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Chemistry > Chromatography And Spectroscopy > Flashcards

Chromatography And Spectroscopy Flashcards

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1
Q

What is chromatography used for

A

Seperate mixtures of liquids with different solubilities

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2
Q

What are the two different components used in every chromatography

A

Stationary and mobile phase

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3
Q

Define stationary phase

A

Solid or liquid on solid that doesn’t move

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4
Q

Define mobile phase

A

Gas or liquid that does move

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5
Q

What are the types of chromatography

A

Thin layer and gas

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6
Q

What is the stationary phase in TLC

A

Adsorbent substance on plastic or glass

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7
Q

How does TLC work

A

Different components have different affinities for the adsorbent so adsorb to surface differently

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8
Q

Describe the method for TLC

A

Draw pencil base line 1cm from. Base of TLC plate.

Spot solution onto baseline using capillary tube

Add solvent to beaker 0.5 cm from base of plate

Add watch glass ontop

Leave until solvent front is 1cm from top

Remove plate and mark solvent front

Use UV lamp or iodine crystals to mark circles

Calculate r.f values and compare to database

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9
Q

What does r.f stand for

A

Retention factor

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10
Q

How do you calculate r.f values

A

Distance traveled by component / distance travelled by solvent front

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11
Q

What is gas chromatography used for

A

To seperate volatile components

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12
Q

How does GC work

A

Different components have different affinities for stationary phase

Slow down with higher affinity and adsorption

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13
Q

What component is eluted first in GC

A

Most volatile with less affinity for SP

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14
Q

What factors affect retention time GC

A

Type of carrier gas and flow

Length of column

Temp of column

Packing material (column material)

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15
Q

What affects r.f in TLC

A

Solvent and adsorbent

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16
Q

How can you calculate the concentration of a component from a GC scan

A

Plot calibration curve

X= conc Y= peak area

Use a dilution series

Compare area with conc

17
Q

What does NMR. Stand for

A

Nuclear magnetic resonance

18
Q

How does NMR use

A

Strong magnetic fields are used to allow radio waves to be absorbed my nuclei causing energy release from nucleus

19
Q

On what types of atoms can NMR be used on

A

Those with odd núcleons

20
Q

What is resonance

A

When the nucleus alternates between two spin states

One is aligned with and one against the magnetic field

Against= higher energy

Dropping back to lower energy causes energy release

21
Q

What is the main advantage of NMR over chromatography

A

The compound can be recovered because it is not broken down.

22
Q

How do you carry out NMR

A

Add sample to solvent

Spin to even put imperfections in megnetic field

Run NMR

Evaporate off solvent to obtain sample again

23
Q

What solvent is used to prevent artefact peaks

A

Used deuterated Solvents

D is 2H so has no magnetic spin so will no show up in 1HNMR

E.g D2O not H2O

24
Q

What must you quote in 13C NMR

A

What C environments are present

Chemical shift

How many different C environments are present

25
Q

What must you quote in proton NMR

A

Number of different environments

The types of environment

Chemical shift

Peak integration

Adjacent groups/ splitting.

26
Q

Describe spin-spin coupling/pairing

A

Protons spin interact with spin state of adjacent protons on different environments

Occurs in pairs

27
Q

Why do OH and NH have a broad peak range in proton NMR

A

Protons are involved in hydrogen bonding

28
Q

What is the consequence of OH and NH having a broad range in proton NMR

A

Not involved in spin pairing

29
Q

How do you determine what peaks are due to OH and NH in proton NMR

A

Compare NMR with and without a deuterated solvent

30
Q

How can you tell what group is adjacent in proton NMR

A

N + 1= number of peaks

N = number of protons in adjacent environments

31
Q

What is the standard for NMR

A

TMS

32
Q

What does a singlet indicate

A

No H on adjacent C

33
Q

What does a doublet indicate

A

1 H on adjacent C

34
Q

What does a triplet indicate

A

2 H on adjacent C

35
Q

What does a quartet indicate

A

3 H on adjacent C

36
Q

What does a pentet indicate

A

4 H on adjacent C

37
Q

What does a multiplet indicate

A

6 + H on adjacent C

Chemistry (28 decks)

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