Results 61 to 70 of about 107,424 (195)

Antibacterial and Antioxidant Activities of Ursolic Acid and Derivatives

open access: yesMolecules, 2014
Ursolic acid, an important bioactive compound, was isolated from ethanol extract of aerial parts of Sambucus australis. In order to develop bioactive ursolic acid derivatives, two semi-synthetic compounds were obtained through modification at C-3.
Patrícia G.G. do Nascimento   +7 more
doaj   +1 more source

Caracterização da dinâmica de nutrientes em solos sob floresta primária e em clareiras de diferentes idades de reflorestamento na província petrolífera de Urucu - Coari, AM. [PDF]

open access: yes, 2014
A retirada da floresta e dos horizontes superficiais do solo provoca a diminuição da fertilidade do mesmo. Com o reflorestamento dessas áreas, ocorre uma recuperação lenta e contínua da qualidade e quantidade de matéria orgânica.
CRUZ, M. E. G. da   +6 more
core  

Alkene Hydrogenation by a Cationic, Nine‐Coordinate Molybdenum(VI) Pentahydride Catalyst

open access: yesChemistry – A European Journal, EarlyView.
While late 3d metals dominate efforts to replace precious metals in homogeneous hydrogenation, molybdenum has remained largely ignored. This work reveals that a nine‐coordinate pentahydrido molybdenum complex can hydrogenate a broad range of alkenes efficiently, demonstrating that early‐metal polyhydrides can serve as genuine catalysts rather than mere
Arno Estival   +9 more
wiley   +1 more source

Bioactive Secondary Metabolites from Phomopsis sp., an Endophytic Fungus from Senna spectabilis

open access: yesMolecules, 2014
Chemical investigation of an acetonitrile fraction from the endophytic fungus Phomopsis sp. led to the isolation of the new natural product 2-hydroxy-alternariol (7) together with the known compounds cytochalasins J (1) and H (2), 5'-epialtenuene (3) and
Vanessa Mara Chapla   +10 more
doaj   +1 more source

Caracterização química do solo e da matéria orgânica na região da Serra do Sudeste sob campo natural no Estado do Rio Grande do Sul. [PDF]

open access: yes, 2019
bitstream/item/30584/1/boletim-114 ...
BORBA, M. F. S.   +5 more
core  

Synthesis and characterization of amphiphilic nitroxide 1,1,3,3–tetraethylisoindoline–2–oxyl–5–sodium sulfonate (TEIOSNa)

open access: yesThe Canadian Journal of Chemical Engineering, EarlyView.
Abstract The synthesis and characterization of an amphiphilic nitroxide to be used as a controlling agent in a nitroxide‐mediated living radical polymerization in aqueous dispersion media is presented. In the first stage of nitroxide synthesis (phthalimide protection), two reaction methods were employed: traditional and microwave.
Enrique García‐Leal   +3 more
wiley   +1 more source

Caracterização química e espectroscópica de solos irrigados com efluente de esgoto tratado [PDF]

open access: yes, 2009
A utilização de efluentes de esgoto tratado na irrigação, ao invés de realizar a disposição deste subproduto nos cursos d'água tem sido uma alternativa antiga, popular e atrativa, com triplo propósito: tratamento complementar do efluente, fonte de água e
MARTIN-NETO, Ladislau   +6 more
core   +2 more sources

Poly(Ionic) Liquid‐Enhanced Ion Dynamics in Cellulose‐Derived Gel Polymer Electrolytes

open access: yesChemSusChem, Volume 18, Issue 6, March 15, 2025.
Advancing Energy Storage: Gel Polymer Electrolytes with Promising Potential Gel polymer electrolytes (GPEs) incorporating methyl cellulose and a range of ionic/polymeric achieved Li+ transference numbers comparable to traditional liquid electrolytes.
Tiago G. Paiva   +7 more
wiley   +1 more source

Efficient access to β-vinylporphyrin derivatives via palladium cross coupling of β-bromoporphyrins with N-tosylhydrazones

open access: yesBeilstein Journal of Organic Chemistry, 2017
This work describes a new approach to obtain new β-vinylporphyrin derivatives through palladium-catalyzed cross-coupling reaction of 2-bromo-5,10,15,20-tetraphenylporphyrinatozinc(II) with N-tosylhydrazones.
Vinicius R. Campos   +5 more
doaj   +1 more source

Elementos estruturadores da química orgânica implícitos na argumentação de professor e alunos de graduação [PDF]

open access: yes, 2013
Mullins (2008) propõe que o bom desempenho em tópicos de Química Orgânica seria consequência do domínio adequado de elementos fundamentais quais sejam, eletronegatividade, ligação covalente polar, efeito estérico, efeito indutivo, ressonância e ...
Filho, M. A. Bueno, Nascimento, G. M.
core   +2 more sources

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