I'll synthesize tert-butylcrotonaldimine from crotonaldehyde and tertiary butyl amine.
In here, I have two main obstacles whether the reaction is complete or not.
First, I cannot determine the formation of imine.
When I use TLC stain, the imine can be decompose by TLC.
Therefore, it is hard to use TLC stain when I observe the reaction progress.
Therefore, I should use other methods for detecting formation of imine. Is there any tips for doing it?
Secondly, It is hard to isolate the product from reactant.
I'll use pentane for solvent. Therefore, it is easy to remove solvent by reduced vacuum, and also, tertiary butylamine also has low boiling points, therefore, it is easy to remove.
However, there are no any other reference about boiling points of tert-butylcrotonaldimine except reduced vacuum condition.
In scifinder, the predicted boiling point is 160 degree.
It is quite large difference between crotonaldehyde's boiling point(104 degree), however, no any other reference under reduced vcauum.
Therefore, it is hard to isolate the product from crotonaldehyde.
Is there any tips for isolate the product?
Thank you.
Hi,
See page 894 of the attached paper for protocol (compound 1a). There you can find boiling point of compound you want to prepare (at 15 Torr).
You might follow reaction progress by GC-MS or NMR. If compound is SiO2 sensitive, you might try deactivating TLC plate with NEt3 before analysis. Or try reverse phase TLC...
Good luck!
Using IR, as suggested above, you could monitor the disappearance of the crotonaldehyde C=O peak and growth of the C=N peak over time.
Several other suggestions:
If you have access to NMR and deuterated solvents, you could run a small scale reaction in CDCl3 or d-10 toluene and use NMR to monitor the progress. Then extrapolate the results to a larger scale reaction with normal solvents.
Or, if you have access to GC or GCMS, you could monitor the disappearance of crotonaldehyde over time.
I'm not sure if imines of aldehydes react the same way that aldehydes do in Tollen's silver mirror test, but if imines and aldehydes react differently, that might be an interesting way to monitor the process chemically.
for separation, it is best to work with an excess of amine (more volatile), so you will be sure to react all the aldehyde. Then the excess of amine can be eliminated under reduced vacuum.
for identification and evolution NMR is also effective. So, you can follow your reaction by determining the evolution of the adehyde peak at 9-10ppm (1H NMR) or the (C = O) group at 170 ppm (13C NMR).
(1) To observe the reaction is complete or not, check this reaction where ur mixtutre if contain aldehyde then it will react with 2,4‑dinitrophenylhydrazine (Brady’s reagent) to form a 2,4‑dinitrophenylhydrozone in the laboratory.
This is a classical organic chemistry test to confirm the presence of a carbonyl group. The reaction produces very colourful and bright precipitates of yellow, orange and red.
(2) You can check formation of C=N imine from FTIR analysis. where u will get a sharp peak at 1640-1690 cm-1.
(3) Another is from 13C nmr in which imine will come near 155 ppm.
- Badges
- Science topic
- Similar topics
- Linguistics
- Composition Studies
- Publication