Unit 3.2.11 - Analytical Techniques Flashcards
Besides the relative isotopic masses of elements what two other things can high resolution mass spectrometry be used to find?
The relative molecular mass of a compound and the molecular formula of a compound
What peak do you look and to find the relative molecular mass from a mass spectra and what is this peak called?
The peak with the second highest m/z ratio - M peak
What does the M peak stand for?
The molecular ion peak
What happens to a molecule for it to form the molecular ion peak on a mass spectra?
The compounds has 1 electron knocked off
Why is there usually lots of peaks when you do a mass spectra of a molecule?
The high speed electrons cause some of the molecular ions to break up into fragments and so they will have smaller m/z ratios and form other peaks
Why is high resolution mass spectrometry more useful compared to ordinary mass spectrometry?
It allows you to distinguish between a slight difference in the molecular mass and so what the molecular formula is, as during a mass spectrometry some compounds can have the same molecular mass so you can’t see a difference
Name two analytic techniques which allows you to identify compounds?
Mass spectrometry and infrared spectroscopy
What happens during infrared spectroscopy?
A beam of infrared radiation is passed through a sample of a compound, the infrared radiation is then absorbed by the covalent bonds. As different functional groups contain different covalent bonds, and different covalent bonds absorb different amounts of infrared radiation. The frequency that the sample absorbed can be used to identify the functional groups within the compound
What is the fingerprint region?
The region between 1000cm-1 and 1550cm-1 that is specific to each compound
What types of peak does the O-H in alcohols and acids produce?
A broad peak
Apart from identify a compound what is another use of infrared spectroscopy?
Identify if there is any impurities in a compound?
How can infrared spectroscopy be used to see if there are any impurities in a compound?
They will produce extra peaks in the finger print region which are specific to that compound
What is one disadvantage of covalent bonds being able to absorb infrared radiation?
They don’t let the infrared radiation leave the earth’s atmosphere causing global warming
Why is there infrared radiation in the earth’s atmosphere?
Electromagnetic radiation emitted by the sun is absorbed by the earth and then emitted as lower frequency infrared radiation
