Vol. 113 No. 1 (2017)

Resumen: La atmósfera que respiramos actualmente es el resultado de un proceso de cambios e interacciones en el que la geología, la entrada de objetos extraterrestres y el nacimiento y evolución de la vida han jugado un papel esencial. En este artículo resumimos el conocimiento sobre el origen y la evolución de la composición de la atmósfera del planeta durante el Precámbrico, desde la formación del planeta hasta la explosión cámbrica, con los principales puntos en discusión. Revisamos los eventos clave de forma cronológica y exponemos algunas preguntas aún no respondidas.
Palabras clave: Tierra primitiva, atmósfera planetaria, sopa primordial, química prebiótica, origen de la vida.
Abstract: The atmosphere we breathe is the result of changes and interactions where geology, incoming extraterrestrial objects and origin and evolution of life have a key role. This article summarizes the current scientific view of the origin and evolution of Earth’s atmosphere during Precambrian and the major events of its evolution sorted chronologically, including a review about controversial points, their implications and a discussion on the open unsolved questions.
Keywords: Early Earth, planetary atmosphere, primordial soup, prebiotic chemistry, origin of life.

Biocatalysis plays a fundamental role in the design of sustainable processes for the preparation of relevant organic molecules. The discovery of enzymatic activity in organic solvents together with the possibility of modifying their surface through immobilization techniques, or alternatively their amino acid sequence by using molecular biology techniques, provide access to robust and attractive catalysts for the industrial sector. The compatibility of different biocatalysts under similar reaction conditions has led to the development of concurrent processes, which allow the design of straightforward chemical routes with excellent yield and selectivity values. Nowadays enzymes are considered as versatile catalysts for synthetic transformations since the implementation of biotransformations has been possible in many chemical multinational enterprises, while the creation of biotechnological companies has suffered an exponential growth since the early xxi century until now.

Resumen: El concepto de camino de enlace fue propuesto por Richard F. W. Bader en 1977 (hace cuarenta años) y, ahora, es parte del conocimiento básico en química teoríca y en cristalografía. No obstante, y fruto de su incomprensión, su importancia es todavía objeto de debate en la literatura. El camino de enlace es una manifestación observable de la densidad electrónica que constituye el único mapeo directo en nuestro espacio físico real tridimensional de la fórmula estructural de un compuesto dibujada sobre la base de su química conocida.
Palabras clave: Camino de enlace, enlace químico, teoría quántica de los átomos en moléculas (QTAIM).
Abstract: The bond path concept has been advanced by Richard F. W. Bader in 1977 (forty years ago) and is now part of the core knowledge of theoretical chemistry and crystallography, yet its usefulness and significance is still debated in the literature occasionally when incorrectly applied. The bond path is an observable manifestation of the electron density that constitutes the unique direct mapping, in the real three-dimensional physical space, of the structural formula of a compound drawn on the basis of its known chemistry.
Keywords: Bond path, chemical bond, the quantum theory of atoms in molecules (QTAIM).

Resumen: Se presenta una primera aproximación a la biografía de Josep Pascual Vila, catedrático de Química Orgánica de la Universidad de Barcelona durante más de treinta años. Su trayectoria permite explicar la evolución de una escuela de investigación iniciada en los años 20 y desarrollada durante el franquismo.
Palabras clave: Josep Pascual Vila, Química Orgánica, Universidad de Barcelona, CSIC.
Abstract: This is a preliminary approach to the biography of Josep Pascual Vila, Professor of Organic Chemistry at the University of Barcelona for more than thirty years. His career helps us to describe a longstanding research school, from the 1920s to Franco dictatorship.
Keywords: Josep Pascual Vila, Organic chemistry, University of Barcelona, CSIC.

Abstract: A simple and inexpensive procedure, based on the electrolysis of copper sulfate, is presented to determine the value of Avogadro’s constant NA. From the weight of the metallic mass deposited in this process (weighted independently of the anode), measured as a function of the duration of the electrolysis, numerical results for NA are obtained in very good agreement with the internationally accepted value. This is a remarkable fact, given the characteristics of the experimental set up employed, which is based in the use of household and low cost materials. Given the quality of the result, as well as the simplicity and economy of devices, this activity represents an excellent complement to the discussion of the concept of mole and the associated numerical quantity.

Keywords: Avogadro’s constant, Electrolysis, Low cost experiments