He was a chemist at the California Institute of Technology, and subsequently headed both the Departments of Chemistry and Chemical Engineering at the university.

From an early age Hammond was charged with running the day-to-day operations of the dairy farm with his mother and older siblings.

He graduated with a Bachelors of Science in chemistry magna cum laude and Phi Beta Kappa in January 1943.

After some months on the job he quit to pursue graduate studies at Harvard University, where he received a Masters of Science (M.S.)

[1] His academic career began in 1948 with a teaching position at Iowa State College; he served as Assistant Professor of Chemistry.

After 14 years teaching and serving as an academic administrator at Caltech he moved in 1972 to the University of California Santa Cruz.

[1][9] Aside from the academic world, during all these years, George Hammond, "made many public speeches on controversial themes, both political (e.g., the invasion of Cambodia, delivered in 1971 at a public rally on Caltech's Olive Walk) and scientific (e.g., the future of chemistry)"[8] Many of these controversial speeches affected his career negatively.

For example, after his speech at Olive Walk, president Richard Nixon's administration removed his name from nomination for a major NSF post.

[8] Nevertheless, he did not back down and continued to criticize the government, and not limiting to delivering speeches, he wrote a letter to the editor of a newspaper saying: “A June 30 front-page article describes the potential bonanza in arms sales to new members as the North Atlantic Treaty Organization expands.

I was favorably inclined toward expansion because of my naive assumption that bringing most of the nations of Europe and North America together as a cooperating group would decrease the likelihood of war.

Also, in the excerpt, a sarcastic side of Hammond can be perceived, a man of strong character with the ability to recognize when he is wrong.

The talks he gave sometimes had negative impacts on his life, exemplified by Nixon's withdrawal of his name for major National Science Foundation positions.

In 1979 he retired from academia and joined the Allied Chemical Corporation as Executive Chairman, serving for ten years.

"[11]Therefore, the geometric structure of a state can be predicted by comparing its energy to the species neighboring it along the reaction coordinate.

Hammond's postulate explains this observation by describing how varying the enthalpy of a reaction would also change the structure of the transition state.

By measuring the effects of aromatic substituents and applying Hammond's postulate it was concluded that the rate-determining step involves formation of a transition state that should resemble the intermediate complex.

[15] During the 1940s and 1950s, chemists had trouble explaining why even slight changes in the reactants caused significant differences in the rate and product distributions of a reaction.

In 1955 George S. Hammond, a young professor at Iowa State University, postulated that transition-state theory could be used to qualitatively explain the observed structure-reactivity relationships.

[3] However, Hammond's version has received more attention since its qualitative nature was easier to understand and employ than Leffler's complex mathematical equations.

Case (c) depicts the potential diagram for an endothermic reaction, in which, according to the postulate, the transition state should more closely resemble that of the intermediate or the product.

Another significance of Hammond's postulate is that it permits us to discuss the structure of the transition state in terms of the reactants, intermediates, or products.

To understand what is meant by an “early” transition state, the Hammond postulate represents a curve that shows the kinetics of this reaction.

[20] An E1 reaction consists of a unimolecular elimination, where the rate determining step of the mechanism depends on the removal of a single molecular species.

[21] Furthermore, studies describe a typical kinetic resolution process that starts out with two enantiomers that are energetically equivalent and, in the end, forms two energy-inequivalent intermediates, referred to as diastereomers.

Factors that affect the rate determining step are stereochemistry, leaving groups, and base strength.

A theory, for an E2 reaction, by Joseph Bunnett suggests the lowest pass through the energy barrier between reactants and products is gained by an adjustment between the degrees of Cβ-H and Cα-X rupture at the transition state.

However, Hammond's postulate indirectly gives information about the rate, kinetics, and activation energy of reactions.

Hence, it gives a theoretical basis for the understanding the Bell-Evans-Polanyi principle, which describes the experimental observation that the enthalpy change and rate of similar reactions were usually correlated.

In these kinds of reactions, especially when run at lower temperatures, the reactants simply react before the rearrangements necessary to form a more stable intermediate have time to occur.

At higher temperatures when microscopic reversal is easier, the more stable thermodynamic product is favored because these intermediates have time to rearrange.