Chenzhong Cao

On molecular polarizability: 3. Relationship to the ionization potential of haloalkanes, amines, alcohols, and ethers

The relationship between the ionization potential and the parameters molecular electronegativity and molecular polarizability for haloalkanes, amines, alcohols, and ethers was investigated. There is no good linear correlation between the ionization potential Ip and molecular electronegativity chi(eq) alone for these compounds. Ip can be modeled well with three parameters: chi(eq), polarizability effect index (PEI) of an alkyl group, and atomic polarizability (P). Further, a single expression for predicting the Ip values of aldehydes, esters, nitriles, and carboxylic acids was developed: Ip(Rz)(eV) = Ip(MeZ) + 1.4544delta chi(eq) - 1.6435delta sigmaPEI(Ri). Here Ip(MeZ) is the experimental ionization potential of monosubstituted methane MeZ. Delta chi(eq) and delta sigmaPEI(Ri) are the difference in the molecular electronegativity and the difference in the polarizability effect index of alkyl groups attached to the functional group Z between molecules MeZ and RZ, respectively.

Enthalpies Estimation of Formation of Monosubstituted Alkanes by Interaction Potential Index

The interaction potential index IPI(X) of 16 kinds of substituents X (X=OH, SH, NH2, Br, Cl, I, NO2, CN, CHO, COOH, CH3, CH=CH2, C≡CH, Ph, COCH3, COOCH3) were proposed, which are derived from the experimental enthalpies of formation (see PDF) values of monosubstituted straight-chain alkanes. Based on the IPI(X) and polarizability effect index, a simple and effective model was constructed to estimate the (see PDF) values of monosubstituted alkanes RX (including the branched derivatives). The present model takes into account not only the contributions of the alkyl R and the substituent X, but also the contribution of the interaction between R and X. Its stability and prediction ability was confirmed by the results of leave-one-out method. Compared with previous reported studies, the obtained equation can be used to estimate enthalpies of formation for much more kinds of monosubstituted alkanes with less parameters. Thus, it is recommended for the calculation of the (see PDF) for the RX.

A QSPR correlation on the 13C NMR chemical shifts of bridge carbons for different series of aromatic Schiff bases

Nuclear magnetic resonance (NMR) spectroscopy has attracted immense attention because of playing an important role in not only determining molecular structures but also explaining reaction mechanisms, molecular dynamics, chemical equilibrium, etc. With the advancement of NMR technology, there is more and more NMR experimental information obtained. Consequently, many efforts have been made to understand relationships between molecular structures and different kinds of NMR chemical shifts. In investigations on C NMR of specific carbons for aromatic systems with a changing substituent, the chemical shift (δC) values are usually calculated with the single substituent parameter treatment or the dual substituent parameter treatment, [15] shown as Eqns (1) and (2), where σ, σF (or σI) and σR are the Hammett parameter, inductive parameter, and resonance parameter, respectively, and C is a constant.