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  2. Lewis structure - Wikipedia

    en.wikipedia.org/wiki/Lewis_structure

    Each bond consists of a pair of electrons, so if t is the total number of electrons to be placed and n is the number of single bonds just drawn, t−2n electrons remain to be placed. These are temporarily drawn as dots, one per electron, to a maximum of eight per atom (two in the case of hydrogen), minus two for each bond.

  3. Isomer - Wikipedia

    en.wikipedia.org/wiki/Isomer

    A double bond between two carbon atoms forces the remaining four bonds (if they are single) to lie on the same plane, perpendicular to the plane of the bond as defined by its π orbital. If the two bonds on each carbon connect to different atoms, two distinct conformations are possible, that differ from each other by a twist of 180 degrees of ...

  4. Topological index - Wikipedia

    en.wikipedia.org/wiki/Topological_index

    In the fields of chemical graph theory, molecular topology, and mathematical chemistry, a topological index, also known as a connectivity index, is a type of a molecular descriptor that is calculated based on the molecular graph of a chemical compound. [1]

  5. Functionality (chemistry) - Wikipedia

    en.wikipedia.org/wiki/Functionality_(Chemistry)

    However, IUPAC definition and the use of the term in organic chemistry differ with respect to the functionality of a double bond. [6] [9] In polymer chemistry, a double bond possesses a functionality of two (because two points of contact for further polymer chains are present, on each of the two adjacent carbon atoms), while in organic ...

  6. Biuret test - Wikipedia

    en.wikipedia.org/wiki/Biuret_test

    The characteristic color of a positive biuret test. In chemistry, the biuret test (IPA: / ˌ b aɪ j ə ˈ r ɛ t /, / ˈ b aɪ j ə ˌ r ɛ t / [1]), also known as Piotrowski's test, is a chemical test used for detecting the presence of at least two peptide bonds in a molecule.

  7. Cross-coupling reaction - Wikipedia

    en.wikipedia.org/wiki/Cross-coupling_reaction

    In organic chemistry, a cross-coupling reaction is a reaction where two different fragments are joined. Cross-couplings are a subset of the more general coupling reactions. Often cross-coupling reactions require metal catalyst

  8. Bridging ligand - Wikipedia

    en.wikipedia.org/wiki/Bridging_ligand

    For doubly bridging (μ 2-) ligands, two limiting representation are 4-electron and 2-electron bonding interactions. These cases are illustrated in main group chemistry by [Me 2 Al(μ 2-Cl)] 2 and [Me 2 Al(μ 2-Me)] 2. Complicating this analysis is the possibility of metal–metal bonding.

  9. Covalent bond - Wikipedia

    en.wikipedia.org/wiki/Covalent_bond

    In organic chemistry, covalent bonding is much more common than ionic bonding. Covalent bonding also includes many kinds of interactions, including σ-bonding, π-bonding, metal-to-metal bonding, agostic interactions, bent bonds, three-center two-electron bonds and three-center four-electron bonds. [2] [3] The term covalent bond dates from 1939 ...