Analysis of organic compounds Flashcards

1
Q

Organic chemical analysis

The measurement of how fast the compound travels through the column is the retardation factor (Rf) value, the formula is

A

distance traveled by component
Rf = ————————————————-
distance traveled by solvent

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2
Q

Organic chemical analysis

Define stationary phase

A

Solid with high SA or a finely divided solid coated with that liquid that selectively attracts/ retains components of the mixture.

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3
Q

Organic chemical analysis

Define mobile phase

A

Solvent that carries the mixture of chemicals

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4
Q

Organic chemical analysis

Principle of Polar/ non polar substances

A

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.

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5
Q

Organic chemical analysis

Principle of solvents

A

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)

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6
Q

Titration curves

-
-

A
  • 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
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7
Q

Titration curves

Following facts

  • Strong acid + strong base
  • Strong acid + weak base
  • weak acid + strong base
A
  • 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
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8
Q

Redox titrations

A

Similar to acid-base titrations except you’re doing a redox reaction. Usually dont need an indicator.

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9
Q

Volumetric analysis

Define equivalence point

A

Point at which the reaction has occured as per the stoioch ratio.

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10
Q

Volumetric analysis

Define endpoint

A

When shown by the indicator the solution has changed colour (permanently)

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11
Q

NMR spectroscopy

How are peaks generated

A

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.

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12
Q

NMR spectroscopy

____ number of nucleons have magnetic moments- respond to magnetic fields

A

Odd

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13
Q

NMR spectroscopy

The stronger the magnetic field experienced by the nucleus, the ….

A

more energy required to force nucleus to flip.

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14
Q

NMR spectroscopy

Higher chemical shift means….

A

a more exposed nucleus in general (lower magnetic field required to force nuclei arrows to spin towards the field.

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15
Q

NMR spectroscopy

Nuclei that are next to more electronegative atoms are generally…

A

more ‘exposed’ because there is less electron density around them

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16
Q

NMR spectroscopy

  • High magnetic field means…
  • Low magnetic field means…
A
  • 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
17
Q

NMR spectroscopy

  • Inside NMR, nuclei are in a low energy spin so …
  • Eventually the nuclei flip back to…
A
  • radio transmitter is used to provide energy to flip nucleic into higher energy state.
  • lower energy spin and when it does this releases energy.
18
Q

Volumetric analysis

Define standard solution

A

is one in which the concentration is accurately known

19
Q

Volumetric analysis

What are the characteristics of a primary standard 
-
-
-
-
A
  • Must have a known formula
  • Must have a relatively high molar mass
  • Must not react with the atmosphere
  • Should be soluble in water
20
Q

Volumetric analysis

A pipette is known as an …

A

aliqout

21
Q

Volumetric analysis

A burette is known as the…

A

titrant

22
Q

Volumetric analysis

-
-

A
  • Burette; dont wash with water, it will dilute solution
  • Pipette; Same^
  • Conical flash; wash with water, not solution
23
Q

High performance liquid chromatography (HPLC)

What is it used for

A

analyse organic compounds with high boiling points and those that decompose when heated eg proteins

24
Q

High performance liquid chromatography (HPLC)

  • Stationary phase is generally…
  • Mobile phase is generally…
  • Rf (retention time) value is used to…
A
  • Alumina or silica
  • Non polar organic solvent
  • Identify compounds, therefore location of peak identifies the compound
25
Q

High performance liquid chromatography (HPLC)

-
-

A
  • pressure
  • temp
  • length of column
26
Q

High performance liquid chromatography (HPLC)

How can plot calibration curves

A

by taking samples of the compound of known amounts and determining the area under the peak at its retention time

27
Q

High performance liquid chromatography (HPLC)

Calibration curves cannot….

A

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.