Quantification of hyperconjugative effect on the proton donor X–H bond length changes in the red- and blueshifted hydrogen-bonded complexes

2012 ◽  
Vol 137 (8) ◽  
pp. 084311 ◽  
Author(s):  
Pan-Pan Zhou ◽  
Wen-Yuan Qiu ◽  
Neng-Zhi Jin
Keyword(s):  
Bond Length ◽  
Proton Donor ◽  
Length Changes ◽  
Bonded Complexes ◽  
Hydrogen Bonded

Ab initio studies of the vibrational spectra of some hydrogen-bonded complexes of fluoroacetylene

2010 ◽  
Vol 88 (8) ◽  
pp. 716-724 ◽  
Author(s):  
Ponnadurai Ramasami ◽  
Thomas A. Ford
Keyword(s):  
Hydrogen Bond ◽  
Ab Initio ◽  
Vibrational Spectra ◽  
Molecular Structures ◽  
Stationary Points ◽  
Bond Energies ◽  
Length Changes ◽  
Hydrogen Bond Energies ◽  
Bonded Complexes ◽  
Hydrogen Bonded

Ab initio molecular orbital theory has been used to compute the properties of a number of hydrogen-bonded complexes between fluoroacetylene as proton donor and ammonia, water, hydrogen fluoride, phosphine, hydrogen sulfide, and hydrogen chloride as proton acceptors. The properties considered were the vibrational spectra, the molecular structures, the hydrogen-bond energies, and the electron densities, and one of the aims of the study was to ascertain whether there was any evidence of blue-shifting hydrogen-bond character in the complexes formed. The adducts with NH3, H2O, PH3, and H2S were of the conventional CH···X kind (X = N, O, P, S), with hydrogen-bond energies decreasing in the order NH3 > H2O > PH3 ≈ H2S. Those formed with HF and HCl showed the presence of three alternative structures; in addition to the CH···F(Cl) complexes, adducts of the F(Cl)H···F and F(Cl)H···π type were also found to be stationary points on the potential energy surfaces, with stabilities in the order F(Cl)H···π > CH···F(Cl) > F(Cl)H···F. The hydrogen-bond energies of the CH···X series correlated with the gas-phase basicities of the proton acceptors; moreover, the CH bond-length changes, the wavenumber shifts, the complex–monomer infrared intensity ratios of the CH stretching modes, and the amounts of charge transferred on complex formation were all found to track with the hydrogen-bond energies. All those properties considered here are consistent with the formation of red-shifting hydrogen bonds, to the exclusion of the blue-shifting alternatives.

scholarly journals Dielectric Relaxation Studies of Hydrogen Bonded Complexes of Benzamide and Acetamide with 4-substituted Phenols Using X-band Microwave Frequency

2021 ◽  
Vol 38 (3) ◽  
Author(s):  
A. Aathif Basha ◽  
F. Liakath Ali Khan
Keyword(s):  
Relaxation Time ◽  
Dielectric Relaxation ◽  
Proton Donor ◽  
Single Frequency ◽  
Hydroxyl Group ◽  
Molar Ratio ◽  
Frequency Method ◽  
Dielectric Parameters ◽  
Bonded Complexes ◽  
Hydrogen Bonded

At 308 K, using a 9.37 GHz dielectric relaxation setup, dielectric studies of hydrogen bonded complexes of benzamide and acetamide with 4-fluorophenol, 4-bromophenol, 4-chlorophenol, and 4-iodophenol in benzene were performed. Various dielectric parameters (such as ??, ??, ?0, and ??) were tested. The steric interactions of the proton donor determined the group rotation relaxation time t(2), whereas the significance of Higasi’s single frequency method for multiple relaxation time t(1) was determined by the hydrogen bonding power of the phenolic hydrogen. The presence of a 1:1 complex system between the prepared samples, as well as a charge transfer between the free hydroxyl group of phenols and the carbonyl group of amides was confirmed by the fact that the relaxation time and molar free energy activation of the 1:1 molar ratio were greater than some other higher molar ratios (i.e. 3:1, 2:1, 1:2, 1:3).

Hydrogen-Bonded Complexes of Phenylacetylene–Acetylene: Who is the Proton Donor?

2015 ◽  
Vol 119 (51) ◽  
pp. 12656-12664 ◽  
Author(s):  
Kanupriya Verma ◽  
Kapil Dave ◽  
K. S. Viswanathan
Keyword(s):  
Proton Donor ◽  
Bonded Complexes ◽  
Hydrogen Bonded
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