Intra- and intermolecular N–H•••O=C hydrogen bonds in 1-acyl urea compounds: Synthesis, X-ray structure, conformational and Hirshfeld surface analyses of 1-(2,3-dichlorophenyl)-3-pivaloylurea

• Published in: Journal of molecular structure 2021-12, Vol.1245, p.131271, Article 131271
• Main Authors: Saeed, Aamer, Hökelek, Tuncer, Bolte, Michael, Erben, Mauricio F.
• Format: Article
• Language: English
• Subjects: Acyl urea; Crystal structure; Hirshfeld surface analysis; Hydrogen bond; Natural Bond analysis
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2021.131271

•X-ray crystal structure was determined for a simple 1-acyl-urea species.•Strong intramolecular N–H•••O=C hydrogen bond is present in the crystal.•Planar pseudo six-membered ring occurs in the central 1-acyl urea group.•1,6-Remote lpO → σ*(N–H) hyperconjugative interaction is found.•Amide bonds form R22(8) dimer motifs. Reaction of freshly prepared pivaloyl isothiocyanate with 2,3-dichloroaniline afforded the 1-(2,3-dichlorophenyl)-3-pivaloylthiourea intermediate (2) which was efficiently converted into the title urea (3) by grinding with wet silica supported potassium permanganate under solvent-free conditions in an excellent yield and purity. The structure was confirmed by the spectroscopic, elemental analysis and single crystal X-ray diffraction data. In the most stable conformation, the two C=O groups adopt a mutually opposite orientation. Intramolecular N–H•••O=C hydrogen bond occurs between the carbonyl (C=O) and urea (–NH) groups forming a six membered pseudo-ring that stabilize the most stable form. The bonding nature of this interaction has been scrutinized by using Natural Bond Orbital (NBO) population analysis, demonstrating the occurrence of a strong hyperconjugative remote interaction between the donor lone pairs located on the carbonyl oxygen and the N–H group. To visualize the intermolecular interactions in the crystal of the title compound, a Hirshfeld surface (HS) analysis was also carried out demonstrating that hydrogen-bonding and van der Waals interactions were the dominant interactions in the crystal packing. The urea groups form centrosymmetric dimers connected by intermolecular N–H•••O=C hydrogen bonds in a R22(8) motif. The 2,3-dichloro substitution has important effects on the packing stability, mostly via H•••Cl contacts, with H•••Cl/Cl•••H contributions of 26.1% of the intermolecular interactions. [Display omitted]