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  2. Retardation factor - Wikipedia

    en.wikipedia.org/wiki/Retardation_factor

    In chromatography, the retardation factor (R) is the fraction of an analyte in the mobile phase of a chromatographic system. [1] In planar chromatography in particular, the retardation factor R F is defined as the ratio of the distance traveled by the center of a spot to the distance traveled by the solvent front. [2]

  3. Resonance frequency analysis - Wikipedia

    en.wikipedia.org/wiki/Resonance_Frequency_Analysis

    Resonance frequency analysis was first suggested as an alternative method of analyzing peri-implant bone in a scientific paper by Meredith N et al in 1996. [4] As stated in the paper’s abstract, in measuring implant stability and osseointegration, “radiographs are of value, but a standardised technique is necessary to ensure repeatability.” [4] The new technique tested involved ...

  4. Glossary of chemistry terms - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_chemistry_terms

    Also acid ionization constant or acidity constant. A quantitative measure of the strength of an acid in solution expressed as an equilibrium constant for a chemical dissociation reaction in the context of acid-base reactions. It is often given as its base-10 cologarithm, p K a. acid–base extraction A chemical reaction in which chemical species are separated from other acids and bases. acid ...

  5. Absolute configuration - Wikipedia

    en.wikipedia.org/wiki/Absolute_configuration

    In chemistry, absolute configuration refers to the spatial arrangement of atoms within a molecular entity (or group) that is chiral, and its resultant stereochemical description. [1] Absolute configuration is typically relevant in organic molecules where carbon is bonded to four different substituents .

  6. Reactivity–selectivity principle - Wikipedia

    en.wikipedia.org/wiki/Reactivity–selectivity...

    The sulfur radical was found to be more reactive (6*10 8 vs. 1*10 7 M −1.s −1) and less selective (selectivity ratio 76 vs 1200) than the carbon radical. In this case, the effect can be explained by extending the Bell–Evans–Polanyi principle with a factor δ {\displaystyle \delta \,} accounting for transfer of charge from the reactants ...

  7. Stevens rearrangement - Wikipedia

    en.wikipedia.org/wiki/Stevens_rearrangement

    The Stevens rearrangement in organic chemistry is an organic reaction converting quaternary ammonium salts and sulfonium salts to the corresponding amines or sulfides in presence of a strong base in a 1,2-rearrangement. [1] Stevens rearrangement overview. The reactants can be obtained by alkylation of the corresponding amines and sulfides.

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  9. Cope rearrangement - Wikipedia

    en.wikipedia.org/wiki/Cope_rearrangement

    The Cope rearrangement is the prototypical example of a concerted sigmatropic rearrangement. It is classified as a [3,3]-sigmatropic rearrangement with the Woodward–Hoffmann symbol [π 2 s + σ 2 s + π 2 s] and is therefore thermally allowed.