The purpose of this work is to determine the geometric parameters of methylene and six (6) analogues in the first electronic states: singlet state (S0) and triplet state (T1) with advanced quantum chemistry methods for a better knowledge of their structures. For this reason, we used Hartree-Fock (HF), MP2, B3LYP, G3, CBS -Q and CBS APNO levels of theory associated with correlated Dunning basis set (cc-pVTZ), using the Gaussian 03 suite of programs. According to this study, we observe that C -H bond lengths are always larger in the S0 state than in the T1 state for the methylene; according to the results of all computational methods used. For C -X (X = Cl) bond, we have the same behavior as for C -H bond in the methylene. When X = F, we have an opposite behavior. Indeed, C -X bond is always longer in the state T1 than in the state S0. Concerning bond angles, we observe that, the angle XCY is always smaller (100 ° -110°) in the S0 state than the T1 one (118° -135°). The valence angle increases from F to Cl; this may be explained both by the decrease of electronegativity and the steric hindrance of atoms becoming increasingly large. In the particular case of the monohydroxycarbene and dihydroxycarbene, we have a slightly more complex geometry than methylene and group of the halogenocarbenes because here, a dihedral angle is in addition to other internal drawcords.

Quinoline derivatives have several reactionnels sites conferring them a hight reactivity. This makes them excellent precursors in the synthesis of new bioactive compounds. Considering the interest of quinoline chemistry and diversity of their applications, a study based on a theoretical approach of reactivity of 4,4-dimethyl-3,4-dihydro-quinolin-2(1H)-one and derivatives is carried. This study determines interaction sites of these derivatives in order to understand the mechanisms involved. Calculations are carried in gaseous phase and solution in N, N-dimethylformamide (DMF). Density Functional Theory (DFT/B3LYP) method associated with 6-311G(d) and 6-311+G (d) bases is used to perform these calculations. Results of the thermodynamic parameters showed that there is a tautomeric equilibrium relationship between the different derivatives Reactivity analysis based on Frontier Molecular Orbitals theory revealed that tautomers ketone are less reactive than tautomers enol. Calculation of Fukui indices indicates that the carbon atoms C 2 , C 3 , C 5 , C 7 and C 8 of quinoline-2-one ring are sites favorable to nucleophilic attack. Atoms N 1 , C 4 , C 6 and O 11 are nucleophilic sites therefore favorable to an electrophilic attack. Methoxyl substituent (CH 3 O) decreases the acidity of nitrogen and oxygen atoms of quinolin-2-one while bromine atom increases acidity of these same sites. These results predict a deprotonation of the nitrogen (N 1 ) of the brominated quinoline-2ones less energetic than that of the methoxylated derivatives. Conclusively, this work provides data to elucidate the mechanisms to understand the reactivity of 4,4-diméthyl-3,4-dihydroquinolin-2(1H)-one derivatives.