Structure Determination

Question 0

What is plotted on the graph?
What is the peak at the max m/z relative to?
Under what condition?
What’s the general equation for the formation of a molecular ion?
What is the m/z of the molecular ion relative to?
What can the molecular ion peak be used to determine?
What is the molecular ion peak also known as?
What is the molecular ion peak not necessarily?

Answer 0

Abundance against m/z
Molecular ion 
The molecule is not completely fragmented 
M>M•+ + e-
The relative molecular mass of a compound 
The structure of an unknown 
Base peak 
The tallest/most abundant peak

Question 1

Fragmentation of the molecular ion
What causes ions to fragment ?
What does the molecular ion split to?
General equation for this?
Rarely formed in equal amounts and X+ and Y+ can't be formed by same ion 
Which is detected and which isn't?
What do other peaks give?

Answer 1

High energy of ionising beam 
Positively charged ions and uncharged radicals 
M+• > X• + Y+
\+ detected • not detected 
Useful info about compound

Question 2

Molecular ion
Where is fragmentation more likely to take place?
What does a more stable bond have?
Why is the mass spec of hydrocarbons complex?

Answer 2

Weaker bonds
Higher abundance
C-13 isotopes

Question 3

Fragmentation of Carbonyl Compounds
What is this useful for?
Where’s predominant decomposition?
General equation

Answer 3

Structural determination
Carbonyl compound
[RCOR]•+>[RCO]+ +R•

Question 4

Isotope peaks
What does M+1 peak relative to?
If M+1 peak is 5% of M what does that mean?

Answer 4

The number of carbons

There are 5 carbons

Question 5

Fingerprinting

How is used to identify unknown?

Answer 5

Compare with a known substance