Propellanes—XXXI : The diels-alder reaction of [4.4.2]propellanes with 4-phenyl-1,2,4-triazoline-3,5-dione

Attack of a number of [4.4.2]propellanes by the dienophile named in the title occurs, when one equivalent of dienophile is used, for the direction anti- to the 4-membered ring.     

31P NMR spectroscopy in the quality control and authentication of extra-virgin olive oil: a review of recent progress

This review is a brief account on the application of a novel methodology to the quality control and authentication of extra-virgin olive oil. This methodology is based on the derivatization of the labile hydrogens of functional groups, such as hydroxyl and carboxyl groups, of olive oil constituents with the phosphorus reagent 2-chloro-4,4,5,5-tetramethyldioxaphospholane, and the use of the (31)P chemical shifts to identify the phosphitylated compounds. Various experimental aspects such as pertinent instrumentation, sample preparation, acquisition parameters and properties of the phosphorus reagent are reviewed. The strategy to assign the (31)P signals of the phosphitylated model compounds and olive oil constituents by employing 1D and 2D NMR experiments is presented. Finally, the capability of this technique to assess the quality and the genuineness of extra-virgin olive oil and to detect fraud is discussed.     

Non-Kramers' behavior of the chain local dynamics of PVC in dilute solution. Carbon-13 NMR relaxation study

Carbon-13 spin-lattice, spin-spin relaxation times, and NOE values were measured as a function of temperature at two magnetic fields for poly(vinyl chloride) (PVC) in three solvents: chloroform, dioxane, and dimethyl sulfoxide. The relaxation data were interpreted in terms of chain local motions by using the bimodal time-correlation function of the Dejean-Laupretre-Monnerie (DLM) model. Using this model, the correlation times obtained in this study, as well as those from an earlier study in dibutyl phthalate and 1,1,2,2-tetrachloroethane did not follow a linear relationship with solvent viscosity. Instead, the chain local dynamics showed a 0.60 power dependence on solvent viscosity, indicating that PVC deviates from the hydrodynamic Kramers' theory. © 1997 John Wiley & Sons, Inc.     

On the feasibility of applying capture–recapture experiments for web evolution estimations

This paper proposes a novel application for estimating the size and evolution of web page populations, based on the capture–recapture methodology, which is mainly used in wildlife biological studies. Firstly, we present the necessary modifications and amendments needed for the web capture–recapture paradigm, and then we discuss the limitations confronted. The paper provides the implementation details of the proposed web capture recapture model along with its initial assessment. The anticipated outcome was to examine whether we can conduct capture–recapture experiments on the web (or a web sub-universe such as an Internet search engine directory), in order to further estimate evolution rates in web page populations.     

Detection of refined olive oil adulteration with refined hazelnut oil by employing NMR spectroscopy and multivariate statistical analysis

NMR spectroscopy was employed for the detection of adulteration of refined olive oil with refined hazelnut oil. Fatty acids and iodine number were determined by ¹H NMR, whereas ³¹P NMR was used for the quantification of minor compounds including phenolic compounds, diacylglycerols, sterols, and free fatty acids (free acidity). Classification of the refined oils based on their fatty acids content and the concentration of their minor compounds was achieved by using the forward stepwise canonical discriminant analysis (CDA) and the classification binary trees (CBTs). Both methods provided good discrimination between the refined hazelnut and olive oils. Different admixtures of refined olive oils with refined hazelnut oils were prepared and analyzed by ¹H NMR and ³¹P NMR spectroscopy. Subsequent application of CDA to the NMR data allowed the detection of the presence of refined hazelnut oils in refined olive oils at percentages higher than 5%. Application of the non-linear classification method of the binary trees offered better possibilities of measuring adulteration of the refined olive oils at a lower limit of detection than that obtained by the CDA method.     

On the equations defining toric l.c.i.-singularities

Based on Nakajima's Classification Theorem we describe the precise form of the binomial equations which determine toric locally complete intersection (``l.c.i.') singularities.

     

A novel 2,3-dioxo-norcar-4-ene-7-carboxylic acid via rearrangement of an α-diketone

The structural rearrangement product of an α-diketone from a singlet oxygen reaction has been identified. The proposed intermediate has been trapped by diazomethane esterification.     

Halide-directed nitrile hydrolysis

Sodium bromide is an effective catalyst for promoting the hydrolysis of aroyl cyanides such that loss of the cyano group is greatly minimized.