The cis/trans ratio of N-methylformamide (NMF), N-methylacetamide (NMA), and N-(2-endo-norbornyl)formamide (NNF) in dilute solutions in chloroform, methanol, and water have been experimentally measured by 1 H NMR. Unlike NMA and NMF, the cis/trans ratio of NNF is sensitive to the solvent environment. To understand the anomalous behavior of NNF, we have performed calculations of ∆G and other observables between the cis and trans isomers of NMA, NMF, and NNF both in gas phase and in solution using several ab initio and DFT methods and SCRF models. The strikingly predominance of the trans isomers of N-alkyl substituted formamides can be rationalized in terms of close contact interactions between the formyl group and the C-H bond of the N-alkyl group. The molecular geometries and dipole moments of the studied amides using the RHF and B3LYP theoretical levels and split valence sets are in good accordance with the experimental values. The rotational barriers (ca. 7.0 kcal/mol) around the C2-N bond of cis-and trans-NNF were determined with the RHF/3-21G and B3LYP/6-31G* methods. On the other hand, the PCM model of the SCRF theory offers a satisfactory explanation of the different solvent dependence of NMA and NNF but fails in the computation of the cis/trans ratio of NMF in polar solvents.

A series of p,p‘-disubstituted 7-phenyl-7-(2-fluorophenyl)norbornanes 5xy has been prepared, and the barrier (ΔG #) to 160° libration around the 2-fluoroaryl-norbornane bond has been measured by DNMR. There is spectroscopic evidence of strong homoconjugative and charge-transfer (CT) interactions between both aryl groups of 5xy. However, the relationship between ΔG # and the nature of the substituents X and Y is accounted for only by electrostatic interactions between both aryl groups in the ground state as well as in the transition state of the libration. Therefore, the notion of CT and aromatic homoconjugation as strong attractive forces between aryl groups should be definitively rejected.

Stringent emissions limits introduced for internal combustion engines impose a major challenge for the research community. The technological solution adopted by the manufactures of diesel engines to meet the NOx and particle matter values imposed in the EURO VI regulation relies on using selective catalytic reduction and particulate filter systems, which increases the complexity and cost of the engine. Alternatively, several new combustion modes aimed at avoiding the formation of these two pollutants by promoting low temperature combustion reactions, are the focus of study nowadays. Among these new concepts, the dual-fuel combustion mode known as reactivity controlled compression ignition (RCCI) seems more promising because it allows better control of the combustion process by means of modulating the fuel reactivity depending on the engine operating conditions. The present experimental work explores the potential of different strategies for reducing the energy losses with RCCI in a single-cylinder research engine, with the final goal of providing the guidelines to define an efficient dual-fuel combustion system. The results demonstrate that the engine settings combination, piston geometry modification, and fuel properties variation are good methods to increase the RCCI efficiency while maintaining ultra-low NOx and soot emissions for a wide range of operating conditions.

composition of donor : acceptor = 1 : 0.4, its upper bands are not half-filled. Whereas all other k-type superconductors have the composition of donor : acceptor = 2 : 1 and therefore, half-filled upper bands. The deviation from halffilling makes the on-site Coulomb repulsion comparatively unimportant; this stabilizes the metal state, but is disadvantageous with respect to superconductivity. [15] The same situation has been found in (EOET±TTP) 3 AsF 6 , [5b] and (CH± TTP)(I 3 ) 0.31 . [5c] In summary, we have found a k-type organic metal based on a newly prepared TTP derivative CPEO±TTP. To our knowledge, there is no report on metallic k-type salt base on ethylenedioxy-substituted TTF. [16] In contrast, CPEO± and EOET±TTP afford k-type salts retaining metallic conductivity down to low temperature. Therefore, combination of TTP framework and ethylenedioxy substituent would be suitable for exploring new k-type metals. The preparation of radical-cation salts based on the other ethylenedioxy substituted TTPs is actively in progress. Experimental CPEO±TTP: Red microcrystals; m.p. = 246±247 C (decompose.); 1 H NMR (270 MHz, CS 2 -[ 2 H 6 ]benzene) d 4.17 (s, 4H), 2.49±2.56 (m, 4H), 2.35± 2.45 (m, 2H); I.R. (KBr) u (cm ±1 ) 1653, 1452, 1168. (CPEO±TTP)(SbF 6 ) 0.4 : C 15 F 2.4 H 10 O 2 S 8 Sb 0.4 , M = 573.02, monoclinic, space group C2/c, a = 45.144(3), b = 7.984(4), c = 10.999(5) . b = 99.72 (2), V = 3907(2) 3 , Z = 8, D c = 2.235 g/cm 3 , Mo Ka radiation, l = 0.71069 , m = 23.06 cm ±1 , F(000) = 2576.00. The data were collected on a Rigaku AFC7R diffractometer equipped with graphite monochromated Mo Ka radiation using the o±2y scan technique to a maximum 2y of 55. The structure was solved by direct methods and refined by full-matrix least squares analysis (anisotropic for non-hydrogen atoms) to R = 0.065, R w = 0.070 for 1359 observed (I ³ 3s (I)) reflections from 4816 unique data. All calculations were performed using the teXsan crystallographic software package of Molecular Structure Corporation. Atomic coordinates, bond distances and angles, and thermal parameters have been deposited at the Cambridge Crystallographic Data Center.