A correlation between proton affinities and intramolecular hydrogen bonds in bifunctional organic compounds

Abstract

10261detected by ESR (3%), the second part comprises the electron pairs which participate in superconductivity, and the third part comprises electron spins arranged antiferromagnetically. ColleldoILsDuring about 24 h the ESR signals of Rb3Ca evolve with time. This is suggested to be related to diffusion of the Rb atoms within the Cm crystallites. Near T, the ESR susceptibility is found to change from antiferromagnetic to paramagnetic behavior. The magnitude of the ESR susceptibility is described by a two-component model of localized and conduction electrons. The ESR signals of K3Ca and Cs3Ca also show a similar timedependent behavior. Acknowledgment.Raseinsky, M. J.; Murphy, D. W.; Duclos, S. J.; Lyons, K. B.; Miller, B.; Rosamillia, J. M.; Fleming, R. M.; Kortan, A. R.; Glarum, S. H.; Makhija, A. V.; Muller, A. J.; Eick, R. H.; Zahurak, S. M.; Tycko, R.; Dabbagh, G.; Thiel, F. A. Nature 1991,350,320. (3) Zhakhidov, A. A,; Ugawa, A.; Imaeda, K.; Yakushi, K.; Inokuchi, H.; Kikuchi, K.; Ikemoto, I.; Suzuki, S.; Achiba, Y. Solid State Commun. 1991,

The role of proton bridges in selective cleavage of Ser-, Thr-, Cys-, Met-, Asp-, and Asn-containing peptides

“…As an example, the proton affinity of CH 3 COCH 2 CH 2 COCH 3 , which forms a 7-membered cyclic proton bridge upon protonation, is 885.50 kJ/mol as opposed to 868.76 kJ/mol, the proton affinity of CH 3 COCH 2 COCH 3 that forms a 6-membered cyclic proton bridge. This is also consistent with Yamabe's studies on intramolecular proton bridges (X-H + -X) of bifunctional molecules X-(CH 2 ) n -X (X = -NH 2 , -OR) [59]. According to this study, there is a good correlation between the hydrogen bond linearity and the stabilities of proton bridges for n = 2-4, which was confirmed by both ab inito calculations and experimental data.…”

A density functional theory study of the conformational properties of 1,2-ethanediamine: protonation and solvent effects

“…Inclusion of solvent interactions through the SCIPCM lowers the rotational barrier from 60.7 to 53.2 kJ mol )1 . Solvation of EDA2 using explicit water molecules [23] lowers the rotational barrier by 22.2 kJ mol )1 . We can use our results for EDA2 to calculate the PA for the EDA1 molecule.…”

Complexation of nickel(II) by ethylenediamine investigated by means of electrospray ionization mass spectrometry

“…Investigations of the conformational energy and the structural stability of ethylenediamine by ab initio methods show that the two most stable conformations are stabilized by intramolecular hydrogen bonding (N-H · · · N) with stabilization energies up to 20 kcal mol −1 [20,21]. In aqueous solutions, ethylenediamine interacts strongly with water molecules through hydrogen bonds, therefore, the mixtures exhibit negative deviations from ideality [22,23].…”