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  2. Charge-transfer band - Wikipedia

    en.wikipedia.org/wiki/Charge-transfer_band

    Absorption spectrum of an aqueous solution of potassium permanganate, showing a vibronic fine structure in the LMCT band. The tetraoxides of d 0 metal centers are often deeply colored for the first row metals. This coloration is assigned to LMCT, involving transfer of nonbonding electrons on the oxo ligands to empty d-levels on the metal.

  3. List of unsolved problems in chemistry - Wikipedia

    en.wikipedia.org/wiki/List_of_unsolved_problems...

    Protein folding problem: Is it possible to predict the secondary, tertiary and quaternary structure of a polypeptide sequence based solely on the sequence and environmental information? Inverse protein-folding problem: Is it possible to design a polypeptide sequence which will adopt a given structure under certain environmental conditions?

  4. Lists of unsolved problems - Wikipedia

    en.wikipedia.org/wiki/Lists_of_unsolved_problems

    List of unsolved problems may refer to several notable conjectures or open problems in various academic fields: Natural sciences, engineering and medicine [ edit ]

  5. Charge-transfer complex - Wikipedia

    en.wikipedia.org/wiki/Charge-transfer_complex

    A well-known example is the complex formed by iodine when combined with starch, which exhibits an intense purple charge-transfer band. This has widespread use as a rough screen for counterfeit currency. Unlike most paper, the paper used in US currency is not sized with starch. Thus, formation of this purple color on application of an iodine ...

  6. Transition metal - Wikipedia

    en.wikipedia.org/wiki/Transition_metal

    For example, the colour of chromate, dichromate and permanganate ions is due to LMCT transitions. Another example is that mercuric iodide , HgI 2 , is red because of a LMCT transition. A metal-to-ligand charge transfer (MLCT) transition will be most likely when the metal is in a low oxidation state and the ligand is easily reduced.

  7. Chemical oscillator - Wikipedia

    en.wikipedia.org/wiki/Chemical_oscillator

    In chemistry, a chemical oscillator is a complex mixture of reacting chemical compounds in which the concentration of one or more components exhibits periodic changes. They are a class of reactions that serve as an example of non-equilibrium thermodynamics with far-from-equilibrium behavior.

  8. Ring expansion and contraction - Wikipedia

    en.wikipedia.org/wiki/Ring_expansion_and_contraction

    Ring opening as a means of ring expansion can also be applied to larger systems to give access to even larger ring syscyclization. The Grob fragmentation can be applied as an example of such an expansion. Like the pinacol type migration the Grob fragmentation relies on an electron donating group to promote the bond migration and encourage the ...

  9. Chemical similarity - Wikipedia

    en.wikipedia.org/wiki/Chemical_similarity

    Chemical similarity (or molecular similarity) refers to the similarity of chemical elements, molecules or chemical compounds with respect to either structural or functional qualities, i.e. the effect that the chemical compound has on reaction partners in inorganic or biological settings.