Intramolecular Hydrogen Bonds and Fermi Resonance in N-Substituted N'-(2-Fluorobenzoyl)thiourea Derivatives

Abstract

The presence of intramolecular NH...O=C bonds was proved in N-substituted N'-(2-fluorobenzoyl)thiourea derivatives by analysis of their infrared spectra. The intramolecular vibrational effects bring about a shift of the ν(NH) vibrational band to lower frequencies to the extent that the band gets into a vicinity to the δ(NH) overtone and Fermi resonance occurs between them. In addition, the ν(NH) vibration is also affected by Fermi resonance with the ν(CO) + δ(NH) combination. Double absorption bands were observed in the ν(CO) region for some of the derivatives. Based on perturbation theory applied to three-level interactions and using the Langseth and Lord equations, the band frequencies corrected for Fermi resonance were calculated and the hydrogen bond strength was examined in the compounds studied.

Vibrational spectra of solid cis- and trans-2-thioxohexahydroquinazolin-4(1H)-one and theoretical calculations towards the interpretation of its thermal reactivity

“…21 In several cases, 19,20,[22][23][24] this effect is enough to explain the experimental/calculated spectral differences, but when the molecule shares both N-H and C-H groups, the bands attributed to the Fermi effect appear in the 3650-3300 cm À1 region while in the Raman spectra, they are observable as broad low intensity signals (centered at 3161 and 3184 cm À1 , for cis and trans NH tautomers, respectively). 25,26…”

1-(2-Fluorophenyl)-3-(3,4,5-trimethoxybenzoyl)thiourea

“…Fluorinated bis-thiourea derivatives are used as organocatalyst in Morita-Baylis-Hillman reaction (Berkessel et al, 2006). N-Substituted N′-(2-fluorobenzoyl)thiourea derivatives are suitable substrates for studying Intramolecular Hydrogen Bonds and Fermi Resonance (Hritzová & Koščík 2008). Fluorinated thioureas have shown potent microbial (Saeed et al, 2009) and insecticidal activities (Xu et al, 2003).…”

“…For fluorinecontaining heterocycles, see: Lipunova et al (2008). For intramolecular hydrogen bonds and Fermi resonance measurements, see: Hritzová & Koščík (2008). Table 1 Hydrogen-bond geometry (Å , ).…”

1-(4-Fluorophenyl)thiourea

“…For the use of fluorinated thioureas in organic synthesis, see: Nosova et al (2006Nosova et al ( , 2007; Lipunova et al (2008); Berkessel et al (2006). N 0 -(2-fluorobenzoyl)thiourea derivatives are suitable substrates for studying intramolecular hydrogen bonds and Fermi resonance, see: Hritzová & Koščík (2008).…”

“…Fluorinated thioureas exhibit a variety of biological activities: potent influenza virus neuraminidase inhibitors (Sun et al, 2006), antimicrobial (Saeed et al, 2009) and insecticidal activities (Xu et al, 2003). Moreover, fluorinated bis-thiourea derivatives are also used as organocatalyst in Morita-Baylis-Hillman reaction (Berkessel et al, 2006) and N-Substituted N′-(2-fluorobenzoyl)thiourea derivatives are suitable substrates for studying Intramolecular Hydrogen Bonds and Fermi Resonance (Hritzová & Koščík 2008). The aromatic ring plane and the thiourea moiety are twisted with a torsion angle C2-C1-N1-C7 of 44.6 (2)°.…”