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a level spectroscopy help

Hello I keep getting the M/Z value wrong for mass spectroscopy and I also sometimes find it hard to know if I should include a wavelength value in infrared spectroscopy.

For example for Mass spectroscopy in this example: https://ibb.co/x6dYMWN

Allery says it's 58 M/Z and hence 58 Mr but isn't 60 M/Z the last peak shown in this graph?

For infrared spectroscopy:
https://ibb.co/Vm690bt

Do we include that little peak right after 1500? Are the two peaks around 3000 counted as separate peaks or is it considered a broad peak?

This whole topic feels like doing those google captchas where you think to yourself "should I include this" when the thing they are asking for has one pixel on the photo lol.

What should I do for these spectras?
Reply 1
Original post by DukeAim
Hello I keep getting the M/Z value wrong for mass spectroscopy and I also sometimes find it hard to know if I should include a wavelength value in infrared spectroscopy.
For example for Mass spectroscopy in this example: https://ibb.co/x6dYMWN
Allery says it's 58 M/Z and hence 58 Mr but isn't 60 M/Z the last peak shown in this graph?
For infrared spectroscopy:
https://ibb.co/Vm690bt
Do we include that little peak right after 1500? Are the two peaks around 3000 counted as separate peaks or is it considered a broad peak?
This whole topic feels like doing those google captchas where you think to yourself "should I include this" when the thing they are asking for has one pixel on the photo lol.
What should I do for these spectras?

You pay attention to the peaks with the strongest intensity in MS. As the IR spectrum shows that it is an alcohol (broad peak at around 3300cm-1) and only saturated C-H stretching (2 separate absorption peaks below 3000 cm-1), the relative molecular mass of 58 fits a saturated 4-carbon alcohol. The peak above 1500cm-1 is not a carbonyl absorption peak which must be the strongest peak in the IR spectrum. I always advise my students, practice makes perfect. Work on as many problems as possible. There is no easier way to learn organic chemistry.
Reply 2
Original post by tkms2009
You pay attention to the peaks with the strongest intensity in MS. As the IR spectrum shows that it is an alcohol (broad peak at around 3300cm-1) and only saturated C-H stretching (2 separate absorption peaks below 3000 cm-1), the relative molecular mass of 58 fits a saturated 4-carbon alcohol. The peak above 1500cm-1 is not a carbonyl absorption peak which must be the strongest peak in the IR spectrum. I always advise my students, practice makes perfect. Work on as many problems as possible. There is no easier way to learn organic chemistry.


Thank you!

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