exp076_3-23-07_(1).JPG

Objective

To combine piperonal and tertbutylamine, obtain almost complete conversion of the imine. Then add Boc-Gly-OH and see if the imine is reversed

Procedure

To remove water from starting solvents, added 3A molecular sieves and MgSO4 to about 10mL of Methanol to use for making solutions. Made a solution of piperonal(148.1mg, 2mL, 0.986mmol, 0.49M, MeOH) and a solution of tertbutylamine(105uL, 1mmol in 2 ml MeOH, 0.5M). Combined the two solutions in the presence of 77 x 3A molecular sieves(Ymg) with stirring letting reaction go over weekend. Took an NMR of the resulting solution. Prepared a solution of Boc-Gly-OH(176.1mg, 2mL, 1mmol, 0.502M, MeOH) and added to the resulting imine solution. After about 4 hours took and HMR.

Results

Characterization of Starting materials in CDCl3

tertbutylamine
piperonal

Characterization of Imine

HMR 3hrs 076A
HMR 66hrs 076B

Characterization after addition of acid

HMR 076C
Exp076 Excel

Discussion

  1. After 66 hours, because the aldehyde (peak 9.8ppm) is the only other compound present in the solution besides the imine, it can only be said that 66% is imine while 33% is aldehyde. The sample for the NMR was prepared by evaporating the methanol to dilute the product in CDCl3. In this case there is no amine left after evaporation. It is difficult to conclude how much was converted to the imine.
  2. After the addition of the acid, the imine (peak 8.16ppm) decreases to about 0.02% of the total solution after 3 hours. The percentage of aldehyde does not increase though there is a sharp decline in the imine. There does seem to be a greater quantity of amine as the integration gives it as 90% of the total solution. This is probably due to an NMR error where the hydrogens are not being seen equally for some reason and others are being given greater emphasis. This was also seen in Exp084 where an impurity was seen to be much greater than it really was.

Conclusion

The imine participates and/or reverts back but the evaporation process makes it difficult to conclude as to the amount that reverts back to the amine and aldehyde.

Log

2007-03-23

10:10 Took and unknown amount of 3A molecular sieves and in a crucible, put over a Bunsen burner.
10:18 Took molecular sieves off Bunsen burner and put in a marked 13mL vial.
10:45 Took about 10mL of reagent grade methanol and added 66 x 3A molecular sieves. Put in stir bar and spun on stir plate.
11:10 Stopped spinning methanol. Decanted of methanol and removed molecular sieves.
11:25 Prepared a solutions of piperonal (148.1mg, 2mL, 1mmol, 0.5M, MeOH) and tertbutylamine (105uL, 2mL, 1mmol, 0.5M, MeOH) Solutioons were preparred by taking the methanol that had been exposed to the sieves and adding approx 178mg of MgSO4. The methanol was then taken up by glass pipette and steadily passed through a cotton filter in a separate glass pipette which went directly into the volumetric 2mL flasks for the solutions.
11:38 Combined the aldehyde and amine solutions and started stirring in the presence of 77 x 3A molecular sieves(did not get weight).
12:15 Took NMR of starting materials in CDCl3 on 300MHZ instrument.
14:48 Took a 0.5mL sample and evaporated the methanol by warming it on a hot plate at LOW setting and then drying with compressed nitrogen gas. This was done due to no available attachments for the RotoVap. Added about 1mL CDCl3 to get NMR.
15:35 Took HMR on 500mHz NMR instrument. First analysis of NMR spectra showed that the reaction is only half complete. Allowing the reaction to spin further.
18:00 Stopped solution spinning. Some of the sieves were crushed. Filtered the solution and allowing the reaction to continue over the weekend. (so you removed the sieves at this point? If so then this is a problem - sieves may be slow in taking up water)

2007-03-26

11:30 Took a 0.5mL sample and put it on high vacuum to remove the Methanol.
12:00 Took HMR of imine solution in CDCl3.
12:35 Prepared a solution of Boc-Gly-OH(176.1mg, 2mL, 1mmol, 0.5M, MeOH) in the remaining 2mL of the dried methanol. Also added about 8 x 3A molecular sieves.
13:00 Added acid solution to the imine solution in a 13mL vial and allowed it to sit.
15:15 Started stirring acid/imine solution in the presence of X x 3A molecular sieves. Put imine solution that was used for the previous HMR in a 13mL vial.
16:15 Took HMR of acid/imine solution after evaporation of MeOH and adding CDCl3.
17:15 Weighed out 503mg of MgSO4 and added to the acid/imine solution in a centrifuge tube. Shook well and let it sit allowing it to absorb water that is in the solution and any that is formed from the forward reaction.

Tags

PiperonalInChI=1/C8H6O3/c9-4-6-1-2-7-8(3-6)11-5-10-7/h1-4H,5H2
tert-butylamine InChI=1/C4H11N/c1-4(2,3)5/h5H2,1-3H3
Boc-Gly-OHInChI=1/C7H13NO4/c1-7(2,3)12-6(11)8-4-5(9)10/h4H2,1-3H3,(H,8,11)(H,9,10)
imine: InChI=1/C12H15NO2/c1-12(2,3)13-7-9-4-5-10-11(6-9)15-8-14-10/h4-7H,8H2,1-3H3/b13-7-