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Chemistry (Tara) > Organic Chem 9 > Flashcards

Organic Chem 9 Flashcards

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1
Q

what is chromatography used for?

A

to separate different substances in a mixture

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2
Q

principle of chromatography

A

a mobile phase will carry a dissolved mixture through a stationary phase. The separation occurs, as some of the components of the mixture tend to be held by the stationary phase and move more slowly than those that mix well with the mobile phase

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3
Q

mobile phase

A

a solvent

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4
Q

stationary phase

A

paper or thin layer of aluminium oxide

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5
Q

TO SEPARATE A MIXTURE OF INDICATORS USING CHROMATOGRAPHY

those that do not dissolve easily in the solvent

A

will come out of the solution and appear on the paper as a spot

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6
Q

TO SEPARATE A MIXTURE OF INDICATORS USING CHROMATOGRAPHY

those that dissolve well

A

will be carried up the paper further and will eventually appear as spots on the paper at different intervals

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7
Q

TO SEPARATE A MIXTURE OF INDICATORS USING CHROMATOGRAPHY

how to get results

A

by finding Rf values

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8
Q

TO SEPARATE A MIXTURE OF INDICATORS USING CHROMATOGRAPHY

Rf=

A

distance travelled by solvent front

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9
Q

TO SEPARATE A MIXTURE OF INDICATORS USING CHROMATOGRAPHY

first step

A

solvent added to the bottom of the glass jar, to a depth of about 1 cm and allow to stand for a while

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10
Q

TO SEPARATE A MIXTURE OF INDICATORS USING CHROMATOGRAPHY

why do you allow to stand

A

to allow the tank to become saturated with the solvent’s vapour

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11
Q

TO SEPARATE A MIXTURE OF INDICATORS USING CHROMATOGRAPHY

what do you do to the paper

A

make a line near the top with a pencil and another near the bottom

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12
Q

TO SEPARATE A MIXTURE OF INDICATORS USING CHROMATOGRAPHY

next step - making a small concentrated spot of mixture

A

a small spot of mixture of indicators was placed on the line with a capillary tube and dried with a hair dryer. repeat several times

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13
Q

TO SEPARATE A MIXTURE OF INDICATORS USING CHROMATOGRAPHY

putting paper into jar

A

place in glass jar with spot side down, do not immerse spot, paper just touches solvent, attach paper to glass rod using sellotape

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14
Q

TO SEPARATE A MIXTURE OF INDICATORS USING CHROMATOGRAPHY

everything is set up

A

allow to run until the solvent reached the line at the top of the paper

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15
Q

TO SEPARATE A MIXTURE OF INDICATORS USING CHROMATOGRAPHY

when solvent reaches top

A

paper is removed and dried

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16
Q

TO SEPARATE A MIXTURE OF INDICATORS USING CHROMATOGRAPHY

what does not allow for accurate results?

A

the particles of the stationary phase are not small and uniform in size 1

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17
Q

USING THIN LAYER CHROMATOGRAPHY

what do TLC plates have the stationary phase as

A

a layer of aluminium oxide or silica gel spread thinly and evenly over aluminium foil

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18
Q

USING THIN LAYER CHROMATOGRAPHY

what does the foil provide

A

support for the stationary phase

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19
Q

USING THIN LAYER CHROMATOGRAPHY

why is it more efficient than paper chromatography

A

the particles in the stationary phase are smaller and uniform in size, more accurate separation of the components in the mixture

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20
Q

USING THIN LAYER CHROMATOGRAPHY

what speeds up saturation of jar with solvent

A

a piece of filter paper was cut to fit around the walls of the glass jar

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21
Q

USING THIN LAYER CHROMATOGRAPHY

what was first added?

A

industrial methylated spirits was added to allow it to saturate the paper and give a depth of about 1cm

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22
Q

USING THIN LAYER CHROMATOGRAPHY

after spirits added

A

jar is covered and let stand for a wile

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23
Q

USING THIN LAYER CHROMATOGRAPHY

what do you do the plate

A

line drawn at the top and the bottom of the plate

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24
Q

USING THIN LAYER CHROMATOGRAPHY

after line drawn

A

a small drop of the mixture is placed on the line at the bottom of the plate and dried using a hairdryer

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25
Q

USING THIN LAYER CHROMATOGRAPHY

where do you put the plate

A

the plate was stood in the jar making sure that the spot was above the solvent level

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26
Q

USING THIN LAYER CHROMATOGRAPHY

after everything has been set up

A

the chromatogram was allowed to run until the solvent had risen to the pencil line at the top of the plate

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27
Q

USING THIN LAYER CHROMATOGRAPHY

when it has reached the top

A

plate removed and allowed to dry

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28
Q

USING THIN LAYER CHROMATOGRAPHY

why is filter paper placed around the walls of the glass jar

A

to speed up saturation of the tank with solvent vapour

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29
Q

USING THIN LAYER CHROMATOGRAPHY

why are two lines drawn on the TLC plate

A

one line is needed to indicate where the samples start from, and the other to indicate the distance travelled by the solvent front, which enables the Rf values to be calculated

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30
Q

USING THIN LAYER CHROMATOGRAPHY

when is it possible to separate components of a mixture using thin layer chromatography?

