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chemistry > module 6 (p2) > Flashcards

module 6 (p2) Flashcards

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1
Q

what does no neighbouring protons suggest

A

no change in external magnetic field strength

therefore one peak will be present

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2
Q

what are the -OH and -NH2 bonds in terms of chemical shift peak

A

labile

can be rapidly exchanged with neighbouring molecules

therefore their chemical shift is variable

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3
Q

how do we remove the labile particles

A

add D2O

D2O is involved in proton exchange

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4
Q

give the equation for the addition of D2O into a solution of ethanol

A

CH3CH2OH + D2O <=> CH3CH2OD + HOD

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5
Q

what can be gathered from proton NMR

A

no. of different proton environments

types of proton environments

relative numbers of each type of proton

non-equivalent protons adjascent to proton

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6
Q

how do we obtain the no. of different proton environments

A

no. of peaks

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7
Q

how do we obtain the types of proton environments

A

chemical shift

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8
Q

how do we obtain the relative numbers of each type of proton

A

ratio number of relative peaks

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9
Q

how do we obtain the non-equivalent protons adjacent to proton

A

splitting pattern

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10
Q

what does equivalent protons mean

A

absorb at the same chemical shift

increases the size of peak

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11
Q

what does non-equivalent protons mean

A

protons have different chemical environments

absorb different chemical shifts

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12
Q

what does the ratio of relative areas under peak give

A

ratio of number of protons responsible for each peak

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13
Q

what are the relative peak areas within splitting for a singlet, doublet, triplet and a quartet

A

singlet = 1

doublet = 1:1

triplet = 1:2:1

quartet = 1:3:3:1

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14
Q

what do aromatic protons form

A

one or more multiplets

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15
Q

what are -NH and -OH

A

labile protons

have variable chemical shift

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16
Q

how do we remove the chemical shift of OH and NH

A

add D2O

17
Q

how does D2O work

A

exchanges and replaces the protons on OH and/or NH

deuterium doesn’t absorb in chemical range so peak disappears

18
Q

what are the uses of TLC

A

forensic testing

quality control

clinical analysis

19
Q

what is the stationary phase and mobile phase in TLC

A

SP = silica or alumina

MP = solvent

20
Q

what do we add when we are doing TLC

A

lid

for volatile liquids and gases

21
Q

what are the advantages of TLC

A

works well with small samples

3x faster than paper chromatography

recovers the sample after

22
Q

define absorption

A

how much a surface takes something in

23
Q

define adsorption

A

how much something binds to a surface

24
Q

if a component moves up the TLC plate further, what does this mean about its adsorption

A

low

25
Q

if a component moves slightly along the TLC plate, what does this mean about its adsorption

A

high

26
Q

what is the method for TLC

A
  1. draw base line with pencil
  2. spot sample onto base line
  3. prepare chromatography tank and place solvent
  4. place TLC plate in tank (beaker)
  5. after, mark solvent front in pencil and allow plate to dry
  6. circle any spots
  7. calculate Rf value
27
Q

what is the stationary phase and mobile phase in gas chromatography

A

SP = high b.p. liquid adsorbed onto solid support

MP = inert carrier gas

28
Q

what are the steps in gas chromatography

A
  1. sample injected into apparatus
  2. carried through capillary column
  3. samples separated by solubility or adsorption
  4. different components and different retention times
29
Q

what happens in the capillary column

A

components interact with the SP and slow down

more soluble = moves slower through column

reach detector at different times

30
Q

define retention time

A

time taken for each component to travel through column

31
Q

what is the retention time used for

A

compared with components with known retention time

peak integrations used to determine concentrations of components in the sample

32
Q

how do we find the concentration of components

A
  1. prepare std. solution
  2. obtain gas chromatograms for each std. solution
  3. plot calibration curve of peak area against conc.
  4. obtain gas chromatogram of compound being investigated under the same conditions
  5. use calibration curve to find the concentration

chemistry (6 decks)

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