c = 6,751 (6) Å, α = 90.61° (10), β = 92.17° (10), γ = 90.98° (12.) The structure was solved by analogy with Mo₃Se₄ and refined by a full-matrix least squares program to R = 0,093 for 822 independent reflexions. The channels present in Mo₃Se₄ are occupied by Ni so that Ni_0,33Mo₃Se₄ is always a metallic compound.     

Marine adhesives. IV: Hexosamine content of Balanus eburneus adhesive

The adhesive secreted by the barnacle, Balanus eburneus, has been demonstrated to contain two hexosamines, glucosamine and galactosamine. Degradation of the hexosamines during hydrolysis of the adhesive appears to be the reason why previous studies of the adhesive have indicated the absence of hexosamines, or the presence of only one hexosamine.