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OChem 1 lab > Final CHM 254 > Flashcards

Final CHM 254 Flashcards

1
Q

lab 6

Procedure for Steam Distillation

A
  1. Add cinnamon sticks + water to round bottom flask
  2. set up distillation apparatus and boil mixture until a clear distillate is formed
  3. perform extraction with ethyl acetate
  4. rotovap
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2
Q

lab 6

simple distillation

A

used to separate a solid, liquid mixture or a liquid mixture with two liquids that have very different boiling points

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3
Q

lab 6

fractional distillation

A

separates liquid mixtures with similar boiling points by providing a greater surface area for condensation

results in best kind of separation

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4
Q

lab 6

Steam Distillation

A

used to separate two immiscible liquids where one has a very high boiling point and one is more volatile

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5
Q

lab 6

(sum of vapor pressures) Pt =

A

Pa + Pb

vapor pressures of the two liquids

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6
Q

lab 6

if you use the equation to find the amount of each compound in the distillate and you get .292 what does that mean?

A

for every .292 g of a there is 1 g of b

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7
Q

lab 6

(amnt of each compound in the distillate) ma/mb=

A

Pa * MMa/Pb *MMb

MM= molar mass from periodic table

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8
Q

lab 6

Why does your distillate start cloudy and turn clear over time?

A

Bc/ it is a mixture of water + cinnamaldehyde, which is why we perform an extraction after

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9
Q

lab 6

If you were performing a fractional distilliation would you need to perform an extraction after?

A

likely not, fractional distilliation has good separation

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10
Q

lab 6

Will a branched molecule have a lower or higher bp?

A

lower, the branching decreases the surface area which allows for bonds to be broken faster

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11
Q

lab 6

Describe a liquid phase diagram

A

the top curve is a vapor curve
the bottom curve is a liquid curve
x-axis: % of A or B
y-axis: temperature

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12
Q

lab 6

A vapor in eq. with a liquid will always be richer in the — — comound

A

more volatile

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13
Q

lab 6

Describe the differences in a simple distillation curve vs a fractional distillation curve

A

a simple distillation curve will have a less steep incline because the resulting distillate is impure, unlike a fractional distillation which will yield a more pure compound

x-axis: volume distillate y-axis: temperature

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14
Q

HNMR

How do you calculate a J value?

A

by measuring the distance between two peaks

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15
Q

HNMR

what can a J value tell you?

A

equivalent J values will signal that two protons are near each other on the molecule, coupled protons should have the same J values

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16
Q

HNMR

what does the multiplicty rely on?

A

the number of neighboring hydrogens

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17
Q

HNMR

the area under the peak/ integration is directly proportional to —–

A

the number of hydrogens contributing to the signal

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18
Q

HNMR

why dont chemically equivalent protons produce multiple peaks?

A

the roofing effect

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19
Q

HNMR

what is the z atom test?

A

replace an atom, C or H, with Z and compare. Are the molecules the same? Are they different? if so how?

homotopic, enantiotopic, diastopic, hetereotopic

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20
Q

HNMR

what does it mean if a molecule is determined to be enantiotopic by the Z atom test?

A

the atoms are chemically equivalent and enantiomers of each other

does the z atom test create a chiral center?

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21
Q

HNMR

what does it mean if an atom is heterotopic by the z atom test?

A

they are not chemically equivalent and are constitutional isomers

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22
Q

HNMR

what does it mean if an atom is diatopic by the z atom test?

A

they are diastereomers and non equivalent

23
Q

HNMR

what does it mean if a atom is homotopic by the Z atom test

A

they are the same molecule and equivalent

24
Q

HNMR

what does it mean for a proton to be deshielded?

A

this proton will likely be found further up the graph as the surrouding molecules are pulling electron density

25
Q

How can you tell right off the bat tell if a molecule is going to be homotopic or not?

A

if the z atom test creates a chiral center then it is not homotopic

26
Q

if you do the z atom test and it creates the only chiral center on the molecule what relationship is it?

A

enantiotopic

27
Q

if you do the z atom test and it creates more than one chiral center or there is already a chiral center on the molecule what is the relationship?

