Grafting of cellulose by ring-opening polymerisation – A review

In this review, homogeneous and heterogeneous grafting from cellulose and cellulose derivatives by ring-opening polymerisation (ROP) are reported. Cellulose is biorenewable and biodegradable as well as a stiff material with a relatively low specific weight, foreseen to be an excellent replacement for synthetic materials. By utilising ROP of monomers such as ε-caprolactone or l-lactide from cellulose, composite materials with new and/or improved properties can be obtained. Grafting of solid cellulose substrates, such as cotton, microfibrillated cellulose (MFC) or cellulose nanocrystals, renders cellulose that can easily be dispersed into polymer matrices and may be used as reinforcing elements to improve mechanical and/or barrier properties of biocomposites. A surface grafted polymer can also tailor the interfacial properties between a matrix and the fibrillar structure of cellulose. When derivatives of cellulose are grafted with polymers in homogenous media, amphiphilic materials with interesting properties can be achieved, anticipated to be utilised for applications such as encapsulation and release.     

A Bayesian spatio-temporal model for precipitation extremes—STOR team contribution to the EVA2017 challenge

This paper concerns our approach to the EVA2017 challenge, the aim of which was to predict extreme precipitation quantiles across several sites in the Netherlands. Our approach uses a Bayesian hierarchical structure, which combines Gamma and generalised Pareto distributions. We impose a spatio-temporal structure in the model parameters via an autoregressive prior. Estimates are obtained using Markov chain Monte Carlo techniques and spatial interpolation. This approach has been successful in the context of the challenge, providing reasonable improvements over the benchmark.     

η5-Pentadienyltricarbonylmanganese,an “open” analog of cymantrene

2,4-Pentadienyltrimethyltin, obtained by the reaction of pentadienyllithium with trimethyltin chloride, reacted with bromopentacarbonylmanganese in refluxing tetrahydrofuran to give η⁵-pentadienyltricarbonylmanganese in 52% yield.     

Thermogravimetry/mass spectrometry analysis of energy crops

The aim of this work was to study the thermal decomposition of different plant species obtained from energy plantations. Thermogravimetry/ mass spectrometry (TG/MS) experiments have been performed with two herbaceous crops (Miscanthus sinensis, pelletized energy grass) and two wood samples (willow, water locust) in inert and oxidative atmospheres. Owing to the large number of data obtained in the experiments, a chemometric tool, principal component analysis (PCA) has been used to help the interpretation of the results. It has been found that the thermal decomposition of the studied wood species is similar, whereas that of the studied herbaceous samples exhibits significant differences. PCA has been found to be useful for finding correlations between the various experimental data.     

Reasons for and Consequences of the Mysterious Behaviour of Newly Prepared Hemipyridine Solvate of Bis(pyridine)silver(I) Permanganate,Agpy<Subscript>2</Subscript>MnO<Subscript>4</Subscript>*0.5py

Compositions and chemical identities of compounds formed in silver–permanganate–pyridine–water systems, as well as of their recrystallization products obtained from benzene–acetone solutions, have been elucidated. Three compounds: Agpy₂MnO₄ (1), 7Agpy₂MnO₄*Agpy₄MnO₄ (Agpy_2.25MnO₄) (2) and Agpy₂MnO₄ * 0.5py (Agpy_2.5MnO₄) (3) were isolated. The compositions of the products obtained by a method described previously [1] for the preparation of ‘Agpy₂MnO₄’ (1*) and ‘Agpy_2.5MnO₄’ (2*) were determined and the constituent compounds identified. It has been established that the instability of compound (3) is due to the presence of the benzene, substituting for pyridine at the solvate sites. The benzene, however, is released at room temperature, disrupting the crystal lattice of (3), and the whole process leads to the loss of the solvate pyridine and to the formation of (1).     

HPLC-SPE-NMR in pharmaceutical development: capabilities and applications

High-performance liquid chromatography-solid phase extraction-NMR spectroscopy (HPLC-SPE-NMR) has recently become commercially available and has been evaluated with regard to its applicability in a pharmaceutical environment. The addition of an automated SPE unit to an HPLC-NMR system for peak trapping results in an improved NMR signal-to-noise ratio (S/N) and also has other practical advantages. The trapping efficiency is shown to depend on compound polarity and is highest for compounds eluting late on reversed-phase HPLC systems. Multiple peak trapping further increases the S/N, again with the best results for less polar compounds. For polar compounds, multiple peak trapping resulted in no S/N gain as the amount of material retained on the SPE cartridge was equivalent to that from a single injection. When compared with conventional HPLC-NMR, a S/N gain of up to five-fold could be achieved for some compounds in a single trapping step. A major advantage of the technique is the independence of the chromatographic step from the NMR step, resulting in greater versatility than conventional HPLC-NMR in the HPLC solvents and NMR solvents that can be used. Practical applications from both drug metabolite and drug impurity identification are presented.     

Lead-tin mirror formation from mixtures of red lead and tin sulphide

Mosaic gold, tin (IV) sulphide, is a yellow pigment which was known in antiquity but whose use was superseded by other more easily obtainable yellow pigments by the Renaissance. The identification of mosaic gold residues in a burnished golden mirror decoration on a XIIIth Century Spanish polychrome statue is important in that the first reference to the use of mosaic gold in the European literature dates from the XIVth Century, although the use of this material in China had been recorded some time before. In this paper, Raman spectroscopy, XRD and SEM are used in the analysis of the conditions required for the formation of golden mirrors using tin (IV) sulphide in admixture with dilead (II) lead (IV) tetroxide and mercury (II) sulphide. From these results, it is proposed that the major reactions are the reduction of Sn(IV) to Sn(0) with the accompanying oxidation of lead (II) oxide to lead (IV) oxide and the formation of lead (0) and lead (II) sulphide. From these results it was possible to explain the process of creation of the golden mirror from mosaic gold in the XIIIth Century.     

Ring-closing double reductive amination route to aza-heteroannulated sugars

1,4-Dicarbonyl derivatives of glycosides are produced by ozonolysis or Wacker oxidation. A stable ozonide is isolated and a carbonyl group reduced whilst maintaining the ozonide functionality. The 1,4-dicarbonyl compounds are converted to various N-substituted pyrrolidines by diastereoselective double reductive amination The resulting aza-heteroannulated sugars no significant inhibition of any glycosidase, with the exception of compound 12g, which is a weak inhibitor of β-galactosidase.