11 Jul Zoe Schiffer – Chemistry at TSRI – Engle Lab – Week 4

Hi everyone, just a recap: my name is Zoe Schiffer, and I have had the amazing opportunity to spend 6 weeks in San Diego, interning at the Scripps Research Institute in the Engle Lab. The lab is run by Keary Engle. I have been working with Madison Wagner, a 4th-year PhD candidate, as my mentor. It’s crazy that it’s already been 4 weeks, but this week in particular has been one of my favorites.

This week we ran a Sonogashira reaction overnight. We did this reaction so we could make starting material to use for more reactions next 

week. This reaction required weighing out multiple things, including copper iodide, which I found out the hard way weighs more than you’d think. Though Madison had warned me, I underestimated her warning. The way I was supposed to weigh out the material was to put the full vial on the scale and tare it, then remove some and put the vial back on the scale to see how much I’d removed and make sure I didn’t go over. I made the mistake of adding the material to the flask

first, then checking how much I’d added. I ended up adding almost double the amount I was supposed to, and since it looked like so little, it would have been very difficult to remove the extra. We decided to just double the reaction instead, and I definitely paid more attention to my steps when weighing out reactants after that. It ended up not being a problem, but in the future I’ll be more careful. We then added the rest of the liquid reactants in the hood, which turned the mixture very dark because of the palladium.

After letting the reaction run overnight, we filtered out the palladium and any other solids from the product. The product still had byproducts, so it needed to be purified. I did a lot of purifying this week. First, we had to load the product onto silica, which means mixing it with silica and rotovapping out the acetone. It’s then loaded into the Biotage to run a column. The polarity of the product is tested as different ratios of ethyl acetate and hexane are added. From there, Madison tells me which vials to take a TLC from so we can figure out which ones contain the product.

Once the product is located, I combine those fractions in a large flask and rotovap them down. Sometimes I have to add the fractions in steps so the rotovap doesn’t bump too much. Bumping is when the product tries to shoot out of the flask and into the rotovap itself. It can be prevented by momentarily decreasing the vacuum so the solution doesn’t boil as vigorously. After the product is rotovapped down, I transfer it into smaller vials with a pipette and rotovap out the remaining solvent.

We then took NMRs of the products to determine whether they were pure. Some were, and some weren’t, so we’ll have to purify those again next week.

Outside the lab, I went to a lab dinner and had a run-in with vegan cheese, which looked very convincing. I also somehow ended up with a massive cone of mango sorbet. Madison and I also got breakfast, where we found a passion fruit and tried it. It was hard to eat with all the seeds and quite sour, though I wasn’t too surprised. Along with the questionable taste tests, I’ve also been climbing a bit. I’ve made some progress, and it feels good to move around after a day in the lab.

One of the main activities we did this week was touring the Mormon temple. The building itself was gorgeous, and it was a nice change of pace for us. I also made it down to the glider port and watched people paragliding over the cliffs of La Jolla.

This week was busy but a lot of fun. I can’t believe I only have 2 weeks left; it’s gone by so fast. I can’t wait to see what next week looks like.