Theoretical Investigation of the Cooperativity in CH₃CHO·2H₂O, CH₂FCHO·2H₂O, and CH₃CFO·2H₂O Systems

Abstract

The hydrogen bond interaction between CH3CHO, CH2FCHO, and CH3CFO and two water molecules is investigated at the B3LYP/6-311++G(d,p) level. The results are compared with the complexes involving the same carbonyl derivatives and one water molecule. The calculations involve the optimization of the structure, the harmonic vibrational frequencies, and relevant NBO (natural bond orbital) parameters such as the NBO charges, the occupation of antibonding orbitals, and intra- and intermolecular hyperconjugation energies. Two stable cyclic structures are predicted. The two structures are stabilized by C=O⋯HO hydrogen bond. The A structures are further stabilized by CH⋯O bond involving the CH3(CH2F) group. This bond results in an elongation of the CH bond and red shift of theν(CH) vibration. The B structures are stabilized by CH⋯O interaction involving the aldehydic CH bond. The formation of this bond results in a marked contraction of the CH bond and blue shift of theν(CH) vibration indicating the predominance of the lone pair effect in determining the CH distances. The total interaction energies range from −12.40 to −13.50 kcal mol−1. The cooperative energies calculated at the trimer geometry are comprised between −2.30 and −2.60 kcal mol−1.

Roles of H2O to hydrogen bonds, structure and strength of complexes of CH3CHS and H2O

“…RESULTS AND DISCUSSION The result is consistent with the report of A. K. Chandra and coworkers when studing the CH3CHO complexes with H2O molecule(s). [10] The interaction energies of CH3CHO•••1H2O (from -14.9 to -15.6 kJ.mol -1 ) and RCHO•••1H2O (R=H, C2H5, CH2F) (from -12.2 to -15.2 kJ.mol -1 ) are more negative than the CH3CHS•••1H2O complexes. [9] Similarly, the interaction energies of CH3CHS•••2H2O (from -30.7 to -35.5 kJ.mol -1 ) are larger than those of CH3CHO•••2H2O (from -54.6 to -56.4 kJ.mol -1 ) [10] , indicating that when the O atom in CH3CHO is replaced by a S atom, the system becomes less stable.…”

“…[10] The interaction energies of CH3CHO•••1H2O (from -14.9 to -15.6 kJ.mol -1 ) and RCHO•••1H2O (R=H, C2H5, CH2F) (from -12.2 to -15.2 kJ.mol -1 ) are more negative than the CH3CHS•••1H2O complexes. [9] Similarly, the interaction energies of CH3CHS•••2H2O (from -30.7 to -35.5 kJ.mol -1 ) are larger than those of CH3CHO•••2H2O (from -54.6 to -56.4 kJ.mol -1 ) [10] , indicating that when the O atom in CH3CHO is replaced by a S atom, the system becomes less stable. However, the interaction energies of CH3CHS•••1H2O (from -12.0 to -12.9 kJ.mol -1 ) is more negative than those of RCHX•••1CO2 (X=O, S; R=H, CH3) complexes (from -9.1 to -10.5 kJ.mol -1 ) [11] , proving that H2O greatly affects to the durability of the complex rather than CO2.…”

“…[9] Another study by A. K. Chandra and co-workers found a large blue-shift associated with the contraction of the Csp2-H length with an increase of the corresponding vibrational frequencies compared to the original monomer upon formation of Csp2-H•••O H-bonds in the CH3CHO•••nH2O (n=1-2) complexes. [10] However, the study has not deeply analyzed and explained the reason for the blue shift phenomenon of the ν(Csp2-H) vibration. Therefore, we want to have an insight into this issue in the complexes of CH3CHS with nH2O (n=1-3) and explain the role of water in hydrogen bonding to help us understand more about stability and the nature of H-bond in these systems, the effect of water on cooperativity and strength of complexes.…”

Roles of H2O in comparison with H2S in the complexes of thioaldehydes and hydrogen chalcogenides

“…[12][13][14] In a recent study, Chandra et al has found a strong blue shift of Csp2-H stretching frequency in Csp2-H•••O H-bonds in the CH3CHO•••nH2O (n = 1-2) complexes. [15] The Csp2-H blue shifts in Csp2-H•••O H-bonds were also reported in the systems of RCHO (R = F, Cl, Br, CH3, H) with HNO, CO2, and HCOOH. [11,16,17] However, most recent reports have not deeply clarified the characteristics of the blue-shifts of the Csp2-H bonds.…”

Effect of substituents on complex stability and characteristics of Csp2‐H∙∙∙O/S and O/S‐H∙∙∙S/Se hydrogen bonds in the systems of monosubstituted selenoformaldehyde with H2O and H2S

“…These result are consistent with the previous report of Chandra et al when investigating the CH3CHO•••1/2H2O systems. [34] Overall, the characteristic of the investigated H-bonds depends on the electron transfer from n(Z) and n(Se) to σ*(Csp2/Z-H) orbital. Besides, the magnitude of Csp2/Z-H red shift of Csp2/Z-H•••Z H-bond is proportional to the proton affinity and the polarizability of X-H covalent bonds.…”