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MIdterm Flashcards

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1
Q

Why are boiling points and refractive indexes used to characterize liquids

A

because they are specific to each molecule and easy to measure.

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2
Q

Why is concentrated sulfuric acid the strong acid of choice in many reactions as opposed to HCL

A

because HCL would produce water and push the reaction toward the reactants and away from the products. This is because HCL is a stronger acid, so it needs more water in solution to make it of equal acidity

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3
Q

Why in the reaction did we extract acetic acid instead of isopentyl alcohol. (Why is acid easier to extract than alcohol)

A

because it has a lower pka than alcohol, which means that it is easier to deprotonate. This induces a charge, which moves it into the aqueous phase

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4
Q

How does using silica beads take advantage of lechatliers principle

A

the silica beads absorb water, removing it from the products side, and pushing the reaction towards the products.

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5
Q

how do you calculate percent yield

A

%yield = (actual yield/possible yield) *100

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6
Q

What will happen if you leave water in your reaction vessel

A

it will push the reaction one way or the other

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7
Q

what will happen if your thermometer is further away from the solution than it should be

A

the measured boiling point will be lower

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8
Q

What does reduction mean

A

(making less bonds to oxygen) going from

=0 to -0-H

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9
Q

What does oxidizing mean

A

(making more bonds to oxygen)

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10
Q

How do you know if a molecule has enantiotopic H’s or diasteriotopic H’s

A
  1. Draw your molecule twice
  2. pick two hydrogens, switch one of them in each drawing to D
  3. Are the drawings superimposable
    (Yes = equivalent H’s)
  4. No = are they mirror images
    (Yes = Enantiotopic H’s)
    (No = Diasteriotopic H’s)
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11
Q

how many stereocenters chage with diastereotopic H’s

A

1

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12
Q

How many stereocenters change with enantiotopic H’s

A

all of them

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13
Q

Which is the order of densities

  1. Diethyl ether
  2. Water
  3. Methylene chloride
A

diethyl ether is least dense, water is middle, methylene chloride is most dense

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14
Q

why is it more effective to perform an extraction with many small portions of solvent as opposed to one large wash

A

because each organic compound has a partition coefficient, which means that only certain amounts of your product will be in both the aqueous and organic phase with each wash. so the more you wash it the more you will be able to extract.

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15
Q

how can you improve resolution during gas chromatography.

A

lower temperature

lower flow rate

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16
Q

Can impurities cause higher melting points

A

nope

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17
Q

how could having more substance affect melting point readings

A

it can cause it to have a broader melting point range because of the time that it will take for the whole substance to melt

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18
Q

what can happen if you have too high of a ramp rate when finding melting points

A

it will cause you to read a lower melting point than normal because the thermometer can’t keep up with the actual temperature increase

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19
Q

what makes a good recrystallization solvent

A

it has to have the right amount of solubility. if it has too low solubility, it won’t dissolve it all. If if has too high solubility then it will be hard to get the crystals to reform.

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20
Q

how does the rate of crystal growth affect it’s purity

A

if it crystallizes too rapidly then impurities will be trapped inside. so if it goes slower then there will be enough time for the impurities to escape.

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21
Q

can you conclude that 2 substances who have both moved to RF = 1 on a TLC plate are the same. Why or why not

A

no you can’t. You could use different solvents, but even then you can’t conclude that they are the same.

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22
Q

what are two advantages of using steam distillation over simple distillation

A
  1. it doesn’t take as much heat to get the product to distillate, which means you don’t have to worry as much about breaking apart your product
  2. since you are distilling it with water, and because it immiscible in water you can then use methylene chloride to separate your product from water.
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23
Q

why is the distillate from the steam distillation of cinnemaldehyde cloudy

A

because the cinnamaldehyde is insoluble in chilled water.

