Browsing Química by Title
Now showing items 200-219 of 316
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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 ... -
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, ... -
Photoreactivity of Oil and Alcoholic Diterpenic Varnishes: Key Role of the Polymerization Process
(2020)he conservation of artworks is a key issue in cultural heritage. The alterations of the varnish could be linked mainly to the photopolymerization of the natural resin. The photodegrada- tion of sandarac and rosin under ...