Thinking About Organic Chemistry Through the Lens of Underlying Physics
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Thinking About Organic Chemistry Through the Lens of Underlying Physics

Author: Vera KoesterORCID iD, Peter R. SchreinerORCID iD (Photo: David Ausserhofer)

Professor Peter R. Schreiner holds the Liebig Chair and serves as the Director of the Institute of Organic Chemistry at Justus Liebig University Giessen, Germany.

In this interview, Vera Köster from ChemistryViews speaks with Peter Schreiner about his groundbreaking work on quantum mechanical tunneling, his views on modern interdisciplinary education, the broader aims of chemistry education in promoting collaboration, critical thinking, and international engagement, the importance of responsibility and leadership in professional societies such as the GDCh, and his involvement in music.

 

What led you to research quantum mechanical tunneling in organic chemistry, and when did you realize the topic held such great potential for breakthroughs?

Well, as usually or often happens, I did not think about the topic—it came to me. It was an accidental discovery. We had synthesized a new molecule, hydroxycarbene, so HCOH, a tautomer of formaldehyde. It was a great moment: Wow, a new molecule, new properties, the whole nine yards. But when we tried to study it, the molecule simply disappeared.

First, we thought it was a mistake, but it was not—we could reproduce the experiment. Basically, overnight, the molecule rearranged into formaldehyde, and the transformation was not explicable.

And, of course, if you do not know what you are doing, you say it is a stereoelectronic effect. My students laughed, saying the molecule was too small for that to make sense. Then, if you really do not know, you say it is tunneling. With time, we realized that it truly was tunneling. The only real epiphany I had was this: something was happening that I did not understand at all. That likely meant others did not understand it either—so it was worth looking into it. And indeed, it turned out to be well worth it.

 

But it takes a lot of effort to discover and follow something so unusual?

It is not so difficult if you know where to look. Tunneling has always been present—it was actually predicted in 1927 by Fritz Hund, not by Gamow in 1928 as most people believe, in the context of alpha decay. A year earlier, Hund had considered whether amino acids that might occur in space are configurationally stable, or if they could escape their absolute stereochemistry through a tunneling process by inverting at the carbon.

The answer is no—it does not happen, as that takes longer than the age of the universe. That was the first indication of tunneling. Over time, it popped up every so often, often used to explain unusually fast kinetics. But I asked: Is there more to it? Do you need to know tunneling to make molecules synthetically? Would it screw your plan in a total synthesis? Would it matter for organic chemistry? And what are the systems to try that?

 

And what are systems to try that?

Generally speaking, rearrangements of strong bonds are more likely to undergo tunneling because the potentials are stiff and the barrier widths small.

 

What are you most interested in your research at the moment?

In the broader context of experimental organic quantum chemistry, I am interested in exploring how atoms and molecules manifest as quantum objects, not just classical objects. Most organic chemists—and likely many inorganic chemists—tend to think of molecules as balls connected by springs. It is a beautiful mechanical model, and it makes perfect sense for 90% of the cases.

However, at the end of the day, atoms and molecules are quantum objects. Their positions and energies are not precisely defined, as Heisenberg taught us. They also behave in weird ways—like tunneling, for example. Another such weird behavior is that the electrons of atoms and molecules, even at a long distance, talk to each other. That is called electron correlation. This interaction leads to dispersion forces, another quantum effect we have looked into very much.

Both tunneling and dispersion are a direct consequence of the quantum nature of atoms and molecules. Unfortunately, this quantum nature has been largely neglected in organic chemistry education and thinking, leading to incomplete models of mechanisms, catalysis, and transition states.

 

How did you reach the point where you began integrating quantum chemistry into your work, moving beyond traditional organic chemistry?

Well, this goes far back to my student days. I was generally interested in the natural sciences. I began with physics and chemistry and, after completing the intermediate diplomas, chose to go for chemistry—because in chemistry, you can create the object of desire yourself. You can make a molecule. The fascination with physics was always present but I thought, making a molecule—this is the coolest thing on Earth. Looking at a vial containing a new substance and realizing, this is the world’s entire supply of the substance, and you made it, was absolutely unbelievable. But, of course, the attraction to physics was always there.