A

when one of the components is attracted to significantly different extents by the stationary phase and/or the mobile phase

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31
Q

USING THIN LAYER CHROMATOGRAPHY

when two substances are found to have identical Rf values, what does this mean?

A

the two substances may be the same, but further evidence is necessary to establish this conclusively

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32
Q

2 social and applied aspects of TLC

A

used in the pharmaceutical industry to determine the purity of drugs
used in forensic science to separate colours in dyes extracted from fibres

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33
Q

USING COLUMN CHROMATOGRAPHY

stationary phase and where does it go

A

silica gel, placed in a long glass tube (column)

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34
Q

USING COLUMN CHROMATOGRAPHY

what prevents the material from running out

A

glass wool at the end

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35
Q

USING COLUMN CHROMATOGRAPHY

solvent for non-polar substances

A

ethanol

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36
Q

USING COLUMN CHROMATOGRAPHY

solvent for polar substances

A

water

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37
Q

USING COLUMN CHROMATOGRAPHY

how and why is silica kept saturated

A

kept saturated with the solvent to prevent it from drying out

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38
Q

USING COLUMN CHROMATOGRAPHY

where does the mixture go?

A

added to the top of the column

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39
Q

USING COLUMN CHROMATOGRAPHY

how does it separate

A

the components are adsorbed to a different extent along the column

40
Q

elution

A

passing solvent through the column

41
Q

eluent

A

solvent

42
Q

USING COLUMN CHROMATOGRAPHY

first step

A

the solid phase extraction column was flushed through with methanol using the plunger of the syringe

43
Q

USING COLUMN CHROMATOGRAPHY

second step

A

the column is then flushed through with water

44
Q

USING COLUMN CHROMATOGRAPHY

what do you do with the mixture

A

a sample was placed on top of the column to a depth of 1mm

45
Q

USING COLUMN CHROMATOGRAPHY

methanol solution

A

added to the syringe

46
Q

USING COLUMN CHROMATOGRAPHY

once everything is set up

A

mixture flows down through column

47
Q

USING COLUMN CHROMATOGRAPHY

separation

A

separation occurs as the mixture appears as bands of different colours

48
Q

USING COLUMN CHROMATOGRAPHY

final step

A

different components of the mixture were collected in separate beakers

49
Q

USING COLUMN CHROMATOGRAPHY

when is it possible to separate components of a mixture using column chromatography?

A

when one of the components is attracted to significantly different extents by the stationary phase and/or the mobile phase

50
Q

USING COLUMN CHROMATOGRAPHY

what is the purpose of the syringe in this experiment?

A

to allow the solvent to be forced through the column under pressure, thereby achieving a rapid separation

51
Q

USING COLUMN CHROMATOGRAPHY

why is an adapter necessary?

A

to enable the syringe to be fitted exactly into the column, without this, it is not possible to force the liquid through the column under pressure

52
Q

USING COLUMN CHROMATOGRAPHY

why is it necessary to flush the column with methanol and then water before using it?

A

methanol will remove any residual organic material from the column, water will then remove any remaining methanol

53
Q

TO SEPARATE A MIXTURE OF INDICATORS USING CHROMATOGRAPHY

why is the gas jar not used for a time after the solvent has been added?

A

to allow time for the tank to become saturated with solvent vapour

54
Q

TO SEPARATE A MIXTURE OF INDICATORS USING CHROMATOGRAPHY

why are two lines drawn on the paper

A

one line is needed to indicate where the samples start from, and the other to indicate the distance travelled by the solvent front, which enables the Rf values to be calculated

55
Q

TO SEPARATE A MIXTURE OF INDICATORS USING CHROMATOGRAPHY
when 2 substances are found to have 2 different Rf values in an experiment carried out under the same conditions, what does this mean?

A

the 2 substances are not identical

56
Q

5 instrumental methods of separation and analysis

A 
mass spectrometry 
gas chromatography (GC)
high performance liquid chromatography (HPLC)
Infra-Red spectrometry (IR) 
Ultra-violet spectrometry (UV)
57
Q

GAS CHROMATOGRAPHY

gas is in

A

mobile phase

58
Q

GAS CHROMATOGRAPHY

stationary phase

A

a high boiling point liquid spread on silica gel packed into a long coiled tube of small diameter

59
Q

GAS CHROMATOGRAPHY

where is tube kept

A

in a temperature controlled oven

60
Q

GAS CHROMATOGRAPHY

where do you put the sample

A

injected into the column

61
Q

GAS CHROMATOGRAPHY

what is done to the column when sample is in

A

column is heated to vaporise the sample and it is carried through by a gas such as nitrogen or helium, as these are
unreactive gases

