Methylene theoretical estimates

The aim of this work is a study of electronic stmcture of molecule l-methylene-4-vinylcyclohexane [1] and theoretical estimation its acid power by quantum-chemical method MNDO. The calculation was done with optimization of all parameters by standard gradient method built-in in PC GAMES S [2]. The calculation was executed in approach the insulated molecule in gas phase. Program MacMolPlt was used for visual presentation of the model of the molecule [3]. 

In neat or dilute aqueous solutions the vicinal coupling between hydroxyl and methylene protons is also measurable (J[OH,CH2] = 5 Hz), but additional H-O-C—H torsional conformers would be needed to obtain the appropriate Boltzmann-weighted theoretical estimate. ... 

There is only one example which makes use of a biopolymer, starch, imprinted with a dye [60]. Methylene Blue could be adsorbed on starch which was crosslinked with cyanuric chloride to almost 100% with respect to the concentration of theoretically available binding sites. The blank adsorbed a mere 17% under identical conditions. It is estimated that 7-8 glucose units form a single cavity for the template, somewhat reminiscent of a- or P-cyclodextrins, but shape selectivity has not been investigated. It seems remarkable but these investigations seem to have been initiated without any awareness of the earlier work on imprinting. 

ANO basis set used gives a separation in good agreement with, but smaller than, the value deduced from a combination of theory and experiment. From the convergence of the result with expansion of the ANO basis set, it is estimated that the valence limit is about 9.05 + O.lkcal/mole. The remaining discrepancy with experiment is probably mostly due to core-valence correlation effects. However, as the valence correlation treatment is nearly exact, finer effects such as Bom-Oppenheimer breakdown and relativity must also be considered. While FCI calculations have shown that a very high level of correlation treatment is required for an accurate estimate of the CV contribution to the separation, theoretical calculations indicate that CV correlation will increase the separation by at most 0.35 kcal/mole (see later discussion). Therefore, it is now possible to achieve an accuracy of considerably better than one kcal/mole in the singlet-triplet separation in methylene. 

As an introduction, our previous studies on the conformations of maleic acid copolymers with aromatic vinyl monomers are summarized. To characterize the compact form and the pH-indueed conformational transition of the maleic acid copolymer with styrene in aqueous NaCl, 400 MHg H-NMR spectra were measured. The spectral form depended on the molecular conformation. Because each of proton resonance peaks could not be separated, the spin-lattice relaxation time T was estimated by using the inversion recovery technique (tf-t-tf/2). The T s for both side chain and backbone protons reflected the transition, and the protons were considered to be in a more restricted motional state in the compact form than in the coil form. Also, from temperature dependence of each Tj, motion of the copolymer in the coil form was described in terms of the local segmental jump (D) combined with the isotropic rotational motion (O), when a ratio between both the correlation times tq and Tq was about 0.07. For the compact form, the ratio was found to be about 10. By referring to theoretical diagram of Tj vs. tq for the methylene protons on the backbone, value of Tn for the compact form was compared with that for the coil form at 35 C. 

Provide an estimation of the theoretical work of adhesion of formamide, of acetone, and of methylene iodide with PS. 

In order to compare experimental and theoretical heat capacity changes at Tg, a baseline heat capacity - temperature curve below Tg must be constructed. This was accomplished by measuring the Cp - T behavior for poly(dimethyl itaconate). That for the octyl derivative was then estimated by adding a contribution from each additional methylene unit measured from the vibrational frequencies for this unit and the acoustical frequencies used by Dole for polyethylene. It was then... 

In order to rationally connect the NMR spectral information to the solution conformation of the oUgomers, the chemical shifts of the main-chain methylene and terminal methine or ethyl protons were computationally estimated by density functional theory (DFT) [78] calculation for some optimized conformers of 1 of n=2 and 2 of n=2 and 4. The conformer structures optimized by the semiempirical PM5 method [51] are shown in Fig. 17 with their heats of formation (PM5) and theoretical chemical shifts obtained by the LORG method [79] using B88 [80]... 

---