A

diatopic

28
Q

lab 7

Procedure for Column Chromotography

A
  1. set up column with sand, silica and hexanes (NEVER LET SILICA RUN DRY)
  2. Pack silica by applying air pressure and forcing the solvent through
  3. once silica is level and packed run sample to be separated through column, apply air pressure to let solvent run through
  4. begin collecting, spot TLC plates to identify when each mixture is being collected
  5. combine the fractions that you are sure only have the 1st compound (np) and then combine the fractions that are are sure only have the 2nd compound (p)
  6. rotovap combinations
29
Q

lab 7

why can column chromotography be more helpful than TLC?

A

because you can perform larger scale separations with column chromotography, unlike with TLCs

30
Q

lab 7

What is the order of elution?

A

Non polar will be collected in fractions first, then polar compound will be collected when more polar solvent is run through

31
Q

lab 7

A — flow rate will provide poor separation and low flow rate will give — separation

A

high flow = bad
low flow = good

32
Q

lab 8

Procedure of a williamson ether synthesis

A
  1. dissolve, potassium carbonate, acetaminophen, butanone, and ethyl iodide in a rb flask
  2. perform an extraction
  3. wash with NaOH after extraction
  4. dry over MgSO4 and filter
  5. rotovap
  6. recrystallize
33
Q

lab 8

good solvent

A

the solvent the sample is most soluble in, what the sample will be heated in

34
Q

lab 8

bad solvent

A

the solvent the sample is not miscible in, added in small amounts once the good solvent + sample is hot

35
Q

lab 8

yield of the reaction

NOT PERCENT YIELD

A

mol b/mol a * m/n * 100%

m and n are coefficents

36
Q

lab 8

why do you need the condenser tube for reflux?

A

so all the solvent does not escape

37
Q

lab 8

How would you choose solvents for recrystallization from mixed solvents?

A
  • the two must be miscible with each other and similar bp
  • one must be a good solvent and one must be a bad solvent
38
Q

lab 8

in the presence of strong — most phenols are completely dissociated

A

bases

39
Q

lab 8

In what layers of extraction would you expect to see phenols and ethers in?

A

phenols: aq layers
ethers: org layer

40
Q

lab 8

why do you need to wash with NaOH after extraction?

A

to deprotonate any remaining phenols so the reaction may proceed

41
Q

lab 9

Procedure for biodiesel synthesis

A
  1. vegetbale oil + sulfuric acid heated to reflux
  2. cool and extract glycerol
  3. wash x3 with NaCl
  4. dry over MgSO4 and filter
  5. test combustion + viscosity
42
Q

lab 9

washing

A

the process to pull out compounds you dont want

43
Q

lab 9

extraction

A

the process to pull out compounds you do want

44
Q

lab 9

green chemistry

A

being the most chemically, monetarily and environmentally efficent with our chemical processes

efficent, safe responsible

45
Q

lab 9

At the conclusion of the lab which was more vicous? Which had better combustion properties?

between biodiesel and vegetbale oil

A

the biodiesel was less viscous and had much better combustion properties

46
Q

lab 9

Why do you wash 3x with NaCl?

A

To be rid of any water soluble impurities

47
Q

lab 10

Procedure for polymerization

A
  1. add the EGDMA and DMPA to six vials
  2. cap three of the vials and deoxygenate the other three
  3. place the vials in UV, violet, and red lights and observe over 45 min
  4. Create your diff. ratios of polymers and place in the most successful photoreactor
48
Q

lab 10

Which photo reactor was the most sucessful?

A

the UV light

49
Q

lab 10

What was the observed trend as the ratio of HEA to EGDMA increased

A

the polymers got softer as the ratio increased

50
Q

lab 10

mass EGDMA =

A

2(Megdma/Megdma +r*Mhea)

51
Q

lab 10

mass HEA =

A

2- mass EGDMA

52
Q

lab 10

when it comes to radicals what is most important for their stabilization?

A

resonance! if it has resonance that trumps all, if there is no resonance tertiary> secondary> primary

53
Q

lab 10

Why is oxygen bad for polymerization?

A

It inhibits high cross linking by capping the chain ends

54
Q

lab 10

The shorter the wavelength the — the E

A

the higher the energy

OChem 1 lab (2 decks)

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