For context: I'm a senior and a chemistry major in CC, I'm writing this a few years after taking orgo. Professor Merrer is easily one of the best STEM professors in all of Barnard and Columbia combined; the best professor I personally have had during all of my four years here. Her use of Sapling and her creation of handouts for EACH mechanism, yes each, is simply the best way to teach organic chemistry and I have no idea why no other professor does this. Well, actually I do, it's because creating handouts takes time and effort, which Dina does because she genuinely cares about her students succeeding, and I can't say the same about Columbia professors. She's also great about encouraging class participation: she asks the class low-baller questions and remembers faces and names really well when you answer those questions. She's got great handwriting and her trademark colored chalk is simply the best way to learn orgo visually. She also takes care to notice when the class does poorly on an exam: when we got a D average on the second midterm she made sure to go over concepts again in the next lectures before moving on. The only negative aspect I have to say is that she does seem very intimidating: she can be quite pointed and even though I ended up asking her for a letter of recommendation I still felt a little scared to email her each time lol. She doesn't have patience for lazy students.
Two things I wanted to focus on in particular: her problem sets and her office hours.
P sets: are incredibly helpful, because she usually assigns extra problems which you can save to study for midterms/finals, and she assigns you to a mandatory study group. Study groups in the class are picked randomly to submit the pset for grading, so you get practice doing all the problems but you don't have to stress every week about being graded. It's literally the most effective learning process ever, she's absolutely brilliant for coming up with it.
Office hours: she answers questions very thoughtfully and concisely during office hours. She hosts more during midterm weeks or when she can tell the class is struggling. If no one comes, or if everyone in the office wants to work on the same problem, she allows you to solve the problem on the board and walk the others through your method, which gives YOU teaching practice and reinforces the material, or she'll allow you to work out with the other students what you're stumped on if you got the question wrong.
Professor Merrer made orgo as painless as the subject can possibly be, was an entertaining and insightful lecturer, and gave ample study material to prepare everyone for the exams. I have no idea why anyone would take orgo at Columbia if their major allows them to take it at Barnard. I also have no idea why she and Rojas don't have gold nuggets on here. When I think of pedagogy, and the kind of professor I aspire to be, I think of no one, in my entire time at Columbia, other than Professor Merrer.