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Various MCAT Flashcards > TPR Lab Techniques > Flashcards

TPR Lab Techniques Flashcards

1
Q

Particular atoms give characteristic peaks (mass spec), the two most important are _____ and _____. Bromine naturally occurs in two isotopes _____ and _____. Chlorine also occurs as two isotopes _____ and _____.

A

Br and Cl; 79 and 81; 35 and 37

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2
Q

Wavenumber is directly proportional to both the ______ and the _____ of the _____. The higher the wavenumber, the higher the _____ and the greater the _____.

A

Frequency, energy of the radiation; frequency, energy

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3
Q

Thin-layer chromatography

A

TLC is a solid-liquid partitioning technique in which the mobile liquid phase ascends a thin layer of absorbent (generally silica, SiO2). The thin layer absorbent acts as a polar stationary phase for the sample to interact with. A very small sample is spotted near the base of the plate and via capillary action, the components of the spotted sample are partitioned between the mobile phase and the stationary phase.

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4
Q

Stretching frequency of common functional groups:
O-H

A

3600-3200 cm^-1

*Is strong and very broad

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5
Q

UV/Vis spectroscopy is very useful in monitoring complexes of _____ _____ and is used to study highly _____ _____ systems.

A

Transition metals; conjugated organic

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6
Q

Extraction

A

Allows the chemist to separate one substance from a mixture of substances by adding a solvent in which the compound of interest is highly soluble

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7
Q

Stretching frequency of common functional groups:
Carbonyls

A

1700 cm^-1

*Very strong and intense, should look for this stretch first

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8
Q

Size exclusion chromatography is usually used for…

A

1) Separation of large polymers from small oligiomeric fragments 2) Separation of full proteins from smaller peptide chains

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9
Q

Stretching frequency of common functional groups:
C-H for sp3

A

3000-2850 cm^-1

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10
Q

Ratio to front (Rf)

A

Is the distance traveled by an individual component divided by the distance traveled by the solvent ***Rf is always positive and never greater than 1

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11
Q

Chemical Shift

A

TBD***

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12
Q

HPLC for charged compounds (amino acids)

A

The stationary phase is often an ion exchange column, usually cation exchange. The mobile phase is polar, protic or acidic solvent that ensure solubility and suppresses the dissociation of the COOH group on the amino acid. Difference in affinity to the column has to do with the R groups.

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13
Q

Hydrogen bonding occurs between a ______-______ ______ -a hydrogen covalently bonded to a N, O, or F atom, and a _____-_____ _____ - a lone pair of electrons on a N, O, or F in another molecule, or part of the first molecule.

A

Hydrogen-bond donor; hydrogen-bond acceptor

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14
Q

Characteristic chemical shifts:
vinyl (RRC double bond CRH)

A

5-6 ppm

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15
Q

Stretching frequency of common functional groups:
C-H for sp2

A

3150-3000 cm^-1

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16
Q

HPLC Takes advantage of different ________ of various compounds for other a stationary phase or a mobile phase. However because the mobile phase is forced through the stationary phase at very _______ ______, both the ______ and ______ of the separation is increased.

A

Affinities; high pressures, speed, efficiency

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17
Q

Characteristic chemical shifts:
R-OH

A

2-5 ppm

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18
Q

Mass Spectrometry

A

Allows researchers to determine the mass of compounds in a sample. Within the mass spectrometer, molecules are ionized in a high vacuum, compounds enter a region of the spectrometer where they are acted on by a magnetic field. Field causes a flight path of the charged species to alter and the degree to which the path is changed is determined by the mass of the ion.

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19
Q

Characteristic chemical shifts:

(RCHO aldehyde)

A

9.0-10.0 ppm

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20
Q

Solubility largely depends on two things: the ______ of the solute and of the solvent.

A

Polarity

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21
Q

Bp an Mp of hydrocarbons: ______ tends to inhibit van der Waals forces by reducing the surface area available for the intermolecular interaction. It tends to ______ both melting and boiling points.