62
Q

GAS CHROMATOGRAPHY

separation

A

the components of this mixture separate out at different rates as they are carried through the column

63
Q

GAS CHROMATOGRAPHY

how results are recorded

A

as each component leaves the column, a detector records a signal and plots a chart called a gas chromatogram

64
Q

GAS CHROMATOGRAPHY

how do components show up on the chromatogram

A

as a peak

65
Q

GAS CHROMATOGRAPHY

what is it used for

A

to measure the level of alcohol in our blood or urine and in drug test samples from athletes

66
Q

HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

function

A

used to determine non-volatile components of a mixture

67
Q

HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

particles of the solid phase and what can you do

A

very small, pressure is used to force the mixture through

68
Q

HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

temperature and why

A

temperature not as high as GC so this prevents the decomposition of substances at high temperatures

69
Q

HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

pressure

A

the column is not as long and made of material that can withstand the high pressures used

70
Q

HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

where is it used

A

in food analysis - growth promoters in meat and vitamins in food

71
Q

INFRA-RED SPECTROMETRY

organic compounds

A

organic compounds absorb infra-red radiation (the bonds do) and the bonds begin to vibrate

72
Q

INFRA-RED SPECTROMETRY

different bonds

A

different bonds absorb different amounts of energy and so vibrate differently

73
Q

INFRA-RED SPECTROMETRY

finger-print

A

the vibrations are like a fingerprint for each molecule and the molecules can be identified by checking them against a data-base

74
Q

INFRA-RED SPECTROMETRY

what is it used for

A

to identify plastics and drugs

75
Q

ULTRA-VIOLET SPECTROMETRY

what may happen when a substance absorbs ultra-violet light

A

an electron may be promoted o a higher energy level and a spectrum is obtained

76
Q

ULTRA-VIOLET SPECTROMETRY

max absorption

A

max absorption usually occurs at a certain wavelength, and this helps to identify the compound and its concentration, as absorbance is related to concentration

77
Q

ULTRA-VIOLET SPECTROMETRY

what is it used for?

A

quantitive determination of organic compounds e.g drug metabolites and plant pigments

78
Q

RECRYSTALLISATION OF BENZOIC ACID AND DETERMINATION OF ITS MELTING POINT
principle

A

more solute is soluble in hot solvent than in cold solvent

79
Q

RECRYSTALLISATION OF BENZOIC ACID AND DETERMINATION OF ITS MELTING POINT
first step

A

5g benzoic acid placed in a beaker and dissolved in a minimum of hot water

80
Q

RECRYSTALLISATION OF BENZOIC ACID AND DETERMINATION OF ITS MELTING POINT
why a minimum of hot water

A

to maximise the yield - benzoic acid does not remain in solution on cooling

81
Q

RECRYSTALLISATION OF BENZOIC ACID AND DETERMINATION OF ITS MELTING POINT
first filtration

A

this hot solution was filtered through a Buchner funnel (under suction, fast), insoluble impurities remain on the filter paper

82
Q

RECRYSTALLISATION OF BENZOIC ACID AND DETERMINATION OF ITS MELTING POINT
after first filtration

A

filtrate was allowed to cool slowly

83
Q

RECRYSTALLISATION OF BENZOIC ACID AND DETERMINATION OF ITS MELTING POINT
second filtration

A

excess solvent filtered off and crystals remain on filter paper and allowed to dry

84
Q

MELTING POINT DETERMINATION

first step

A

some crystals tapped into the open end of a melting point tube, until 0.5cm full at the end of the tube

85
Q

MELTING POINT DETERMINATION

thermometer

A

attach tube to thermometer with rubber band

86
Q

MELTING POINT DETERMINATION

prepare boiling tuber

A

boiling tube half-filled with liquid paraffin and the tube and thermometer were placed in the boiling tube

87
Q

MELTING POINT DETERMINATION

everything is prepared

A

place boiling tube over bunsen burner and heat, stir liquid paraffin thoroughly throughout

88
Q

MELTING POINT DETERMINATION

find results

A

the temperature at which the crystals started to melt was noted and recorded

89
Q

MELTING POINT DETERMINATION

after it is done

A

allow paraffin to cool to 10ºC and repeat with fresh crystals, heat more slowly and record

90
Q

MELTING POINT DETERMINATION

how is melting indicated

A

by the formation of a visible meniscus

91
Q

MELTING POINT DETERMINATION

if the crystals are pure

A

a sharp melting point will be recorded

92
Q

MELTING POINT DETERMINATION

if the crystals are impure

A

a melting point range will be recorded

93
Q

cracking

A

a process that involves breaking up long chain hydrocarbons for which there is low demand into short chain hydrocarbons for which there is high demand

94
Q

2 types of cracking

A

catalytic cracking or thermal cracking

95
Q

cracking, for every bond broken

A

a double bond must be formed in a product molecule

96
Q

if a molecule is cracked in 2 places

A

there will be 3 products and 2 will have a C=C

Chemistry (Tara) (50 decks)

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