1. Synthesis of fluorinated heterocycles
2. Ring-fluorinated pyrazoles
3. USMA, Center for Molecular Science, 2005. Data based on MP2/cc-pvdz energies and B3LYP/6-31G(d) optimization with frequency calculations followed by solvent calculations. Ab initio calculations show that the s-cis chelated enol forms are usually thermodynamically 2–3kcal/mol lower in energy than the diketo form. Additionally, depending on the molecule, a substantial difference in the energy of the enol forms is also indicated. Non-chelated enols forms have energies higher than the chelated enol forms. A detailed computational study of this and other β-diketone equilibria will be published separately.
4. Kinetic studies of fast equilibrium by means of high-performance liquid chromatography. Part 11. Keto–enol tautomerism of some β-dicarbonyl compounds
5. The literature concerning the study of trifluoromethyl-β-diketone tautomerization reveals wide variations in sample preparation with concentrations ranging from neat liquids to 10−5M. Refs. [5–8,16] Any comparative study of K⇌E or E⇌E equilibria must account for these differences since equilibria may be influenced by solution ionic strength, solute–solute and solute–solvent interactions. To mitigate the difficulties that could arise from sample concentration variation, we have limited the range of solution concentrations in this study from 0.2M for NMR, 0.02M for IR and 0.0020M for UV studies as these concentrations strike a balance between instrumentation sensitivity and species solubility. This concentration range was determined acceptable for our study by NMR experiments conducted 0.20, 0.020 and 0.0020M CDCl3. Under these conditions, 1H, 13C, and 19F NMR for compounds 1a and 1h showed no change in chemical shifts or integrated peak values.