A

Branching, lower

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22
Q

Liquid-liquid extraction

A

Requires two immiscible liquids (aqueous & organic phase) use separatory funnel; lower density on the bottom; like dissolves like; organic non-polar compounds will dissolve in organic phase

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23
Q

The overall result of size exclusion chromatography is the quick elution of _____ _____ and long retention of _____ _____. Th lack of chemical interaction between the mobile and stationary phases results in relatively _____ _____ and _____ _____ of material.

A

Large molecules, smaller species

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24
Q

Column or flash chromatography

A

Columns filled with silica gel and the silica gel is saturated with a chosen organic solvent, and the mixture of compounds to be separated is then added to the top and allowed to travel down through the silica-packed column. Solvent is added periodically to separate compounds.

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25
Q

Wavelength

A

The reciprocal of wavelength, expressed in reciprocal centimeters (cm^-1).

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26
Q

Intramolecular hydrogen bonding interactions ______ melting point and boiling point and intermolecular hydrogen binding interactions ______ melting point and boiling point.

A

Decrease; Increase

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27
Q

Bp an Mp of hydrocarbons: The _______ the molecular weight of a compound, the more surface area there is to interact, the greater the number of van der Waals interaction and the ______ the melting and boiling point.

A

Greater, higher

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28
Q

The wavelength of maximum absorption for any compound is directly related to the ______ of ______ in the molecule. The more extensive the system, the ______ the wavelength of maximum absorption will be.

A

Extent of conjugation; longer

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29
Q

Boiling point

A

The temperature at which a liquid changes to a gas

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30
Q

Characteristic chemical shifts:
Alkyl (RCH)

A

0.3-1.7 ppm

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31
Q

In column or flash chromatography, _______ compounds will spend more time absorbed on the polar solid phase and travel ______ than the non polar compounds.

A

Polar; slower

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32
Q

The influence of molecular weight on melting point and boiling point, following trends for hydrocarbons…

A

1) Small hydrocarbons (1-4 C) tend to be gases at room temp 2) Intermediate hydrocarbons (5-16 C) tend to be liquids at room temperature 3) Large hydrocarbons (more than 16 C) tend to be waxy solids at room temperature

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33
Q

Distillation

A

Is the process of raising the temperature of a liquid until it can overcome the intermolecular forces that hold it together int he liquid phase.

34
Q

The color a compound maximally absorbs is ______ to the color it will appear to our eyes. For a compound that absorbs only UV radiation, ALL of the _____ _____ will be reflected and thus the compound will appear _____ or _____.

A

Complementary; visible wavelengths, white, colorless

35
Q

Gas chromatography partitioning occurs based on their different _______.

A

Volatilities

36
Q

Melting point

A

The temperature at which a substance changes from a solid to a liquid.

37
Q

High performance liquid chromatography (HPLC)

A

A pumping unit causes a pressurization of the mobile phase. The sample is solubilized and injected by syringe and then the mobile phase carries the sample to the column. the sample is separated into components and is analyzed. Eluent can later be isolated with evaporation of solvent.

38
Q

Spin-spin splitting phenomenon

A

Occurs when non-equivalent hydrogens interact with each other; Nearby protons that are non-equivalent to the proton in question will cause a splitting in the observed HNMR signal

*Signal will be split into n+1 lines (n is the number of nonequivalent, neighboring interacting protons)

39
Q

If an electronegative atom is in close proximity to a proton, it will ______ the electron density near the proton and thereby _______ it. This will result in a _______ _______ in the chemical shift value.

A

Decrease; deshield; downfield

40
Q

Equivalent hydrogens in a molecule are those that have ______ ______ ______. These have the ______ locations in the HNMR spectra, therefore represented by the same signal.

