Two anti-2,4-bis(3-R-phenyl)pentane-2,4-diols (1, R = Me; 2, R = SMe) have been synthesized and were characterized by X-ray diffraction, IR and UV spectra. X-ray diffractions indicate that intra- and intermolecular hydrogen bonding interactions form one-dimensional (1D) ribbons. The adjacent infinite 1D ribbons result in 3D supramolecular structures. The dihedral angles between every two benzene rings in the two diols are 31.61(12) and 31.80(7)°, respectively. UV absorption spectra of the title compounds were recorded in MeOH, C2H5OH, CH3CN, n-BuOH and cyclohexane solvents with different dielectric constants.
2,4-diphenylpentane-and 2,4-di-p-tolylpentane-2,4-diols were investigated employing experimental and density functional theory(DFT) method at B3LYP/6-31G(d) level.The structure of syn-2,4-di-p-tolylpentane-2,4-diol(2b) was characterized by X-ray diffraction and compared with the crystal structures of anti-and syn-2,4-diphenylpentane-2,4-diols(1a and 1b).X-ray diffraction indicates that inter and intra-molecular hydrogen bonds are formed in the crystal structures.There is π-π staking interaction in 1b and 2b.Good linear correlations and similar results are found between the experimental 1H and 13C NMR chemical shifts(δexp) and GIAO(Gauge Independent Atomic Orbital) method calculated magnetic isotropic shielding tensors(σcalc),HOMO and LUMO molecular orbitals were calculated at the same levels with the different results.UV-vis absorption spectra of the compounds were recorded in EtOH,MeCN,n-BuOH and cyclohexane with different dielectric constants.It is found that the solvent effect is obvious when ε is 24.85(EtOH),35.69(MeCN) and it is weak when ε is decreased to 17.33(n-BuOH),1.18(cyclohexane).
This paper summarizes significant progress in quantifying organic substituent effects in the last 20 years. The main content is as follows: (1) The principle of electronegativity equalization has gained wide acceptance, and has been used to calculate the intramolecular charge distribution and inductive effect of groups. A valence electrons equalization method was proposed to compute the molecular electronegativity on the basis of geometric mean method, harmonic mean method, and weighted mean method. This new calculation method further extended the application of the principle of electronegativity equalization. (2) A scale method was established for experimentally determining the electrophilic and nucleophilic ability of reagents, in which benzhydryliumions and quinone methides were taken as the reference compounds, and the research field was extended to the gas phase conditions, organometallic reaction and radicals system. Moreover, the nucleophilicity parameters N and electrophilicity parameters E for a series of reagents were obtained. The definition and quantitative expression of electrophilicity index and nucleophilicity index were proposed theoretically, and the correlation between the parameters from experimental determination and the indexes from theoretical calculation was also investigated. (3) The polarizability effect parameter was initially calculated by empirical method and further developed by quantum chemistry method. Recently, the polarizability effect index of alkyl (PEI) and groups (PEI X ) were proposed by statistical method, and got wide applications in explaining and estimating gas-phase acidity and basicity, ionization energy, enthalpy of formation, bond energy, reaction rate, water solubility and chromatographic retention for organic compounds. (4) The excited-state substituent constant ex CC obtained directly from the UV absorption energy data of substituted benzenes, is different from the polar constants in molecular ground state and the radical spin-delocalization effects constants in mo
