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114 Cards in this Set
- Front
- Back
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1. What is an extraction?
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The removal of a compound from a mixture or solid using a solvent
-solid-liquid extraction -liquid-liquid extraction |
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2. How do extractions work?
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Like dissolves like
-polar compound/polar solvent (water, alcohol, acetic acid) -non-polar compound/non-polar solvent (diethyl ether, hexane, benzene) |
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3. What is the difference between polar and non-polar compounds?
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1. Polar Compounds:
-Charged -May have functional groups w/ dipole moment 2. Non-Polar Compounds: -Uncharged -Typically organic |
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4. In a chemically active extraction where is the aqueous layer and where is the organic layer?
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The aqueous layer will always be on the bottom and the organic layer will always be the top layer
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5. What is a chemically active extraction?
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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 |
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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 |
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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) |
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10. What is the substrate substitution preference for both E₁ and E₂ reactions?
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3⁰ > 2⁰ >> 1⁰
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11. What type of leaving group is required for both E₁ and E₂ reactions?
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Good Leaving Group
*OH is not good leaving group, have to make it into water |
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12. Are E₁ reaction concerted?
Are E₂ reaction concerted? |
E₁ reactions are not concerted (carbocation intermediate)
E₂ reactions are concerted (one step) |
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13. What is the zaitsev product?
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Thermodynamic product
-more stable product -i.e. internal double bond |
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14. What is the hoffman product?
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Kinetic product
-forms faster |
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15. What is the rate determining step in an E₁ reaction?
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Departure of leaving group to from a carbocation intermediate
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16. What is a dehydration reaction?
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An E₁ reaction in which water is removed from an alcohol to form an alkene
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17. What is used to catalyze dehydration reactions and how does it help?
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Strong acid catalyzes the transformation of the hydroxyl group into a better leaving group (water)
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19. What are the three definitions of oxidation in organic chemistry?
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1. Insertion of oxygen into a double bond
2. Loss of H₂ across a bond 3. Replace H with a more elctronegative atom |
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20. What happens to most primary alcohols when they are oxidized?
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They are usually over oxidized into a carboxylic acid
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21. What is Jones reagent?
What will it oxidize a primary alcohol to? secondary alcohol to? |
CrO₃/H+
1⁰ alcohol to carboxylic acid 2⁰ alcohol to a ketone |
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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 |
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23. What is PCC?
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Pyridinium Chloro-Chromate
CrO₃/pyridine |
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24. What does PCC oxidize a primary alcohol to?
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An aldehyde
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25. Can tertiary alcohol be oxidized? why or why not?
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Not easily oxidized because there are no H's to remove (very difficult to remove a methyl group)
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26. What reagents can be used to oxidize an aldehyde to a carboxylic acid?
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KMnO₄ w/ H+ or -OH
Tollins [Ag(NH₃)₂+/H+] |
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27. What are the three definitions of reduction in organic chemistry?
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1. Loss of C-O bond
2. Gain of C-H bond 3. Replace an electronegative atom w/ H |
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28. What is used in catalytic hydrogenation method?
What conditions does it require? |
H₂/Pt or Pd
Need high heat and high pressure |
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29. What will catalytic hydrogenation reduce?
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Reduce carbonyls to alcohols
(aldehyde to 1⁰ alcohol) (ketone to 2⁰ alcohol) Reduce alkenes to alkanes |
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30. What are the three hydride reagents used in reduction reactions?
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NaBH₄/H+
LiAlH₄/H+ LiAl(tOBu)₃H |
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31. What does sodium borohydride do?
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A mild reagent (not explosive with water) that selectively reduces aldehydes and ketones
*won't reduce alkenes |
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32. What does lithium aluminum hydride to?
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It reduces aldehydes, ketones, carboxylic acids, and esters
*is explosive with water |
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33. How many molecules will one molecule of LiAlH₄ or NaBH₄ reduce?
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Four molecules because there are 4 moles of H- per 1 mole of hydride reagent
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34. What does LiAl(tBuO₃)H do?