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24
Q

how do you convert from ppm to hertz

A

hertz = ppm x shift (usually 300)

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25
Q

which is usually larger j trans or j cis

A

j trans

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26
Q

What happens when j trans and cis are different

A

a doublet of doublets

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27
Q

what happens when j cis and j trans are equal

A

a triplet

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28
Q

why was the diborane solution added dropwise to the vial in a cooled reaction over time

A

to control the rate of reaction, and prevent runaway reactions. because the reaction is very very reactive.

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29
Q

is 1 octene a lewis acid or a lewis base

A

a lewis base (Electron donor)

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30
Q

is silica gel with silver nitrate a lewvis acid or lewix base

A

acid (electron pair acceptor)

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31
Q

Why does silica gel with silver nitrate bind more readily to 1 octene than the more polar 1 octanol

A

because it forms a complex with the loosly held pi electron s fothe double bond in the octene

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32
Q

What happens if s student runs 1 octene and 1 octanol through a column with ordinary silica gel

A

both will pass through unaffeced becuase silica normally just binds water

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33
Q

what would happen if the solution wasn’t dried well enough before running it through the column

A

the seperation wouldn’t be as effective becuase the water causes it to run through the column too quickly, not giving it time to separate out

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34
Q

what would happen if you ran the hydroboration oxidation reaction in acidic conditions

A

you wouldn’t have the base you need to break up the trialkylborane complex, so that’s what you would get.

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35
Q

how does the cannizarro reaction work

A

one of the ketones is reduced, and the other is made into a carboxylic acid

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36
Q

what are the three steps in performing a recrystallization

A
  1. dissolve the solid and remove the insoluble impurities
  2. let the crystals reform in low temperatures
  3. collect the recrystallized solid via vacuum filtration
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37
Q

what are the steps to separating,
1-4dichlorobenzene
4-chlorobenzoic acid
4-chloroanaline

A
  1. Add MeCl,(all dissolve)
  2. Add base to the solution (deprotonates acid)
    this causes acid to enter water
  3. Remove aqueous layer with acid
  4. add acid to solution (protonates analine)
    analine enters water
  5. extract water layer with analine
  6. evaporate methylene chloride from benzene to isolate benzene
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38
Q

What happens in the diels alder reaction

A

one of the two cis double bonds connects to a double or triple bond. one of those bonds connects to the other of the two cis double bonds. the second cis double bond flips down between where the two double bonds used to be

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39
Q

be able to draw r and s stereocenters

A

oi

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40
Q

do r and s labeled stereocenters always help confirm stereochemistry

A

nope, it doesn’t work on mesocompounds, or compounds with symmetry

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41
Q

how can a compound neither form a racemic mixture or be optically active

A

when you have a mesocompound. mesocompounds have a line of symmetry and are achiral. only achiral compounds are optically active and and they can’t form a racemic mixture

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42
Q

after you quence your solution with ice why did the resulting aqueous layer become acidic

A

H2O + CH3COCl —–> CH3COOH + HCl

because water eliminates the acid chloride and makes an acidic carboxylic acid and HCL

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43
Q

less polar = easier to elute

A

yeah its true

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44
Q

why does cyclopentadiene have such an unusually low pKa value

A

because when the H is pulled off it creates an aromatic ring. aromatic rings are very stable

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45
Q

why do all of the hydrogens for cyclopentadienide have the same chemical shift

A

all of their respective carbons participate equally in resonance/conjugation

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46
Q

what is the 18 electron rule as it pertains to transition metal complexes

A

when a transition metal combines their valence electrons with the valence electrons of the rings binded to it. if the total number of valence electrons = 18 (2s, 6p, 10d) the transition metal has reached a noble gas state

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47
Q

what metals could interact with 2 benzene rings to acheive the stable 18 electron configuration

A

any that have 6 electrons

Fe2+, Cr…

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48
Q

What solvent is found at 7.3 on HNMR and 77 on CNMR

A

CHCL3/CDCL3

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49
Q

What solvent is found at 2.5 on HNMR and 40 on CNMR

A

DMSO

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50
Q

What solvent is found at 3.4 on HNMR

A

DMSO water

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51
Q

What solvent is found at 1.6 on HNMR

A

water

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52
Q

What solvent is found at 0 on both HNMR and CNMR

A

TMS

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53
Q

What is refluxing

A

when you boil your solution with a condenser

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54
Q

What is extraction

A

when we move a compound from one layer to another (organic and aqueous)

