Thin Layer Chromatography This question has two (II) parts. Please provide an an
ID: 890181 • Letter: T
Question
Thin Layer Chromatography
This question has two (II) parts. Please provide an answer for each in order for your answer to be voted as helpful.
*The analgesics used were (1) caffeine, (2) acetylsalicylic acid, (3) acetaminophen, & (4) ibuprofen.
The order of polarity based on my experiment: caffeine > acetaminophen > acetylsalicylic acid > ibuprofen
*The benzene derivatives used were (1) benzaldehyde, (2) benzoic acid, (3) benzyl alcohol, (4) methyl benzoate, & (5) benzamide.
The order of polarity based on my experiment: benzamide > benzoic acid > benzyl alcohol > benzaldehyde > methyl benzoate
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The five known compounds in Part A were (1) benzaldehyde, (2) benzoic acid, (3) benzyl alcohol, (4) methyl benzoate, & (5) benzamide.
Thank you for your help!
4. Given the functional groups on each of the analgesics, do your results reinforce or contradict your results from the benzene derivative TLC?Explanation / Answer
The order in your first experiment is correct for example acetylsalicylic acid has 3 oxygens and one hydrogen bonding hydrogen for a total of 7 sites for hydrogen bonding. Acetaminophen contains 2 oxygens and 1 hydrogen bonding hydrogen for a total of 5 sites for hydrogen bonding.and acetominophen has nitrogen atom in its structure, C-N is a polar group which then bond with C=O and form like amide.
The carbonyl of the aldehyde will be more polar. You can basically look at that carbonyl double bond as that C binding 2 oxygen molecules. Looking then at the alcohol group, with only one oxygen, you can see that the carbonyl would be more polar since it has an additional oxygen. The polarity order in your experiment is correct.
For your 2nd part of question,
you can see the functional group IR stretching the O=C–H stretches in aldehydes in the region 2830-2695 cm-1, especially the shoulder peak at 2745 cm-1 in benzaldehyde. For Benzoic acid, Absorption between 1680-1750 shows that a C=O is present. Absorption around 1300 cm-1 again shows the presence of an OH group. For benzyl alcohol shows 3169 (br) signal. For methyl benzoate 1724 cm-1 . For benzamide the absorptions at 3360 and 3180 cm"1 are due to N-H asymmetric and symmetric stretching vibrations.
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