Presentation Type

Oral Presentation

Area of Focus

Physical and Earth Sciences

Abstract

In organic chemistry, catalysis (speeding up a chemical reaction) has largely been dominated by Lewis and Brønsted acids. While effective, these additives are also usually toxic, reactive, and environmentally unfriendly. Organocatalysts provide an alternative way to increase reaction rates. By appending hydrogen bond donors to a carbon scaffold, organocatalysts can have activity similar to Lewis and Brønsted acids without the negative side effects. Consequently, the field of organocatalysis has been steadily growing for the last twenty years. Chemists can increase preferable traits in their catalyst such as enantioselectivity, solubility, and activity by modifying. These are laudable goals for catalysis research, as they have provided us with many organocatalysts that work well. However, some of the fundamentals are still incompletely understood. With a better understanding of the basics, more efficient and better designed organocatalysts can be developed. The research presented here describes progress towards understanding some of these basic features.

The fundamental question being asked here is: what is the optimal binding geometry of a substrate in the active site of a hydrogen bonding organocatalyst? In other words, what is the best orientation for chemicals to have relative to an organocatalyst? Enzymes (biological catalysts) form hydrogen bonds with planar molecules to increase their reactivity. Ideal hydrogen bonds would be formed in the same plane. However, published research has shown that most enzymes form hydrogen bonds orthogonal to the plane (with a large portion shifted as far as ninety degrees). The chemistry performed by these biological molecules is much more advanced than anything developed in a lab, so trying to emulate their methods could result in a better organocatalyst. The hypothesis is: forming hydrogen bonds orthogonal to planar molecules will improve the performance of organocatalysts. To test this hypothesis, urea was chosen as our scaffold. Substituted ureas have been used extensively as organocatalysts, making them an appropriate choice for this study. By modifying the molecular periphery of urea, the three-dimensional space around the active site can be controlled. Put simply, the urea can have things dangling off it that will force chemicals into a specific orientation. These ureas can be made using basic organic synthesis. A variety of techniques were utilized to study how they interact with other chemicals. Crystals of the urea and planar molecule were grown and subjected to x-ray diffraction. This illuminated the orientation in the solid state. 1H NMR spectroscopy was used to characterize novel compounds and monitor reactions to determine rate constants. By investigating the system in the solid and solution phases, the hypothesis can begin to be validated.

Share

COinS
 
Apr 27th, 1:25 PM Apr 27th, 1:40 PM

Using Biomimicry to Enhance Urea Catalysts

UC Ballroom, Pod #2

In organic chemistry, catalysis (speeding up a chemical reaction) has largely been dominated by Lewis and Brønsted acids. While effective, these additives are also usually toxic, reactive, and environmentally unfriendly. Organocatalysts provide an alternative way to increase reaction rates. By appending hydrogen bond donors to a carbon scaffold, organocatalysts can have activity similar to Lewis and Brønsted acids without the negative side effects. Consequently, the field of organocatalysis has been steadily growing for the last twenty years. Chemists can increase preferable traits in their catalyst such as enantioselectivity, solubility, and activity by modifying. These are laudable goals for catalysis research, as they have provided us with many organocatalysts that work well. However, some of the fundamentals are still incompletely understood. With a better understanding of the basics, more efficient and better designed organocatalysts can be developed. The research presented here describes progress towards understanding some of these basic features.

The fundamental question being asked here is: what is the optimal binding geometry of a substrate in the active site of a hydrogen bonding organocatalyst? In other words, what is the best orientation for chemicals to have relative to an organocatalyst? Enzymes (biological catalysts) form hydrogen bonds with planar molecules to increase their reactivity. Ideal hydrogen bonds would be formed in the same plane. However, published research has shown that most enzymes form hydrogen bonds orthogonal to the plane (with a large portion shifted as far as ninety degrees). The chemistry performed by these biological molecules is much more advanced than anything developed in a lab, so trying to emulate their methods could result in a better organocatalyst. The hypothesis is: forming hydrogen bonds orthogonal to planar molecules will improve the performance of organocatalysts. To test this hypothesis, urea was chosen as our scaffold. Substituted ureas have been used extensively as organocatalysts, making them an appropriate choice for this study. By modifying the molecular periphery of urea, the three-dimensional space around the active site can be controlled. Put simply, the urea can have things dangling off it that will force chemicals into a specific orientation. These ureas can be made using basic organic synthesis. A variety of techniques were utilized to study how they interact with other chemicals. Crystals of the urea and planar molecule were grown and subjected to x-ray diffraction. This illuminated the orientation in the solid state. 1H NMR spectroscopy was used to characterize novel compounds and monitor reactions to determine rate constants. By investigating the system in the solid and solution phases, the hypothesis can begin to be validated.