A

Identical electronic environment, identical

41
Q

Fractional Distillation

A

Is used when the difference in boiling points of the components in the liquid mixture is not large. Column is packed with an appropriate material; packing of column results in liquid mixture being subjected to many vaporization -condensation cycles it moves up the column. Composition of the vapor gradually becomes enriched in the lower boiling component. Near top of column, nearly pure vapor reaches condenser and condenses back to liquid.

42
Q

In gas chromatography, as the mixture passes through the column, the components equilibrate between the ______ _______ and the ______ ______. The _____ _____ components will spend more time dissolved int he liquid stationary phase than the ______ ______ component that will be carried along by the carrier gas at a faster rate.

A

Carrier gas; liquid phase; less volatile, more volatile

43
Q

Stretching frequency of common functional groups:
C-H for sp

A

3300 cm^-1

44
Q

Affinity chromatography (magnet)

A

Magnetic beads can be used as the solid phase. Beads are isolated from solution by using a magnet to hold them against the sides while solution is decanted.

45
Q

Simple distillation

A

Is performed when trace impurities need to be removed from a relatively pure compound, or when a mixture of compounds with significantly different boiling points need to be separated.

46
Q

Stretching frequency of common functional groups:
Alkenes

A

1650 cm^-1

47
Q

UV/Vis spectroscopy

A

Focuses on slightly shorter, more energetic wavelengths of radiation in the ultraviolet and visible area of the spectrum.

48
Q

Stretching frequency of common functional groups:
C-C (triple bond) or C (triple bond) N

A

2260-2100 cm^-1

49
Q

Hybridization Effect

A

TBD***

50
Q

Extraction with dilute weak base

A

Extraction with a dilute weak base -typically 5% NaHCO3 results in converting carboxylic acids or phenols into their corresponding anionic salts. These anionic salts are generally soluble in aqueous solution and can be removed. ***Extraction of carboxylic acids and phenols

51
Q

In ion exchange chromatography, the materials to be separated have varying ______ ______. It is frequently used in the separation of mixtures of ______.

A

Charge states; proteins

52
Q

Distribution (or partition) coefficient

A

The ratio of the substance’s solubilities in the two solvents

53
Q

If protein of interest does not have a commercial antibody, researchers use an ______ ______. Using recombinant technology, small ______ ______ is added to the N-terminus or the C-terminus.

A

Affinity tag, molecular tag

54
Q

If a mixture of proteins where passed through an cationic resin, those proteins with pI values _______ than the pH of the mobile phase will elute ______ compared to those with pI values below the solution pH.

A

Greater; faster

55
Q

Organic extraction involving acidic or basic water solutions

A

Organic compounds that are basic can be extracted from organic compounds with dilute acid (5-10% HCl). This protonates the basic functional group, forming a positively charged ion. Results in cationic salts of these basic compounds that remain dissolved in organic phase. ***Extraction of Organic amines

56
Q

Characteristic chemical shifts:
Benzylic (RCH2C6H5)

A

2.5-3.5 ppm

57
Q

Simplest liquid-liquid extraction

A

An organic compound is extracted with water. A simple water extraction can remove substances that are highly polar or charged.

58
Q

Stretching frequency of common functional groups:
N-H

A

3150-2500 cm^-1

59
Q

Integration

A

Measuring the area under each absorption peak (resonance); the area under each peak is proportional tot he relative number of protons giving rise to each peak

60
Q

TLC is good for separating ______ amounts of material in order to assess how many compounds make up a mixture.

A

Small

61
Q

Ion exchange chromatography

A

IEC uses a polymeric resin functionalized with either positive or negatively charged moieties on the polymer surface. Ion charges that are the same or neutral to the resin quickly pass through the material and are eluted first. Ion charges opposite to those in the resin coordinate to the functionalities tethered to the polymer surface. Their progress through the column is retarded.

62
Q

In thin layer chromatography (TLC), compounds are separated based on differing _______.

