Modern analytical techniques 1 Flashcards
(15 cards)
What happens in mass spec
Molecules in a small sample are bombarded with high energy electrons which knocks off an electron from the sample.
What does bombarding the sample result in
A positively charged ion with one unpaired electron.
What is the m+1 peak in carbon
The small peak as a result of the natural abundance of the isotope carbon 13.
The peak is small as carbon 13 is very rare at just around 1 percent
What happens to fragments of ions
They are accelerated by an electric field which are then seperated depending on their mass to charge ratio. By being deflected into a detector.
Which ions are detected first.
Smaller and more positively charged fragments. As they are more attracted to the negative pole of the magnet
What is the base peak
The peak corresponding to the most abundant ion
What re isotopes
Atoms of the same element with the same number of protons and electrons but a different number of neutrons.
Why do fragments appear
Due to the formation of characteristic fragments or the loss of small molecules
Why do halogens alkanes often have many peaks in fragmentation
Lots of combinations as the halogens have isotopes , carbons can and c-c can be broken.
What is IR spectroscopy
s a technique used to identify compounds based on changes in vibrations of atoms when they absorb IR of certain frequencies
What is a spectrophotometer
irradiates the sample with electromagnetic waves in the infrared region and then detects the intensity of the wavelength of IR radiation which goes through the sample
What happens when all organic molecules absorb IR
They will vibrate by stretching, bending and twisting
Each vibration will absorb specific wavelengths of IR
This is shown as the reciprocal of the wavelength
What changes with different absorb acids
Have characteristic widths and intensities
How to identify an unknown compound on a IR spectrum
Look for specific peaks and match these up in the data booklet but look for for the heights and widths of these peaks