During my PhD, I earned a doctorate in organic chemistry with Paul Schleyer in Erlangen, Germany, and at the same time one in computational/theoretical chemistry with Fritz Schaefer in the United States. My idea was always to bring together the solid theoretical foundation with the creative power of organic synthesis. This has remained our guiding principle—thinking within organic chemistry, but always with a keen eye on the underlying physics.

 

… making a molecule—this is the coolest thing on Earth. Looking at a vial containing a new substance and realizing, this is the world’s entire supply of the substance, and you made it …
—Peter R. Schreiner

 

Why is there a Schreiner catalyst?

Well, others have named the N,N-bis[3,5-(trifluoromethyl)phenyl]thiourea the Schreiner catalyst [1] because we were the first to use it at a time when people were not really interested in hydrogen-bonding organocatalysis. This is the topic of my habilitation, the qualification for a professorship. I remember I wrote the proposal for organometallic catalysis without ligands, and the reviews I got were along the lines of: “This is a cute idea, but it will not work. However, Schreiner might learn a lot along the way.” At the time, I was on a fellowship from the Foundation of the Chemical Industry, and we were thrilled to try it. We started with high hopes, but no one was interested because no one else was working on it.

The moment when the competition entered the field—Eric Jacobson, Yoshio Takamoto—suddenly the field exploded. The development of organic catalysis with nucleophiles, for example proline, and iminium catalysis developed roughly at the same time, and suddenly, both interest and the field grew rapidly. Of course, the first thing people did was use the catalysts of others and see what else could be done with them, including modifications. And that is how the catalyst became the name.

 

Do you have any advice for PhD students, post-docs, or new group leaders on how to identify a research topic?

Well, I will share something that Roald Hoffmann told me—he probably told everyone: Try to be orthogonal. I had never thought about this; I just wanted to do something no one else had done before. Essentially, that is orthogonal to the main thread. And this is what I can always recommend.

Of course, we stand on the shoulders of giants to see further, but it is also important to find something you know a little about, something you are willing to learn more about, and that has practical implications. Ask yourself: What if I can prove my hypothesis to be correct? What are the implications? If the implications are worthwhile—if you can create a better reaction, catalyst, material, or pharmaceutical—then it is worth pursuing. But do not be deterred by all the obstacles or doubts about what you do not know. You can learn, but you need the confidence to believe that if successful, your work could change a particular direction in chemistry.

 

This means you must be very honest with yourself, especially since we are often trained to justify our research through potential applications for funding?

Yes, you have to be honest. You have to be also hopeful that people will recognize there is a new idea.
I was extremely lucky that people generally have recognized the value of my work without needing me to claim it would cure cancer or make us fly to the moon—things that, in various disguises, are often used to justify research. I never did that, because it is dishonest, and it is not realistic, especially within the typical three-year funding period.

If you can say that your idea is truly new, and if successful, it will have a positive impact, I think that is fair. Good reviewers will recognize this, and I have been lucky to have good reviewers on my papers and proposals who saw the potential and agreed that it was worth pursuing.

 

How important is quantum chemistry in understanding all of chemistry?

It is of utmost importance; it is the basis of everything. For me, I find it unacceptable to teach chemistry without incorporating the quantum part. For instance, you learn in chemistry that branched alkanes are more stable than linear alkanes. Go to the textbook and try to find an explanation, and you will not find one. The answer lies in intramolecular dispersion; one-three interactions are attractive, and the branched molecules have more of those interactions, making them more stable. It is a consequence of quantum mechanics, but it is not fully appreciated or embraced. I believe we really need to embrace it and incorporate it into our thinking.

In my teaching, for example, I always use a molecular orbital theory. I start even in the first chemistry courses with qualitative molecular orbital theory, and I use it constantly throughout every explanation. This provides a solid foundation and serves as the main argument for interpreting both my findings and the work of others.

 

What motivates you in your research?

I am very easily motivated, especially by finding out how things work and understanding the inner workings of everything. I am fascinated by questions like, “Why is this color blue?” “Is it absorption, or is it the surface that causes it?” “Is it the microstructure of the surface, and if so, what is that structure?” Anything related to chemistry and understanding is exciting to me. Just the joy of learning new things is what motivates me.

 

How do you balance teaching with doing research?

Well, research and teaching are deeply interconnected, as Justus Liebig taught us. When I interact with my students and coworkers, it becomes a back-and-forth of teaching—sometimes they teach me something, and sometimes I teach them something. It is a scholarly exchange.

