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Mostrando ítems 233-252 de 360
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One-Pot Conversion of Aldehydes and Ketones into 1-Substituted and 1,4-Disubstituted 1,3-Enynes
(2018)Sequential treatment of 2,3-dichloropropene with magnesium and n-BuLi generates the operational equivalent of 1,3-dilithiopropyne, which upon treatment with aldehydes or ketones, produces the corresponding alkoxy lithium ... -
Operando tracking of oxidation-state changes by coupling electrochemistry with time-resolved X-ray absorption spectroscopy demonstrated for water oxidation by a cobalt-based catalysts film
(2021)Transition metal oxides are promising electrocatalysts for water oxidation, i.e., the oxygen evolution reaction (OER), which is critical in electrochemical production of non-fossil fuels. The involvement of oxidation state ... -
Optimization of semiochemical-based trapping of Metamasius hemipterus sericeus (Olivier) (Coleoptera: Curculionidae)
(1996-08)Response of adults of the West Indian sugarcane weevil,Metamasius hemipterus sericeus, to various semiochemical treatments and physical trap designs was studied in southern Florida in field-grown banana and Canary Island ... -
Oral administration of Costa Rican guava (Psidium friedrichsthalianum) juice induces changes in urinary excretion of energy-related compounds in Wistar rats determined by 1H NMR
(2020-08)Introduction: Psidium friedrichsthalianum fruits have in vitro antioxidant activity and their intake has been suggested to have potential health benefits; however, there is still no evidence on the potential in vivo effect ... -
Orbitals in general chemistry, Part I: The great debate
(2020-08)In Part I of a three-part series, we present an objective survey of the technical literature discussing the inclusion of orbitals in highschool and post-secondary general chemistry. We start with the definition of orbitals. ... -
Orbitals in general chemistry, Part II: Mathematical Realities
(2021)In Part II of a three-part series, we discuss two factors absent from textbooks of general chemistry that are important in a discussion of teaching orbitals. First, atomic orbitals are shown systematically to comprise ... -
Orbitals in general chemistry, Part III: Consequences for Teaching
(2021)In Part III of this series, we undertake a critique of the nature of application of orbitals to describe or to explain the structure and the binding within molecules and materials. Teaching orbitals in introductory chemistry ... -
Organic Acids without a Carboxylic Acid Functional Group
(Journal of Chemical Education 77(7):910-915. July 2000, 2000-07)This paper presents several organic molecules that have been labeled as acids but do not contain a carboxylic acid functional group. The rationale for the nomenclature and appropriate explanations for the apparent acidity ... -
Organic Carbon Determination by the Walkley-Black and Dry Combustion Methods in SurfaceSoils and Andept Profiles from Costa Rica
(1979-01)The efficiency of oxidation of organic C by the Walkley-Black method was studied by comparing with determinations using dry combustion equipment and gravimetric determination for the evolved CO2. Fifty surface soils (0-30 ... -
Palladium-Catalyzed One-Pot Conversion of Aldehydes and Ketones into 4‑Substituted Homopropargyl Alcohols and 5‑En-3-yn-1-ols
(2017)Sequential treatment of 2,3-dichloropropene with magnesium and n-BuLi generated the equivalent of 1,3- dilithiopropyne, which adds regiospecifically to aldehydes and ketones to produce homopropargyl alcohols. The ... -
Paraquat Behavior in Costa Rican Soils and Residues in Coffee
(1990)The paraquat deactivation capacities of soils, from 20 coffee plantations, generally ranged from 100 to 500 mg of paraquat/kg of soil. Even when paraquat had been applied up to twice per year (1.2 kg ha-1 year) for 20 ... -
Parámetros físico-químicos en aguas costeras de la Isla del Coco, Costa Rica (2001-2007)
(2008-11-17)Four cruises to Isla del Coco (Cocos Island), Costa Rica, were carried out in order to gather oceanographic data related to surface temperature, salinity, dissolved oxygen concentration, Secchi disk depth, nutrient ... -
Phenolic compounds as antiangiogenic CMG2 inhibitors from costa rican endophytic fungi
(2012)Targeting and inhibiting CMG2 (Capillary Morphogenesis Gene protein 2) represents a new strategy for therapeutic agents for cancer and retinal diseases due to CMG2’s role in blood vessel growth (angiogenesis). A high ... -
Phenolic variation among Chamaecrista nictitans subspecies and varieties revealed through UPLC-ESI(-)-MS/MS chemical fingerprinting
(2019-01-19)Introduction Comparative analysis of metabolic features of plants has a high potential for determination of quality control of active ingredients, ecological or chemotaxonomic purposes. Specifically, the development of ... -
Pheromone chirality of african palm weevil, Rhynchophorus phoenicis (F.) and palmetto weevil, Rhynthophorus crueniatus (F.) (Coleoptera: Curculionidae)
(1994-09)There are four stereoisomers of both 3-methyl-octan-4-ol, the aggregation pheromone of the African palm weevil,Rhynchophorus phoenicis (F.) and 5-methyl-octan-4-ol, the aggregation pheromone of the palmetto weevil,Rhynchophorus ... -
Pheromone chirality of asian palm weevils,Rhynchophorus ferrugineus (Oliv.) andR. vulneratus (Panz.) (Coleoptera: Curculionidae)
(1996-02)Production of 4-methyl-5-nonanol, and 4-methyl-5-nonanone by two sympatric Asian palm weevils,Rhynchophorus ferrugineus (Oliv.) andR. vulneratus (Panz.) suggested that enantiospecificity of either compound could impart ... -
Phosphate recovery from wastewater with magnetic particles and enrichment of the reclaimed solution as a source for struvite precipitation
(2016-05-30)In this study phosphate was recovered from different wastewaters (WW) by using magnetic particles modified with layered double hydroxides (LDH). Afterwards, the enriched reclaimed solution was used for the precipitation ... -
Photochemische Umlagerung von 1-Acyloxy-1-alkoxy-λ5-phosphorin-Derivaten
(1976)Während bei 1-Akoxy-1-benzoyloxy-2,4,6-triphenyl-λ5-phosphorin-Derivaten 1a-e photochemisch in Ausbeuten von 46 - 96% dieselben 1-Alkoxy-6c-benzoyl-1r-oxo-2,4,6-triphenyl-1λ5-phospha-2,4-cyclohexadiene 2a-e isoliert werden, ...