Analysis of organic compounds Flashcards
Organic chemical analysis
The measurement of how fast the compound travels through the column is the retardation factor (Rf) value, the formula is
distance traveled by component
Rf = ————————————————-
distance traveled by solvent
Organic chemical analysis
Define stationary phase
Solid with high SA or a finely divided solid coated with that liquid that selectively attracts/ retains components of the mixture.
Organic chemical analysis
Define mobile phase
Solvent that carries the mixture of chemicals
Organic chemical analysis
Principle of Polar/ non polar substances
Polar substances tend to adsorb onto the polar stationary phase to a greater degree and non polar substances tend to dissolve into the mobile phase better.
Organic chemical analysis
Principle of solvents
As the component in the ink are swept upwards over the stationary phase by the solvent, they undergo a continual process of adsorption (into the stationary phase), followed by desorption and dissolving (into the mobile phase)
Titration curves
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- A strong acid has a conjugate base that is so weak that it basically accepts no protons
- A weak acid has a conjugate base that is also a weak base
- An acid so weak that it barely donates any protons has a conjugate base that is strong
Titration curves
Following facts
- Strong acid + strong base
- Strong acid + weak base
- weak acid + strong base
- extremely weak conjugate base + extremely weak conjugate acid. Here both products dont accept or donate protons so equivalence point pH is 7
- extremely weak conjugate base and weak conjugate base. We have a weak acid in solution so equivalence point pH is <7
- Extremely weak conjugate acid + weak conjugate base. pH >7
Redox titrations
Similar to acid-base titrations except you’re doing a redox reaction. Usually dont need an indicator.
Volumetric analysis
Define equivalence point
Point at which the reaction has occured as per the stoioch ratio.
Volumetric analysis
Define endpoint
When shown by the indicator the solution has changed colour (permanently)
NMR spectroscopy
How are peaks generated
Radio waves can cause the nucleic to flip of they have enough energy to beak the magnetic field. When the spin flips, the radio waves are absorbed and a peak is generated.
NMR spectroscopy
____ number of nucleons have magnetic moments- respond to magnetic fields
Odd
NMR spectroscopy
The stronger the magnetic field experienced by the nucleus, the ….
more energy required to force nucleus to flip.
NMR spectroscopy
Higher chemical shift means….
a more exposed nucleus in general (lower magnetic field required to force nuclei arrows to spin towards the field.
NMR spectroscopy
Nuclei that are next to more electronegative atoms are generally…
more ‘exposed’ because there is less electron density around them
NMR spectroscopy
- High magnetic field means…
- Low magnetic field means…
- radio waves are not enough to allow arrows to spin away from the field
- radio waves are enough to allow arrows to spin away from the field
NMR spectroscopy
- Inside NMR, nuclei are in a low energy spin so …
- Eventually the nuclei flip back to…
- radio transmitter is used to provide energy to flip nucleic into higher energy state.
- lower energy spin and when it does this releases energy.
Volumetric analysis
Define standard solution
is one in which the concentration is accurately known
Volumetric analysis
What are the characteristics of a primary standard - - - -
- Must have a known formula
- Must have a relatively high molar mass
- Must not react with the atmosphere
- Should be soluble in water
Volumetric analysis
A pipette is known as an …
aliqout
Volumetric analysis
A burette is known as the…
titrant
Volumetric analysis
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- Burette; dont wash with water, it will dilute solution
- Pipette; Same^
- Conical flash; wash with water, not solution
High performance liquid chromatography (HPLC)
What is it used for
analyse organic compounds with high boiling points and those that decompose when heated eg proteins
High performance liquid chromatography (HPLC)
- Stationary phase is generally…
- Mobile phase is generally…
- Rf (retention time) value is used to…
- Alumina or silica
- Non polar organic solvent
- Identify compounds, therefore location of peak identifies the compound
High performance liquid chromatography (HPLC)
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- pressure
- temp
- length of column
High performance liquid chromatography (HPLC)
How can plot calibration curves
by taking samples of the compound of known amounts and determining the area under the peak at its retention time
High performance liquid chromatography (HPLC)
Calibration curves cannot….
be extrapolated outside its range accurately; if the area under the peak of an unknown amount is outside the range of the calibration curve, its not valid to use that curve to determine the amount of compound in that sample.
