Quantitative Correlation On The Physico-chemical Property Of The Monosubstituted Alkanes And Primary Investigation Of The Interrelations Among The Propeties

In this work, a segmentation method that had been proposed by our work group was employed in which the property of a molecule RX can be contributed by three parts (that is, the contribution of the alkyl R in RX to the property of RX, the contribution of the X group and the contribution of the interaction of the alkyl R with the substituent X). The segmentation method can be expressed by the following equationwhere, p(RX) is the property of RX, h(R) and h(X) are the contribution of R and X to the property of RX respectively,and the item (?)(R)(?)(X) denotes the contribution of the interaction of the substituents in RX. Based on the electrostatic effects of the alkyl R and the substituent X in the monosubstituted alkane RX, the rule of the interaction of R and X was found in this paper. Combining the topological electronegativity index of alkyl which had been proposed by our work group. The estimating models for the properties (including the heat of formationΔH_f⁰, heat capacities Cp⁰, Gibbs energies of formationΔ_fG⁰, boili point Tb, density and refractive index n_D) of monosubstituted alkane were established. The obtained models in this paper can give good results; what'more, these models have an explicit physical meaning.In this paper, based on the relationship between the heat of formation and the change of valence electronic energy in the formation of a compound from its component atoms, and combined with the relationship between the first ionization potential and the average valence electronic energy, the direct link of ionization potential, I_P, with the heat of formation,ΔH_f⁰, was deduced for organica homologous compounds, that is,where N_ve,m is the number of valence electrons in molecule, SVEE_X is the sum of valence electronic energy of isolated atoms forming the molecule, the symbol R_m represents its final-state effect (polarizability effect). a, band c are all constants. The above equation was confirmed by the correlations between the ionization potentials and the heat of formation of alkanes, alkenes, monosubstituted alkanes RX(X=OH, NH₂, SH, Cl, Br and I), in which all the expressions have good correlations (correlation coefficient and standard error showed the equations have good stability and predictability). According to the changeable characteristic of the atom volum when a molecular is formed, the direct relations between density and the heat of formationΔ_fH⁰ was proposed which can be used to predict the property of more expensive or time-comsuming test from that of less expensive and measured. The primary research of the relation of the physico-chemical properties will be a new thought and a new way for the research of physico-chemical properties.