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55
Q

What is the first thing to consider with extractions

A

which is more dense

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56
Q

what is the density of water

A

1 g per cm cubed

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57
Q

how do we move something into the aquoues layer

A

make it polar

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58
Q

What is on a TLC plate

A

silica

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59
Q

is silica polar or non polar

A

polar

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60
Q

How do we know which compound is more polar on a TLC plate

A

the one that moves least

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61
Q

What happens as we change the solvent

A

the more polar the solvent is the more the stuff moves, the less polar it is the less it moves

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62
Q

what does nujol mull do to your compound

A

it simply suspends your compound

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63
Q

what is an azeotrope

A

when a compound that when mixed with water they both distill together

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64
Q

what is the purpose of the ice bath in recrystallization

A

to make sure the solution is completely saturated

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65
Q

what makes a good recrystalization solvent

A

high solubility in high temps, low solubility in low temps

66
Q

what are the steps to percent yield finding

A
  1. find the limiting reagent (Check moles in the balanced equation and moles added
  2. change everything to moles
  3. consider the mole ratio
  4. % yield = actual moles/theoretical moles x 100
67
Q

When is an azeotrope formed

A

steam distillation, it allows the organic compound to be separated at a lower bp so it doesn’t disintegrate

68
Q

What is percent recovery

A

the amount of grams you isolated from another source (grams recovered/grams starting material)

69
Q

Safety diamond

A 
0 = no danger
4 = extreme danger
Red = flammability
blue = health hazard
yellow = reactivity
70
Q

how fast should you heat up the sample when looking for mp

A

1-2 degrees per minute

71
Q

in Gas Chromatography what will come out first

A

the less polar stuff

72
Q

what does the area of the peak in GC mean

A

the amount of product

73
Q

what are diastereotopic H’s

A

they are on the same C but give different signals

1C, 2H

74
Q

What are enantiotopic H’s

A

they are on different C’s but give the same signals

2C, 1H

75
Q

how to determine diastereotopic H’s

A
  1. find a stereocenter
  2. find 2 h’s on a carbon (or ch3)
  3. change one of the h’s to d and label the stereocenter
  4. swap the h and d and label the stereocenter
    IF the stereocenter changed then the H’s are diastereotopic
76
Q

which H’s show up more downfield? axial or equitorial?

A

equitorial

77
Q

What are axial and equitorial h’s in relation to eachother

A

diastereotopic

78
Q

What can we figure out from reference molecules

A

h

79
Q

what is the order of operations in HNMR

A
  1. integration
  2. resonance/inductive effects
  3. splitting
80
Q

What is the order of operations to deduce structures

A
  1. Mass spec
  2. IR
  3. CNMR
  4. HNMR
  5. Does everything agree?
81
Q

what is the fischer esterification reaction

A

carboxylic acid + alcohol = ester

82
Q

what is the reaction of the reduction of a ketone

A

ketone to alcohol

83
Q

what is the reaction in photoisomerization

A

used light to switch between cis and trans isomers

84
Q

What is the reaction in hydroboration oxidation

A

alkene to alcohol

85
Q

what is the reaction in the cannizzaro reaction

A

aldehyde = alcohol and carboxylic acid

86
Q

What is the reaction in the Diels alder reaction

A

diene + dienophile = new product

87
Q

What is the reaction in the friedel crafts

A

electrophilic aromatic substitution

88
Q

Where does the csp3-h signal show up on IR

A

just below 3000

89
Q

Where does the OH peak show up on IR

A

broad around 3300

90
Q

where does the C=O peak show up on IR

A

1700

91
Q

Where does the aldehyde peak show up on IR

A

2750

92
Q

what will an aldehyde peak also have on IR

A

a carbonyl peak

93
Q

Where does the carboxylic acid peak show up on IR

A

broad and monstrous around 3500

94
Q

Where does the Csp2-h peak show up on IR

A

above 3000

95
Q

Where does the nujol mull peak show up

A

just under 3000

96
Q

what is the aromatic region in CNMR

A

120 - 160 (CNMR)

