organic analysis

Question 1

mass spectrometry

Answer 1

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

Question 2

mass spectrometer - instrumentation

Answer 2

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

Question 3

base peak

Answer 3

highest peak - largest absorbance and intensity

Question 4

molecular ion peak

Answer 4

shows the molar mass of compound / highest m/z

Question 5

why is there a small peak after molecular ion peak

Answer 5

an isotope (often carbon)

Question 6

fragmentation

Answer 6

M+ -> X+ +R.

Question 7

region of electromagnetic spectrum used in IR

Answer 7

infrared

Question 8

region of electromagnetic spectrum used in NMR

Answer 8

radio waves

Question 9

principles of spectroscopy

Answer 9

atoms/ molecules absorb and emit electromagnetic radiation of specific energies

Question 10

purpose of IR

Answer 10

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

Question 11

features of IR

Answer 11

expensive
fast
absorption spectroscopy

Question 12

uses of IR

Answer 12

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

Question 13

IR spectrum analysis

Answer 13

• 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

Question 14

NMR

Answer 14

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

Question 15

principles of nuclear spin and NMR

Answer 15

• 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

Question 16

NMR

Answer 16

ANALYSES THE H OR C ENVIRONMENTS

Question 17

chromatography

Answer 17

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

Question 18

common uses of HPLC

Answer 18

-COVID tests and pregnancy
- drugs present in blood

Question 19

how chromatography works

Answer 19

• 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

Question 20

stationary phases

Answer 20

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

Question 21

mobile phase

Answer 21

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

Question 22

talking about which sample is most strongly adsorbed to sp

Answer 22

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

Question 23

HPLC analysis

Answer 23

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

Question 24

measurements HPLC

Answer 24

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

Question 25

Retention time

Answer 25

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

Question 26

factors influencing Rt

Answer 26

- composition of sp and mp - increase SA - length of column -temperature and increase flow rate/pressure

Question 27

reliability - interp. vs extrap

Answer 27

within range = interpolation outside range = extrapolation

Question 28

primary standards

Answer 28

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

Question 29

preparing a standard solution

Answer 29

- 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

Question 30

dilution equation

Answer 30

C1V1=C2V2

Question 31

what are the implications if dilutions are / are not performed

Answer 31

- standard solution = if X diluted then higher conc of solution and larger or very small titres

Question 32

equivalence point

Answer 32

- point where exact mole ratio is reached - point in reaction when neither reactant is in ecess

Question 33

end point

Answer 33

when indicator used in reaction results in a colour change

Question 34

rinsing - burette or pipette

Answer 34

rinse with acid or base that will be put in it - with water = diluted

Question 35

rinsing- volumetric + conical flask

Answer 35

rinse with deionised water

Question 36

strong acid strong base - pH curve

Answer 36

equivalence point approx. 7

Question 37

strong acid weak base - pH curve

Answer 37

equivalence point below 7 pH

Question 38

strong base weak acid

Answer 38

equivalence point above 7 pH

Question 39

problematic form of pH curve?

Answer 39

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

Question 40

volumetric analysis

Answer 40

an analytical technique that measures volume - analyses solution

Question 41

what does rinsing pippette or burette with deionised water do

Answer 41

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

Question 42

adsorption

Answer 42

adhering to stationary phase

Question 43

why does seperation occur in chromatography

Answer 43

- 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

Question 44

why do primary standards have high molar mass

Answer 44

allow for discrepencies in calculations - less impact

Question 45

density

Answer 45

mass/ volume

Question 46

calibration curves - inaccurate or not?

Answer 46

interpolation extrapolation

Question 47

m/z

Answer 47

mass to charge

Question 48

chemical shift

Answer 48

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

Question 49

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

Answer 49

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