Global Journal of Science Frontier Research, H: Environment & Earth Science, Volume 23 Issue 1

Figure 3: The Equilibrium Geometry of H 2 CO ⋅⋅⋅ HF Complex Calculated at mp2/6-311++g(3df,3pd) Approximation Upon the formation of the complex, H–F stretching frequency shortened by 9.89 cm -1 and the C=O stretching band of formaldehyde also shortened about 9,7 cm –1 . The C–H stretching frequency is blue shifted by about 39 cm –1 , and the atomic distance between C and O is increased. The H–F frequency is equal ν 12 (3546 cm –1 ) according to the computational results and this value equals to 3573 cm –1 which is calculated in experiment [14]. The frequency of HF molecule according to experimental investigation equals to 3961.40 cm -1 . This value shifts toward to the low energy side upon the complex formation by about 345.6 cm -1 according to quantum chemical calculation findings. Geometrical and spectral parameters of the complex are in good agreement with the calculated parameters in [6] Table 1: Calculated Stabilization Structural Parameters of the H 2 CO ⋅⋅⋅ HF Complex Distances, (Å) Monomers Complex Angles, (°) Monomer Complex r(H 3 –F) 0.915 0.936 ∠ OCH 1 121.5 121.3 r(C = O) 1.207 1.215 ∠ OCH 2 121.5 121.1 r(C–H 1 ) 1.101 1.096 ∠ OH 3 F 166.4 r(C–H 2 ) 1.102 1.097 ∠ COH 3 111.2 r(O ⋅⋅⋅ H 3 ) 1.753 ∠ COF 141.4 r(O ⋅⋅⋅ F) 2.649 Dipole moment of the complex calculated in CCSD(T)6311++G(3df,3pd) approximations equals to 3.81D. Change of geometrical parameters upon complex formation of the complex are shown in Table 2. Table 2: The Changes of the Selected Geometrical Parameters of the H 2 CO···HF upon the Complex Formation H 2 CO···HF Interatomic distances (Å) ∆ r(C=O) 0.0057 ∆ r(CH 2 ) -0.0047 ∆ r(CH 3 ) -0.0039 ∆ r(HF) 0.0186 In Table 3. calculated and experimental determined frequency and intensities are shown. The banding energy of the complex equals to –4.91 kJ·mol –1 , and r (H–F) atomic distance to be 0.921 Å. Table 3: Selected Harmonic Fundamental Transition Frequencies Ν (Cm -1 ) And Intensities S(Km·Mol -1 ) and Experimental Results of the H 2 CO···HF Complex and Monomers Assignments Harmonic Experiment ν S ν S C = O stretch 1758 75 1744 61 C–H in phase stretch 3017 47 2763 42 C–H out of phase 3120 44 2882 39 In this work H 2 CO···HF complex is studied with the help of FTIR spectroscopy and quantum chemical calculations. High-resolution absorption spectra of the complex in regions of C=O, and C-H are presented. Although, the fact that no changing reasons in ν (HF), stretching bands upon the complexation are explained. Investigation of Formaldehyde+Hydrogen Fluoride Complex in Gas Phase by the Help of Ftir Spectroscopy and Computational Methods © 2023 Global Journals 1 Year 2023 18 Global Journal of Science Frontier Research Volume XXIII Issue ersion I VI ( H ) C onclusion VI.