3.6 - Organic Analysis

Question 1

How do you represent the time of flight ionisation equations?

Answer 1

M(g) + e- -> M+• + 2e-

M+• = molecular ion or radical cation

Question 2

Where does fragmentation occur to give a major peak?

Answer 2

At an acyl group

RCO

Question 3

How do you draw write a fragmentation equation using CH3COCH3?

Answer 3

[CH3COCH3]+• -> CH3CO (+ on the C) + CH3 (• on the C)

The + and the • could also be on opposite molecules but the + on the acyl is more stable

Question 4

What is the base peak?

Answer 4

RCO (+ on the C)

The most common
Most stable
Easiest to form
Always has 100% relative abundance

Question 5

What should you watch out for with mass spectrometry graphs?

Answer 5

Chlorine and Bromine have 2 isotopes that appear

Cl35 and Cl37 1:3 ratio
Br79 and Br81 1:1 ratio

So there will be more peaks two units apart
(There are different combos of the isotopes)

Question 6

What is the full scale in infrared spectroscopy?

Answer 6

4000 - 400

Question 7

What is the difference in peaks of O-H alcohol and O-H acid?

Answer 7

O-H alcohol = perfect isolated curve

O-H acid = merges in to the spikes of C-H bonds therefore very wide

Question 8

What does the C≡N peak look like?

Answer 8

Tiny range so looks like a needle

Question 9

How should you approach matching Infrared spectroscopy graphs to compounds?

Answer 9

Label the main identifying features of the graph, such as functional groups