Rhodium trichloride promoted hydroboration of alenyl nitriles and alkenyl chlorides

Previous studies of the rhodium trichloride (RhCl3) catalyzed hydroboration mechanisms of alkenes showed rearrangements and unusual regiochemistry compared to simple uncatalyzed hydroboration, and complex mechanisms have been proposed to explain these results. Earlier studies suggested that isomerization of alkenes in the presence of RI1CI3 prior to hydroboration accounted for these results. Studies of alkene rearrangements in the presence of RI1CI3 also suggest that the results are due to a different mechanism. The elimination-addition promoted elimination of R-Rh-B structures was shown to be responsible for isomerization and formation of different alcohol isomers after hydroboration. These interesting results prompted us to study the hydroboration reactions of alkenes with functional groups in the presence of RI1CI3. Previous studies on the uncatalyzed hydroboration reactions of alkenes with functional groups showed that the presence of substituents can introduce marked directive influences on the hydroboration reaction. In the case of alkenyl chlorides this is followed by elimination reactions. Hydroboration reaction of alkenyl nitriles has been studied for the first time in this work in detail. The presence of RI1CI3 exerted a profound effect upon the hydroboration reactions of alkenyl nitriles and alkenyl chlorides. RI1CI3 mainly served to reduce this substituent effect and to isomerize the elimination products. An unexpected processtrimerization reaction of acetonitrile has also been observed from the result of carboncarbon bond breaking in allyl cyanide. The mechanism of this process has been studied in detail. Alkenyl chlorides favored the formation of racemic mixtures of chiral compounds in the presence of rhodium trichloride. In addition to that the effect of temperature on the hydroboration of alkenyl nitriles and chloride has been studied for the first time

MODERN RELIEF MODELING METHODS

The article discusses various methods of modeling the relief used in the practice of engineering and design work. In particular, the geometrical, mathematical and digital representation of the relief is considered

Generation of electrical energy at gas pipelines using a transported natural gas technological pressure drop

The article discusses the possibilities of generating electricity without burning fuel by expanding high-pressure natural gas at gas distribution stations with lower specific capital costs. It is proposed to reduce the pressure of the transported natural gas using expander-generator units instead of traditional throttle devices. Document type: Articl

Nordihydroguaiaretic acid recovery from Larrea tridentata by microwave-assisted extraction

Nordihydroguaiaretic acid (NDGA) is a powerful antioxidant with biological activities of great interest in several health areas, including antiviral, cancer chemopreventive, and antitumorgenic. Little information is available on extraction methods of NDGA from Larrea tridentata. Hence, the aim of this study was to develop a rapid and effective microwave-assisted extraction (MAE) method for NDGA recovery from Larrea tridentata leaves, and to compare the results obtained with those found using conventional heatreflux extraction (HRE)

Improving ruminal digestibility of various wheat straw types by white-rot fungi

Background: This study investigated the ruminal degradability of various wheat straw types by the white-rot fungi Ceriporiopsis subvermispora (CS) and Lentinula edodes (LE). Different cultivars (CV) of wheat straw at different maturity stages (MS) were treated with the fungi for 7weeks and assessed for chemical composition and in vitro gas production (IVGP). Results: Both fungi showed a more pronounced degradation of lignin on a more mature straw (MS3; 89.0%) in comparison with the straw harvested at an earlier stage (MS1; 70.7%). Quantitative pyrolysis coupled to gas chromatography and mass spectrometry, using 13C lignin as an internal standard 13C-IS Py-GC/MS revealed that lignin inmoremature straw was degraded and modified to a greater extent. In contrast, cellulose was less degraded in MS3, as compared to MS1 (8.3% versus 14.6%). There was no effect of different MS on the IVGP of the fungus-treated straws. Among the different straw cultivars, the extent of lignin degradation varied greatly (47% to 93.5%). This may explain the significant (P < 0.001) effect of cultivar on the IVGP of the fungal-treated straws. Regardless of the factors tested, both fungi were very capable of improving the IVGP of all straw types by 15.3% to 47.6%, (as compared to untreated straw), with CS performing better than LE – on different MS (33.6% versus 20.4%) and CVs (43.2% versus 29.1%). Conclusion: The extent of lignin degradation caused by fungal treatment was more pronounced on the more mature and lignified straw, while variable results were obtained with different cultivars. Both fungi were capable of improving the IVGP of various straw types

