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Ambident
In chemistry, ambident is a molecule or group that has two alternative and interacting reaction sites, to either of which a bond may be made during a reaction. Ambident dienophile Ambident dienophile 57 reacts with DAPC 54 at the cyclobutene π-bond to produce ligand 58; in contrast, the related ambident dienophile 59 reacts with DAPC 54 at the naphthoquinone π-center to produce adduct 60 (lack of shielding of the methylene protons supports the stereochemical assignment). Ambident Nucleophile An Ambident nucleophile refers to an anionic nucleophile In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they a ... that exhibits resonance delocalization of its negative charge over two unlike atoms or over two like but non-equivalent atoms. Enolate ions are Ambident Nucleophile. References { ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nucleophile
In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are Lewis bases. ''Nucleophilic'' describes the affinity of a nucleophile to bond with positively charged atomic nuclei. Nucleophilicity, sometimes referred to as nucleophile strength, refers to a substance's nucleophilic character and is often used to compare the affinity of atoms. Neutral nucleophilic reactions with solvents such as alcohols and water are named solvolysis. Nucleophiles may take part in nucleophilic substitution, whereby a nucleophile becomes attracted to a full or partial positive charge, and nucleophilic addition. Nucleophilicity is closely related to basicity. History The terms ''nucleophile'' and ''electrophile'' were introduced by Christopher Kelk Ingold in 1933, replacing the terms ''anionoid'' and ''cation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ambident
In chemistry, ambident is a molecule or group that has two alternative and interacting reaction sites, to either of which a bond may be made during a reaction. Ambident dienophile Ambident dienophile 57 reacts with DAPC 54 at the cyclobutene π-bond to produce ligand 58; in contrast, the related ambident dienophile 59 reacts with DAPC 54 at the naphthoquinone π-center to produce adduct 60 (lack of shielding of the methylene protons supports the stereochemical assignment). Ambident Nucleophile An Ambident nucleophile refers to an anionic nucleophile In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they a ... that exhibits resonance delocalization of its negative charge over two unlike atoms or over two like but non-equivalent atoms. Enolate ions are Ambident Nucleophile. References { ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemistry
Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers the elements that make up matter to the compounds made of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during a reaction with other substances. Chemistry also addresses the nature of chemical bonds in chemical compounds. In the scope of its subject, chemistry occupies an intermediate position between physics and biology. It is sometimes called the central science because it provides a foundation for understanding both basic and applied scientific disciplines at a fundamental level. For example, chemistry explains aspects of plant growth ( botany), the formation of igneous rocks ( geology), how atmospheric ozone is formed and how environmental pollutants are degraded ( ecology), the properties of the soil on the moon ( cosmochemistry), how medications work (pharmacology), and how to collect DNA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Reaction
A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking of chemical bonds between atoms, with no change to the nuclei (no change to the elements present), and can often be described by a chemical equation. Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive elements where both electronic and nuclear changes can occur. The substance (or substances) initially involved in a chemical reaction are called reactants or reagents. Chemical reactions are usually characterized by a chemical change, and they yield one or more products, which usually have properties different from the reactants. Reactions often consist of a sequence of individual sub-steps, the so-called elementary reactions, and the information on the precise co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Bond
A chemical bond is a lasting attraction between atoms or ions that enables the formation of molecules and crystals. The bond may result from the electrostatic force between oppositely charged ions as in ionic bonds, or through the sharing of electrons as in covalent bonds. The strength of chemical bonds varies considerably; there are "strong bonds" or "primary bonds" such as covalent, ionic and metallic bonds, and "weak bonds" or "secondary bonds" such as dipole–dipole interactions, the London dispersion force and hydrogen bonding. Strong chemical bonding arises from the sharing or transfer of electrons between the participating atoms. Since opposite electric charges attract, the negatively charged electrons surrounding the nucleus and the positively charged protons within a nucleus attract each other. An electron positioned between two nuclei will be attracted to both of them, and the nuclei will be attracted toward electrons in this position. This attraction co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pi Bond
In chemistry, pi bonds (π bonds) are covalent chemical bonds, in each of which two lobes of an orbital on one atom overlap with two lobes of an orbital on another atom, and in which this overlap occurs laterally. Each of these atomic orbitals has an electron density of zero at a shared nodal plane that passes through the two bonded nuclei. This plane also is a nodal plane for the molecular orbital of the pi bond. Pi bonds can form in double and triple bonds but do not form in single bonds in most cases. The Greek letter π in their name refers to p orbitals, since the orbital symmetry of the pi bond is the same as that of the p orbital when seen down the bond axis. One common form of this sort of bonding involves p orbitals themselves, though d orbitals also engage in pi bonding. This latter mode forms part of the basis for metal-metal multiple bonding. Pi bonds are usually weaker than sigma bonds. The C-C double bond, composed of one sigma and one pi bond, ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Naphthoquinone
Naphthoquinones constitute a class of organic compounds structurally related to naphthalene. Two isomers are common for the parent naphthoquinones: * 1,2-Naphthoquinone * 1,4-Naphthoquinone Natural products * Alkannin * Hexahydroxy-1,4-naphthalenedione * Juglone * Lapachol * Lawsone * Menatetrenone * 2-Methoxy-1,4-naphthoquinone, a compound found in ''Impatiens'' species * Nigrosporin B * 2,3,5,6,8-Pentahydroxy-1,4-naphthalenedione * Phylloquinone * Plumbagin * 2,3,5,7-Tetrahydroxy-1,4-naphthalenedione * Vitamin K and related compounds Synthetic naphthoquinones * Menadione (2-Methyl-1,4-naphthoquinone), a vitamin K mimic * 5,8-Dihydroxy-1,4-naphthoquinone and dihydroxynaphthoquinones * Atovaquone * Buparvaquone, an antiprotozoal drug used in veterinary medicine * Diazonaphthoquinone Diazonaphthoquinone (DNQ) is a diazo derivative of naphthoquinone. Upon exposure to light, DNQ converts to a derivative that is susceptible to etching. In this way, DNQ has become a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enol
In organic chemistry, alkenols (shortened to enols) are a type of reactive structure or intermediate in organic chemistry that is represented as an alkene (olefin) with a hydroxyl group attached to one end of the alkene double bond (). The terms ''enol'' and ''alkenol'' are portmanteaus deriving from "-ene"/"alkene" and the "-ol" suffix indicating the hydroxyl group of alcohols, dropping the terminal "-e" of the first term. Generation of enols often involves removal of a hydrogen adjacent (α-) to the carbonyl group—i.e., deprotonation, its removal as a proton, . When this proton is not returned at the end of the stepwise process, the result is an anion termed an enolate (see images at right). The enolate structures shown are schematic; a more modern representation considers the molecular orbitals that are formed and occupied by electrons in the enolate. Similarly, generation of the enol often is accompanied by "trapping" or masking of the hydroxy group as an ether, such as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