I think if you really try to understand something, you must be able to explain it to others, and I try to instill this attitude in my students. When they find something new, I encourage them to explain it to me, and in doing so, they take on the teacher’s role. I find it extremely rewarding when they realize, “Oh, I had not fully thought this through,” and they return to refine their understanding.

The same is true for me: students sometimes ask questions that make me think, “Wow, I have not considered this.” In such cases, I admit I do not know and will come back with an answer. This mutual learning is central to teaching.

For me, teaching is not about directly imparting specific knowledge but guiding students on how to learn, offering advice, and testing whether they have understood the material. For instance, I cannot tell them that one plus two is three. That is something they can learn or have to learn for themselves and internalize themselves. What I can do is ask them harder questions, like proving that one is a number, and then we can engage in a scholarly dialogue and see how we go about it.

 

Are you happy with your teaching?

No. I always feel that we are too old-fashioned. Maybe I am too old-fashioned, or maybe everyone else is doing a better job. But I have this feeling that, with all the hardcore chemistry—the deep subject matter—we get lost in the details.

I think we need to rethink how we teach chemistry, especially now that all knowledge is available at your fingertips on your cell phone. How do we truly teach students to think about chemistry as a natural science? It is not just about learning, memorizing, and recalling information. That is something I am still grappling with—how can we truly modernize chemistry education for the 21st century?

 

I think we need to rethink how we teach chemistry, especially now that all knowledge is available at your fingertip on your cell phone.
—Peter R. Schreiner

 

You just mentioned Liebig, and you hold the Liebig-Chair at Justus Liebig University Giessen. Is he a role model for you?

In some respects, yes. Of course, he lived in a very different time but he is a role model because he understood the symbiosis of teaching and research, and he was not afraid to go into uncharted territory. He did things where he had absolutely no idea about the outcomes. This inspires me and every single time you learn something.

There is a story about Liebig, where Wöhler asked him: “Whatever you try, everything works, how come? “, and Liebig replied, “It is very simple, I try everything.” I am unsure of the exact source, but I have taken this spirit of experimentation to heart. I try to pass it on to my students: “Do not overthink it, just do the experiment and fail, and then do the next experiment, and eventually you will see why you are failing or why you are successful.”

 

How do you handle situations when things go wrong, especially when this persists longer than expected?

As an organic chemist and, of course, chemists in general develop an amazing tolerance for frustration. After a difficult lab day, I tell myself that in the next experiment, I do something different and this time it will work. This is the general attitude.

However, with longer bad luck streaks you have to reflect and think whether it is worth continuing or if it is time to abandon the project. I personally set myself deadlines—number one is time. How much effort does this take? Do I see progress that is sufficient to justify the effort? That is also a question of cost and proper time management, but I also have a content timeline. Are we progressing fast enough to develop this field within a finite time, or is it going to take us 20 years to get somewhere? And then I will and have to abandon the topic. It does happen rarely. Sometimes it is enough to let it sit for a while and do something else and come back. But lots of things do not work and then you need to be careful with your time management.

Young people’s energy is also a great motivator. Engaging in discussions and brainstorming chemistry with them, often scribbling on napkins, is energizing. Their unaffectedness by all the knowledge accumulated over time, which is sometimes a hindrance as you get older, is refreshing. You know more and you try less and they are so optimistic; they would try just about anything to get from point A to point B.

Very often they take paths you had not considered because you said, “Oh, somebody else had tried this before. It did not work.” But has this person really tried the right way and hard enough and long enough and with modern methods? That spirit of just doing things with an open mind and lots of energy is what I enjoy most.

It also keeps you young. If you are always in touch with young people, it is hard to age in your mind. At least that is what I try to believe. They have all these new things that I only know by word and they just do them.

 

What motivates you to engage in honorary work, such as your presidency of the GDCh in 2000 and 2001?

The main motivation for my involvement is that I am a critical person. At the same time, I dislike those who criticize all the time without taking responsibility. Since I want to remain critical, I believe I must sometimes take responsibility, say okay I have criticized it, so I try to do better. I may fail, shame on me, but maybe we advance something, get a little bit better.

It is a lot of work, but ultimately, it is very rewarding to be involved in processes where things are changing and to reflect on whether things have improved or if you need to step back. Taking responsibility and being accountable within a system is very good; if you take on a leadership role, you must be accountable, or else you risk losing your credibility.

