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Alternate Methods for Visualizing and Constructing
Published in Patrick E. McMahon, Rosemary F. McMahon, Bohdan B. Khomtchouk, Survival Guide to General Chemistry, 2019
Patrick E. McMahon, Rosemary F. McMahon, Bohdan B. Khomtchouk
A covalent bond is a shared pair of electrons between two atoms. The shared electron pair can most simply be described as occupying a region of space formed by orbital overlap of one atomic orbital from each of the two atoms forming the bond. This overlap is called a bonding molecular orbital and always takes only two electrons.
The Reactivity Of Copper Sites In The “Blue” Copper Proteins
Published in René Lontie, Copper Proteins and Copper Enzymes, 1984
The above observation that the metal ion in the blue copper proteins is substantially buried in the solvent-inaccessible interior of the protein is most probably a reflection of the functional evolution of these proteins, allowing for the required control and specificity of the electron-transfer processes mediated by them. In these reactions the redox centers are widely separated, hence a direct orbital overlap between the metal ions is not possible without a major rearrangement of the surrounding amino-acid side chains. With the flattened tetrahedral geometry of the copper center, we have a situation where coordination-sphere reorganization associated with the electron transfer is minimized. This is attained by the particular ligand geometry which accommodates both redox states of the copper ion (cf. above).
Applications of fluorine to the construction of bioisosteric elements for the purposes of novel drug discovery
Published in Expert Opinion on Drug Discovery, 2021
Influencing conformational preferences in aliphatic chains without introducing significant levels of steric bulk presents a subtle approach to fine-tuning the physicochemical properties of small-molecule drug candidates. In such acyclic systems, fluorine can profoundly impact this when situated vicinal to an electron deficient motif (X = F, N, O, S) as the interplay between stereoelectronic (σC-H → σC-F*) and electrostatic (R+……Fδ-) interactions ensures that the syn-clinal conformers are significantly populated. The so-called gauche effect presents dihedral angles approaching 60 to ensure maximal orbital overlap, and in the case of the 1,2-difluoroethylene moiety leads to a large dipole moment that directly influences a compounds physicochemical and pharmacological properties [183–192]. The vicinal 1,2-difluroethylene has recently emerged as a bioisostere of the trifluoromethyl and ethyl groups (BITE) with the further possibility based on its chirality to allow evaluation of the enantiomers of a series of bioactive molecules [193].