4.7 Spectroscopy Flashcards
When atoms are in constant motion, what can be absorbed and what does this cause ?
Infrared radiation can be absorbed making them bend and stretch more.
What are the 2 types of vibrations of bonds ?
1) Stretch = distance between 2 atoms increases and decreases.
2) Bend = results in a change in bond angles.
What are the 2 factors that the amount a bond stretched or bends depends on ?
-Mass of atoms in bond (heavier atoms vibrate slower)
-Strength of bond (stronger bonds vibrate faster)
What is a key feature about bonds absorbing energy and the frequency of radiation ?
Bonds can only absorb radiation that has the same frequency as the bond that is absorbing it.
Why are greenhouse gases a problem with IR radiation ?
They absorb the longer wavelength of IR because it has the same frequency as the frequency of their natural bonds. Eventually they re-emitt this energy as radiation, which increases temperature of atmosphere.
What is fingerprint region on IR graph ?
Below 1500 wavelength that is generally not useful as they are hard to distinguish bonds without computer software.
How to use IR graph ?
Look at distinct peaks on graph and match the peaks to a bond based off wavelength of IR that each bond absorbs.
What are some distinct bond frequencies to look for ?
C=O
O-H
C=C
Where can IR spectroscopy be applied to ?
Used in breathalysers by passing a beam of IR through breath sample and detects IR absorption of compounds in breath. The more IR absorbed, the higher the reading, so more ______ in breath.
What is the first step in mass spectra ?
Molecules are ionised and an electron is fired at molecule making it lose an electron. This forms the molecular ion.
What is the molecular ion ?
Shows the relative molecular mass of molecule and the detects detects the m/z ration of this ion. This shows the highest peak on the mass spectra.
What is fragmentation in mass spectra ?
In mass spectrometer, some M+ ions break down into smaller pieces known as fragments. These form smaller peaks on mass spectra.
