Pd
N
O
Cl
C
H Most of the H atoms are not in the model, they are implied
SPARTEINE
1-PHENYLETHANOL
MODEL BEHAVIOR You could say this molecular model was the catalyst for Professor Jason Keith’s career — both literally and figuratively. “This was the molecule that started it,” says the chemistry professor. The model has accompanied Keith from graduate school at California Institute of Technology, to his post-doc at Texas A&M, to his fellowship at Las Alamos National Labs, and finally, its current stop at Colgate. “It’s my chemical totem,” says Keith, who traveled cross-country to Colgate in 2013. A computational chemist, Keith doesn’t work with test tubes and beakers. His lab is his computer, where he uses mathematical equations, quantum physics, and computer science to look at chemical reactions. He built the model from a kit in graduate school as he was co-authoring his first published paper, “A Computational Model Relating Structure and Reactivity in Enantioselective Oxidations of Secondary Alcohols by (−)-Sparteine−PdII Complexes.” The model shows (−)-Sparteine−PdII; Keith and his office mate were using it to help them visualize their theory. Keith and his coauthors were testing why certain types of chemicals were or were not reacting. “Selectivity is where everything is at in synthetic chemistry,” he says. “If you can do a reaction that oxidizes one type of chemical environment but doesn’t oxidize some other ones, it can help you build specific molecular targets.” The real-world implications of this work could apply to myriad natural and manmade products, from fuels to pharmaceuticals. In Keith’s work, he computationally evaluates a system and tries to learn based on first principles. In other words, he asks: Based on the underlying physics and mathematics of a system, why does it do what we observe? “And hopefully we can understand why it does what we think it does,” Keith says. “You’re sort of 40
scene: Spring 2018
limited by your own creativity. You only get the answers to the questions you ask, so you have to figure out what questions are the right ones to ask.” In this particular system, they modeled the selectivity of two molecules called enantiomers, which have the same structure but are mirror images of each other — “like your left and right hands,” Keith says. One reacted and the other one didn’t. “This is like your right hand fitting into your right glove while your left hand doesn’t fit,” he explains. Stepping away from the computer to build models is a useful exercise for new chemists, Keith says, because it helps them visualize how chemical reactions happen. “One of the biggest factors is the spatial arrangement of the atoms,” he explains. “It’s all about how the individual atoms interact with each other. So we need to look at the model, understand the visual landscape, and imagine there are places the reaction happens.” Visualizing chemical reactions can be a hurdle for students, so in his Inorganic Chemistry class, Keith teaches undergrads to build models and think about three-dimensional structures. With years of experience, Keith himself can grasp the spatial components by turning them over in his head. “Being able to see a two-dimensional stick drawing and imagine what that looks like in three dimensions, and then being able to rotate that three-dimensional object in your mind so you can understand how that three-dimensional object reacts with other threedimensional objects — that’s the type of chemistry I do,” he says. Getting to play with model kits not only teaches Keith’s students a valuable skill but can also be diverting for the professor. “They’re like Tinker Toys,” he says. “It’s childhood, hands-on fun — especially if you’re a computational guy like me who spends all day building things in computers.”