NMR Magnetic Shielding and Isotropic Chemical Shift Studies on Gas Phase, Chloroform and Water Solvent of Urea Molecule

Antonio Luiz Almeida

Resumo


The importance of UREA (CH4N2O) as fertilizer[1] in the agricultural industry has grown enormously in recent years and according to all forecasts. Thus, a detailed understanding of its reaction mode with the soil is of fundamental importance. In this work we study the NMR (Nuclear Magnetic Ressonance) chemical shift, δ, for the urea molecule atoms, defined as  where  is the absolute shielding of the reference compound and  is the absolute shielding of the urea molecule atoms in gas phase and chloroform solvents. The absolute shielding were calculated with GIAO (Gauge-Including Atomic Orbitals),  CSGT (Continuous Set of Gauge Transformations)  and IGAIM (Individual Gauges for Atoms in Molecules)  methods. Solvent effects were analyzed with the use for calculations of the Polarizable Continuum Model (PCM) as the default in self-consistent reaction field (SCRF) method. The PCM method treats the continuum as a polarizable dielectric ℰ. For Gas Phase , for Chloroform and water solvent. For  we have used Tetramethylsilane (TMS) [Si(CH3)4], Nitromethane [CH3NO2] and water [H2O].  For all calculations we used Density Functional Theory (DFT) with WP04/aug-cc-pVTZ fuctional and basis set.

 


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