A

TBD***

63
Q

Affinity chromatography

A

Is most commonly used to purify proteins or nucleic acids from complex chemical mixtures. The target molecule is trapped on the stationary phase and then washed. Target protein is then released (or eluted) off the solid phase in a highly purified state. Sold phase can be mixed in a small tube mixed with sample to allow interaction. Sample is centrifuged so heavy solid resin settles in bottom (has protein of interest) and liquid is decanted.

64
Q

Gas chromatography

A

Form of column chromatography in which partitioning of the components to be separated takes place between mobile gas phase and a stationary liquid phase. The sample is loaded in and is then vaporized by a heater and carried along by a stream of inert gas. Vaporized gas is moved into column with liquid absorbent and interact based on volatilities. As each component exists, its burned, and resulting ions are detected by an electrical detector that generates a signal recorded by a chart recorder. ***Usually for small amounts of substance

65
Q

The more polar components of TLC interact more with the ______ ______ ______ and travel at a ______ rate. The lesser polar components have a greater affinity for the ______ and travel with the mobile phase at a ______ rate.

A

polar stationary phase, slower; solvent, faster

66
Q

Characteristic chemical shifts:

(X=NR2, OR, halogen)

A

2.5 - 3.7 ppm

67
Q

Characteristic chemical shifts:
Alkyne (RC triple bond CH)

A

2 ppm

68
Q

Isolating protein in affinity chromatography

A

To isolate protein of interest, highly specific interactions of antibodies can be used. To isolate the antigen-antibody complex, one of the three common microbe derived proteins is linked to solid support. Target is then isolated after centrifuging and decanting supernatant.

69
Q

If a mixture of proteins where passed through an anionic resin, those proteins with pI values _______ than the pH of the mobile phase will be positively charged and elute ______ compared to those with pI values below the solution pH.

A

Greater; slowly

70
Q

In column or flash chromatography compounds can be expected to leave the column, and be collected, in order of _______ ( _____ _____ to ______ ______).

A

Polarity; least polar —> more polar

71
Q

In mass spectrometry, small peaks with masses larger than the main peak represent molecules that have one or more of the ______ ______ ______. Masses lower than the main peak can represent the masses of ______ ______.

A

Less abundant isotopes; molecular fragments

72
Q

The more _______ compounds elute first in HPLC as they have a high affinity for the mobile phase. The less polar compounds are slowed by their interactions with the ______ ______ ______, and therefore elute first.

A

Polar; nonpolar stationary phase

73
Q

Four essential features of a molecule can be deduced from HNMR Spectroscopy:

A

1) Number of sets of peaks tells the number of chemically nonequivalents sets of protons in the molecule
2) The splitting pattern of each set of peaks tells how many protons are interacting with the protons in that set
3) The mathematical integration = relative numbers of protons in each set
4) Chemical shift values = environment of protons in that set

74
Q

The ______ ______ components emerge from the column first, while the _____ _____ components emerge from the column later.

A

More volatile, less volatile

75
Q

Infrared (IR) Spectrometry

A

Measures molecular vibrations that can be seen as bond stretching, bending, or combinations.

76
Q

Size exclusion chromatography

A

Is a technique used to separate bulk materials based on molecular size. The stationary phase consists of chemically inert, porous polymer beads. The size of the pores in the beads are controlled to allow permeation of small molecules in the fluent, while excluding larger ones.

77
Q

Heteroatoms

A

Atoms in an organic compound other than carbon and hydrogen

78
Q

HOLC separations of organic compounds, the stationary phase is a silica gel that has been bonded to a ______ ______, creating a relatively _______ stationary phase. Called ______ phase HPLC.

A

Non polar group; non polar, reverse

79
Q

_______ or ______ ______ employs the same basic principles as TLC but is used for isolating bulk compounds.

A

Column or flash chromatography

80
Q

Characteristic chemical shifts:
R-CO2H

A

10-13 ppm

Various MCAT Flashcards (5 decks)

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