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Manuel Colomina ConceptiŌn Turrión Pilar Jiménez M. Victoria Roux Joel F. Liebman 《Structural chemistry》1994,5(2):141-143
The relative steric demands of carboxyl and methyl groups are compared by contrasting the difference quantity H
f
o
(g, ArCOOH) — H
f
o
(g, ArCH3) for a collection of alkylated benzoic acids and toluenes with the value for Ar=C6H5, the archetypical (i.e., unsubstituted) benzoic acid and toluene. We conclude that carboxyl and methyl groups are nearly the same size. 相似文献
2.
Tomás Pérez-Ruiz Carmen Martínez-Lozano Virginia Tomás Conceptión Paredes 《Mikrochimica acta》1995,118(3-4):203-211
The color-forming reactions of molybdenum(VI) and vanadium(IV) with carminic acid (CA) in the presence of cetyltrimethylammonium bromide (CTAB) were used in the flow-injection determination of these metals. The micellar medium enhances the spectrophotometric features of the Mo(VI)-CA and V(IV)-CA binary complexes, and the higher solubility of these complexes when the CTAB concentration is above critical micelle concentration permits the easy application of flow-injection systems. Under the optimum conditions, linear calibration graphs were obtained from 0.76 to 28.8 g/ml for molybdenum and from 0.30 to 9.1 g/ml for vanadium. The detection limits were 0.33 and 0.16 g/ml for molybdenum and vanadium, respectively. The selectivity of the method was investigated and the procedure was successfully applied to the determination of molybdenum in steels and pharmaceuticals and of vanadium in petroleum products. 相似文献
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