Patricia Amador

Enantioselective addition of et2zn to benzaldehyde catalyzed by n-(s)-α-methylbenzyl-β-aminoalcohols

Abstract The enantioselective alkylation of benzaldehyde by diethylzine in the presence of catalytic amounts of N-(S)-α-methylbenzyl-β-aminoalcohols as the dilithium salts was studied. The extent of asymmetric induction was found to depend strongly upon the structure of catalyst used and also on the presence of lithium chloride.

Experimental and Computational Thermochemistry of 3- and 4-Nitrophthalic Anhydride.

In order to understand the influence that the position of the nitro group on the aromatic ring has on the relative stability of two isomers, the standard enthalpies of formation of 3- and 4-nitrophthalic anhydride in the gaseous phase, at T = 298.15 K, were obtained by experimental thermochemistry and theoretical studies. The standard enthalpies of formation in the crystalline phase, at T = 298.15 K, were obtained by combustion calorimetry and the enthalpies of sublimation by the Knudsen method. For the theoretical calculations, a standard ab initio molecular orbital method at the G3 level was used. The enthalpies of formation in the gaseous phase were obtained from atomization and isodesmic reactions. A theoretical study of the molecular and electronic structures of these compounds was also performed. Differences of -9.7 kJ·mol-1, for 3-nitrophthalic anhydride, and -2.6 kJ·mol-1 for 4-nitrophthalic anhydride, were found from a comparison between our theoretical and experimental results.

d-Galactono-1,4-lactone: a case of wrong absolute configuration surviving three decades

The title compound, C6H10O6, had been previously characterized by X-ray analysis but was reported with the wrong absolute configuration [Jeffrey, Rosenstein & Vlasse (1967). Acta Cryst. 22, 725–733]. This structure has now been redetermined at higher resolution and including precise positions for H atoms.

Experimental and Theoretical Thermochemistry of the Isomers: 3- and 4-Nitrophthalimide

This work presents a thermochemical study of two derivatives of phthalimide: the isomers 3-nitrophthalimide and 4-nitrophthalimide. The enthalpies of formation for these compounds in the solid phase were obtained by combustion calorimetry. Using ths thermogravimetry technique, the enthalpies of vaporization were obtained. The enthalpies of sublimation were calculated from enthalpies of fusion and vaporization. From experimental data and by ab initio methods, the enthalpies of formation in the gas phase were calculated. With these results, it was possible to determine their relative stability, and it was found that 4-nitrophthalimide is more stable than its isomer 3-nitrophthalimide. This tendency is similar to that of 3-nitrophthalic anhydride and 4-nitrophthalic anhydride, as reported in a previous work by our research group. The enthalpy of isomerization was also obtained, and a good correlation with that of phthalic anhydride derivatives was found. Finally, with the values obtained, the enthalpic difference resulting when the imide group is substituted by an anhydride group was determined.