Modern Analytical techniques Flashcards
What are the factors that affect vibration of a covalent bond?
Bond length
Bond strength
Mass of atoms involved in the bond
What can an infrared spectrum tell us?
The chemical structure of a compound and the presence of functional groups
What causes covalent bonds to vibrate
The absorption of infrared radiation.
Bonds either…
Stretch or bend
What kind of bonds vibrate when absorb infrared radiation?
Covalent
What are the bonds that you need to be able to identify in infrared spectroscopy?
C=O
C-H
COOH
What is mass spectrometry used for?
Identify unknown compounds
Determine the abundance of each isotope
Gain further information about the structure and properties
What can be found out by analysing the mass spectra?
The relative atomic mass and therefore the structure. Also any isotopes present
What are the key features of the spectrum?
The no. Of peaks shows no. Of isotopes
The heights of the peaks give relative abundances
The results can show us the relative atomic mass
How does a mass spectrometer work?
It bombards compounds with electrons and dislodges an electron in the compound to make it a molecular ion
What is a molecular ion and what can it tell us?
A molecular ion is the positive ion formed in mass spectrometry when a molecule loses an electron
It can show is the RAM and we can work out the structure
Example of equation showing ionisation
C2H5OH + e- > C2H5OH+ + 2e-
What is fragmentation and when does it happen?
Fragmentation is the process in mass spectrometry that causes a positive ion to split into pieces, one of which is a positive fragment ion
The excess energy from ionisation can be transferred to the molecular ion and
