MIdterm Flashcards
(161 cards)
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.
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
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
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.
5
Q
how do you calculate percent yield
A
%yield = (actual yield/possible yield) *100
6
Q
What will happen if you leave water in your reaction vessel
A
it will push the reaction one way or the other
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
8
Q
What does reduction mean
A
(making less bonds to oxygen) going from
=0 to -0-H
9
Q
What does oxidizing mean
A
(making more bonds to oxygen)
10
Q
How do you know if a molecule has enantiotopic H’s or diasteriotopic H’s
A
- Draw your molecule twice
- pick two hydrogens, switch one of them in each drawing to D
- Are the drawings superimposable
(Yes = equivalent H’s) - No = are they mirror images
(Yes = Enantiotopic H’s)
(No = Diasteriotopic H’s)
11
Q
how many stereocenters chage with diastereotopic H’s
A
1
12
Q
How many stereocenters change with enantiotopic H’s
A
all of them
13
Q
Which is the order of densities
- Diethyl ether
- Water
- Methylene chloride
A
diethyl ether is least dense, water is middle, methylene chloride is most dense
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.
15
Q
how can you improve resolution during gas chromatography.
A
lower temperature
lower flow rate
16
Q
Can impurities cause higher melting points
A
nope
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
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
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.
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.
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.
22
Q
what are two advantages of using steam distillation over simple distillation
A
- 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
- 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.
23
Q
why is the distillate from the steam distillation of cinnemaldehyde cloudy
A
because the cinnamaldehyde is insoluble in chilled water.
24
Q
how do you convert from ppm to hertz
A
hertz = ppm x shift (usually 300)
25
which is usually larger j trans or j cis
j trans
26
What happens when j trans and cis are different
a doublet of doublets
27
what happens when j cis and j trans are equal
a triplet
28
why was the diborane solution added dropwise to the vial in a cooled reaction over time
to control the rate of reaction, and prevent runaway reactions. because the reaction is very very reactive.
29
is 1 octene a lewis acid or a lewis base
a lewis base (Electron donor)
30
is silica gel with silver nitrate a lewvis acid or lewix base
acid (electron pair acceptor)
31
Why does silica gel with silver nitrate bind more readily to 1 octene than the more polar 1 octanol
because it forms a complex with the loosly held pi electron s fothe double bond in the octene
32
What happens if s student runs 1 octene and 1 octanol through a column with ordinary silica gel
both will pass through unaffeced becuase silica normally just binds water
33
what would happen if the solution wasn't dried well enough before running it through the column
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
34
what would happen if you ran the hydroboration oxidation reaction in acidic conditions
you wouldn't have the base you need to break up the trialkylborane complex, so that's what you would get.
35
how does the cannizarro reaction work
one of the ketones is reduced, and the other is made into a carboxylic acid
36
what are the three steps in performing a recrystallization
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
37
what are the steps to separating,
1-4dichlorobenzene
4-chlorobenzoic acid
4-chloroanaline
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
38
What happens in the diels alder reaction
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
39
be able to draw r and s stereocenters
oi
40
do r and s labeled stereocenters always help confirm stereochemistry
nope, it doesn't work on mesocompounds, or compounds with symmetry
41
how can a compound neither form a racemic mixture or be optically active
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
42
after you quence your solution with ice why did the resulting aqueous layer become acidic
H2O + CH3COCl -----> CH3COOH + HCl
| because water eliminates the acid chloride and makes an acidic carboxylic acid and HCL
43
less polar = easier to elute
yeah its true
44
why does cyclopentadiene have such an unusually low pKa value
because when the H is pulled off it creates an aromatic ring. aromatic rings are very stable
45
why do all of the hydrogens for cyclopentadienide have the same chemical shift
all of their respective carbons participate equally in resonance/conjugation
46
what is the 18 electron rule as it pertains to transition metal complexes
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
47
what metals could interact with 2 benzene rings to acheive the stable 18 electron configuration
any that have 6 electrons
| Fe2+, Cr...
