17.1 Mass spectrometry Flashcards
What happens when an organic compound is placed in a mass spectrometer?
It loses an electron and forms a positive ion
A molecular ion
What can the mass spectrometer use to give molecular mass?
The mass-to-charge ratio of the molecular ion
What does the peak at the end indicate (highest m/z value)?
The molecular ion peak indicates the molecular mass
Why is there a very small peak after the M+ peak?
Because 1.1% of carbon is present as the carbon-13 isotope
What happens during fragmentation?
Some molecular ions break down into smaller pieces known as fragments in the mass spectrometer
What are other peaks caused by?
Fragment ions (formed from the breaking down of molecular ions)
What does the simplest fragmentation involve?
Breaking molecular ions into two pieces
What two pieces are formed during simple fragmentation?
A positively charged fragment ion and a radical
What can be detected by the mass spectrometer after simple fragmentation?
The positive ions
Why are the mass spectrum of each compound unique?
Molecules all fragment slightly differently depending on their structures
Why is the fact that the mass spectrum of each compound is unique useful?
Helps identify the compound despite it having the same molecular ion peak (molecular mass)
by looking at the fragments
How do you use peaks to find how many carbon atoms are present?
Height of M+1 peak / Height of M peak
x100
units are mm for height
