Thursday, February 02, 2006

Exp 001


Objective: To convert adrenaline to a catechol aldehyde under acid catalysis in methanol/water. How this fits into the synthesis of anti-malarials is explained here.

2006-01-24

1. Prepared a 50mL stock solution of 0.100g adrenaline, 5mL 1M sulfuric acid and methanol in a flask.
2. 14:47 Placed 1.86mL of adrenaline solution and 2.0mL 1M sulfuric acid in a round bottom flask. A 0.5mL sample of the starting reaction solution was pippetted out (sample A) and placed into a 1 dram vial. Attached the flask to a condenser and into a sand bath and turned the heat on low.

3. 15:17 Pippetted out 0.5mL of the reaction. (sample B)

4. 15:47 Pippetted out 0.5mL of the reaction. (sample C)

5. 16:47 Pippetted out 0.5mL of the reaction. (sample D)

6. 18:47 Pippetted out 0.5mL of the reaction. (sample E)

7. TLC was performed on all samples of the reaction using methanol as the eluent.

sample A Rf= 0.338
sample B Rf= 0.571 The sample began to spread out.
sample C Rf= 0.661 The sample continued to spread out.
sample D Rf= 0.625 The sample is less spread out than previous samples.
sample E Rf= 0.642

Reaction was allowed to run overnight.

2006-01-25

Contents of the reaction flask decomposed. Aborted.

Discussion
Based on this experiment we were able to conclude that no aldelhyde was formed and that the reaction needed to be ran under nitrogen in order to avoid oxidation. In addition there was not enough sample in the reaction flask to produce significant results.

2006-01-26

1. 15:25)Prepared solution 26.6mg (0.148mmol) of Adrenaline, 20mL of Methanol and 5mL of a 1M aqueous sulfuric acid solution. Put solution in a 50mL round bottom flask and attached to a reflux condenser under nitrogen gas and started heating the flask.
Sample was taken at t=15:25 (t=0)
2. 15:55) Sample was taken at t=15:55. It was noted that the sample had started to reflux. (t=0.5)
3. 16:25) Sample was taken at t=16:25 (t=1)
4. 17:25) Sample was taken at t=17:25. The samples were approximately 1mL-2mL. (t=2)

2006-01-27

5) Micropipetted 0.5mL of each sample (A, B, C, and D) and placed them into a new sample vial.
6) Added a small amount of sodium bicarbonate powder to these vials until bubbling ceased.
7) TLC was used to assess production of an aldehyde
8) Using an eluent of 4:1 Hexane:Methylene Chloride
i) None of the samples migrated on the TLC plates (7A, 7B, 7C, & 7D)
9) Using an eluent of pure methylene chloride
i) None of the samples previously spotted on plates 7A, 7B, 7C, or 7D migrated with this eluent
10) Using an eluent of methanol
i) New plate 8A created using dotted sample from t=0 vial and t=0 with sodium bicarbonate vial (left lane t=0, right lane t=0 with sodium bicarbonate)
a) Solvent traveled 6.0cm. Tip of spot: left lane: 3.8cm, right lane: 3.3cm
ii) New plate 8B created using dotted sample from t=0.5 vial and t=0.5 with sodium bicarbonate vial. Set-up same as in (i)
a) Solvent traveled: 5.9cm. Tip of spot: left lane: 4.0cm, right lane: 3.1cm
iii) New plate 9A created using dotted sample from t=1 vial and t=1 with sodium bicarbonate vial. Set-up same as in (i and ii)
a)Solvent traveled: 6.5cm. Tip of spot: left lane: 4.1cm, right lane: 2.0cm
iv) New plate 9B created using dotted sample from t=2 vial and t=2 with sodium bicarbonate vial. Set-up same as in (i, ii, and iii)
a) Solvent traveled: 5.5cm. Tip of spot: left lane: 3.8cm, right lane: 3.3cm

The following picture was taken of plates 8A, 8B, 9A, and 9B.



Aborted.











Conclusion
Adrenaline (5.8 mMolar), sulfuric acid (0.2 M) in 4:1 methanol/water refluxed for 2h in air did not generate DOPAL, based on the absence of a faster moving spot in TLC.

1 Comments:

At 3/2/06 12:58, Blogger ah346 said...

Today I was able to get an IR spectra of the 2hr methylene chloride extract by evaporating a 20 microliter sample on a KBr pellet. After inspecting the spectra, it doesn't appear that we were able to make the aldehyde. This is evidenced by the absence of a carbonyl stretch at approximately 1700 wavenumbers.

 

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