Selective and reversible base-induced elimination of a ruthenium dithioether yields a vinyl metallosulfonium complex

Chemical oxidation of tris(2-diphenylphosphinebenzenethiolato)ruthenate(II) [Ru-1](-) with ferrocenium hexafluorophosphate in the presence of ethylene yields [(2-diphenylphosphinebenzenethiolato)(ethane-1,2-diylbis(thio-2,1-phenylene)diphenylphosphine)ruthenium(II)] hexafluorophosphate, [Ru-1·C(2)H(4)]PF(6), from addition of the alkene across cis sulfur sites. The [Ru-1·C(2)H(4)](+) complex displays a single redox couple at +794 mV versus ferrocenium/ferrocene. (1)H NMR of [Ru-1·C(2)H(4)](+) displays ethylene resonances at δ = 1.29 (td, 1H), 1.59 (td, 1H), 2.78 (dd, 1H), and 3.03 (dd, 1H). In the presence of base [Ru-1·C(2)H(4)](+) is selectively deprotonated at the pseudoequatorial proton on the carbon α to the sulfur trans to phosphorus, yielding the vinyl metallosulfonium derivative [Ru-1·C(2)H(3)]. (1)H and (31)P NMR spectra of [Ru-1·C(2)H(3)] are temperature dependent, associated with inversion of the sulfur lone pair at the vinyl metallosulfonium. The activation energy for the fluxional process calculated using density functional theory (B3LYP/LANL2DZ+6-31g) of 14.36 kcal/mol is consistent with the experimentally determined value of 13.08 kcal/mol. The complex [Ru-1·C(2)H(3)] crystallizes as yellow blocks in the triclinic space group P-1 with unit cell dimensions of a = 11.2718(5) ?, b =12.0524(3) ?, c = 23.6075(10) ?, α = 101.715(3)°, β = 98.154(4)°, and γ = 105.209(3)°. Addition of hydrochloric acid to [Ru-1·C(2)H(3)] regenerates [Ru-1·C(2)H(4)](+). Addition of DCl confirms the selectivity of this reverse reaction.     

Reflectance and Cyclic Electron Flow as an Indicator of Drought Stress in Cotton (Gossypium hirsutum)

The response and the functioning of the photosynthetic machinery of cotton, Gossypium hirsutum during water stress was studied by leaf optical properties, linear (ETRII) and cyclic electron flow (CEF) and chlorophyll a fluorescence. We observed that in G. hirsutum, during water limitation, Chlorophyll b showed the best correlation with reflectance at 731 nm and is a better indicator of drought. F_v/F_m was observed to be very insensitive to mild water stress. However, during severe water stress the leaves exhibit considerable inhibition in F_v/F_m and an increase in anthocyanin levels by about 20‐fold. CEF was very responsive to mild water stress. The mild drought stress caused large decrease in the ability of the leaves to utilize the light energy. Photosystem I and photosystem II is protected from photoinhibition by high CEF and nonphotochemical quenching under mild water stress. While during severe drought stress, linear electron flow showed a sharp decrease in comparison to CEF. CEF play a major role in G. hirsutum leaves during mild as well as under severe water stress condition and is thus a good indicator of water stress.     

Poly(meth)acrylate grafted EPDM via reverse atom transfer radical polymerization: A single pot process

This investigation reports a one pot preparation of poly(meth)acrylate grafted EPDM via reverse ATRP and evaluation of their physical and mechanical properties. The graft copolymerization of 2-ethylhexyl acrylate and methyl methacrylate was carried out from EPDM using reverse ATRP in toluene at 90 °C using CuBr₂ as catalyst in combination with PMDETA as ligand and AIBN as thermal initiator. The grafted EPDMs were separated from the reaction mixture, purified and then characterized by FT-IR, ¹H NMR, DMA and TGA analyses. Surface energies and tensile properties were evaluated by Goniometer and UTM respectively. Acrylate grafted EPDMs showed better thermal stability, better tensile property, whereas methacrylate grafted EPDMs showed higher surface energy and better oil resistance property than the pristine EPDM. Surface morphologies of grafted EPDMs were analyzed by AFM and SEM analyses. This one pot grafting approach led to very high grafting percentage without undesirable homopolymerization and gelation.     

