Mass Spec

Question 1

How do you calculate the degree of unsaturation?

Answer 1

(2C+2-H-X+N)/2 Oxygen doesn’t show up

Question 2

What mass would come up for a benzyl cation?

Answer 2

77

Question 3

What mass would come up for a pentyl cation?

Answer 3

65

Question 4

What mass would come up for a methyl cation?

Answer 4

15

Question 5

What would come up for an acetyl cation?

Answer 5

43

Question 6

What mass would come up for an ethyl cation?

Answer 6

29

Question 7

What is the retro Diels-Alder reaction?

Answer 7

The opposite of Diels Alder so involves a cyclic cation/radical cations containing a six membered ring with a double bond to break into two fragments - a diene and an alkene

Question 8

What is the McLafferty arrangement?

Answer 8

B-cleavafe with a hydrogen shift via a 6-membered ring.
Think of benzyl benzoate and how a hydrogen is taken from the beta carbon and the ketone takes it to transform in to a hydrogen and in doing so this cleaves a bond.

Question 9

What is decarbonylation?

Answer 9

Removing a CO molecule from a phenol

Question 10

How would you be able to spot a bromine or chlorine atom from the mass spec?

Answer 10

There would be two peaks 2 mass apart representing both isotopes. For chlorine the intensity would appear at a 3:1 ratio and for bromine they would appear at a 1:1 ratio