17.1 Mass Spectrometry

Question 1

Describe how mass spectrometry works

Answer 1

Organic compounds are ionised so they lose an electron and form a positive ion, the molecular ion.

It detects the mass-to-charge (m/z) ratio which gives the molecular mass of the compound.

Question 2

How do you find the molecular mass, from mass spectrometry ?

Answer 2

The molecular ion peak ( M+ peak) has to be located.

This peak is the clear peak at the highest m/z value on the right - hand side of the mass spectrum.

There’s usually a small peak one unit after the M+ peak ( called the M+1 peak). This is because 1.1% of carbon is present as the carbon -13 isotope.

Question 3

Define the terms fragmentation and fragment ions

Answer 3

Fragmentation : when molecules ions break down into smaller pieces know as fragments in a mass spectrometry

Fragment ions : the other leaks in a mass spectrum formed from the breakdown of the molecular ion

Question 4

How can you identify a compound from mass spectrometry ?

Answer 4

See all the pieces it could break down into and see if it correlates

Find out it’s molecular mass as well