Insertion reactions of 1S carbon atoms in double bonds

The Nature of the Azonium Cation as Evidenced by X‐Ray Photoelectron Spectroscopy

“…In agreement with this, CND0/2 as well as MIND0/2-calculations indicate that [14] [35]. We have now calculated the proton affinities of azomethane (R = Me) and azobenzene (R = Ph), considering the debated structures for the conjugate acid mentioned in the introductionary section.…”

“…We have now calculated the proton affinities of azomethane (R = Me) and azobenzene (R = Ph), considering the debated structures for the conjugate acid mentioned in the introductionary section. We did not minimize the total molecular energy of these specics with respect to all geometrical degrees of freedom because of the following reasons: (i) for R = Ph, the costs of computation would be prohibitive, (ii) al.1 semiempirical procedures of the type used here yield unsatisfactory lengths for bonds between heteroatoms due to the inadequate description of lone pair orbital repulsion [14], and (iii) the same procedures yield unrealistic conformations for conjugated systems containing essential single bonds [36] *). We used instead experimentally determined geometrical parameters, where known.…”

Stereochemistry at trivalent nitrogen. XI. Effect of polar substituents on the barrier to rotation about the sulfenyl sulfur-nitrogen bond in N-alkyl-N-arenesulfonylarenesulfenamides

“…In all cases, the rates of degenerate racemization, i.e., the interconversion of enantiomers in a racemate, could be measured by observing coalescence of signals of diastereotopic methyl groups in the nmr spectrum since this degenerate racemization corresponds to a topomerization. 5 We identify the rate-determining step in the topomerization as torsion about the sulfenyl S-N bond. We may reject slow inversion at nitrogen by analogy with the , -dialkylsulfenamides in which a torsional barrier has been demonstrated.…”

“…In the sulfenamide system, where the heteroatom is divalent sulfur, the ratedetermining step has been firmly established as rotation about the N-S formal single bond.43 Among the largest torsional barriers in compounds of this type are those in sulfenamides, ranging from 12 to 20 kcal/mol. As such, sulfenamides represent useful substrates for studying the influence of structural (5) Topomerization has been suggested as a useful term to describe degenerate processes which alter the time-averaged stereochemical relationships of groups in molecules.4b This includes processes by which diastereotopic groups are rendered enantiotopic or equivalent on the nmr time scale. Often, as in the present instance, topomerization may be effected by degenerate racemization, the interconversion of two enantiomers in a racemic modification.…”

Structural chemistry of the benzotropone system. III. The crystal and molecular structure of 2,7-dimethyl-4,5-benzotropone

“…CNDO/2* and MINDO/2 (Dewar & Haselbach, 1970) calculations were performed based on the three models, (i) the observed geometry, (ii) a boat form with C~ symmetry in which the boat angles have the same value as those observed and (iii) an extended planar form with C2v symmetry. The calculated total energies of the molecule are summarized in Table 6.…”