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Specifically reduces acid chlorides
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35. What is the mechanism for sodium borohydride reduction?
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Mechanism
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36. What is an extraction?
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Remove product from solid reaction mass or a crude reaction solution
*use organic solvent |
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37. What is recrystallization used for?
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Purify a non-volatile solid
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38. How does recrystallization work?
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Dissolve impure compound in hot solvent then cool slowly and as solution cools pure crystals grow
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39. What are the three stages of solubility?
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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 |
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40. What are the six characteristics of a good solvent for recrystallization?
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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 |
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41. Why are hot filtrations important in the recrystallization process?
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It helps to remove impurities that are not soluble in the hot solvent
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42. Why is charcoal added when the solution is hot?
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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) |
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43. What is the most common way to grow crystals?
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Cool slowly at room temperature
*if cool too rapidly impurities will be trapped inside the crystal lattice |
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44. What are three ways to induce nucleation (crystal growth)?
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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 |
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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 |
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46. What are intensive properties?
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Not dependent on amount of material present
-BP, MP, density, molecular weight |
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47. What are extensive properties?
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Dependent on the amount of material present
-volume, mass, concentration |
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48. What is the purpose of taking the melting point?
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1. Check purity of known compound
2. Identify an unknown compound |
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49. How should the melting point be reported?
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Report as a range of temperatures (when first begins to melt and when completely liquefied)
*for pure compound, range is within 2⁰ C |
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50. Why do impurities in a solid typically lower the MP compared to the pure compound?
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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 |
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51. What is an eutectic mixture?
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A mixture of 2 solids that melt like a pure compound
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52. What is the definition of boiling point?
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Temperature at which the partial pressure of a liquid equals atmospheric pressure
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53. What are two processes that can cause a liquid to boil?
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1. Increase the temperature
2. Decrease pressure (outside pressure) |
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54. Why is simple distillation used?
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1. Technique to purify volatile liquids
2 Method for determining BP |
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55. How does simple distillation work?
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a liquid is purified by vaporization and condensation
Vaporized by heat and condenses back to liquid when touches cold condensor |
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56. What does the condenser do?
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It keeps it at a constant volume
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57. What is column chromatography used for?
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Used to separate a crude mixture based upon polarity
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58. What is inside the column?
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Stationary Phase (solid; polar)
-silica (acidic) -alumina (basic) |
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59. What is the mobile phase is column chromatography?
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Liquid organic solvent
*stationary phase does not dissolve in mobile phase |
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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 |
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61. When a non-polar solvent is added to column what happens?
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Solvent dissolves the non-polar compounds and they elute first
*polar compounds remain in column and stick to stationary phase |
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62. How does one remove other polar compounds from the compound?
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Gradually switch to a more polar solvent
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63. As molecules move through the column what is happening?
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Adsorption and desorption
-like sticks to like |
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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) |
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65. What are the two ways to pack?
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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) |
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66. What is the eluent?
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Mobile Phase
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67. What are the three uses for thin-layer chromatography (TLC)?
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1. Check purity
2. Identify compound 3. Check reaction progress |
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68. Why do you have better resolution in TLC?
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Particles are more thinly divided and have more surface area for adsorption and desorption thus get better separation/resolution
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69. What is the stationary phase in TLC?
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SP is silica or alumina and it is on a glass plate
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70. How does TLC work?
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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 |
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71. What is the mobile phase in TLC?
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Mobile phase is a liquid (organic solvent) that is in beaker of developing chamber
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72. What is the retention factor
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The retention factor is the distance traveled by a particular spot divided by the distance traveled by the solvent front
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73. What is the retention factor important?
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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) |
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74. How can purity be determined for TLC?
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If one spot: one component
(pure compound) 2 or more spots: Impure (starting material present or side rxns) |
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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) |
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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 |
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77. How do the components elude in gas chromatography?
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Lowest BP elute first then middle BP and last are the highest BP
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How is separation achieved in TLC?
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Separation by capillary action
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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 |
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79. What is the stationary phase in GC?
