Question

How would you distinguish between each pair of compounds using high-resolution mass spectrometry? ОН НЮ, Х ОН но тz = 126.3152 mіz= 126.4104 ОН но он тz= 126.0315 m/z= 126.1404 он НО ХОН miz = 126.4021 miz = 126.0243 ОН но он miz = 126.3152 m/z= 126.1441

Please explain, thank you!

Answer 1

High Resolution Mass Spectrometry
In assigning mass values to atoms and molecules, we have assumed integral values for isotopic masses. However, accurate measurements show that this is not strictly true.

Using this technique mass spectrometers can be used to determine m/z values accurately to four decimal places, it is possible to distinguish different formulas having the same nominal mass.

Atom	Exact masss
Carbon	12.000 00
Hydrogen	1.007 83
Nitrogen	14.003 07
Oxygen	15.994 92

1. Molecular formula :

C₆H₆O₃   and C₉H₁₈   : on adding exact masses of atoms.

Molecular masses in 4 digits after decimal : C₆H₆O₃ (126.0316) and C₉H₁₈ (126.1404) (B)

2. Molecular formula :

C₆H₈O₂ and C₈H₁₆ : on adding exact masses of atoms.

Molecular masses in 4 digits after decimal : C₆H₈O₂ (112.0524) and C₈H₁₆ (112.1252) (C)