STO-4G-SCF-MO calculations and NMR measurements for alkenylphosphonic acids

• Published in: Journal of molecular structure 1990-03, Vol.218, p.175-181
• Main Authors: Smeyers, Y.G., Hernandez-Laguna, A., Sainz-Diaz, C.I., Fernandez-Ibañez, M., Galvez-Ruano, E., Arias-Perez, M.S.
• Format: Article
• Language: English
• Subjects: Atomic and molecular physics; Exact sciences and technology; Molecular properties and interactions with photons; Physics; Properties of molecules and molecular ions
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/0022-2860(90)80263-J

SCF-MO ab-initio calculations (STO-4G//STO-4G and 3-21G//3-21G) and 13C NMR measurements of the vinyl ( I), E/Z propenyl ( II/III) and E/Z 2-carboxy-vinyl ( IV/V) phosphonic acids are performed. The rotational potential energy hypersurface has been studied around the bonds CP (CCPO) and CC (CCCO). Moreover the dispositions of minimum energy of the bonds HOP (HOPO), HOC (HOCO) and HCC( HC(H) 2-CC) have been studied. We have found in all these compounds that the more stable disposition of HOP is the “syn” one (HO/PO). In IV the more stable dispositions of HO/CO and CC/CO are “syn” and s-cis respectively, but in V adopt both the anti one, due to the formation of a intramolecular hydrogen bond “COH…OP”. The bond HCC has the disposition θ(HCCC)=180 o in II and θ(HCCC)= O o in III. In relation to the rotation of CP, the more stable conformer is the s-cis coplanar (CC/PO are s-cis coplanar, θ(OPCC)O o and s-trans no coplanar, θ(OPCC) 114–118 o . A reasonable agreement between the charge distributions and 13C NMR chemical shifts is observed except for IV and V.