2.8 Chemical Analysis Flashcards
1
Q
How does infrared spectroscopy work?
A
- IR laser excites molecule causing it to vibrate
- each bind vibrates differently and gives varying peaks, hence functional groups can be identified
—> greater mass means lower frequency
2
Q
Wave number calculation
A
1
————
wavelength
3
Q
What is a sign on IR that you do not have an alkene?
A
- if all C-H below 3000
4
Q
What is a sign there is a double bond (alkene) on IR?
A
- if C-H peaks above 3000
5
Q
NMR
A
Nuclear magnetic resonance
6
Q
How does NMR work?
A
- uneven nucleon number resulting in magnetic spin and a magnetic field
- strong magnets used to align nuclei
- radio waves fired at nuclei which absorb energy and align in the opposite direction which will be higher in energy
- the same nuclei flip to a lower energy and emit energy which is measured
7
Q
Explain chemical shift
A
- result of nuclear shielding
—> withdrawing atoms leave atom exposed to stronger field - place in spectra that absorbs energy
8
Q
What determines peaks present?
A
Number of carbon and hydrogen environments
9
Q
Less shielding results in
A
A higher chemical shift
