Search results for "Yield"
showing 10 items of 1338 documents
Reactions of 3-vinylindole derivatives with dienophiles
1991
Reactions of 3-(1-cyclohexenyl)-1,2-dimethylindole (1a) and the 1,2-dihydrocarbazole 1b with some carbo- and heterodienophiles are described. Thus, compound 1a reacts to give ene, Michael-type, and Diels-Alder adducts, depending on the dienophile and reaction conditions. The 3-vinylindole 1b reacts with 4-phenyl-1,2,4-triazoline-3,5-dione or N-phenylmaleimide in a dehydrogenative reaction to yield the fully aromatized carbazole 8.
A combined experimental and theoretical study of the unimolecular elimination kinetics of 2-alkoxypropionic acids in the gas phase
1999
Abstract The reaction mechanism associated with the decomposition of three 2-alkoxypropionic acids (2-methoxy-, 2-ethoxy- and 2-isopropoxypropionic acid) in gas phase to form acetaldehyde, carbon monoxide, and the corresponding alcohol has been analyzed by a combination of experimental and theoretical studies. The kinetics of these systems were determined in a static system over the temperature and pressure range of 301.2–370.7°C and 61–190 Torr, respectively, in seasoned vessel, with the free-radical inhibitor cyclohexene. The experimental data show that these decompositions are homogeneous, unimolecular and follow a first-order rate law. A detailed characterization, at MP2/6-31G** computa…
New reaction of 1H-pyrazoles with selenium dioxide: one-pot synthesis of bis(1H-pyrazol-4-yl)selenides
2010
Abstract A novel reaction between 3- and 3,5-substituted pyrazoles with selenium dioxide proceeds with formation of bis(3R,5R′-1H-pyrazol-4-yl)selenides in high yield. On this basis, an efficient one-pot synthetic procedure has been developed. In the case of the unsubstituted pyrazole a selenonium compound has been obtained. The identity and structure of the isolated selenium derivatives have been confirmed by spectral methods and their molecular structures investigated by X-ray analysis.
One electron transfer chain decomposition of trifluoroacetone diperoxide: The first 1,2,4,5-tetroxane with O-transfer capability
1992
Abstract Reaction of 1,1,1-trifluoropropanone (trifluoroacetone) ( 1a ) with 30% hydrogen peroxide in the presence of conc. sulfuric acid afforded in good yield 3,6-bis(trifluoromethyl)-3,6-dimethyl-1,2,4,5-tetroxane or trifluoroacetone diperoxide ( 2a ). Peroxide 2a is quantitatively converted into trifluoroacetone ( 1a ) and dioxygen by a catalytic amount of tetrabutylammonium iodide through a reductive electron transfer chain reaction carried out by the superoxide ion. Trifluoroacetone diperoxide ( 2a ) is capable of O-atom transfer to alkenes and sulfides.
Nickel-catalyzed carboxylation of aryl zinc reagent with CO2: A theoretical and experimental study
2019
Abstract Two Ni-complexes with 1,1′-bis(diphenylphosphino)ferrocene (dppf) and tricyclohexylphosphine (PCy3) ligands were tested for the Ni-catalyzed cross-coupling of aryl zinc reagent with CO2 to form aryl carboxylic acid. Theoretical study with the aid of density functional theory (DFT) was carried out to understand the detailed reaction mechanism. The reasonable reaction pathway was deduced. The simulation results suggested that the free energy barrier of the rate-limiting step with (dppf)Ni is only 1.64 kcal mol−1 higher than the barrier with (PCy3)2Ni. However, our experiment provided an unexpectedly low yield by using (dppf)Ni complex as the catalyst. Further theoretical study ascrib…
Remote sensing data for crop yield in CONUS
2023
I) SUMMARY This database contains harmonized time series for the study of crop yields using remote sensing data and meteorological data. We collected information on soybean, corn, and wheat yields (t/ha) over the CONUS (continuous US) from USDA-NASS for years 2015–2018 at a county level, and collocated time series for the following variables: Enhanced Vegetation Index (EVI) from MODIS satellite (MOD13C1 v6 product) Soil Moisture (SM) from SMAP satellite through MT-DCA algorithm Vegetation Optical Depth (VOD) from SMAP satellite through MT-DCA algorithm Maximum temperature (TMAX) from Daymet v3 Precipitation (PRCP) from Daymet v3 II) CONTACT For questions, please email Laura Mart&iacut…
Methane production from maize in Finland – Screening for different maize varieties and plant parts
2012
Abstract The objective of the study was to determine how the harvest time and maize variety (12 varieties) affects the methane yield and dry matter yield per hectare in southern Finland (Piikkio) and in Central Finland (Laukaa). The specific methane yields and methane yields per hectare were also determined for different plant parts (stem, leaves and cobs). The methane yield per hectare varied from 2130 to 9170 m 3 ha −1 . The methane yields per hectare were ∼50% lower in Laukaa than in Piikkio due to a shorter growing season and lower total solid (TS) yields. TS yields were on average 16.7 and 15.5 Mg ha −1 in Piikkio and 8.7 and 6.8 Mg ha −1 in Laukaa in 2007 and 2008, respectively. The …
One-stage H2 and CH4 and two-stage H2+ CH4 production from grass silage and from solid and liquid fractions of NaOH pre-treated grass silage
2009
Abstract In the present study, mesophilic CH4 production from grass silage in a one-stage process was compared with the combined thermophilic H2 and mesophilic CH4 production in a two-stage process. In addition, solid and liquid fractions separated from NaOH pre-treated grass silage were also used as substrates. Results showed that higher CH4 yield was obtained from grass silage in a two-stage process (467 ml g−1 volatile solids (VS)original) compared with a one-stage process (431 ml g−1 VSoriginal). Similarly, CH4 yield from solid fraction increased from 252 to 413 ml g−1 VSoriginal whereas CH4 yield from liquid fraction decreased from 82 to 60 ml g−1 VSoriginal in a two-stage compared to …
Oilseed treatment by ultrasounds and microwaves to improve oil yield and quality: An overview.
2016
International audience; Efficiency is a key point to ensure the profitability in the production of vegetable oils from oilseeds. To maximize the recovery yields of seed oils, the traditional process involves mechanical expression followed by subsequent chemical extraction using organic solvents (e.g. hexane). Besides health, environmental, and economic related issues to the use of organic solvents, thermal treatment of seeds during conventional oil extraction process inevitably leads to chemical changes (e.g. changes in macronutrients such as protein denaturation/degradation in the meal, oil oxidation, and changes in minor constituents such as fatty acids, sterols, phenolic compounds and to…
Estimating soil loss of given return period by USLE-M-type models
2020
Many field investigations have clearly shown that rare and severe events control total soil erosion occurring over a long time period with up to 92% of total soil erosion over a 7‐year period resulting from just three daily events. Therefore, soil conservation strategies should be developed taking into account large events rather than long‐term average erosion. From an engineering point of view, establishing the soil loss of a given return period is needed. This can be obtained by the frequency analysis of soil loss measurements or by suitable soil erosion models. The USLE‐M modified and USLE‐M based are two empirical Universal Soil Loss Equation‐Modified (USLE‐M) type models which were dev…