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114 Cards in this Set

  • Front
  • Back
1. What is an extraction?
The removal of a compound from a mixture or solid using a solvent
-solid-liquid extraction
-liquid-liquid extraction
2. How do extractions work?
Like dissolves like

-polar compound/polar solvent (water, alcohol, acetic acid)
-non-polar compound/non-polar solvent (diethyl ether, hexane, benzene)
3. What is the difference between polar and non-polar compounds?
1. Polar Compounds:
-May have functional groups w/ dipole moment
2. Non-Polar Compounds:
-Typically organic
4. In a chemically active extraction where is the aqueous layer and where is the organic layer?
The aqueous layer will always be on the bottom and the organic layer will always be the top layer
5. What is a chemically active extraction?
Use acid/base chemistry to change the preference of an organic compound from one solvent to another

-use organic base to accept proton and organic acid to donate proton
8. What is the rate for an E₁ reaction?

What is the rate for an E₂ reaction?
E₁ rate = k[substrate]
*1st order

E₂ rate = k[substrate][base]
*2nd order
9. What type of base is used in an E₁ reaction?

What type of base is used in an E₂ reaction?
E₁: weak, uncharged base
(water, ROH, :NR₃)

E₂: strong base
(RO-, -OH, nbutyl Li, -NR₂)
10. What is the substrate substitution preference for both E₁ and E₂ reactions?
3⁰ > 2⁰ >> 1⁰
11. What type of leaving group is required for both E₁ and E₂ reactions?
Good Leaving Group

*OH is not good leaving group, have to make it into water
12. Are E₁ reaction concerted?

Are E₂ reaction concerted?
E₁ reactions are not concerted (carbocation intermediate)

E₂ reactions are concerted
(one step)
13. What is the zaitsev product?
Thermodynamic product
-more stable product
-i.e. internal double bond
14. What is the hoffman product?
Kinetic product
-forms faster
15. What is the rate determining step in an E₁ reaction?
Departure of leaving group to from a carbocation intermediate
16. What is a dehydration reaction?
An E₁ reaction in which water is removed from an alcohol to form an alkene
17. What is used to catalyze dehydration reactions and how does it help?
Strong acid catalyzes the transformation of the hydroxyl group into a better leaving group (water)
19. What are the three definitions of oxidation in organic chemistry?
1. Insertion of oxygen into a double bond

2. Loss of H₂ across a bond

3. Replace H with a more elctronegative atom
20. What happens to most primary alcohols when they are oxidized?
They are usually over oxidized into a carboxylic acid
21. What is Jones reagent?

What will it oxidize a primary alcohol to? secondary alcohol to?

1⁰ alcohol to carboxylic acid
2⁰ alcohol to a ketone
22. What type of conditions does KMno₄ require?

What KMnO₄ oxidize a primary alcohol to? secondary alcohol to?
Can use in basic (-OH) or acidic (H+) conditions

1⁰ alcohol to carboxylic acid
2⁰ alcohol to ketone
23. What is PCC?
Pyridinium Chloro-Chromate

24. What does PCC oxidize a primary alcohol to?
An aldehyde
25. Can tertiary alcohol be oxidized? why or why not?
Not easily oxidized because there are no H's to remove (very difficult to remove a methyl group)
26. What reagents can be used to oxidize an aldehyde to a carboxylic acid?
KMnO₄ w/ H+ or -OH

Tollins [Ag(NH₃)₂+/H+]
27. What are the three definitions of reduction in organic chemistry?
1. Loss of C-O bond

2. Gain of C-H bond

3. Replace an electronegative atom w/ H
28. What is used in catalytic hydrogenation method?

What conditions does it require?
H₂/Pt or Pd

Need high heat and high pressure
29. What will catalytic hydrogenation reduce?
Reduce carbonyls to alcohols
(aldehyde to 1⁰ alcohol)
(ketone to 2⁰ alcohol)

Reduce alkenes to alkanes
30. What are the three hydride reagents used in reduction reactions?
31. What does sodium borohydride do?
A mild reagent (not explosive with water) that selectively reduces aldehydes and ketones

*won't reduce alkenes
32. What does lithium aluminum hydride to?
It reduces aldehydes, ketones, carboxylic acids, and esters

*is explosive with water
33. How many molecules will one molecule of LiAlH₄ or NaBH₄ reduce?
Four molecules because there are 4 moles of H- per 1 mole of hydride reagent
34. What does LiAl(tBuO₃)H do?
Specifically reduces acid chlorides
35. What is the mechanism for sodium borohydride reduction?
36. What is an extraction?
Remove product from solid reaction mass or a crude reaction solution

*use organic solvent
37. What is recrystallization used for?
Purify a non-volatile solid
38. How does recrystallization work?
Dissolve impure compound in hot solvent then cool slowly and as solution cools pure crystals grow
39. What are the three stages of solubility?
1. Collision: hot molecules of solvent collide with crystal lattice of impure solid

