A quantitative approach to nucleophilic organocatalysis

• Herbert Mayr,
• Sami Lakhdar,
• Biplab Maji and
• Armin R. Ofial

Beilstein J. Org. Chem. 2012, 8, 1458–1478, doi:10.3762/bjoc.8.166

• -diazabicyclo[2.2.2]octane (DABCO, 38) and (4-dimethylamino)pyridine (DMAP, 39). As shown in Figure 22, DABCO (38) reacts approximately 103 times faster with benzhydrylium ions than DMAP (39), i.e., DABCO (38) is considerably more nucleophilic than DMAP (39) [94]. On the other hand, the equilibrium constant for

Interaction of cyclodextrins with pyrene-modified polyacrylamide in a mixed solvent of water and dimethyl sulfoxide as studied by steady-state fluorescence

• Akihito Hashidzume,
• Yongtai Zheng and
• Akira Harada

Beilstein J. Org. Chem. 2012, 8, 1312–1317, doi:10.3762/bjoc.8.150

• residues in pAAmPy carrying a Py residue may not form Py2. The fraction of Py° is defined as f. Scheme 2a indicates a simplified equilibrium of the formation of Py2 from two Py residues. On the basis of the derivation of equations in the Supporting Information File 1, the equilibrium constant for the Py2

• described in the Supporting Information File 1, the concentrations of all species can be calculated by using the equilibrium constant (Kβ) for the inclusion complex formation, and I480/I376 can be also obtained as given in Equation 3. Here [Py], [Py°], [CD], [CD·Py], and [CD·Py°] denote the concentrations

• favorable with increasing xDMSO. In the γ-CD/pAAmPy system, γ-CD forms inclusion complexes with Py2, in which Py° is not involved. On the basis of the derivation described in the Supporting Information File 1, the concentrations of all species can be calculated by using the equilibrium constant (Kγ) for the

The importance of the rotor in hydrazone-based molecular switches

• Xin Su,
• Timo Lessing and
• Ivan Aprahamian

Beilstein J. Org. Chem. 2012, 8, 872–876, doi:10.3762/bjoc.8.98

• equilibrium constant of the protonation step, KI is the equilibrium constant for the rotation process, and KS is the overall equilibrium constant for the switching reaction. The pKa of PPH-1 is actually log10KP, so KS also equals . From the above equations, it becomes clear that KS can be used as an index to

Equilibrium constants and protonation site for N-methylbenzenesulfonamides

• José A. Moreira,
• Ana M. Rosa da Costa,
• Luis García-Río and
• Márcia Pessêgo

Beilstein J. Org. Chem. 2011, 7, 1732–1738, doi:10.3762/bjoc.7.203

• anilinium ions and the respective aniline. Results and Discussion The determination of the classical equilibrium constant, Kc, requires knowledge of the ionization ratio I = [BH+]/[B]. Usually this is obtained by UV–vis spectroscopic measurements, as I relates to the absorbance according to Equation 4 where

Valence isomerization of cyclohepta-1,3,5-triene and its heteroelement analogues

• Helen Jansen,
• J. Chris Slootweg and
• Koop Lammertsma

Beilstein J. Org. Chem. 2011, 7, 1713–1721, doi:10.3762/bjoc.7.201

• methyl groups in benzene oxide (4) [38][40][51]. Thus, in contrast to the cycloheptatriene–norcaradiene (1–2) pair, the equilibrium constant for oxepine (3) and bicyclic benzene oxide (4) varies widely with solvent polarity and to some extent with temperature and substituents, making it possible to work

Stereoselectivity of supported alkene metathesis catalysts: a goal and a tool to characterize active sites

• Christophe Copéret

Beilstein J. Org. Chem. 2011, 7, 13–21, doi:10.3762/bjoc.7.3

• -butene (Z-C4). Surface coverage describes the concentration of a gas at the surface as a function of the partial pressures of all components (Pi) and their equilibrium constant (λi). For (Z)-2-butenes, it can be expressed according to Equation 2, which explains the hyperbolic relationship obtained for