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MCAT chem > spectroscopy and seperation techniques > Flashcards

spectroscopy and seperation techniques Flashcards

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1
Q

seperation techniques

A

seperate molecules based on their components
- distillation, chromatography, extraction

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2
Q

analytic techniques

A

identify compound or determine its properties

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3
Q

spectropscopy

A

analysis of organic compounds exposed to electromagnetic radiation

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4
Q

bonds appearing in IR spectra

A

must be polar and have a dipole moment
- OH

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5
Q

what do areas of IR graph show during absorption

A

valleys, not peaks

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6
Q

fingerprint region

A

area below 1500 cm-1 on IR graph

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7
Q

where is c=o valley on IR specrta

A

sharp peak at 1700 cm-1

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8
Q

oh group on IR spectra

A

broad peak at 3500 cm-1

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9
Q

c=n on IR spectra

A

1550-1650

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10
Q

c=c on ir spectra

A

1600-1800

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11
Q

c trip c on ir spectra

A

2100- 2200

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12
Q

cyanide on ir

A

2200

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13
Q

nh on ir

A

3300-3500

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14
Q

what does IR specrta idenfitfy

A

presence of specific bonds

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15
Q

what does NMR spectroscopy characterize

A

atoms of a molecule

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16
Q

proton NMR

A
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17
Q

resonance frequencies

A

chemical shifts from 0 on right to positive values on left

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18
Q

TMS

A

reference point on NMR spectra with a peak at 0

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19
Q

upfield shifts

A

to the right

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20
Q

down field

A

to the left

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21
Q

what produces an individual peak in proton nmr

A

each unique hydrogen

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22
Q

area under a peak in proton nmr

A

represents the number of protons that represent that peak (equivalent)

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23
Q

shift in h NMR depends on

A

shielding or deshielding of H

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24
Q

if protons are more shielded, what kind of shift do they experience

A

upfield (right)

25
Q

if protons are deshielded what kind of shift do they experience

A

downfield (L)

26
Q

trend for deshielding

A

the closer the hydrogens are to an EWG, the more deshielded they will be

27
Q

aromatic ring shift

A

about 6.0-8.5

28
Q

COOH shift

A

10-11

29
Q

splitting

A

n + 1 rule
- peak will split into number of smaller peaks equal to the number of adjacent hydrogen atoms + 1

30
Q

a carbon with 2 hydrogens and a neighboring carbon with 3 hydrogens would have what kind of peak

A

a quadruplet

31
Q

carbon NMR

A

all peaks are singlets
- equvalent c atoms are a single peak

32
Q

UV-vis spectroscopy

A

analyzes absorbance of UV light by organic compounds
- higher frequency than visible light

33
Q

wavelength of visible light

A

400 to 700 nm

34
Q

what kind of molecules tend to absorb UV light

A

aromatic compounds with conjugated pi systems
- aromatic amino acids

35
Q

mass spectroscopy

A

identifying unknown organic compounds by injecting them into a mass spectrometer and high E electrons cause the sample to ionize and become charged
- mass and charge of fragments are plotted on a mass spectrum
x axis - mass to charge ration
y axis is abundance
- largest peak is the base peak which is most abundant fragmemt and gives info about funcitonal group

36
Q

distillation

A

seperate liquid from liquid by utilizing differences in the liquids BPs
to ensure purity must do repeated distillations

37
Q

which liquid will leave the flask first in simple distillation

A

the one with the lower BP

38
Q

fractionating column

A

difference between simple and fractional distillatiom
- not included in somple

39
Q

simple distillation

A

seperation of two liquids with very different boiling points
- at least 25 C apart

40
Q

simple distillation

A

seperation of two liquids with very different boiling points
- at least 25 C apart
- no fractioning column

41
Q

fractional distillation

A

seperate liquids with similar bps (less than 25 C)

42
Q

vaccum distillation

A
  • when bp reach 400 c, cannot raise the tempretaure, must decrease the atmospheric pressure to meet vapor p
43
Q

boiling pt

A

temperature at which vapor pressure is equal to atosopheric pressure

44
Q

liquid- liquid extraction

A

seperate liquids based on solubitility in organic or aqueous media using a seperatory funnel
- require 2 immiscible liquids
- should be conducted several times to purify

45
Q

chromatography

A

seperation technique with a mobile phase and a stationary phase

46
Q

Thin Layer chromatography

A

stationary phase : polar
mobile phase : non polar
- nonpolar molecules move farther and have a larger RF

47
Q

do polar molecules in TLC have a high or low RF

A

retention factor low because doesn’t move

48
Q

retention factor RF

A

distance traveled by the molecule compared to the total distance the solvent travels
0< RF < 1
- RF closer to 1 means non polar
RF closer to 0 means polar

49
Q

column chromatography

A

isolates and purifies
stationary phase: solid
mobile phase liquid

50
Q

size exclusion chromotography

A

omit larger molecules first, smaller molecules remain in the column
stationary phase: gel beads that trap small molecules

51
Q

cation exchange chromotography

A

want to keep cations in the column, anions are eluted
- anions are lined within the column to attract cations `

52
Q

anion exchange chromotography

A

want anions to remain in the stationary colimn
- cations eluted
- cations line the column

53
Q

affinity chromotography

A

seperate molecules based on ligands and affinity for them
stationary column lined with ligands and keep molecules that bind, elute the ones that dont q

54
Q

gas liquid chromotography

A

only technique that involves a gas mobile stage
stationary phase coated in liquid
- time taken to move through denotes affinity for gases and liquids - longer time to elute = stronger affinity for liquid
- quicker time to elute = stronger gas affinity

55
Q

high performance liquid chromotography

A

liquid mobile phase and absorbant column
- differentiation: high pressure so resolution is more rapid
- stationary phase: polar
- mobile phase: liquid nonpolar

56
Q

requirement for gas chromotography

A

need a substance that can easily be forced into gas phase , one that does not vaporize below 700C is a bad choice

57
Q

reverse phase - high performance liquid chromotography

A

reverse phases of HPLC and TLC
mobile phase: polar
stationary: nonpolar

58
Q

recrystallization

A

solid percipitates out of solution and do over several times to purify
- in solvent that crystal is highly siluble in at high temp
- insolible at low temp

MCAT chem (11 decks)

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