97
Q

where do carboxylic acids and thier derivatives show up on CNMR

A

150 - 180

98
Q

Anything above 180 on CNMR is

A

aldehyde or ketone

99
Q

where is the aromatic region on HNMR

A

6-8ppm

100
Q

how do you know if the benzene ring is mono substituted or disubstituted

A

mono - integration of all = 5

Di - integration of all = 4

101
Q

how can you tell when the benzene ring substituants are para or ortho

A 
para = 2 doublets
meta = a singlet
ortho = 2 doublets, 2 triplets
102
Q

how many signals will a monosubstituted benzene ring have on a CNMR

A

4

103
Q

can you get 5 signals from a disubstituted benzene ring on a CNMR

A

nope, if there are 5 you must have an sp2 C there

104
Q

aldehyde vs ketone

A

IR
both have carbonyl peaks
aldehyde has an sp2 bond
HNMR aldehyde would have an H singlet by 10-11

105
Q

Carboxylic acid vs. alcohol

A 
IR 
carbox acid would have a carbonyl peak
both have oh peak
carbox would usually be broader
HNMR
carbox has a peak at 10-13
alcohol has a singlet around 2-3
CNMR
the carboxylic acid C has a peak 150-180
106
Q

Carbox acid vs. ester

A 
IR 
carbox has an OH peak
HNMR
carbox has h peak 10-13
ester has alpha to o peak around 4
107
Q

Ester vs. aldehyde

A

IR
aldehyde has is signature peak around 2700
HNMR
aldehyde has a singlet around 10-11

108
Q

Ester vs. Ketone

A

HNMR
ester alpha to O peak around 4
ketone alpha to carbonyl peak around 2-3
CNMR

109
Q

What happens with an RI when the temperature increases

A

the RI decreases

110
Q

What does an RI actually measure

A

the speed at which the light travels through the liquid

111
Q

What is the word ending for a carboxylic acid

A

oic acid

112
Q

What is the order of increasing polarity of solvents

A

hexane is the least polar
CHCl2
MeOh is most polar

113
Q

what does too much nujol look like

A

every other peak will be pretty small, the CO2 peak will likely be upside down

114
Q

What is an azeotrope

A

when two liquids can’t be seperated by simple diffusion

115
Q

What is the order of common solutes from most polar to leas

A 
H2O
methanol 
ethanol
ethyl acetate
acetone
DCM
ethyl ether
toluene
pet ether
hexane
116
Q

What would happen if all of the solvent was boiled out during reflux

A

the temperature of the reaction would increase and possibly degrade the reactants

117
Q

When you reflux does it boil at the point of your product or the solven

A

the solvent

118
Q

What is extraction

A

organic/polar layers

119
Q

How do we move things to different layers

A

make them polar, protonation/deprotonation

120
Q

What are the steps of recrystallization

A
  1. dissolve
  2. cool
  3. collect
121
Q

What makes a good recrystalization solvent

A

high solublility and high temp, low and low

122
Q

How to do a percent yield

A

find limiting reagent
change everything to moles
consider the mole ratio
yield = moles got/moles possible x 100

123
Q

What is percent recovery

A

moles stuff got/moles stuff used x 100

124
Q

how do you test for diasteriotopic/enantiotopic H’s

A
  1. find equivalent H’s
125
Q

why is it important to know if H’s are enantiotopic or diasteriotopic

A

if they are enantiotopic they are equivalent

if they are diastereotopic they aren’t equivalent

126
Q

What are the rules for aromaticity

A

cyclic
conjugated
planar
4n+2 (electrons)