Potential of Potassium Hydroxide Pretreatment of Switchgrass for Fermentable Sugar Production

Chemical pretreatment of lignocellulosic biomass has been extensively investigated for sugar generation and subsequent fuel production. Alkaline pretreatment has emerged as one of the popular chemical pretreatment methods, but most attempts thus far have utilized NaOH for the pretreatment process. This study aimed at investigating the potential of potassium hydroxide (KOH) as a viable alternative alkaline reagent for lignocellulosic pretreatment based on its different reactivity patterns compared to NaOH. Performer switchgrass was pretreated at KOH concentrations of 0.5–2 % for varying treatment times of 6–48 h, 6–24 h, and 0.25–1 h at 21, 50, and 121 °C, respectively. The pretreatments resulted in the highest percent sugar retention of 99.26 % at 0.5 %, 21 °C, 12 h while delignification up to 55.4 % was observed with 2 % KOH, 121 °C, 1 h. Six pretreatment conditions were selected for subsequent enzymatic hydrolysis with Cellic CTec2® for sugar generation. The pretreatment condition of 0.5 % KOH, 24 h, 21 °C was determined to be the most effective as it utilized the least amount of KOH while generating 582.4 mg sugar/g raw biomass for a corresponding percent carbohydrate conversion of 91.8 %.     

General methodology for synthesis of fused tricyclic oxazino-2-quinolones under phase-transfer catalyzed conditions

A one-pot synthesis of substituted oxazino-2-quinolones is described. The cornerstone of this methodology involves PTC catalyzed addition of an ethylene dihalide to a quinol to generate the corresponding O-alkylated intermediate in situ followed by ring closing and subsequent formation of a carbonyl group in the oxazinoquinolone in a one-pot sequence.     

Rare Earth Doped Optical Fibre From Oxide Nanoparticles

Rare earth (RE) doped optical fibres were fabricated by using RE oxides coated silica nanoparticles. The fibre properties are comparable to those prepared by conventional techniques. The process offers better control over RE incorporation and homogeneity in the preform.     

Solid-phase synthesis of five-dimensional libraries via a tandem Petasis-Ugi multi-component condensation reaction

Five-dimensional libraries of dipeptide amides are readily prepared using a solid-phase tandem Petasis-Ugi multi-component condensation protocol on either a RINK amine or Universal RINK isonitrile resin. The method is practical and can be automated to prepare a large number of compounds useful for high throughput biological screening.     

The synthesis of aza-β-lactams via tandem Petasis-Ugi multi-component condensation and 1,3-diisopropylcarbodiimide (DIC) condensation reaction

The synthetic utility of a tandem Petasis-Ugi multi-component condensation and 1,3-diisopropylcarbodiimide condensation reactions have been employed to efficiently prepare two to four-dimensional libraries of aza-β-lactams.     

Basic alumina supported tandem synthesis of bridged polycyclic quinolino/isoquinolinooxazocines under microwave irradiation

Basic alumina supported, solvent-free synthesis of novel oxazocines, medium size heterocycles, has been achieved in excellent yields by tandem C-alkylation followed by intramolecular O-alkylation of hydroxyquinoline/isoquinoline(s) with quinolinium salts under microwave irradiation. The method provides a facile and efficient route for the construction of polynuclear bridge-head oxazocines.     

Preparation of polypropylene (PP)/ethylene octene copolymer (EOC) thermoplastic vulcanizates (TPVs) by high energy electron reactive processing

Thermoplastic vulcanizates (TPVs) based on 50/50 composition of PP/EOC blend were prepared by electron induced reactive processing. To facilitate dynamic crosslinking in the PP/EOC blend, a 1.5 MeV electron accelerator was directly coupled to an internal mixer to induce chemical reactions via high energy electrons under dynamic conditions of melt mixing process. This kind of setup has been conceptualized for the first time in our laboratory and termed as electron induced reactive processing (EIReP) technique. Mechanical, morphological, and rheological properties of PP/EOC TPVs were studied with special reference to the exposure time (16–64 s) keeping absorbed dose (100 kGy) and electron energy (1.5 MeV) invariable. Chain scission dominates over chain crosslinking in both EOC as well as PP phases with the increase in exposure time. The primary factor is found to be the predominance of oxidative degradation during electron induced reactive processing in air atmosphere. The above observation was supported by Fourier Transform Infrared analyses and gel content values. Furthermore, it was found that mechanical properties depend not only on the extent of degradation in the blend system but also on the state and the mode of dispersion of the blend components.