summary & applications (synthesis) s n 1 / e1 vs. s n 2 / e2
DESCRIPTION
Summary & Applications (Synthesis) S N 1 / E1 vs. S N 2 / E2. E2 and E1 Reactions. Substitution vs. Elimination. Alkyl halides can undergo S N 2, S N 1, E2 and E1 Reactions. 1) Which reaction conditions favor S N 2/E2 or S N 1/E1? S N 2/E2 reactions are favored by a high - PowerPoint PPT PresentationTRANSCRIPT
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Summary & Applications (Synthesis)Summary & Applications (Synthesis) S SNN1 / E1 vs. S1 / E1 vs. SNN2 / E22 / E2
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E2 and E1 Reactions
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Substitution vs. EliminationAlkyl halides can undergo SN2, SN1, E2 and E1 Reactions
1) Which reaction conditions favor SN2/E2 or SN1/E1?
•SN2/E2 reactions are favored by a high concentration of nucleophile/strong base
•SN1/E1 reactions are favored by a poor nucleophile/weak base
2) What will be the relative distribution of substitution product vs. elimination product?
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Consider the Substrate
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NOTE: a bulky base encourages elimination over substitution
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Returning to Sn2 and E2:Returning to Sn2 and E2:Considering the differences Considering the differences
Can you predict the products?Can you predict the products?
Br
O
C
H
3
B
r
C
H
3
O
-
+
+
O
C
H
3
Can you explain the products?Can you explain the products?
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Substitution and Elimination Reactions in Synthesis
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A hindered alkyl halide should be used if you want to synthesize an alkene
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Which reaction produces an ether?
CH3CH2Br CH3CO-CH3
CH3
+
CH3CH2O- CH3CBrCH3
CH3
+
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Consecutive E2 Elimination Reactions:Alkynes
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Intermolecular vs. Intramolecular Reactions
• A low concentration of reactant favors an intramolecular reaction• The intramolecular reaction is also favored when a five- or six-membered ring is formed
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Three- and four-membered rings are less easily formed
Three-membered ring compounds are formed more easily than four-membered ring compounds
The likelihood of the reacting groups finding each other decreases sharply when the groups are in compounds that would form seven-membered and larger rings.
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Designing a synthesis …
?
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?CH3 CH3
Br
Br
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