1. More About the Families in Group II
The families in Group II all have an electronegative atom or group
that is attached to an sp3 carbon.
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2. Strongly Basic Leaving Groups Cannot Be Displaced
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3. Acid Converts the Poor Leaving Group into a Good Leaving Group
Alcohols have to be “activated” before they can react.
Only weakly basic nucleophiles can be used.
Strongly basic nucleophiles would react with the proton.
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4. Primary and Secondary alcohols require heat; tertiary alcohols do not.
Converting Alcohols to Alkyl Halides
Primary and Secondary alcohols require heat; tertiary alcohols do not.
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5. The Reactions of Secondary and Tertiary Alcohols
with Hydrogen Halides are SN1 Reactions
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6. An SN1 Reaction Creates a Carbocation Intermediate,
So Watch Out for Carbocation Rearrangements
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7. Ring Expansion
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8. The Reactions of Primary Alcohols
with Hydrogen Halides are SN2 Reactions
Recall that Br– is a good nucleophile in a protic solvent.
Alcohols undergo SN1 reactions unless they would have to form a primary carbocation.
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9. Cl– is the Poorest Nucleophile of the Halide Ions
ZnCl2 increases the rate of the reaction
by creating a better leaving group than water.
רשות
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10. Why is It Important to Be Able to Convert Alcohols to Alkyl Halides?
Alcohols are readily available but unreactive.
Alkyl halides are less available but reactive and
can be used to synthesized a wide variety of compounds.
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11. phosphorus tribromide, phosphorus trichloride, thionyl chloride
Other Methods to Convert
Alcohols into Alkyl Halides
phosphorus tribromide, phosphorus trichloride, thionyl chloride
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12. The Mechanism for the Reaction with PBr3 or PCl3
רשות
A bromophosphite (chlorophosphite) group
is a better leaving group than a halide ion.
Pyridine is the solvent and acts as a base.
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13. The Mechanism for the Reaction with SOCl2
רשות
A chlorosulfite group is a better leaving group than a halide ion.
Pyridine is the solvent and acts as a base.
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14. Converting Alcohols to Alkyl Halides
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15. Primary and Secondary Alcohols Can Be Activated by Being Converted to Sulfonate Esters
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16. A Sulfonic Acid is a Strong Acid
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17. Common Sulfonyl Chlorides
tosyl chloride = TsCl
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18. The Mechanism
רשות
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19. A Sulfonate Ester Reacts with Nucleophiles
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20. Dehydration of an Alcohol
Dehydration of an alcohol is an elimination reaction.
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21. Dehydration is a Reversible Reaction
To prevent the alkene from adding water and reforming the alcohol,
the water is removed as it is formed.
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22. Dehydration of Secondary and Tertiary Alcohols are E1 Reactions
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23. Dehydration The major product is the more stable alkene.
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24. The More Stable Alkene Has the More Stable Transition State
Leading to Its Formation
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25. Tertiary Alcohols are the Easiest to Dehydrate
The rate of dehydration reflects the ease of carbocation formation.
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26. An E1 Reaction Creates a Carbocation Intermediate, So Watch Out for Carbocation Rearrangements
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27. Dehydration of a Primary Alcohol is an E2 Reaction
Both E2 and SN2 products are obtained.
Alcohols undergo E1 reactions unless they would have to form a primary carbocation.
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28. Dehydration The major product is the stereoisomer with the
largest groups on opposite sides of the double bond.
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29. Oxidation of Secondary Alcohols
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30. Oxidation of Primary Alcohols
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31. Tertiary Alcohols Cannot Be Oxidized to a Carbonyl Compound
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32. Oxidation by Hypochlorous Acid (HOCl)
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33. The Mechanism
רשות
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34. Alcohols and Ethers Have Similar Leaving Groups
Alcohols and ethers have to be “activated” before the compounds can react.
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35. The Leaving Group of an Ether Can Be Activated by Protonation
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36. The Mechanism
If a relatively stable carbocation is formed when ROH leaves,
it will be an SN1 reaction.
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37. it will be an SN2 reaction.
The Mechanism
If a relatively stable carbocation would not be formed when ROH leaves,
it will be an SN2 reaction.
Ethers undergo SN1 reactions unless they would have to form a primary carbocation.
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38. Nomenclature of Epoxides
6-אלקנים

39. Epoxides are More Reactive Than Ethers Because of Ring Strain
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40. The Acid-Catalyzed Mechanism
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41. If the Epoxide is Not Symmetrical,
Which Carbon Does the Nucleophile Attack?
The nucleophile attacks the more substituted ring carbon.
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42. Under Acidic Conditions the Nucleophile Attacks the More Substituted Ring Carbon
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43. Under Neutral or Basic Conditions the Nucleophile Attacks the Less Substituted Carbon
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44. The Conditions Determine the Site of Nucleophilic Attack
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45. Using Epoxides in Synthesis
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46. ריאגנט גריניאר
Grignard Reagents: Alkylmagnesium halide, RMgX, produced from reaction of alkyl halides, RX, with magnesium metal in ether or tetrahydrofuran (THF) solvent
The carbon atom is both nucleophilic and basic
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47. ריאגנט גריניאר
They react with weak acids such as H2O, ROH, RCO2H, and RNH2 to abstract a proton and yield hydrocarbons
Since hydrocarbons are weak acids, with pKa’s in the range of 44 to 60, carbon anions are very strong bases
Because even trace amounts of moisture can destroy an organometallic compound, it is important that all reagents be dry when organometallic compounds are being synthesized and when they react with other reagents
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48. מחמצנים ומחזרים ביולוגיים
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49. מנגנון [רשות]
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50. An Unusual Antibiotic[העשרה]
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