What is the mobile phase in GC? |
Stationary phase: liquid w/ high BP
Mobile Phase: gas |
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80. What is the method of separation in column chromatography? GC?
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CC: adsorption/desorption
GC: dissolve in SP |
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81. What compounds can be separated by CC? by GC?
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CC: solid or liquid
GC: liquids at room temperature |
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82. Describe the liquid stationary phase?
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1. High boiling liquid coating on inside of coil
2. Thermally stable 3. Chemically inert 4. Typically polar 5. Non-volatile |
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83. What two things can learned from GC via calculations?
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1. Retention time
2. Percent composition |
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84. How are the results of GC interpreted?
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Interpretation
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85. What are four ways to increase the retention time of compounds in a GC separation?
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1. Decrease temperature
2. Lengthen the column 3. Decrease the flow rate 4. Change the chart speed |
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86. How do you determine retention time for TLC? for GC?
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TLC: Y/X
(origin to spot / origin to solvent front) GC: injection port to middle of peak/ chart recorder speed |
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87. How do you determine percent composition?
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area of peak/Σarea for all peaks
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88. What is fractional distillation?
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Purification technique used to purify or separate a mixture of two liquids through vaporizations and condensations
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89. What are the requirements for the two liquids in fractional distillation?
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1. BP of 2 liquids are within 25⁰C of one another
2. Miscible (soluble w/in one another) |
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90. The boiling point of a mixture of liquids depends on what two things?
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1. Partial Pressure of each component
2. Concentration of each component |
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91. What is separation based upon in fractional distillation?
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Separated by BP
-Lowest BP boils first so removed first |
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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 |
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93. In what order does elution occur in fractional distillation?
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Low BP compound stays in vapor phase and is removed first while the high BP compound remains in the liquid phase
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94. What does the height equivalent per theoretical plate (HETP) measure?
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Measure of the efficiency of separation for a given column
-each type of column has a different HETP -increase HETP = greater resolution |
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95. What is a theoretical plate?
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A cycle of vaporization and condensation
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96. How does an ideal chart from fractional distillation look?
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Ideal
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97. How does the chart look if the variac is too low?
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Too Low
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98. How does the chart look if the variac is too high or have an azeotrope?
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Too High/Azeotrop
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99. What is an azeotrope?
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A mixture of two liquids that boil as a pure compound
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100. What are the two types of azeotropes?
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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 |
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101. What is one way to get better separation in fractional distillation?
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Use a longer column
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102. What is reflux?
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Heating without loss of volume
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103. What is sublimation?
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Purify a volatile solid
(go from solid to gas directly and then back to solid by using a cold finger) |
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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 |
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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. |
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106. What is the main difference between simple distillation and fractional distillation?
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Use of fractionating column used during fractional distillation
(numerous simple distillations) |
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107. What is the purpose of adding a drying agent
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To remove water from an organic solvent
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108. What is washing?
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Remove water soluble impurities and salts
*use an aqueous solution (saturated NaCl, water) |
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109. Which is done first, extraction or washing?
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Extract before washing
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110. What is IR spectroscopy used for?
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Good for determining functional groups
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111. What is the formula for determining degrees of unsaturation?
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⁰ unsat.= 2(#C)+2+#N-#X-#H(given)
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112. What are the 3 parts to NMR (nuclear magnetic resonance)?
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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 |
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113. Which spin state is higher in energy? Why?
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-1/2 spin state is higher in energy
-Higher in energy because it is against the B field |
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114. What three things can be learn from a NMR?
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1. Types of H: 1 type = 1 signal
2. # of identical H's (integration # on spectrum) 3. Chemical environment of each H (chemical shift) |
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115. What does the n+1 rule tell us about?
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Splitting pattern
-n is number of adjacent H's -n+1 tells how many lines will be in a signal |
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116. How many neighbors would a singlet have? a doublet have? a triplet have? a multiplet have?
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Singlet: no neighbor H's
Doublet: 1 neighbor H Triplet: 2 neighbor H's Multiplet: many neighbor H's |
