B4 organic analysis Flashcards
What does the furthest right peak on a mass spectrometer show?
Total molecular mass
What to look for on a mass spectrometer?
Peak furthest right
Fragmentation peaks with high relative intensities
What do fragmentation peaks with high relative intensities show on a mass spectrometer?
Common fragments
How to explain mass spectrometry fragmentation?
Molecular ion of X shows total molecular mass
M/Z of 29 suggests Ch3Ch2+
Include all peaks with high relative intensities
What must be included on all mass spectrometry annotations?
A positive charge
What does infrared do to covalent bonds?
Causes them to vibrate more and absorb more energy
What is the issue with methane?
Causes and contributes to global warming
What is infrared spectroscopy used in?
Monitor gases causing air pollution
Breathalyzers to measure ethanol in the breath
What must you always ignore in infrared analysis?
The fingerprint region to the right
1500 below
What to always look out for in infrared analysis?
C=O (aldehyde or ketone)
O-H (alcohol)
C=O and Broad O-H (carboxylic acid)
When explaining in infrared, what must always be included with each point?
Peak range and where peak is present
Type of bond
Functional group
What type of functional group and bond is shown in this infrared?
C=O
Aldehyde or ketone
What type of functional group and bond is shown in this infrared?
C=O
C-O (BROAD)
Carboxylic Acid
What type of functional group and bond is shown in this infrared?
O-H (Not broad)
Alcohol
On C-13 NMR, what does the number of peaks tell you?
The number of carbon environments
On a C-13 NMR, what does the ppm shift indicate?
What atom each carbon in each environment is bonded to
On a C-13 NMR, what are all ppm shifts relative to?
The TMS peak
On a Proton-NMR, what do the number of peaks on the spectrum tell you?
The number of proton environments
On a Proton-NMR, what does the ppm shift indicate?
To what atom, each proton in the environment is bonded to
On a Proton-NMR, what does the length of the peak indicate?
How many protons are part of that environment (done as a ratio)
On a Proton-NMR, what does the splitting pattern indicate?
How many hydrogens are on the neighbouring carbon atom
On a Proton-NMR, what rule is used to determine splitting patterns?
n+1 rule
Splitting Pattern: 1 peak
Singlet
Splitting Pattern: 2 peaks
Doublet
Splitting Pattern: 3 peaks
Triplet
Splitting Pattern: 4 peaks
Quartet
On a Proton-NMR, what does a large splitting pattern indicate?
Methyl groups
Why are deuterated solvents used in NMR spectra?
They don’t have hydrogen in, so don’t show up on the spectrum
What region of the electromagnetic spectrum is used in Proton-NMR?
Radiowaves
What is D2O added to Proton-NMR spectra sometimes, and why?
O-H and N-H peaks can appear anywhere
D2O removes these peaks
What solvent is most commonly used in NMR?
CDCl3
Proton NMR: What does symmetry in environments at c7-8ppm suggest?
Benzene ring
Proton NMR: What does a singlet with 3H in the environment suggest?
Methyl group (-CH3)
Proton NMR: What does an environment with 2H in by itself suggest?
-CH2
Before fully developing an NMR response, what must always be stated first?
The number of environments that there are
After the whole number of environments have been given, what information must be given about each environment for a thorough explanation?
Splitting pattern - so how many H on adjacent C atoms
Peak area - so how many H in that environment
PPM of peak - due to which bond present
What do covalent bonds in molecules do?
Possess energy + vibrate around a central point
Can covalent bonds absorb IR radiation?
Yes
What can happen when covalent bonds absorb IR radiation?
The bonds can bend or stretch
What does the amount that a bond stretches or bends depend on?
- The mass of atoms in the bond
- The strength of the bond
Heavier atoms vibrate more _______ than lighter atoms.
Slowly
Stronger bonds vibrate _________ than weaker bonds.
Faster
What are the 3 possible vibrations of a molecule?
- Bend
- Symmetrical stretch
- Asymmetrical stretch
What does the frequency of the IR radiation absorbed by a molecule demonstrate?
The functional group of a molecule
What functional group is 1700cm-1?
C=O
What functional group is 2850 - 3100cm-1?
C-H
What functional group is 3200 - 3600cm-1?
O-H -> in ALCOHOLS
What functional group is 2500 - 3300cm-1?
O-H -> in CARBOXYLIC ACIDS
What is the peak like for alcohols?
Wide
What is the peak like for carboxylic acids?
Wide + jagged
What is a peak below 1500cm-1 called, and what do you do with it?
Fingerprint region -> IGNORE
