- IR absorption spectra of aniline cation, anilino radical, and phenylnitrene isolated in solid argon
-
Electron bombardment of aniline (PhNH2) in an Ar matrix mainly generated the aniline cation (PhNH2+), anilino (PhNH) and phenyl (Ph) radicals, and phenylnitrene (PhN). Further irradiation of the electron-bombarded matrix s
- Chou, Sheng-Lung,Lin, Shu-Yu,Tseng, Chien-Ming,Wu, Yu-Jong
-
-
- Kinetics and mechanism of the pyridinolysis of N-aryl-P,P-diphenyl phosphinic amides in dimethyl sulfoxide
-
Kinetic studies for the reactions of Z-N-aryl-P,P-diphenyl phosphinic amides with X-pyridines have been carried out in dimethyl sulfoxide at 85.0 °C. The two strong π-acceptor substituents, X = 4-Ac and 4-CN in the X-pyridine, exhibit positive deviations
- Guha, Arun Kanti,Kim, Chan Kyung,Lee, Hai Whang
-
p. 474 - 479
(2012/02/04)
-
- Models for Strong Interactions in Proteins and Enzymes. 1. Enhanced Acidities of Principal Biological Hydrogen Donors
-
The acid dissociation energies of several key biological hydrogen donors are found to fall into a narrow range, ΔHoacid=352-355 kcal/mol.The strong acidities of these donor groups enhance the hydrogen bond strengths involved in the protein α-helix, imidazole enzyme centers and DNA.Specifically, the peptide link is modeled by the dipeptide analogue CH3CO-Ala-OCH3.Its acidity is strengthened, i.e. ΔHoacid is decreased by 8 kcal/mol compared with other amides, due to electrostatic stabilization by the second carbonyl in the peptide -CON-CH(CH3)CO- grouping.The acidity of imidazole is also strengthened by 8 kcal/mol compared with that of the parent molecule, pyrrole, primarily due to resonance stabilization of the ion.Hydrogen donor NH2 groups of adenine and cytosine are modeled by 4-aminopyrimidine, and the acidity of this amine group is strengthened by ring aza substitution.An intrinsic acidity optimized for hydrogen bonding strength therefore emerges as a common property of the diverse hydrogen donors in the protein α-helix, enzymes and DNA.This property may therefore be in part responsible for the natural selection of these molecules as principal biological hydrogen donors.
- Meot-Ner (Mautner), Michael
-
p. 3071 - 3075
(2007/10/02)
-
- EFFETS DE CRYPTANDS ET ACTIVATION DE BASES-IV. ACTION DES HYDRURES ALCALINS SUR LES ACIDES FAIBLES. GENESE DE PHENATES, ALCOOLATES, AMIDURES ET CARBANIONS DANS LE THF ET LE BENZENE.
-
Metallation of a series of weak acids (phenols, alcohols, amines, and aryl methanes, pKa 7.2-33.4) by sodium and potassium hydride in presence of 2.2.1 (with NaH) et 2.2.2 (with KH) cryptands in tetrahydrofuran and benzene seems to involve activation at t
- Le Goaller,Pasquini,Pierre
-
p. 237 - 243
(2007/10/02)
-