Dr. Mario Jose Molina (1943 – ) Mexican chemist

Mario Molina was born on March 19, 1943, in Mexico. He received his bachelor's degree from the National Autonomous University of Mexico in 1965 and his Ph.D. in physical chemistry from the University of California at Berkeley in 1972. After teaching for a year at the National Autonomous University, he returned to Berkeley as a research associate for one year.

In 1973, Molina joined the research laboratory of F. Sherwood Rowland at the University of California at Irvine. Molina was looking for a topic on which he could do his post-doctoral research with Rowland, and Rowland was ready with a suggestion because he had just come from a scientific meeting where he became interested in the possible effects of an important commercial chemical, trichlorofluoromethane, also known as chlorofluorocarbon-11, or CFC-11. The compound was a member of a widely-successful group of chemicals , called freons, produced by Dow Chemical Company.

In particular, the question that interested Rowland was what effects, if any, this compound would have on atmospheric gases. CFC-11 was rapidly becoming very popular as a propellant in hair sprays, spray paints, and other aerosol products. By 1974, more than $2 billion of CFC-11 and related chlorofluorocarbons were being used each year.

Rowland and Molina developed a theory about the fate of CFC molecules released in the troposphere , the layer of the atmosphere in which we live. They predicted that those molecules would rise into the stratosphere , the layer of air above the troposphere. There, they said, solar energy would cause CFC molecules to decompose, releasing free chlorine atoms.

If that were to happen, they hypothesized, the free chlorine would be likely to attack ozone molecules, converting them to ordinary oxygen. The chlorine oxide formed in that reaction might then react with single oxygen atoms, to form more oxygen and regenerate the original chlorine.

Two important conclusions can be drawn from this series of reactions. First, a single atom of chlorine would be capable of destroying many (Rowland and Molina predicted about 100,000) molecules of ozone. Second, since ozone in the stratosphere absorbs ultraviolet radiation , this process would result in more ultraviolet radiation reaching the earth's surface and causing an increase of skin cancer among humans.

When Rowland and Molina first proposed this theory, no measurements had ever been made of chlorine in the stratosphere. By 1979, they had carried out the first of those measurements and obtained results that closely matched their predictions. An important new environmental problem, ozone layer depletion , had been identified.

Molina held positions as a research associate, assistant professor, and associate professor at the University of California at Irvine. In 1983, he left Irvine to become Senior Research Scientist at the Jet Propulsion Laboratory at the California Institute of Technology in Pasadena. Molina was awarded the Society of Hispanic Engineers Award in 1983. He is also the recipient of more than a dozen awards including the 1987 American Chemical Society Esselen Award, the 1988 American Association for the Advancement of Science Newcomb-Cleveland Prize, the 1989 NASA Medal for Exceptional Scientific Advancement, and the 1989 United Nations Environmental Programme Global 500 Award. In 1995, he received the Nobel Prize in Chemistry along with F. S. Rowland and P. Crutzen.

[David E. Newton ]

RESOURCES

PERIODICALS

Molina, M. J., et al. "Experimental Study of Intermediates from OH-initiated Reactions of Toluene." Journal American Chemical Society 121 (1999): 10225—10226.

——, and M. J. Molina. "Chlorofluoromethanes in the Environment." Review of Geophysical Space Research (January 1975): 1–35.

Rowland, F. S. "Atmospheric Chemistry: Causes and Effects." MTS Journal (Fall 1991): 12–18.

OTHER

Mario Molina Web Page. [cited July 2002]. <http://eaps.mit.edu/molina>.