Question

100 5.400-w-SH Relative Intensity 0 + + 15 20 ZS OD 45 B. m/z

The MS spectra shows the following unknown. It is either Toluene (C6H5CH3), Benzyl Bromide (C6H5CH2Br), m-cresol (C6H4(OH)CH3), or Ethanol (C2H5OH)
Show work and label the appropriate peak and discuss the peaks in text.
*Please explain how to do this*

Answer 1

Hi it is Ethanol

1. By looking at molecular ion m/z = molar mass, ethanol molar mass = 46 amu

2. remaining other three have M⁺ radical cation m/ z > 80

3. m/z 31 is characteristic peak of alcohols due to fragment [H₂C=OH]⁺

Reason: 1^o alcohol usually has prominent peak at m/z = 31corresponding to [H₂C=OH]⁺

4. loss of hydroxyl radical (-OH^o) gives a peak m/z 29

5. loss of water molecule (H₂O) gives a peak at m/z 28

6. Fragmentation pattern is shown below

100 -С —О—Н Н—С 80 60 40 Н—С 20 O 10 15 20 25 30 35 40 45 m/z I C-I I I I-C-I IUI IC-I I-C-I I Relative Intensity

Hope this helped you!

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