Substituent effects leading to ultra-slow proton removal from an intramolecular hydrogen bond

1995 ◽  
pp. 1 ◽  
Author(s):  
Alex Coker ◽  
Frank Hibbert
Keyword(s):  
Hydrogen Bond ◽  
Intramolecular Hydrogen Bond ◽  
Substituent Effects ◽  
Intramolecular Hydrogen

scholarly journals Unusual Para-Substituent Effects on the Intramolecular Hydrogen Bond in Hydrazone-Based Switches: Insights from Chemical Landscape Analysis and DFT Calculations

Physchem ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 189-201
Author(s):  
Vesselina Paskaleva ◽  
Stefan Dobrev ◽  
Nikolay Kochev ◽  
Silvia Angelova ◽  
Liudmil Antonov
Keyword(s):  
Hydrogen Bond ◽  
Dft Calculations ◽  
Intramolecular Hydrogen Bond ◽  
Substituent Effects ◽  
Substitution Effect ◽  
Automatic Generation ◽  
Standard Quantum ◽  
Structure Representation ◽  
Intramolecular Hydrogen ◽  
Quantum Chemical Dft Calculations

Тhe adequacy of chemical property predictions strongly depends on the structure representation, including the proper treatment of the tautomeric and isomeric forms. A combination of an in-house developed open-source tool for automatic generation of tautomers, Ambit-Tautomer, based on H-atom shift rules and standard quantum chemical (DFT) calculations is used for a detailed investigation of the possible geometric isomers, conformers and tautomers of unsubstituted and para-substituted phenylhydrazones, systems with experimentally observed unusual para-substituent effects on the intramolecular hydrogen bond (IMHB) for E-isomers of the compounds. The computational results show that the energetically preferred E-isomers are characterized by stronger IMHBs than the corresponding Z-isomers. The HN–N=C–C=N molecular fragment in the E-configurations is less sensitive to the substitution effect than the HN–N=C–C=O fragment in the isomers with Z-configuration. A probable reason for this decreased sensitivity of E-isomers to phenyl ring substitution is the more efficient conjugation and charge distribution in the HN–N=C–C=N fragment.

Dielectric enrichment in binary solvent mixtures. The intramolecular hydrogen bond in N-alkyl-substituted o-nitroanilines. Substituent effects

1992 ◽  
Vol 70 (10) ◽  
pp. 2677-2682 ◽  
Author(s):  
Rosa Cattana ◽  
Juana J. Silber ◽  
Jorge Anunziata
Keyword(s):  
Hydrogen Bond ◽  
Intramolecular Hydrogen Bond ◽  
Preferential Solvation ◽  
Substituent Effects ◽  
Solvent Mixture ◽  
Binary Solvent ◽  
Solvent Mixtures ◽  
Hydrogen Bond Acceptor ◽  
Intramolecular Hydrogen ◽  
Strong Intramolecular Hydrogen Bond

In this work we report solvatochromism studies on o-nitroaniline and several N-alkyl-o-nitroaniline derivatives used as solutes in solvent mixtures of an "inert" nonpolar cosolvent, cyclohexane, and THF as a solvent with hydrogen bond acceptor ability. These studies allowed us to establish the competition between inter- and intramolecular hydrogen bond in solutes. This was done by comparing the magnitude of the local inhomogeneity induced by the solute-in-solvent mixture, that is, "preferential solvation," using Suppan's dielectric enrichment model as modified by us to be applied to electronic transitions. Since preferential solvation accounts for dielectric as well as specific interactions while dielectric enrichment only for the former, it was shown by comparison that it is possible to separate both effects and even quantify them. It was deduced that N-alkyl-o-nitroanilines form a strong intramolecular hydrogen bond, which remains unbroken even in polar solvents and hydrogen bond acceptors such as dimethyl sulfoxide. This was also confirmed by solvatochromic studies in pure solvents. On the other hand, a symmetrical dependence of the effects of alkyl substituents and solvents on the shifts of the absorption spectra was observed.

Theoretical calculations of intramolecular hydrogen bond of the 2-Amino-2, 4, 6-cycloheptatrien-1-one in the gas phase and solution: Substituent effects and their positions

2016 ◽  
Vol 15 (07) ◽  
pp. 1650063 ◽  
Author(s):  
Narges Khatoon Attaran Toosy ◽  
Heidar Raissi ◽  
Maryam Zaboli
Keyword(s):  
Hydrogen Bond ◽  
Gas Phase ◽  
Intramolecular Hydrogen Bond ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Substituent Effects ◽  
Dft Method ◽  
Basis Set ◽  
Parent Molecule ◽  
Intramolecular Hydrogen

The density functional theory (DFT) method with 6-311[Formula: see text]G[Formula: see text] basis set has been used to calculate the intramolecular hydrogen bond, molecular structure, vibrational frequencies, nuclear quadrupole resonance (NQR) parameters, 1HNMR, and resonance parameters of 2-Amino-2, 4, 6-cycloheptatrien-1-one (2-amino tropone) and its 18 derivatives in 5 positions. The natural bonding orbital (NBO) and quantum theory of atoms in molecules (QTAIM) analyses have been studied. The strongest and weakest hydrogen bonds exist for NO2 substituent in R3 position and OH in R7 position, respectively. In general, the substituted systems in position 3 indicate the stronger hydrogen bond in comparison with the parent molecule (R[Formula: see text]H), while, it is comparatively weaker for position 5. The energy of the N-H[Formula: see text]O interaction is found to be medium in strength ([Formula: see text][Formula: see text]kJ mol[Formula: see text] to [Formula: see text][Formula: see text]kJ mol[Formula: see text]). The low [Formula: see text], positive [Formula: see text] values and [Formula: see text] show that the nature of O [Formula: see text] H bonding is electrostatic. Also, our theoretical results show that the hydrogen bond strength in solution phase and the first singlet excited state is weaker in comparison with the gas phase ground state.

Substituent effects on the isomerization of hydrazone switches driven by the intramolecular hydrogen bond

Tetrahedron ◽  
2019 ◽  
Vol 75 (30) ◽  
pp. 4010-4016
Author(s):  
Chaocao Lu ◽  
Bu Htan ◽  
Shitao Fu ◽  
Chunmiao Ma ◽  
Quan Gan
Keyword(s):  
Hydrogen Bond ◽  
Intramolecular Hydrogen Bond ◽  
Substituent Effects ◽  
Intramolecular Hydrogen

Unusual para-substituent effects on the intramolecular hydrogen-bond in hydrazone-based switches

2012 ◽  
Vol 48 (85) ◽  
pp. 10490 ◽  
Author(s):  
Xin Su ◽  
Märt Lõkov ◽  
Agnes Kütt ◽  
Ivo Leito ◽  
Ivan Aprahamian
Keyword(s):  
Hydrogen Bond ◽  
Intramolecular Hydrogen Bond ◽  
Substituent Effects ◽  
Intramolecular Hydrogen
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