Week of 10/30-11/3
Monday 10/30
Going under the assumption I would need to make a large batch bromination involving about half a liter of HBr, I decided to make a liter of HBr with the blessing of my PI. The reaction was about a kilogram of NaBr split in two batches, with about half a liter of H2SO4 added to the ~1L aqueous salt solution. Keeping the total reaction below 75oC was difficult, but with a custom made intercooler (coolant pump and a dead-end condenser + gas tap) I cooled it effectively to room temperature, where I precipitated and filtered out K2SO4. This left about 4 liters of dilute HBr that I needed to distill into concentrated acid azeotrope.
Tuesday 10/31
I synthesized isoamyl nitrite from isoamyl alcohol, H2SO4 and NaNO2. This was following the procedure done on Thursday, 10/19 at a 4x scale compared to the first reaction. Starting with 80mL of isoamyl alcohol I finished with about 50mL isoamyl nitrite, a 62.5% volumentric yield consistent with past reactions.
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The acid distilled from Monday was subpar. at 1.3g/cm3 it was well under the density of HBr, so I needed to re-distill the acid into a proper azeotrope. This distillation turned 1.4L into 1L of azeotropic HBr. I bottled it in 2 550mL bottles, final density matching literature of 1.49g/cm3. This was good enough, and I am happy with how the acid turned out.
Wednesday 11/1
Today was a lab cleanup day since apparently the grad student just about lost his shit over the mess of partially cleaned glassware and gross, bumped through rotavap. We cleaned all the glassware, then the rotavap, then all the countertops. I also managed to clean the inside of the fume hood glass, which makes instrument sensitive reactions easier. The lab is clean for the first time in a long time.
Thursday 11/2
Synthesized 1,8-napthotriazine at a 4x scale with 22 grams of 1,8-diaminonaphthalene following past syntheses. In a 500mL round bottom flask, I added 200mL ethanol and 50mL glacial acetic acid, stirred the reaction and added the diaminonaphthalene. Using a seperatory funnel, I added in 28mL of the isoamyl nitrite. I did not monitor the temperature, but it was added in a much larger water bath than I normally used. It was left stirring overnight.
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The NMR machine was finally repaired! I ran 8 NMRs (2 for the senior in our lab, 4 unknowns and 2 calibration runs), and managed to get a stronger lock by manual shimming than with gradient shimming. It was about 12 minutes for each NMR, which isn't bad. I think with enough practice I can shim faster than the machine can shim itself.
Friday 11/3
I worked up the 1,8-napthotriazine. Suction filtration and precipitating the excess triazine out of the alcohol. I put it into a round bottom flask and attempted to rotavap it. It didn't end well. I just gave up and dried it under vacuum.
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I showed up to my first cheminar, lured in by the promises of extra credit and an organic chem lecturer. It was very interesting, I learned about indole synthesis and ergot alkaloid derivatives as a use in medicinal chemistry and the total synthesis of the ergot alkaloids.
Afterword: Now that the NMR machine is operational, the lab is slowly starting to pick up in pace. As for my pace, i've slowed down a bit, doing one, maybe two reactions per day, instead of the two or three on average in weeks past. My reactions haven't been working as well as i've anticipated and we've hit a wall, so to say. I will be trying different procedures on a small scale to better control reaction variables. I might try a different bromination procedure and better control the variables of the diazonation reaction that oxidizes an amine into a nitro group (in preparation for a bartoli indole synthesis).