127
Q

What is typical of an aldehyde

A

name ends with al

IR has 1700 peak and one at 2700

128
Q

What is an amide

A

an NH group hooked onto a carbonyl

129
Q

what is typical of primary amides

A

carbonyl peak

2 NH peaks around 3300

130
Q

what is typical of secondary amides

A

carbonyl peak

1 NH peak around 3300

131
Q

What is typical of a primary amine

A

2 NH peaks around 3300 with no carbonyl

132
Q

What is typical of a secondary amine

A

1 NH peak aroudn 300 with no carbonyl

133
Q

What is an anhydride

A

two carbonyl’s connected by an O

134
Q

What is typical of an anhydride

A

two C=O peaks

135
Q

What is typical of esters

A

C=O stretch
name ends with ate
two C–O peaks

136
Q

How do you name esters

A

name the group not hooked to C=O,

then name the group hooked to C=O and add oate

137
Q

How do you name ethers

A

name simpler group and add oxy then name the rest

138
Q

What is typically of ethers

A

two C-O peaks

139
Q

What is typical of nitriles

A

end with nitrile

have the 2200 C triple bond to N

140
Q

What is typical of nitro groups

A

have nitro in the name

double NO peaks around1500 and 1300

141
Q

what is aniline

A

benzene with an NH2 group

142
Q

does Iodide attack the more or less substituted carbon

A

less

143
Q

how do crown ethers work as phase transfer catalysts

A

they are able to hold cations in the middle and pull them into the organic phase

144
Q

What is the reaction in the william ether synthesis

A

Adding a methyl group to an alcohol with ICH3

uses tetrabutylammonium bromide

145
Q

what is the reaction in aldol condensation

A

addition of two benzaldehydes to acetone

146
Q

What is the reaction in the gringard reaction

A

addition of a benzene ring and OH to benzophenone

147
Q

what determines the broadness of the peak of something that can hydrogen bond

A

the more broad it is, the more that thing hydrogen bonds

148
Q

What is the reaction in benzoin condensation

A

the addition together of 2 benzaldehydes with thiamine

149
Q

what is a meso compound

A

something that can superimpose it’s own mirror image

150
Q

are meso compounds optically active or inactive

A

optically inactive

151
Q

why must you use water and ethanol as solvents sometimes

A

because one you may have to dissolve two compounds that both don’t dissolve in either

152
Q

what are the four criteria that determine whether or not you can purify by sublimation

A
  1. the compound must vaporize without melting
  2. it must be stable enough to vaporize without decomposing
  3. the vapors must be able to condense back to the solid
  4. impurities within the compound do not also vaporize
153
Q

why is sodium carbonate used in caffeine extraction

A

carbonate acts as a buffer to ensure the solubility of the alkaloid

154
Q

When comparing the vapor pressures of different molecules, which ones will sublime first

A

the ones with the highest vapor pressure

155
Q

What happens in the nitration reaction

A

nitro groups are added ortho to phenol

156
Q

why is p nitrophenol a stronger acid than phenol itself?

A

because it withdraws electrons, making the ring more positive, which can stabilize the negative conjugate base

157
Q

how can mixture melting points be helpful when you have two compounds of about the same melting point

A

if it is pure it would have it’s normal melting point, even if it was mixed with something that had the same melting point it would melt lower

158
Q

Why didn’t that one Nitrophenol (most acidic) come out of the column first

A

becuase it was able to intra H bond so that it no longer was as polar as it was before

159
Q

what was the white solid that formed in aspirin when methyl salicylate was added to the sodium solution

A

sodium salicylate

160
Q

Which is more acidic, aspirin or salicylic acid

A

salicylic acid, because it is able to stabilize the conjugate base better because the carbonyl is an electron withdrawing group, the benzene is more positive which stabilizes the negative conjugate base

161
Q

What happens if you let water sit with your aspirin

A

it will revert back to salicylic acid

O. Chem Lab (3 decks)

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