48
What solvent is found at 7.3 on HNMR and 77 on CNMR
CHCL3/CDCL3
49
What solvent is found at 2.5 on HNMR and 40 on CNMR
DMSO
50
What solvent is found at 3.4 on HNMR
DMSO water
51
What solvent is found at 1.6 on HNMR
water
52
What solvent is found at 0 on both HNMR and CNMR
TMS
53
What is refluxing
when you boil your solution with a condenser
54
What is extraction
when we move a compound from one layer to another (organic and aqueous)
55
What is the first thing to consider with extractions
which is more dense
56
what is the density of water
1 g per cm cubed
57
how do we move something into the aquoues layer
make it polar
58
What is on a TLC plate
silica
59
is silica polar or non polar
polar
60
How do we know which compound is more polar on a TLC plate
the one that moves least
61
What happens as we change the solvent
the more polar the solvent is the more the stuff moves, the less polar it is the less it moves
62
what does nujol mull do to your compound
it simply suspends your compound
63
what is an azeotrope
when a compound that when mixed with water they both distill together
64
what is the purpose of the ice bath in recrystallization
to make sure the solution is completely saturated
65
what makes a good recrystalization solvent
high solubility in high temps, low solubility in low temps
66
what are the steps to percent yield finding
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
When is an azeotrope formed
steam distillation, it allows the organic compound to be separated at a lower bp so it doesn't disintegrate
68
What is percent recovery
the amount of grams you isolated from another source (grams recovered/grams starting material)
69
Safety diamond
```
0 = no danger
4 = extreme danger
Red = flammability
blue = health hazard
yellow = reactivity
```
70
how fast should you heat up the sample when looking for mp
1-2 degrees per minute
71
in Gas Chromatography what will come out first
the less polar stuff
72
what does the area of the peak in GC mean
the amount of product
73
what are diastereotopic H's
they are on the same C but give different signals
| 1C, 2H
74
What are enantiotopic H's
they are on different C's but give the same signals
| 2C, 1H
75
how to determine diastereotopic H's
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
which H's show up more downfield? axial or equitorial?
equitorial
77
What are axial and equitorial h's in relation to eachother
diastereotopic
78
What can we figure out from reference molecules
h
79
what is the order of operations in HNMR
1. integration
2. resonance/inductive effects
3. splitting
80
What is the order of operations to deduce structures
1. Mass spec
2. IR
3. CNMR
4. HNMR
5. Does everything agree?
81
what is the fischer esterification reaction
carboxylic acid + alcohol = ester
82
what is the reaction of the reduction of a ketone
ketone to alcohol
83
what is the reaction in photoisomerization
used light to switch between cis and trans isomers
84
What is the reaction in hydroboration oxidation
alkene to alcohol
85
what is the reaction in the cannizzaro reaction
aldehyde = alcohol and carboxylic acid
86
What is the reaction in the Diels alder reaction
diene + dienophile = new product
87
What is the reaction in the friedel crafts
electrophilic aromatic substitution
88
Where does the csp3-h signal show up on IR
just below 3000
89
Where does the OH peak show up on IR
broad around 3300
90
where does the C=O peak show up on IR
1700
91
Where does the aldehyde peak show up on IR
2750
92
what will an aldehyde peak also have on IR
a carbonyl peak
93
Where does the carboxylic acid peak show up on IR
broad and monstrous around 3500
94
Where does the Csp2-h peak show up on IR
above 3000
95
Where does the nujol mull peak show up
just under 3000
96
what is the aromatic region in CNMR
120 - 160 (CNMR)
97
where do carboxylic acids and thier derivatives show up on CNMR
150 - 180
98
Anything above 180 on CNMR is
aldehyde or ketone
99
where is the aromatic region on HNMR
6-8ppm
100
how do you know if the benzene ring is mono substituted or disubstituted
mono - integration of all = 5
| Di - integration of all = 4
101
how can you tell when the benzene ring substituants are para or ortho
```
para = 2 doublets
meta = a singlet
ortho = 2 doublets, 2 triplets
```
102
how many signals will a monosubstituted benzene ring have on a CNMR
4
103
can you get 5 signals from a disubstituted benzene ring on a CNMR
nope, if there are 5 you must have an sp2 C there
104
aldehyde vs ketone
IR
both have carbonyl peaks
aldehyde has an sp2 bond
HNMR aldehyde would have an H singlet by 10-11
105
Carboxylic acid vs. alcohol
```
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
Carbox acid vs. ester
```
IR
carbox has an OH peak
HNMR
carbox has h peak 10-13
ester has alpha to o peak around 4
```
107
Ester vs. aldehyde
IR
aldehyde has is signature peak around 2700
HNMR
aldehyde has a singlet around 10-11
108
Ester vs. Ketone
HNMR
ester alpha to O peak around 4
ketone alpha to carbonyl peak around 2-3
CNMR
109
What happens with an RI when the temperature increases
the RI decreases
110
What does an RI actually measure
