Module 4: Analysis

Question 1

Mass spectrometry
What happens in the mass spectrometry

Answer 1

High energy electron bombards a molecules in a mass spectrometer which results in the molecule losing an electron

Question 2

Mass spectrometry
What is the resulting species when a molecule is bombarded by the higher energy electron

Answer 2

Molecular ion

Question 3

Mass spectrometry
Equation for formation of molecular ion

Answer 3

Molecule —-> Molecule+. + e-

Question 4

Mass spectrometry
Notation for molecular ion

Answer 4

M+

Question 5

Mass spectrometry
What is the definition of a molecular ion

Answer 5

Positive ion formed when molecule loses an electron

Question 6

Mass spectrometry
What is on the axis of a spectra

Answer 6

X- m/z -mass to charge ratio
Y- %abundance

Question 7

Mass spectrometry
Where is the M+ ion on a spectra

Answer 7

Last peak on the right

Question 8

Mass spectrometry
What is fragmentation

Answer 8

Process in mass spec that causes positive ion (M+) to split into pieces of a positive ion (which produces a peak) and a radical

Question 9

Mass spectrometry
What is the M+1 peak

Answer 9

Smallll peak just after M+

Question 10

Mass spectrometry
Why is the M+1 peak there

Answer 10

Due to C-13 present

Question 11

Mass spectrometry
How is it used for isotopes

Answer 11

Positions of peaks show different isotopes prescence and is used to find relative atomic mass with abundance

Question 12

Mass spectrometry
How can organic molecules be identified from eac other

Answer 12

Each have different peaks from fragments

Question 13

Mass spectrometry
How does fragmentation occur and how does it show on spectra

Answer 13

One bond broken in the M+ to form a positive ion and radical
Peak at the positive ion formed with its m/z value (mr)

Question 14

Mass spectrometry
Where is the Mr of the whole product found

Answer 14

At the M+ ion

Question 15

Mass spectrometry
For analysis questions what is the typical way to find the molecular formula

Answer 15

Find the empirical formula and find mr
Find mr of whole product at the M+ peak
mr of whole product / Mr of empirical
Scale up the ration of the empirical formula

Question 16

Mass spectrometry
What are fragmentation patterns of functional groups

Answer 16

Specific positions of peaks and differences between major peaks which makes it possible to identify the type of compound

Question 17

Mass spectrometry
What is the peak due to at m/z 15

Answer 17

CH3+

Question 18

Mass spectrometry
What is the peak due to at m/z 29

Answer 18

C2H5+

Question 19

Mass spectrometry
What os the peak due to at m/z 43

Answer 19

C3H7+

Question 20

Mass spectrometry
For alkanes what affects the abundance of a peak

Answer 20

The stability of the carbo cation

Question 21

Mass spectrometry
For alkanes as the stability of the carbocation increases what happens to the peak

Answer 21

Larger abundance

Question 22

Mass spectrometry
For haloalkanes why is there often multiple peaks in the molecular ion region

Answer 22

Due to the different isotopes of the halogen

Question 23

Mass spectrometry
For ketones and aldehydes what is the characteristic fragmentation

Answer 23

Cleavage of bonds next to carbonyl (C=O)

Question 24

Mass spectrometry
Where do carbonyl compound fragments

Answer 24

Ether side of the carbonyl group

Question 25

Infra red spectroscopy What is IR based on

Answer 25

Atoms molecules and ions ability to absorb electromagnetic radiation of specific frequencies and this can be used to identify them

Question 26

Infra red spectroscopy What is the energy from IR used to do the molecules

Answer 26

Vibrate bonds

Question 27

Infra red spectroscopy What is specific about each bind which allows them to be identifie

Answer 27

Vibrate at different frequency

Question 28

Infra red spectroscopy What are the three types of bond vibration

Answer 28

Symmetric stretch Asymmetric stretch Bending

Question 29

Infra red spectroscopy What is the graph called in IR

Answer 29

IR spectra

Question 30

Infra red spectroscopy What is the range for IR to be absorbed

Answer 30

400-4000

Question 31

Infra red spectroscopy What is below 1500 on a spectra

Answer 31

Fingerprinting -not used

Question 32

Infra red spectroscopy What is above 1500 used for

Answer 32

Identifying functional group

Question 33

Infra red spectroscopy Where is the info for where the identification of each functional group is

Answer 33

On data sheet

Question 34

Infra red spectroscopy What does a C=C bond look like

Answer 34

Short spike around 1600 half way down spectra

Question 35

Infra red spectroscopy What does a C=O bond look like

Answer 35

Long spike around 1700

Question 36

Infra red spectroscopy What does )-H in an alcohol look like

Answer 36

Smooth peak wider around and above 3000

Question 37

Infra red spectroscopy What does an O-H in a carbpxylic acid look like

Answer 37

Wide jaggeder peak at and above 3000

Question 38

Infra red spectroscopy What are the two uses

Answer 38

Greenhouse gases identifying Breathalysers

Question 39

Infra red spectroscopy What are the green house gases 3

Answer 39

Carbon dioxide Water vapour Methane

Question 40

Infra red spectroscopy How can carbon dioxide be identifies

Answer 40

C=O bond

Question 41

Infra red spectroscopy How can water vapour be identified

Answer 41

O-H bonds

Question 42

Infra red spectroscopy What does the greenhouse effect of a given gas depend onn

Answer 42

Atmospheric pollution Ability to absorb infrared radiation

Question 43

Infra red spectroscopy Why do bond have different strengths resulting in diffeeent frequencies vibrated at

Answer 43

Masses of different atoms at either end of bond

Question 44

Infra red spectroscopy What is the type of vibration in water

Answer 44

Bending and stretching

Question 45

Infra red spectroscopy What does infra red have to do with global warming

Answer 45

It’s the absorption of IR that contributes to global warming

Question 46

Infra red spectroscopy How does iR work in breathalysers to measure alcohol levels

Answer 46

Ray of IR passed throught the breath that’s exhaled into breathalyser chamber Characteristic bonds of ethanol are detected and measured higher absorbance-more ethanol