 

How do you see chemical societies like the GDCh in our modern times changing or evolving?

First of all, professional associations are crucial for representing the interests of chemists, particularly in today’s interconnected world. Chemistry is deeply embedded in society—we have a large industry related to it, it is taught in schools and universities, and it provides jobs and materials, you name it, everything is chemistry. We need to have a professional agency that serves our best interests.

So it is very important that there is one society that really reflects the major interest of all its members. It is important to collect the ideas in this community. As a large, organized community, we must speak with a unified and loud voice to ensure our interests are heard. Without such an organization, our collective voice would be drowned in the noise, as can happen in the humanities, where smaller fields struggle for attention.

The GDCh could certainly be louder. We have tried that, I have tried it, it is difficult to be loud because there are lots of screamers and the political arena is a very difficult one. Still, if we do not advocate for chemistry, no one else will.

The success of such a society relies on a balanced representation of both academia and industry, and particularly its younger members. One-third of our members are young people. It is their future and it is crucial they are given the opportunity to shape the future of the profession. This reflects an important asset for our field.

 

How can we teach the next generation of chemists to collaborate effectively and to think beyond the scope of their own research?

I think it starts with university teaching to show them how interconnected disciplines are. It is probably very difficult for students to see how concepts from other fields influence chemistry—I certainly did not see it when I was young.

I think a doctoral period is not just about qualification; it is about personal growth, it is a period of great frustration, it is about learning about yourself and your subject, and also to learn how to teamwork, how to look over the fence of your small area of research, how to interact with people from diverse backgrounds. I mean, internationalization is extremely important. But also working with people you may not like, but you still have to work together. You become professional.

I think this is the most wonderful experience you can have as a student or postdoc to learn how to collaborate and exchange ideas.

 

I think a doctoral period is not just about qualification; it is about personal growth
—Peter R. Schreiner

 

Let us move to a more personal topic: I believe you play the electric guitar and are also in a band—is that true?

Yeah.

So, you are quite a musician.

Music is kind of a—well, I do not know—a great outlet, a way to re-equilibrate. It can touch you in ways that nothing else can. It relaxes you—it relaxes me. Listening to music is great, but playing music is even better, so I really enjoy it.

And, of course, playing in a band is a completely different experience. Some of the members do not have academic backgrounds, so we talk about all kinds of things. It is a good balance for me—immersing myself in something entirely unrelated to science.

 

So, what kind of music do you like and play?

Rock music and jazz. If I were a little better, I would play more jazz, but it is mostly too delicate.

 

And do your students come to your concerts, or do you keep that a secret?

Some have been to my concerts, and it is fun when they suddenly realize, “Oh, we never saw that side of him.” I think it is quite eye-opening for them.

 

Great. Thank you very much for the interview

 

Reference

[1] 803855 Schreiner′s Catalyst, SigmaAldrich (accessed April 8, 2025)

Peter R. Schreiner, born in 1965, studied chemistry at the University of Erlangen-Nürnberg, Germany, where he received his Ph.D. in organic chemistry in 1994. Simultaneously, he obtained a Ph.D. in computational chemistry from the University of Georgia, Athens, USA, in 1995. He completed his habilitation at the University of Göttingen, Germany, in 1999. Peter Schreiner then joined the University of Georgia, Athens, USA, as Associate Professor of Organic Chemistry. Since 2002, he is Professor of Organic Chemistry at the University of Giessen.

His research interests include organic reaction dynamics and reactive intermediates, quantum mechanical tunneling, London dispersion interactions, nanodiamonds, and organocatalysis.

Among other honors, Peter Schreiner has received the Gottfried Wilhelm Leibniz Prize in 2024, the Arthur C. Cope Scholar Awards from the American Chemical Society (ACS) in 2021, the Adolf von Baeyer Memorial Medal from the GDCh in 2017, the Science Award from the German Technion Society in 2014, the Universitatis Lodzienzis Amico-Medal of the University of Lodz, Poland, in 2015, and the Dirac Medal in 2003. Peter Schreiner is a member of the German National Academy of Sciences Leopoldina. He serves as Editor-in-Chief of WIREs Computational Molecular Science and Editor of the Journal of Computational Chemistry

 

Selected Publications

Also of Interest

 

 

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