Org 1 lab final

Question 1

Important properties of a solvent for recrystallization(3)

Answer 1

-not react with compound
-dissolve compound when hot, but not when cold
-dissolve all impurities at all temps or never dissolve any

Question 2

what solvent and solid is recrystallization favored for

Answer 2

-high melting solvent
-thermally unstable solid

Question 3

should you use a warm or cold rinse on crystals

Answer 3

cold or they will dissolve

Question 4

is the stationary phase of TLC polar or non-polar

Answer 4

polar

Question 5

describe the stationary phase for TLC

Answer 5

silica gel on a solid backing

Question 6

is the mobile phase of TLC polar of non-polar

Answer 6

non-polar

Question 7

describe the mobile phase of TLC

Answer 7

solvent mixture carries compounds across stationary phase

Question 8

what determines how far a compound travels on TLC sheet

Answer 8

polarity, the more polar the farther it travels, greatest difference in polarity get best results(too polar may go too far)

Question 9

what information do you get from an IR spectra

Answer 9

what functional groups are present on a molecule

Question 10

what must be present for change on IR to occur(stretch, twist, etc)

Answer 10

bond dipole

Question 11

what IR region is relative to visible light

Answer 11

red

Question 12

which has more energy: bend or stretch (IR)

Answer 12

Stretch

Question 13

which groups are more than 3000 on IR spectra

Answer 13

nitrile
ketones
ester
alkene

Question 14

what methods does distillation use to purify? how does it purify?

Answer 14

heating and cooling
separate mixtures by vaporization point(different boiling points)

Question 15

T/F more plates/fractions in distillation give you a more pure product

Answer 15

TRUE

Question 16

how many theoretical plates is equal to a simple distillation

Answer 16

one

Question 17

T/F as the difference in boiling point decreases the number of theoretical plates for purification increases

Answer 17

TRUE
Ex. 4 degrees needs 65 plates
35 degrees needs 5 plates

Question 18

describe the stationary phase of distillation

Answer 18

inert carrier gas

Question 19

describe mobile phase of distillation

Answer 19

carrier gas and compound run via packed column

Question 20

what factors affect boiling point

Answer 20

-IMFs
-# of carbons in chain
-branching

Question 21

how does # of carbons affect boiling point

Answer 21

as carbon # decreases, BP decreases

Question 22

how does branching impact boiling point

Answer 22

Increased branching = decreased BP

Question 23

how do intermolecular forces impact boiling point

Answer 23

ionic>H bonding>D-D>london dispersion
higher BP Lower BP

Question 24

T/F enantiomers CAN be separated through simple distillation

Answer 24

FALSE

Question 25

T/F constitutional isomers CAN be separated through simple distillation

Answer 25

TRUE, branching changes BP

Question 26

what does the organic phase dissolve

Answer 26

organic substances

Question 27

what does the aqueous phase dissolve

Answer 27

organic and inorganic salts

Question 28

T/F aqueous phase is always the bottom layer

Answer 28

FALSE, position depends on density, most organic layers are less dense than water, but not always

Question 29

what organic phases are more dense than water

Answer 29

-DMSO -CH2Cl2

Question 30

how do you fix emulsion during extraction

Answer 30

add water and shake gently

Question 31

how to tell which phase(organic or aqueous a compound/solvent will be in)

Answer 31

organic -non-polar -basic(can move into aqueous) -neutral substances Aqueous -polar -acid

Question 32

what reaction was used for phase transfer catalyst

Answer 32

Williamson ether synthesis

Question 33

what causes unwanted peaks in an IR spectra

Answer 33

unreacted starting material or impurities

Question 34

definition of solvolysis

Answer 34

solvent acts as reagent(nucleophile) in reaction

Question 35

what increases rate of reaction and stability in solvolysis

Answer 35

-double bonds -ability to form resonance structures

Question 36

what is the rate-determining step of solvolysis

Answer 36

formation of carbocation

Question 37

what reaction type is dehydration of cyclohexanol

Answer 37

E1

Question 38

what is an azeotrope

Answer 38

mixture of 2+ liquids that have a single sharp boiling point

Question 39

properties of azeotrope

Answer 39

-single boiling point lower than individual BPs -compounds will vaporize together even if individual BP are different -cyclohexanol/water will distill at 98C -cyclohexene/water will distill at 71C

Question 40

explain bromine test

Answer 40

add 2 Br in anti positions

Question 41

how to calculate percent yield

Answer 41

(actual yield/theoretical yield) x 100

Question 42

how to calculate theoretical yield

Answer 42

multiply moles by molar mass

Question 43

what is a theoretical plate

Answer 43

one vapor condensation event

Question 44

what stretch/bend does water have

Answer 44

-Bend -asymmetrical stretch -symmetrical stretch

Question 45

fine vs. rough melting point

Answer 45

rough: temp rise 6-10C/min fine: temp rise 1-2C/min

Question 46

how do impurities impact melting point

Answer 46

lowers and broadens melting point

Question 47

what is the point of chromatography

Answer 47

to monitor a reaction

Question 48

what types of stretch are there

Answer 48

symmetrical asymmetrical

Question 49

what types of bend are there

Answer 49

twisting wagging rocking scissoring

Question 50

where is the fingerprint region, what info does it give

Answer 50

-1400-14 cm-1 -tells about exact structure of molecule(don't usually pay attention to)

Question 51

what is shown at the top of a peak on a gas chromatography chart

Answer 51

time it took for compound to pass through column

Question 52

what does it mean if a compound has a lower time on a GC chart

Answer 52

it vaporizes more quickly

Question 53

what does the area under a peak on a GC chart indicate

Answer 53

how much of a certain compound is present

Question 54

how does extraction use the organic and aqueous phase to separate two liquids

Answer 54

react one liquid so it can pass between the phases

Question 55

when is it important to check the fingerprint region

Answer 55

if looking for an ether (phase transfer catalysis experiment)

Question 56

T/F in Sn1 solvolysis water can attack from either side and will form two stereoisomers/a racemic mixture

Answer 56

TRUE

Question 57

how to calculate Rf

Answer 57

dist. spot traveled/dist. solvent traveled

Question 58

first order reaction formula

Answer 58

rate=k[substrate]

Question 59

what impacts the rate determining step in Sn1 solvolysis

Answer 59

polarity of solvent