Theoretical study of intramolecular hydrogen bonding in the halo derivatives of 1-amino-3-imino-prop-1-ene

Abstract

Intramolecular hydrogen bonding (IHB) of 1-amino-3-imino-prop-1-ene (AIP), as the simplest resonance-assisted hydrogen bond system in symmetric N-H• • •N class, and its halo derivatives (F, Cl, and Br) have been studied at the DFT-B3LYP/6-311++G * * level of theory. For better understanding of the nature of substituent effects, nitro and methoxy derivatives of AIP were also added to our consideration. Good linear correlations between IHB energies based on Espinosa's equation and −G(r)/V (r) values, total electronic density, Laplacian of total electronic density in critical points, π-electron delocalization parameter (Q), hyper conjugative interaction energy of lp(N) → σ * (N-H), (F i, j /S i, j) 2 parameter, natural charges of bridged hydrogen, frequency shift of the N-H stretching vibration, and chemical shift of bridged hydrogen were obtained. Keywords. Intramolecular hydrogen bond; 1-amino-3-imino-prop-1-ene (AIM); density functional theory (DFT); natural bond orbital analysis (NBO).

Molecular structure and intramolecular hydrogen bonding in 2-hydroxybenzophenones: A theoretical study

“…The corresponding value for malonaldehyde is obtained at 0.0492 a.u. 45 As shown in 43 These results confirm some covalent nature in the IHB. The −G(rBCP)/V(rBCP) ratio, GVR, is also a descriptor for the nature of IHB.…”

“…(2) the GVR = 1 corresponds to a hydrogen bond energy of 7.87 ± 0.08 kcal/mol, which is in excellent agreement with the corresponding value reported for a bent N-H• • •N system, 8 kcal/mol. 45 A fairly good correlation (R 2 = 0.869) is also obtained between the hydroxyl proton chemical shift and E HB, as demonstrated in figure 3b.…”

“…To obtain a better correlation between Q and E HB , the data due to the 3-substituted derivatives are excluded from regression analysis (R 2 = 0.8814). Figure 5a indicates, as it has also been shown for the N-H• • • N system, 45 that the Gilli's symmetry coordinate, 48 Q, is not a good parameter for description of IHB strength, at least in systems with high degree of steric hindrance.…”

“…It has been shown that for those hydrogen bonds for which their strength is greater than 8 kcal/mol, GVRs are less than unity. 45 The calculated hydrogen bond energies, according to the Espinosa's equation, 47 along with the proton chemical shifts of bridge proton are listed in the last column of table 1. According to this table and considering the Rozas classification, 42 all IHBs investigated in this study are classified as medium strength.…”

Application of Hammett equation to intramolecular hydrogen bond strength in para-substituted phenyl ring of trifluorobenzoylacetone and 1-aryl-1,3-diketone malonates

“…Afterwards, the results related to IHB strength have been compared with the experimental enolic proton chemical shifts, δOH which shows the effect of different substitutions in para-positions of phenyl ring on the IHB strength of the title molecules. The parameters related to IHB, such as EHB, ѵOH, γOH, δOH, geometrical and topological parameters would be correlated with the Hammett's para function, σp [25]. So, the electron donating/withdrawing substituent effects are discussed quantitatively by applying the Hammett equation.…”