2. Dissociation: dissociation of solid mol from lattice

3. Solvation: hydration shell
40. What are the six characteristics of a good solvent for recrystallization?
1. High temperature coefficient
2. Solve dissolves not melts target compound
3. Dissolves impurities even when cold or not at all
4. Inexpensive
5. Volatile
6. Inert
41. Why are hot filtrations important in the recrystallization process?
It helps to remove impurities that are not soluble in the hot solvent
42. Why is charcoal added when the solution is hot?
It helps to remove impurities by adsorbing them

*organic molecules (impurities) stick to its surface
*some of produce will also stick to charcoal (lower percent recovery)
43. What is the most common way to grow crystals?
Cool slowly at room temperature

*if cool too rapidly impurities will be trapped inside the crystal lattice
44. What are three ways to induce nucleation (crystal growth)?
1. Scratch the side of the glass flask with a stirring rod (bits of glass act as seeds)
2. Seeding: add some pure compound to flask as it cools
3. Add another solvent that has a different polarity
45. What does Kd measure?

What does it mean if its greater than or less than one?
Kd measure partitioning

Kd >>>> 1: non-polar compound

Kd <<<< 1: polar compound
46. What are intensive properties?
Not dependent on amount of material present

-BP, MP, density, molecular weight
47. What are extensive properties?
Dependent on the amount of material present

-volume, mass, concentration
48. What is the purpose of taking the melting point?
1. Check purity of known compound

2. Identify an unknown compound
49. How should the melting point be reported?
Report as a range of temperatures (when first begins to melt and when completely liquefied)

*for pure compound, range is within 2⁰ C
50. Why do impurities in a solid typically lower the MP compared to the pure compound?
Impurities will interfere with the crystal lattice and as a result weaken the intermolecular forces

*MP lowers b/c less NRG is need to disrupt the crystal lattice since it is weakened
51. What is an eutectic mixture?
A mixture of 2 solids that melt like a pure compound
52. What is the definition of boiling point?
Temperature at which the partial pressure of a liquid equals atmospheric pressure
53. What are two processes that can cause a liquid to boil?
1. Increase the temperature

2. Decrease pressure (outside pressure)
54. Why is simple distillation used?
1. Technique to purify volatile liquids

2 Method for determining BP
55. How does simple distillation work?
a liquid is purified by vaporization and condensation

Vaporized by heat and condenses back to liquid when touches cold condensor
56. What does the condenser do?
It keeps it at a constant volume
57. What is column chromatography used for?
Used to separate a crude mixture based upon polarity
58. What is inside the column?
Stationary Phase (solid; polar)
-silica (acidic)
-alumina (basic)
59. What is the mobile phase is column chromatography?
Liquid organic solvent

*stationary phase does not dissolve in mobile phase
60. What is packing?

What is conditioning?
Packing is when add stationary phase to glass column

Conditioning is when add mobile phase to column to "wet" the stationary phase
61. When a non-polar solvent is added to column what happens?
Solvent dissolves the non-polar compounds and they elute first

*polar compounds remain in column and stick to stationary phase
62. How does one remove other polar compounds from the compound?
Gradually switch to a more polar solvent
63. As molecules move through the column what is happening?
Adsorption and desorption

-like sticks to like
64. What is an isocratic column?

What is a gradient column?
An isocratic column is when only one solvent is used

A gradient column is when more than one solvent is used (start w/ most non-polar and go to most polar)
65. What are the two ways to pack?
1. Dry pack: add powder (SP) by itself

2. Slurry packing: add SP to column via a slurry in the eluent (mixture of solid and liquid)
66. What is the eluent?
Mobile Phase
67. What are the three uses for thin-layer chromatography (TLC)?
1. Check purity
2. Identify compound
3. Check reaction progress
68. Why do you have better resolution in TLC?
Particles are more thinly divided and have more surface area for adsorption and desorption thus get better separation/resolution
69. What is the stationary phase in TLC?
SP is silica or alumina and it is on a glass plate
70. How does TLC work?
1. Spot on origin line
2. Put into developing chamber
*want spots above MP
3. Stop when reach solvent front and circle spots that appeared
71. What is the mobile phase in TLC?
Mobile phase is a liquid (organic solvent) that is in beaker of developing chamber
72. What is the retention factor
The retention factor is the distance traveled by a particular spot divided by the distance traveled by the solvent front
73. What is the retention factor important?
Useful for determining the polarity of a molecule

*Large retention factor indicates that the molecule is non-polar (traveled a larger distance on the TLC plate)
74. How can purity be determined for TLC?
If one spot: one component
(pure compound)

2 or more spots: Impure (starting material present or side rxns)
75. Where are more polar compounds on a TLC?

Where are non-polar compounds on a TLC?
Polar compounds are close to origin front (stick to polar plate not mobile phase)

Non-polar compounds are further from origin front (dissolve in MP and move along plate)
76. Why is gas chromatograph used?

