Module 4: Analysis Flashcards
Mass spectrometry
What happens in the mass spectrometry
High energy electron bombards a molecules in a mass spectrometer which results in the molecule losing an electron
Mass spectrometry
What is the resulting species when a molecule is bombarded by the higher energy electron
Molecular ion
Mass spectrometry
Equation for formation of molecular ion
Molecule —-> Molecule+. + e-
Mass spectrometry
Notation for molecular ion
M+
Mass spectrometry
What is the definition of a molecular ion
Positive ion formed when molecule loses an electron
Mass spectrometry
What is on the axis of a spectra
X- m/z -mass to charge ratio
Y- %abundance
Mass spectrometry
Where is the M+ ion on a spectra
Last peak on the right
Mass spectrometry
What is fragmentation
Process in mass spec that causes positive ion (M+) to split into pieces of a positive ion (which produces a peak) and a radical
Mass spectrometry
What is the M+1 peak
Smallll peak just after M+
Mass spectrometry
Why is the M+1 peak there
Due to C-13 present
Mass spectrometry
How is it used for isotopes
Positions of peaks show different isotopes prescence and is used to find relative atomic mass with abundance
Mass spectrometry
How can organic molecules be identified from eac other
Each have different peaks from fragments
Mass spectrometry
How does fragmentation occur and how does it show on spectra
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)
Mass spectrometry
Where is the Mr of the whole product found
At the M+ ion
Mass spectrometry
For analysis questions what is the typical way to find the molecular formula
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
Mass spectrometry
What are fragmentation patterns of functional groups
Specific positions of peaks and differences between major peaks which makes it possible to identify the type of compound
Mass spectrometry
What is the peak due to at m/z 15
CH3+
Mass spectrometry
What is the peak due to at m/z 29
C2H5+
Mass spectrometry
What os the peak due to at m/z 43
C3H7+
Mass spectrometry
For alkanes what affects the abundance of a peak
The stability of the carbo cation
Mass spectrometry
For alkanes as the stability of the carbocation increases what happens to the peak
Larger abundance
Mass spectrometry
For haloalkanes why is there often multiple peaks in the molecular ion region
Due to the different isotopes of the halogen
Mass spectrometry
For ketones and aldehydes what is the characteristic fragmentation
Cleavage of bonds next to carbonyl (C=O)
Mass spectrometry
Where do carbonyl compound fragments
Ether side of the carbonyl group
Infra red spectroscopy
What is IR based on
Atoms molecules and ions ability to absorb electromagnetic radiation of specific frequencies and this can be used to identify them
Infra red spectroscopy
What is the energy from IR used to do the molecules
Vibrate bonds
Infra red spectroscopy
What is specific about each bind which allows them to be identifie
Vibrate at different frequency
Infra red spectroscopy
What are the three types of bond vibration
Symmetric stretch
Asymmetric stretch
Bending
Infra red spectroscopy
What is the graph called in IR
IR spectra
Infra red spectroscopy
What is the range for IR to be absorbed
400-4000
Infra red spectroscopy
What is below 1500 on a spectra
Fingerprinting -not used
Infra red spectroscopy
What is above 1500 used for
Identifying functional group
Infra red spectroscopy
Where is the info for where the identification of each functional group is
On data sheet
Infra red spectroscopy
What does a C=C bond look like
Short spike around 1600 half way down spectra
Infra red spectroscopy
What does a C=O bond look like
Long spike around 1700
Infra red spectroscopy
What does )-H in an alcohol look like
Smooth peak wider around and above 3000
Infra red spectroscopy
What does an O-H in a carbpxylic acid look like
Wide jaggeder peak at and above 3000
Infra red spectroscopy
What are the two uses
Greenhouse gases identifying
Breathalysers
Infra red spectroscopy
What are the green house gases 3
Carbon dioxide
Water vapour
Methane
Infra red spectroscopy
How can carbon dioxide be identifies
C=O bond
Infra red spectroscopy
How can water vapour be identified
O-H bonds
Infra red spectroscopy
What does the greenhouse effect of a given gas depend onn
Atmospheric pollution
Ability to absorb infrared radiation
Infra red spectroscopy
Why do bond have different strengths resulting in diffeeent frequencies vibrated at
Masses of different atoms at either end of bond
Infra red spectroscopy
What is the type of vibration in water
Bending and stretching
Infra red spectroscopy
What does infra red have to do with global warming
It’s the absorption of IR that contributes to global warming
Infra red spectroscopy
How does iR work in breathalysers to measure alcohol levels
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
