Chapter 7 - Modern analytical techniques (L)
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What is the molecular ion peak?
The peak furthest to the right (the one with the highest m/z)
What causes the molecular ion peak?
When an organic molecule loses an electron in the mass spectrometer- this can occur when an electron collides with the molecule, knocking out an electron so forming a positive ion
What does the m/z value of the molecular ion peak indicate?
The relative molecular mass of the molecule (as it has just lost an electron)
What causes the M+1 peak?
The naturally occurring isotope of carbon (carbon-13).
What is the M+1 peak?
A very small peak just to the right of the molecular ion peak
What is fragmentation?
Where the molecular ion breaks into smaller pieces
What is the base peak?
The peak with the greatest abundance (the tallest peak)
What are the two possible effects of infrared radiation on bonds?
Stretching and bending
What is stretching?
Where the bond length increases and decreases
What is bending?
Where the bond angle increases and decreases
What type of molecules do not absorb infrared radiation?
Non-polar molecules such as H2 and Cl2
What is infrared radiation?
Part of the electromagnetic spectrum with frequencies below that of red light
What is the transmittance value?
The value in an infrared spectrum that represents the amount of infrared radiation not absorbed (transmitted) at a particular wave number. Often done as a 0-100 percentage
What is the wave number?
The wave number represents the frequency of the infrared radiation that was absorbed by a particular bond in a molecule
What is the intensity of an infrared absorption refer to?
The actual amount of infrared radiation absorbed. A high intensity refers to a low transmittance value and a low intensity refers to a high transmittance value
What are the 4 stages of mass spectrometry?
Ionisation Acceleration Deflection Detection
What happens in the ionisation stage of mass spectrometry?
The atom or molecule is ionised by knocking one or more electrons off to form a positive ion
What happens in the acceleration stage of mass spectrometry?
The ions are accelerated so that they all have the same kinetic energy
What happens in the deflection stage of mass spectrometry?
The ions are then deflected by a magnetic field according to their masses and amount of positive charge.
What happens in the detection stage of mass spectrometry?
The beam of ions passing through the machine is detected electrically.
How does the amount of positive charge on the atom/molecule affect of deflection?
The more the ion is positively charged, the more it gets deflected.