17.1 Mass spectrometry

Question 1

What can mass spectra be used for

Answer 1

To identify the molecular mass of an organic compound and to gain further info about its structure

Question 2

When an organic compound is placed in the mass spectrometer, it loses an electron and forms a ______ ion, the ______ ion. The mass spectrometer detects the mass-to-charge ratio (/) of the molecular ion which gives the ______ mass of the compound.

Answer 2

Positive
Molecular
m/z
Molecular

Question 3

What must be located to find the molecular mass

Answer 3

The molecular ion peak (M+ peak)

Question 4

What is the molecular ion peak

Answer 4

M+ peak
Clear peak at the highest m/z value on the right-hand side of the mass spectrum
Eg. if peak m/z is 60, the molecular mass is 60

Question 5

What is fragmentation

Answer 5

In the mass spectrometer, some molecular ions break down into smaller pieces known as fragments

Question 6

What are the other peaks in a mass spectrum caused by

Answer 6

Fragment ions formed from the breakdown of the molecular ion

Question 7

What does the simplest fragmentation break a molecular ion into

Answer 7

Two species
A positively charged fragment ion
And a radical
Any positive ions formed will be detected by the mass spectrometer but the uncharged radicals are not detected

Question 8

Main features of the mass spectrum of ethanol

Answer 8

Molecular ion peak at m/z=46
Small M+1 peak at m/z=47
A number of fragment ion peaks

Question 9

Equation to find number of carbon atoms from mass spectrum

Answer 9

no. of carbon = height of M+1 peak x 100 / height of M peak

Question 10

What is Clenbuterol

Answer 10

Believed to increase development of muscle
Considered a performance enhancing drug
Banned in athletic competitions