Application of new insoluble dietary fibres from triticale as supplement in yoghurt - effects on physico-chemical, rheological and quality properties

BACKGROUND: The need to increase the daily intake of dietary fibres opens a new chapter in the research of functional foods enriched with fibres. The potential application of an innovative product - insoluble dietary fibres from triticale in yoghurts - was deployed by characterising their food application and evaluating physico-chemical, rheological and sensory properties and was the aim of this research. RESULTS: Detailed characterisations of these fibres are presented for the first time and showed very good hydration properties, optimal pH ( slightly acidic), optimal chemical composition, high antioxidant capacity which was proven by phenolics contents. Besides, these fibres showed negligible calorific value, with no phytates and high antioxidant capacity, mainly from ferulic acid. Therefore they could be successfully added to yoghurt. Enrichment of yoghurt having different milk fat content (1.5 and 2.8% w/w) with triticale insoluble fibre (1.5% and 3.0% w/w) significantly influenced the syneresis level, its apparent viscosity, yield stress and thixotropic behaviour. The overall sensory quality scores indicated that yoghurt enriched with 1.5% triticale insoluble fibres was recognised as 'excellent' and had enhanced antioxidant activity. CONCLUSIONS: Insoluble triticale fibre could therefore be used as a supplement to produce functional yoghurt

Degradation of native and exotic riparian plant leaf litter in a floodplain pond

1. A litter-bag experiment was undertaken in a pond on the margins of a large temperate floodplain in south-western France to assess the potential influence of the replacement of native by exotic riparian species on organic matter degradation. We determined initial litter chemical composition, breakdown rates and the invertebrate assemblages associated with the litter for five pairs of native dominant and exotic invasive species co-occurring at different stages along a successional gradient. 2. Litter chemical composition, breakdown rates and abundance and diversity of detritivorous invertebrates were similar for the exotic and native species overall. No overall changes in organic matter degradation can thus be predicted from the replacement of dominant natives by exotic invasives. Breakdown rates were primarily driven by the C⁄N ratio. 3. One invasive species (Buddleja davidii) showed significantly higher breakdown rates than its native counterpart (Populus nigra), resulting in the disappearance of leaf litter 6 months prior to the next litterfall. In some cases, therefore, invasion by exotic species may result in discontinuity of resource supply for decomposers

Lignin composition and structure differs between xylem, phloem and phellem in Quercus suber

Thecompositionandstructureofligninindifferenttissues—phellem(cork),phloemandxylem(wood)—ofQuercussuberwasstudied.Wholecellwallsandtheirrespectiveisolatedmilledligninswereanalyzedbypyrolysiscoupledwithgaschromatography/massspectrometry(Py-GC/MS),two-dimensionalnuclearmagneticresonancespectroscopy(2D-NMR)andderivatizationfollowedbyreductivecleavage(DFRC).Differenttissuespresentedvariedp-hydroxyphenyl:guaiacyl:syringyl(H:G:S)lignincompositions.WhereasligninfromcorkhasaG-richlignin(H:G:Smolarratio2:85:13),ligninfromphloempresentsmoreS-units(H:G:Smolarratioof1:58:41)andligninfromxylemisslightlyenrichedinS-lignin(H:G:Smolarratio1:45:55).Thesedifferenceswerereflectedintherelativeabundancesofthedifferentinterunitlinkages.Alkyl-arylethers(b–O–4′)werepredominant,increasingfrom68%incork,to71%inphloemand77%inxylem,asconsequenceoftheenrichmentinS-ligninunits.Corkligninwasenrichedincondensedstructuressuchasphenylcoumarans(b-5′,20%),dibenzodioxocins(5–5′,5%),ascorrespondstoaligninenrichedinG-units.Incomparison,ligninfromphloemandxylempresentedlowerlevelsofcondensedlinkages.Theligninfromcorkwashighlyacetylatedattheg-OHoftheside-chain(48%ligninacetylation),predominantlyoverG-units;whiletheligninsfromphloemandxylemwerebarelyacetylatedandthisoccurredmainlyoverS-units.Theseresultsareafirsttimeoverviewoftheligninstructureinxylem,phloem(generatedbycambium),andincork(generatedbyphellogen),inagreementwithliteraturethatreportsthatligninbiosynthesisisflexibleandcellspecificinfo:eu-repo/semantics/publishedVersio