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chemistry 3/4 > organic analysis > Flashcards

organic analysis Flashcards

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1
Q

mass spectrometry

A
  • analysis tool to identify unknown samples using unique mass spectrum
    -measures mass to charge ratio (m/z)
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2
Q

mass spectrometer - instrumentation

A

ionises, accelerate, deflects and detects an atom or molecules so that mass to charge ratio is measured
- produces positive charged fragment

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3
Q

base peak

A

highest peak - largest absorbance and intensity

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4
Q

molecular ion peak

A

shows the molar mass of compound / highest m/z

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5
Q

why is there a small peak after molecular ion peak

A

an isotope (often carbon)

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6
Q

fragmentation

A

M+ -> X+ +R.

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7
Q

region of electromagnetic spectrum used in IR

A

infrared

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8
Q

region of electromagnetic spectrum used in NMR

A

radio waves

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9
Q

principles of spectroscopy

A

atoms/ molecules absorb and emit electromagnetic radiation of specific energies

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10
Q

purpose of IR

A

information about covalent bonds and functional groups present in organic molecule - identify structure and type of molecule

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11
Q

features of IR

A

expensive
fast
absorption spectroscopy

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12
Q

uses of IR

A
  • identify of organic compounds
    -design new drugs
    -tests for blood alcohol
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13
Q

IR spectrum analysis

A
  • specific covalent bond represents each peak
  • a bond that vibrates at higher frequency absorbs IR radiation with higher wavenumber and greater energy bond
    -must specify the O-H bonds but not as necessary for other types
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14
Q

NMR

A

-operates in radio waves
-form of absorption spectroscopy
-very fast and very expensive
- qualitative - structure of compound

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15
Q

principles of nuclear spin and NMR

A
  • in order to interact with radio waves atoms must have nuclear spin
  • in presence of external magnetic field nuclei line up in unstable arrangement
  • normally in low energy state and aligned with strong magnet
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16
Q

NMR

A

ANALYSES THE H OR C ENVIRONMENTS

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17
Q

chromatography

A
  • technique used ti seperate substances present in a mixture
  • can detect the presence of a particular substance/ structure and concentration
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18
Q

common uses of HPLC

A

-COVID tests and pregnancy
- drugs present in blood

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19
Q

how chromatography works

A
  • each substance analyses the different rates they move along the stationary phase depending on strength and solubility of mobile phase
    -absorption to sp and desorption into mobile phase
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20
Q

stationary phases

A

polar sp - polar molecules
non polar sp - non polar molecules
- stronger adsorption tosp. = longer Rt

21
Q

mobile phase

A

polar molecules - polar solvents vise versa
higher solubility in mobile phase= shorter Rt

22
Q

talking about which sample is most strongly adsorbed to sp

A

-______ strongly adsorbed at sp and more readily desorbs to mobile phase
- moved least distance through column and leave later (longest Rt)

23
Q

HPLC analysis

A

measure larger organic compounds and molecules as opposed to small volaile (gas)

24
Q

measurements HPLC

A
  • measures Rt- deduce compounds present SAME /IDENTICAL CONDITIONS -peak area( concentration)
25
Q

Retention time

A

amount of time sample stays in column
- identifies a compound
- longer the Rt = adsorb more strongly and bigger

26
Q

factors influencing Rt

A
  • composition of sp and mp - increase SA
  • length of column
    -temperature and increase flow rate/pressure
27
Q

reliability - interp. vs extrap

A

within range = interpolation
outside range = extrapolation

28
Q

primary standards

A

pure substances whose mol/ amount can be accurately calculated from their mass
- pure form / known chemical formula/ easy to store/ higher molecular mass

29
Q

preparing a standard solution

A
  • weigh the pure solid on balance
  • transfer to a volumetric flask w funnel
  • rinse any remaining solid p w deionised water
  • half fill flask and stopper it - swirl so particles will dissolve
  • add deionised water up to calibration line
    -stopper the flask and shake so even concentration dispersed throughout
30
Q

dilution equation

A

C1V1=C2V2

31
Q

what are the implications if dilutions are / are not performed

A
  • standard solution = if X diluted then higher conc of solution and larger or very small titres
32
Q

equivalence point

A
  • point where exact mole ratio is reached
  • point in reaction when neither reactant is in ecess
33
Q

end point

A

when indicator used in reaction results in a colour change

34
Q

rinsing - burette or pipette

A

rinse with acid or base that will be put in it

  • with water = diluted
35
Q

rinsing- volumetric + conical flask

A

rinse with deionised water

36
Q

strong acid strong base - pH curve

A

equivalence point approx. 7

37
Q

strong acid weak base - pH curve

A

equivalence point below 7 pH

38
Q

strong base weak acid

A

equivalence point above 7 pH

39
Q

problematic form of pH curve?

A

weak acid+ weak base
x sudden change so x determine eq point

40
Q

volumetric analysis

A

an analytical technique that measures volume - analyses solution

41
Q

what does rinsing pippette or burette with deionised water do

A

dilution - require less or more of titre to neutralise - change in conc

42
Q

adsorption

A

adhering to stationary phase

43
Q

why does seperation occur in chromatography

A
  • different molecules = diff speeds
  • different attractions to s and m phase so desorb and adsorb at different rates
  • strongest adsorption = travels least distance and most soluble = greatest distance
44
Q

why do primary standards have high molar mass

A

allow for discrepencies in calculations - less impact

45
Q

density

A

mass/ volume

46
Q

calibration curves - inaccurate or not?

A

interpolation
extrapolation

47
Q

m/z

A

mass to charge

48
Q

chemical shift

A

difference in energy needed to change spin state in sample compared to TMS

49
Q

HPLC chromatogram: the peak at __ minutes is beyond the scope of the vertical axis. how to solve the issue?

A

conc. = very high so should be diluted to fit the range of the standards

chemistry 3/4 (8 decks)

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