Wednesday, January 21, 2009

I. Melting Point Determination (second and third pages)



That picture. Yes, it's a Mel-temp. I was under the impression that the instruction to sketch any apparatus we used was a license to draw pictures of random laboratory equipment in the margins. To be fair, we did use a Mel-temp. But there was no reason why it needed to be poorly penciled into the notebook.
Notice also that my chicanery knows no bounds: the compound I had was the only yellow powder among the six unknowns, and that meant it had to be m-toluic acid. My melting point data suggested otherwise, but I nonchalantly decided to disregard that discrepancy with the blithe nonchalance of a practiced charlatan. I'm sure there is a big bunsen burner wih my name on it in whatever level of hell Lucifer reserves for fraudulent pre-meds.


Transcription:

Unknown: “D”

Fine, pale yellow powder; slightly acrid odor; insoluble in H2O

  • Placed 0.004g of “D” into capillary tube
  • Placed capillary tube into Mel-temp, beginning at a temperature of 84°C.
  • Raised tem[perature at 70V
  • Melting commenced at 99°C Clear, pale amber liquid
  • Melting was complete at 105°C

Differential: o-anisic acid, dimethyl fumarate, (toluic acid?)*

  • Mixed “D” with o-anisic acid in test tube, and mixed “D” with m-toluic acid in different test tube.
  • Placed 0.006g of each mixture into two capillary tubes, and began heating at 84°C, 70V.
  • The mixture of “D” with o-anisic acid began melting almost instantly at 88°C, and the mixture of “D” with m-toluic acid began at 102°C and completed at 106°C.
  • To confirm, ran a sample of pure m-toluic acid, determining a melting point of 98 - 104°C. This correlates exactly with the experimentally-determined mp of “D.”



*Despite the discrepancy in mp, the physical appearance of “D” was similar only to m-toluic acid, and did not resemble either o-anisic acid or dimethyl fumarate.

1 comment:

  1. I had to do a similar experiment in my chem class last year. Boring and fiddly.

    ReplyDelete