Class Two

Question 1

what does solubility depend on

Answer 1

polarity of the solute and the polarity of the solvent

Question 2

polar molecules are soluble in..

Answer 2

polar solvents

Question 3

how to extract organic amines

Answer 3

with acidic water solution

protonates the basic functional group (forms a positively charged ion) → cationic salt

Question 4

how to extract carboxylic acids

Answer 4

extraction with a dilute weak base → anionic salt

Question 5

how to extract phenols

Answer 5

sodium hydroxide → converts phenols into their anionic salts

Question 6

what does a separatory funnel allow for

Answer 6

allows for you to extract a specific substance by separating the other ones

Question 7

uses of chromatography

Answer 7

identification purposes

purification

Question 8

thin layer chromatography

Answer 8

compounds are separated based on differing polarities

Question 9

how does TLC work

Answer 9

a mobile liquid phases ascends a thin layer of absorbent that is coated onto a supporting material (glass plate)

Question 10

purpose of absorbant in TLC

Answer 10

acts as a polar stationary phase for the sample to interact with

Question 11

why does separation occur in TLC

Answer 11

because different compounds travel along the plate at different rates

polar components interact with absorbant → travels slower

Question 12

R_f value - TLC

Answer 12

the distance traveled by an individual component divided by the distance travelled by the solvent front

Question 13

column (flash) chromatography

Answer 13

similar concept to TLC → used for bulk compounds

Question 14

ion exchange chromatography

Answer 14

separates materials with varying charge states

Question 15

when is ion exchange chromatography frequently used

Answer 15

separation of protein mixtures

(proteins within a mixture exist in a variety of charge states)

pI vs pH matters as well (pI > pH is positively charged)

Question 16

high performance liquid chromatography

Answer 16

speed and efficiency of separation is increased (higher pressures mobile → stationary)

Question 17

size exclusion chromatography

Answer 17

used to separate bulk materials based on molecular size

uses polymer beads with pores - allows for small molecules to go through, but not large ones

large ones go through a different (faster) pathway

Question 18

affinity chromatography

Answer 18

used to purify proteins or nucleic acids from biochemical mixtures

target molecule gets trapped on the stationary phase

Question 19

different ways of using affinity chromatography

Answer 19

protein linked beads (target protein binds)

magnetic beads (target protein binds)

Question 20

what is an affinity tag

Answer 20

molecular tags that act as an antibody (binds to target protein)

Question 21

gas chromatography

Answer 21

separation of mixtures based on their different volatilities

less volatile components spend more time dissolved in the liquid stationary phase

the more volatile components leave the column first

Question 22

branching (melting & boiling points)

Answer 22

branching reduces attractive forces (van Der Waals) between molecules → lower melting and boiling points

Question 23

molecular weight (melting & boiling points)

Answer 23

the greater the molecular weight → more SA → more areas for van Der Waals interactions → higher MP and BP

Question 24

small hydrocarbons tend to be ___ at room temp.

Answer 24

gases

Question 25

intermediate hydrocarbons tend to be ___ at room temp.

Answer 25

liquids

Question 26

large hydrocarbons tend to be ___ at room temp.

Answer 26

solids

Question 27

hydrogen bonding ___ MP and BP

Answer 27

increases

Question 28

which has a higher effect on MP and BPs? intra or inter H bonding

Answer 28

intermolecular hydrogen bonding

Question 29

what is distillation

Answer 29

raising the temp of a liquid → vapour → condensed back into the liquid phase in another container

Question 30

when is a simple distillation performed

Answer 30

when trace impurities need to be removed from a relatively pure compound

Question 31

what is fractional distillation

Answer 31

used when the difference in BPs of the mixture components is not large top of the column = pure vapour (condensed + collected in its liquid phase)

Question 32

what is mass spectrometry

Answer 32

technique that can determine the mass of compounds in a sample

Question 33

what is UV spectroscopy used for

Answer 33

transition metals (promotions of their electrons) conjugated organic systems

Question 34

IR spectroscopy

Answer 34

range of 2.5-20 um (causes bonds in organic molecules to become vibrationally excited)

Question 35

the higher the wavenumber..

Answer 35

the higher the frequency and greater the energy

Question 36

C=O stretch

Answer 36

1700 cm^-1 very strong & intense

Question 37

if the C=O stretch is not present..

Answer 37

you can eliminate compounds that contain a carbonyl group e.g. aldehydes, ketones, carboxylic acids, esters, amides, anhydrides etc.

Question 38

C=C stretch

Answer 38

1650 cm^-1

Question 39

triple bond stretch

Answer 39

C to C or C to N 2260-2100 cm^-1

Question 40

O-H stretch

Answer 40

strong and broad 3600-3200 cm^-1

Question 41

why is the O-H stretch broad

Answer 41

due to H bonding

Question 42

C-H stretch

Answer 42

3300-2850 cm^-1

Question 43

aliphatic C-H bonds wavenumber

Answer 43

less than 3000 cm^-1

Question 44

NMR spectroscopy

Answer 44

light from the radio frequency range of the electromagnetic spectrum is used to induce energy absorptions

Question 45

equivalent hydrogens have..

Answer 45

identical electronic environments - identical locations in the NMR spectrum

Question 46

when are hydrogens considered equivalent

Answer 46

when they can be interchanged by a free rotation or symmetry operation

Question 47

when does spin spin splitting occur

Answer 47

when nonequivalent hydrogens interact with eachother

Question 48

degree of splitting

Answer 48

n + 1 where n = number of nonequivalent neighbouring protons

Question 49

what is an integration - NMR

Answer 49

measurement of the area under each absorption peak (resonance) → indicatives the number of protons for each peak

Question 50

what is a chemical shift - NMR

Answer 50

indicates the location of resonance (peaks) in the NMR spectrum

Question 51

less deshielded protons will appear..

Answer 51

upfield (right)

Question 52

more deshielded protons will appear..

Answer 52

downfield (left)

Question 53

factors involved in proton deshielding

Answer 53

the electronegativity of the neighbouring atoms hybridization acidity and hydrogen bonding

Question 54

if an electronegative atom is close to a proton.. (chemical shift)

Answer 54

it decrease the electron density near the iron → deshielding therefore downfield shift

Question 55

what is the hybridization effect

Answer 55

a result of the varying bond characteristics of carbon atoms connected to hydrogens

Question 56

the greater the s-orbital character of a C-H bond.. (chemical shift)

Answer 56

the less electron density on the H → more deshielded so downfield shift

Question 57

protons attached to heteroatoms are..

Answer 57

very deshielded heteroatoms = O or N

Question 58

extreme example of a very large downfield shift

Answer 58

acidic protons on a carboxylic acid

Question 59

fractional distillation is useful for separating..

Answer 59

diastereomers

Question 60

how to resolve enantiomers

Answer 60

convert the enantiomers to diasteromeric salts with a chiral resolving agent (acid) separate the salts revert the salts back to the original compounds

Question 61

length of chain of sp² hybridized atoms & UV

Answer 61

as the chain increases, the wavelength of light absorbed increases (redshifts)

Question 62

the colour we see..

Answer 62

is the complementary colour of the wavelength that is absorbed