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Practical lab writeups see pdf files

Preparation of compound B:
Product weight: 4.22 g

Molecular formula of compound B: 0.7021 * 188 = 11 C atoms
0.0426 * 188 = 8 H atoms
0.2553 * 188 = 3 O atoms
C11H8O3

The 1HNMR spectrum of compound B shows an around 3H singlet peak at 2.8 ppm, which could be the COCH3-group.

The structure of compound B is:



Question:
Compound B can be formed from A through a substitution reaction of the p-hydroxy-group at COO, replacing Et. This forms the secondary ring.
Experiment 3 - The Beckmann rearrangement

4-Bromoacetonhenone oxime:
Product weight: 4.737 g
Molar weight product: 213.99 g/mol
Product: 14.737 g / 213.99 g/mol = 68.86 mmol
Start matter: 37.6 mmol
Reaction proportions: 1 : 1
Product yield: 68.86 / 37.6 * 100% = 183 % (so probably not dry enough)

Melting point: 200 C

Recrystallised weight: 0.399 g
Molar weight product: 213.99 g/mol
Product: 0.399 g / 213.99 g/mol = 1.86 mmol
Start matter: 37.6 mmol - 5 g/213.99 = 14.2 mmol
Reaction proportions: 1 : 1
Product yield: 1.86 / 14.2 * 100% = 13.1 %

The extreme yield loss at crystallization is probably because the crystallization process did not work out in my hands.

4-Bromoacetanilide:

Product weight: 0.218 g
Start matter: 5 g
Molar weights are equal for start matter and product
Product yield: 0.218 / 5 * 100% = 4 %

Melting point was not determined for this product

Questions:

1)





2)
peak
H atoms
2.05
CH3 group from NHCOCH3 adduct
7.40
CH from benzene cycle closest to Br (electronegativity < N)
7.80
CH from benzene cycle closest to N (electronegativity > Br)
11.10
NH from NHCOCH3 adduct

The H atom of NH will exchange with solvent, so if D2O is added it may be replaced with D. This only influences the peak...
So the product is 1,2-dimethoxy-4-nitrobenzene, consistent with the melting point.
The melting point of the semicarbazide derivative of compound A was found to be 224-225 C, which means that compound A is likely to be o-chloro-benzaldehyde or p-hydroxy-benzaldehyde. According to the 1HNMR spectrum, with benzene proton peaks around 7 ppm and aldehyde proton singlet, the second functional group should also contain one proton, showing up as a singlet. Therefore, the second functional group is a hydroxy-group, so compound A is p-hydroxy-benzaldehyde. This hydroxyl-group also gives the possibility to from the bicyclic structure of compound B.
The H atom of NH will exchange with solvent, so if D2O is added it may be replaced with D. This only influences the peak of the H of NH, which will become a doublet with the second peak (of D) at lower intensity and at higher field (lower ). ...Show more

Summary

The melting point of the product was found to be 94 C. This is very close to 95 C, the melting point of 1,2-dimethoxy-4-nitrobenzene, so this is very likely to be the product. Also, according to melting point the product is quite pure.
The filtrate mother liquor has not been run on TLC, so no semi-quantitative data on the relative purities of the crude product and the recrystallised product have been obtained…
Author : cathyking
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