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Summary Analysis of Central Atom Bonding, Hybridization, and Geometry
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
Hybridization of one s-orbital with three p-orbitals results in four equivalent energy orbitals, which point to the corners of a tetrahedral shape. Since all four hybridized orbitals have equal energy, the four valence electrons are distributed singly in each orbital and are available for single bond formation. The notation used for hybridized orbitals shows the identity of each of the orbital types (subshell) used in the mix and the number of orbitals of each type used indicated by a superscript. The hybrid orbitals for carbon in this hybridization example are designated as sp3, representing a combination of one s-orbital and three p-orbitals; the orbitals are stated as being 75% p-character and 25% s-character. An sp2-hybridized orbital would be 67% p-character and 33% s-character; sp-hybridized orbitals are 50% p-character and 50% s-character.
Xenobiotic C-sulfonate derivatives; metabolites or metabonates?
Published in Xenobiotica, 2018
From a non-biological standpoint, it is well known that sulfonic acids may be formed in the laboratory by reaction with sulfuric acid, sulfur trioxide, or a combination of the two as oleum. Indeed, when a compound is activated toward electrophilic attack, especially if it is an aromatic molecule, such a reaction may take place at low temperatures. In aqueous solution, some alkenes may react with sodium sulfite to give an addition across the double bond thereby forming a sulfonic acid salt and epoxides react with sulfite or bisulfite to yield hydroxyl sulfonate salts. Also, the initial phase in the reversible conversion of a naphthol to a naphthylamine (the “Bucherer-Lepetit reaction”) involves the addition of bisulfite to an aromatic double bond (Hoyle, 1991). Sulfonic acids may be formed also by reaction of carbonyl compounds with bisulfite to give “bisulfite addition compounds” (Lacosta & Martell, 1955; Wagner, 1929). Such addition occurs via a nucleophilic attack on the carbonyl group, which is electron deficient, by the lone pair occupying a hybrid orbital resident on the sulfur atom in bisulfite. Initially, a positively charged sulfur atom results but a simple proton transfer alleviates this situation (Rao & Salunke, 1984; Sykes, 1986) (Figure 6). Although the reaction of bisulfite with normal carbon–carbon double bonds appears difficult, especially if they are distanced from a carbonyl group (Nishimura & Iwase, 1976; Schenck & Danishefsky, 1951), it adds readily with ethylenic bonds in α,β-unsaturated compounds, whether they be aldehydes, ketones, acids or esters (Herke & Rasheed, 1992; Joslyn & Braverman, 1954; Morton & Landfield, 1952). Bisulfite undergoes addition to the pyrimidine ring structures of both uracil and cytosine (Hayatsu et al., 1970), across the double bond in the pyran (oxine) ring structure of anthocyanins (Berké et al., 1998) and via the double bond in the five-membered rings of prostaglandin A2 (Cho et al., 1977). However, many of these bisulfite addition reactions appear reversible and some adducts are unstable (Cerfontain, 1968), although other reports have suggested that C-sulfonates (not necessarily formed by the bisulfite route) are quite robust (Wagner & Reid, 1931).