How does it separate compounds?
Used to identify unknown compound and/or check purity

Separates components based on BP
77. How do the components elude in gas chromatography?
Lowest BP elute first then middle BP and last are the highest BP
How is separation achieved in TLC?
Separation by capillary action
78. What is Kp?

What does a Kp less than or greater than one mean?
Kp is partition coefficient

Kp > 1: prefer SP/ high BP

Kp < 1: prefer MP/ low BP
79. What is the stationary phase in GC?

What is the mobile phase in GC?
Stationary phase: liquid w/ high BP

Mobile Phase: gas
80. What is the method of separation in column chromatography? GC?
CC: adsorption/desorption

GC: dissolve in SP
81. What compounds can be separated by CC? by GC?
CC: solid or liquid

GC: liquids at room temperature
82. Describe the liquid stationary phase?
1. High boiling liquid coating on inside of coil
2. Thermally stable
3. Chemically inert
4. Typically polar
5. Non-volatile
83. What two things can learned from GC via calculations?
1. Retention time

2. Percent composition
84. How are the results of GC interpreted?
85. What are four ways to increase the retention time of compounds in a GC separation?
1. Decrease temperature
2. Lengthen the column
3. Decrease the flow rate
4. Change the chart speed
86. How do you determine retention time for TLC? for GC?
(origin to spot / origin to solvent front)

injection port to middle of peak/ chart recorder speed
87. How do you determine percent composition?
area of peak/Σarea for all peaks
88. What is fractional distillation?
Purification technique used to purify or separate a mixture of two liquids through vaporizations and condensations
89. What are the requirements for the two liquids in fractional distillation?
1. BP of 2 liquids are within 25⁰C of one another

2. Miscible (soluble w/in one another)
90. The boiling point of a mixture of liquids depends on what two things?
1. Partial Pressure of each component

2. Concentration of each component
91. What is separation based upon in fractional distillation?
Separated by BP

-Lowest BP boils first so removed first
92. What does the fractionating column do?

How does it do this?
It performs separation of 2 liquids

As mixture travels up column, a series of simple distillations take place on the beads
93. In what order does elution occur in fractional distillation?
Low BP compound stays in vapor phase and is removed first while the high BP compound remains in the liquid phase
94. What does the height equivalent per theoretical plate (HETP) measure?
Measure of the efficiency of separation for a given column

-each type of column has a different HETP
-increase HETP = greater resolution
95. What is a theoretical plate?
A cycle of vaporization and condensation
96. How does an ideal chart from fractional distillation look?
97. How does the chart look if the variac is too low?
Too Low
98. How does the chart look if the variac is too high or have an azeotrope?
Too High/Azeotrop
99. What is an azeotrope?
A mixture of two liquids that boil as a pure compound
100. What are the two types of azeotropes?
1. Minimum boiling azeotrope:
BP of mixture is lower than that of each pure compounds

2. Maximum boiling azeotrope:
BP is higher for mixture than for each pure liquid
101. What is one way to get better separation in fractional distillation?
Use a longer column
102. What is reflux?
Heating without loss of volume
103. What is sublimation?
Purify a volatile solid

(go from solid to gas directly and then back to solid by using a cold finger)
104. What is vacuum filtration?

When is it used most often?
Simplest method of removing solids from solutions

-used quite frequently to remove drying agents or solids after recrystallization
105. What is hot gravity filtration?

When is it used most often?
Method of removing suspended solids from a solution without the use of vacuum

-necessary when attempting to keep a solution warm while filtering
-most often used during recrystallization, due to the need to remove decolorizing carbon or other suspended solid impurities.
106. What is the main difference between simple distillation and fractional distillation?
Use of fractionating column used during fractional distillation
(numerous simple distillations)
107. What is the purpose of adding a drying agent
To remove water from an organic solvent
108. What is washing?
Remove water soluble impurities and salts

*use an aqueous solution (saturated NaCl, water)
109. Which is done first, extraction or washing?
Extract before washing
110. What is IR spectroscopy used for?
Good for determining functional groups
111. What is the formula for determining degrees of unsaturation?
⁰ unsat.= 2(#C)+2+#N-#X-#H(given)
112. What are the 3 parts to NMR (nuclear magnetic resonance)?
1. NMR active nuclei spin

2. An applied B field creates 2 spin state (+1/2 & -1/2)

3. Resonance is a process of excitation and relaxation that produces a peak
113. Which spin state is higher in energy? Why?
-1/2 spin state is higher in energy

-Higher in energy because it is against the B field
114. What three things can be learn from a NMR?
1. Types of H: 1 type = 1 signal
2. # of identical H's (integration # on spectrum)
3. Chemical environment of each H (chemical shift)
115. What does the n+1 rule tell us about?
Splitting pattern

-n is number of adjacent H's
-n+1 tells how many lines will be in a signal
116. How many neighbors would a singlet have? a doublet have? a triplet have? a multiplet have?
Singlet: no neighbor H's
Doublet: 1 neighbor H
Triplet: 2 neighbor H's
Multiplet: many neighbor H's