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Organic chemistry, The task is to read both of the analysis and form a paragraph

ID: 959684 • Letter: O

Question

Organic chemistry, The task is to read both of the analysis and form a paragraph on determining whether the solutions are correct or not



Solved Problem Analysis: Below is an IR & MS analysis for 1-chloro-2-methyl-2-phenylpropane. Read the analyses then critique the presented solutions. Determine if the solutions are correct or not. Write a paragraph on how you would convey the same information (include corrections or supgestions to improve the analysis presented) 7. Cl Analysis: The IR spectrum shows a large bundle of signals around 3000 cm1 which corresponds to the C-H stretches. The aromatic overtones are the medium-strong signals from 1450-1500 cm1. The CH,Cl peak is around 1300 cm and has a medium absorption. The cluster of signals from 700-800 cm 1 is due to the aliphatic C-Cl absorptions. Is from 1450-1500 cm, The CH,Cl peak is around 1300 cm1

Explanation / Answer

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“The IR spectrum shows a large bundle of signals around 3000 cm-1 which correspond to the C-H stretches”

This information is correct however it could be elaborated a little more. In the “bundle of signals” we can distinguish two groups: a group of signals over 3000 cm-1 corresponding to the C-H stretching of aromatic hydrogen, which usually is less intense, than the signal for aliphatic hydrogen stretching. Then we can see a far more intense signal falling in the aliphatic region (2840-3000 cm-1), more intense. This analysis tells us that we have both types of groups in our molecule.

“The aromatic overtones are the medium strong signals from 1450-1500 cm-1” This is not correct. Overtones appear from 1700 to 2000 cm-1, like in this case, and they are weak bands. We can add that this specific pattern of the overtone is typical for aromatic ring with only one substituent.

About the signal from the CH2Cl group, the statement is also incorrect. Band corresponding to the wagging of this group usually appears as a strong band in the 1300-1150 cm-1 region. Also it can be added that the aliphatic absorption band that corresponds to the C-Cl bond is observed in the region of 850 to 550 cm-1.

What other thing you can add: gem-dimethyl groups show a strong doublet around 1370-1365, with both peaks almost equally intense. This IR spectrum shows that doublet.

Mass Spectrum:

Molecular ion: Chlorine atom has two important isotopes 35Cl (100) and 37Cl (32,5). The relation of the peak heights shows that proportion.

Other important peaks: it is correct that the peak at m/z = 91 can be attributed to C4H8Cl+ which also supports our idea of the presence of chlorine in the molecule. But also m/z = 91 can be attributed to C7H7+ which frequently appears in aromatic compounds.

Statement about the m/z = 119 is correct.

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