How to Succeed in Lab
BY YALE HUANG
The hardest change a chemistry student will ever navigate is the departure from the paper cut-inducing comfort zone of their textbooks and the crash landing into their first lab class, where the danger of destroying thousands of dollars worth of equipment looms with every stray elbow. Diagrams, practice problems, and lab manuals are one thing. Rushing to finish an experiment, realizing that you’ve butchered the entire process, and scrambling to scavenge the project with just ten minutes left on the clock is another. Add in the fact that the COVID pandemic forced many introductory labs to go online and left students to fend for themselves as they trickled into higher level courses, and you have yourself the perfect recipe for a stressful and anxiety-ridden time, especially for those new to the in-person lab experience.
If you’re worried about the transition from theoretical chemistry to practical chemistry, you’re not alone! My first days in the lab were nothing short of disastrous, and it was only through the help of my TA and classmates that I emerged with a more thorough understanding of organic chemistry.
In order to smoothen the transition for other students, I spoke with Professor Jeremy Klosterman about his perspective on this intimidating process and his advice for first-time lab students. He makes his first point clear: “The organic chemistry textbooks are highly cleaned up and simplified introductions to the basics of organic chemistry and reactivity. They’re not real chemistry.” He adds, “If you go on to graduate school and advanced organic chemistry, you start seeing where we lied—or rather, simplified—to you in general organic chemistry.”
This means that there’s often a disparity between theory, where everything works as you learned it in CHEM 40, and practice, what actually happens in CHEM 43A. After all, it’s rare for an experiment to work perfectly and give 100% yields. Variables overlooked in textbooks, like reagent purity, heat gradients, and consistent heating/mixing rates are always at play in a real lab setting. Experiments that look ideal on paper seduce students into believing the same will occur in reality as long as they adhere to the procedure.
In truth, the biggest factor in success or failure isn’t the ability to follow instructions on a piece of paper, but the technique used to carry out the experiment, which is much harder to learn. “Mixing a solution” doesn’t convey the speed that you should stir, nor how long you should continue. Knowing that producing a successful distillation temperature graph requires the thermometer be placed below the mouth of the adapter doesn’t prevent you from misjudging the distance and ruining your data.
But there’s good news: students aren’t meant to perfectly replicate the results of a textbook, nor are they expected to. “A lot of the 40 series and basic organic chemistry is really just understanding general reactivity. It’s not necessarily being able to predict exactly what will happen, but being able to understand reactivity and describe what’s most probable,” Professor Klosterman says. And predictions can be inaccurate. “You have a scientific model that explains reality to a certain extent. But because it is a model, it is inherently flawed or simplistic. It is not reality.”
However, that doesn’t mean the models found in the textbooks aren’t useful. Just like how alphabet blocks are used to teach words, Lewis dot structures, Bohr models, and curly arrows introduce the language of organic chemistry to beginners, even if they are oversimplifications of reality. The more students practice those models and understand how they work, the better they’ll perform in a parallel lab setting.
Moreover, the theoretical and practical components of organic chemistry complement each other. Professor Klosterman notes that lecture courses at UCSD emphasize reactivity and functionality, while labs focus on isolation and purification techniques as well as intermolecular interactions, giving a greater appreciation of the complex processes occurring before, during, and after a reaction. By combining these two puzzle pieces, a more cohesive representation of real organic chemistry emerges, allowing the student to grasp not only how something reacts, but why.
For example, an experiment in 43A asks you to convert an unknown alcohol into an ester, then identify the ester using techniques taught over the course of the quarter, such as infrared spectroscopy, gas chromatography, and boiling point analysis. Theory tells us that working backwards from the product ester will inevitably lead us back to the original alcohol, so as long as we can identify the ester, we can identify the alcohol.
In practice, however, the experiment looks completely different. One student might find that their product ester is in equilibria with the starting reactants, meaning the resulting mixture is too impure to yield a conclusive identity. Another student might realize that their attempts to evaporate the excess solvent has also reduced their desired product to nothing. Suddenly, a seemingly simple reaction becomes a maze of misdirection and confusion, requiring the student to slow down and reconsider the experiment process. In order to succeed, the first student might return to their station and add in an excess of reactants to ensure that equilibrium favors the products. The second student might lower the temperature of their hot plate for a slower evaporation rate.
This disparity between the theoretical and the practical compounds in a larger laboratory setting, where processes become far more complex than the conversion of one ester to another. Side reactions, impurities, and equilibriums may result in “major” products as little as 10% or as great as 120%. It’s like managing a group project where members drift off at random intervals to start their own side projects.
What do researchers do to solve this, then? Return to the drawing board, analyze the mechanism by which these minor products are formed, then adjust experimental conditions to reduce competing reactions.
“So from a synthetic perspective, we’re always thinking ‘I want to make this molecule.’ But [in 40a], we’re teaching you other stuff that’s not synthetic, but more general reactivity,” Professor Klosterman states. “It may not be useful directly, but it pops up in ways that you might’ve forgotten about.” He adds that certain reactions taught in 40a—such as unimolecular nucleophilic substitution, SN1—are overlooked in favor of more selective reactions, like bimolecular nucleophilic substitution (SN2), especially when stereocenters are involved.“[So] why do we teach it to you? Because [SN1] might happen as a competing side reaction with an SN2.” Theory offers clarification when an experience goes sideways. Knowing how and why a side product forms is vital to efficient synthesis and lab work.
Easier said than done! Professor Klosterman offers his advice to students who struggle with this aspect of organic chemistry.
“The biggest problem is—in the most positive, optimistic, and encouraging way—student’s fear of mistakes and losing points,” he says. Labs are designed with the knowledge that mistakes are inevitable, he stresses, so it’s better to try to have fun with the experiment than overtaxing yourself with perfection. After all, even the best of researchers are susceptible to errors, and the ones who fixed their mistakes learned far more than the ones who got lucky on the first try. “The less you worry about the points and the more you focus on what you’re doing and understanding and enjoying it, the better you’ll do.”
“Troubleshooting is what makes you a great researcher, or someone who enjoys research,” Professor Klosterman says. “Strive to understand the chemistry behind what you’re doing instead of just following instructions. Think about why you are doing and why (make a flowchart!) and learn from success and failure. but above all, adopt a positive, growth mindset. You can do it!”