UCexp262scheme.png
Researcher
Evan Curtin

Objective

To synthesize four imines from the reactions of two different amines (aniline and 2-chloroaniline) and two different aldehydes (vanillin and 4-chlorobenzaldehyde). [Link to ChemSpider entries and upload missing spectra there JCB]

Procedure

Weigh equimolar amounts of each aldehyde and amine. Add each aldehyde to its own 20mL test tube. Add the amines dropwise to the aldehyde. Filter, then Wash the product with cold ethanol (chilled in ice/water bath). Dry the products in a desiccator under high vacuum.

Results

Exp262plan
Mass and yield calculations

Aniline




2-chloroaniline




vanillin




Chlorobenzaldehyde


Note: Solvent used was a mixture of CDCl3 and DMSO-d6 for 4-chlorobenzaldehyde



Characterization of 1A (product of aniline and vanillin)


appearance: yellow solid
amount: 910.0 mg, 59.32 % yield
mp: 140-142 C
H NMR (embed or link) solvent: CDCl3


Characterization of 2A (product of aniline and p-chlorobenzaldehyde)


appearance: white solid
amount: 362.9 mg, 34.65 % yield
mp: 227-230 C
H NMR (embed or link)
Note: Solvent used was a mixture of CDCl3 and DMSO-d6


Characterization of 3A (product of o-chloroaniline and vanillin)


appearance:
amount: x mg, x % yield
mp:
H NMR (embed or link) solvent: CDCl3


Characterization of 4A (product of o-chloroaniline and p-chlorobenzaldehyde)


appearance: white powder
amount: 331.3 mg, 22.97 % yield
mp: 227-230
H NMR (embed or link)
Note: Solvent used was a mixture of CDCl3 and DMSO-d6


Discussion

- The reaction of aniline and vanillin was successful. For sample 1, The aldehyde peak at 9.815 ppm has an integration of 2.71. The imine peak at 8.34 ppm had an integration of 31.6. The molar ratio of imine to aldehyde is 11.66.
- The aldehyde peak at 9.8 ppm has an integration of 27.6. The imine peak at 8.26 ppm had an integration of 26. The reaction of ortho-chloroaniline and vanillin had about a 50% conversion to imine (product). This suggests that the rate of the reaction is lower than the other reactions.
- Products 2 and 4: The imine and aldehyde peaks were much smaller than expected. There were two doublets in the aromatic region, suggesting that an aromatic ring with two groups para to one another was in the product. Both 2 and 4 had para-chlorobenzaldehyde as starting reactants. In addition, the melting points for both compounds were identical, at 227-230C. Sigma Aldritch's HNMR for para-chlorobenzoic acid matches the HNMRs for products 2 and 4. In addition, the melting point for 4-chlorobenzoic acid is 238C-241C. Accounting for impurities, this matches with the melting points of the 2nd and 4th product. All of this points to the formation of para-chlorobenzoic acid instead of the imine. Para-chlorobenzaldehyde was oxidized at some point in the reaction, with a yield of 34.65% (2) and 22.97% (4).
- The impurities in products 2 and 4 and the relative purity of product 1 suggests that electron-withdrawing groups on the aldehyde aid the formation of the acid. While some of the imine formed, the isolated product was predominately the acid. Further experiments with these groups should be run under nitrogen.
Conclusion
The imine of aniline and vanillin was successfully synthesized. The imine of 2-chloroaniline and vanillin was never isolated. In both reactions with 4-chlorobenzaldehyde, oxidation into 4-chlorobenzoic acid was formed.

Log

2011-03-07

12:45 - Weighed reactants.
13:45 - Added aniline and 2-chloroaniline dropwise to their respective aldehydes.The reaction was carried out in 20mL tubes.
14:06 - Added 1mL ethanol to each mixture. No mixture completely dissolved.
14:12 - Added each mixture to a 40C Water bath.
14:29 - Mixture 3 (vanillin and o-chloroaniline) dissolved noticeably more than the other three.
14:41 - Mixture 3 dissolved completely
14:43 - Cooled mixture 3 in an ice bath.
14:48 - Heated mixture 1, 2, and 4 in a 45C bath.
14:50 - No solid is visible in mixture 3. Added n-hexane to attempt to precipitate the product. No solid was formed.
14:59 - Added 2mL ethanol to mixture 1, 2, and 4. Placed all three in a 50C bath.
15:10 - None of mixtures 1, 2, and 4 completely dissolved. Removed from 50C bath.
15:25 - Rotary evaporated mixture 3 at 50C
15:49 - Washed 1, 2, 4 with 3mL ethanol, vortexing after each addition.
15:55 - Removed mixture 3 from rotary evaporator. Covered with parafilm and set on counter.
16:05 - Washed mixture 1 three more times, the ethanol kept turning yellow after addition to the solid.
16:16 - Put 1, 2 and 4 into desiccator under high vacuum.

2011-03-08

10:56 - Removed 1, 2 and 4 from desiccator under high vacuum. 1A is yellow, 2A and 4A are both white.
11:04 - Weighed each sample
11:30 - Measured the melting point of each sample. In all three samples, liquid formed at the bottom of the capillary tube when the temperature was about 30C. The solid didn't melt at this temperature. Sample 2 and 3 melted at the same temperature range. The melting points are:
Sample 1A: 140-142C
Sample 2A: 227-230C
Sample 4A: 227-230C