Analytical techniques Flashcards
1
Q
Low, mid and high energy effects of light
A
- Low changes spin state, rotational
- Mid causes bonds to strech, vibrational
- High causes electrons to go to a higher energy state, electronic
2
Q
Fingerprint reigon
A
- Below 700
- Different for every molecule
3
Q
Functional groups in IR spectroscopy
A
- OH = Broad around 3000
- COOH = Very broad around 3000
- NH2 = Small peaks around 3250
4
Q
How does mass spectrometry work
A
- Sample vaporised
- Atom ionised (Electron shot from a filiment hits an electron off of the atom making it a radical cation)
- Ions travel through a magnetic field and some are deflected
- An ion will hit a detector
5
Q
What causes fragments
A
The energy used to ionise is strong enough to break bonds and cause fragmentation
6
Q
Why may there be peaks after the molecular ion
A
- Isotopes (same element with different number of neutrons)
- May be C13 isotope
7
Q
What are hydrogens in different environments
A
When hydrogens are bound to differnt things/groups therefore will act different
8
Q
What are NMR’s measuring
A
- Carbons with different things bonded cause different levels of sheilding/desheilding
- This makes them experience different local magnetic fields
9
Q
Why is there a bump at 0 on NMR’s
A
Tetramethylsilane is added as a referance
10
Q
What is a deuterated solvent and why are they used in NMR
A
- Deuterium is a isotope of hydrogen with 1 proton and 1 neutron
- Deuterated solvents have all the hydrogen atoms as this isotope
- Hydrogen would show up on the NMR but Deuterium wont
11
Q
N+1 rule
A
- For NMR
- The signal for a protons will be split according to the adjacent carbons protons+1
- Protons bonded to an oxygen or nitrogen atom will not cause splitting
- Signals on an oxygen or nitrogen dont split
12
Q
The integral of an NMR
A
The area under a peak allowing the determination of the number of protons
13
Q
Labile protons
A
- Protons on OH and COOH are called labile
- When D2O is added to a sample with these groups the labile proton is exchanged for a deuterium atom
- The group dissapears from the NMR
