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Nucleophilic Substitution

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Presentation on theme: "Nucleophilic Substitution"— Presentation transcript:

1 Chapter 6: Organic Halogen Compounds; Substitution and Elimination Reactions

2 Nucleophilic Substitution
Examples of nucleophilic substitution reactions Nucleophile Substrate Leaving group



5 Reaction of sodium ethoxide with bromoethane




9 Nucleophilic Substitution Mechanism
SN2 Mechanism

10 SN2 displacement reactions occure with inversion of configuration
SN2 displacement reactions occure with inversion of configuration. For example, if we treat (R)-2-bromobutane with sodium hydroxide, we obtain (S)-2-butanol




14 Example; Predict the product of the SN2 reaction of cis-4-methylcyclohexyl bromide with cyanide ion

15 Arrange the following compounds in order of decreasing SN2 reactivity toward sodium ethoxide

16 The SN1 Mechanism



19 Which of the following bromides will react faster with methanol (via SN1 reaction)? and what are the reaction products in each case.


21 SN2 reactions in Nature: Biological Methylations

22 HO- > HOH RS- >RSH RO- > ROH
1. Negative ions are more nucleophilic, or better suppliers, than the corresponding neutral molecules. HO- > HOH RS- >RSH RO- > ROH 2. Elements low in the periodic table tend to be more nucleophilic than elements above them in the same column HS- > HO- I- > Br- > Cl- > F- 3. Across a row in the periodic table, more electronegative elements (the more tightly an element holds electron to itself) tend to be less nucleophilic.

23 Which mechanism, SN1 or SN2, would you predict for each of the following reactions?

24 Dehydrohalogenation, and Elimination Reaction; The E2 and E1 Mechanisms


26 E1 mechanism

27 Substitution and Elimination in Competition
Tertiary Halides


29 Primary Halides

30 Ethoxide t-butoxide

31 Secondary Halides

32 Polyhalogenated Aliphatic Compounds

33 Chlorofluorocarbons (CFCs aka Freons)

34 Halons CBrClF2 Bromochlorodifluoromethane (Halon-1211) CBrF3 Bromotrifluoromethane Halon-1301

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