the speed at which the light travels through the liquid
111
What is the word ending for a carboxylic acid
oic acid
112
What is the order of increasing polarity of solvents
hexane is the least polar
CHCl2
MeOh is most polar
113
what does too much nujol look like
every other peak will be pretty small, the CO2 peak will likely be upside down
114
What is an azeotrope
when two liquids can't be seperated by simple diffusion
115
What is the order of common solutes from most polar to leas
```
H2O
methanol
ethanol
ethyl acetate
acetone
DCM
ethyl ether
toluene
pet ether
hexane
```
116
What would happen if all of the solvent was boiled out during reflux
the temperature of the reaction would increase and possibly degrade the reactants
117
When you reflux does it boil at the point of your product or the solven
the solvent
118
What is extraction
organic/polar layers
119
How do we move things to different layers
make them polar, protonation/deprotonation
120
What are the steps of recrystallization
1. dissolve
2. cool
3. collect
121
What makes a good recrystalization solvent
high solublility and high temp, low and low
122
How to do a percent yield
find limiting reagent
change everything to moles
consider the mole ratio
yield = moles got/moles possible x 100
123
What is percent recovery
moles stuff got/moles stuff used x 100
124
how do you test for diasteriotopic/enantiotopic H's
1. find equivalent H's
125
why is it important to know if H's are enantiotopic or diasteriotopic
if they are enantiotopic they are equivalent
| if they are diastereotopic they aren't equivalent
126
What are the rules for aromaticity
cyclic
conjugated
planar
4n+2 (electrons)
127
What is typical of an aldehyde
name ends with al
| IR has 1700 peak and one at 2700
128
What is an amide
an NH group hooked onto a carbonyl
129
what is typical of primary amides
carbonyl peak
| 2 NH peaks around 3300
130
what is typical of secondary amides
carbonyl peak
| 1 NH peak around 3300
131
What is typical of a primary amine
2 NH peaks around 3300 with no carbonyl
132
What is typical of a secondary amine
1 NH peak aroudn 300 with no carbonyl
133
What is an anhydride
two carbonyl's connected by an O
134
What is typical of an anhydride
two C=O peaks
135
What is typical of esters
C=O stretch
name ends with ate
two C--O peaks
136
How do you name esters
name the group not hooked to C=O,
| then name the group hooked to C=O and add oate
137
How do you name ethers
name simpler group and add oxy then name the rest
138
What is typically of ethers
two C-O peaks
139
What is typical of nitriles
end with nitrile
| have the 2200 C triple bond to N
140
What is typical of nitro groups
have nitro in the name
| double NO peaks around1500 and 1300
141
what is aniline
benzene with an NH2 group
142
does Iodide attack the more or less substituted carbon
less
143
how do crown ethers work as phase transfer catalysts
they are able to hold cations in the middle and pull them into the organic phase
144
What is the reaction in the william ether synthesis
Adding a methyl group to an alcohol with ICH3
| uses tetrabutylammonium bromide
145
what is the reaction in aldol condensation
addition of two benzaldehydes to acetone
146
What is the reaction in the gringard reaction
addition of a benzene ring and OH to benzophenone
147
what determines the broadness of the peak of something that can hydrogen bond
the more broad it is, the more that thing hydrogen bonds
148
What is the reaction in benzoin condensation
the addition together of 2 benzaldehydes with thiamine
149
what is a meso compound
something that can superimpose it's own mirror image
150
are meso compounds optically active or inactive
optically inactive
151
why must you use water and ethanol as solvents sometimes
because one you may have to dissolve two compounds that both don't dissolve in either
152
what are the four criteria that determine whether or not you can purify by sublimation
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
why is sodium carbonate used in caffeine extraction
carbonate acts as a buffer to ensure the solubility of the alkaloid
154
When comparing the vapor pressures of different molecules, which ones will sublime first
the ones with the highest vapor pressure
155
What happens in the nitration reaction
nitro groups are added ortho to phenol
156
why is p nitrophenol a stronger acid than phenol itself?
because it withdraws electrons, making the ring more positive, which can stabilize the negative conjugate base
157
how can mixture melting points be helpful when you have two compounds of about the same melting point
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
Why didn't that one Nitrophenol (most acidic) come out of the column first
becuase it was able to intra H bond so that it no longer was as polar as it was before
159
what was the white solid that formed in aspirin when methyl salicylate was added to the sodium solution
sodium salicylate
160
Which is more acidic, aspirin or salicylic acid
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
What happens if you let water sit with your aspirin
it will revert back to salicylic acid
