Organic Chemistry I

7.1
Show the product of the following S
N
2 reaction (CN- is the nucleophile):
7.2
Show reaction mechanism of the reactions.
7.3
Show the detailed mechanism for above reaction of (S)-3-bromo-3-methylhexane and water.
274 | Answers to Practice Questions Chapter 7

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7.4
Show the product(s) of the following reactions:
Answers to Practice Questions Chapter 7 | 275

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276 | Answers to Practice Questions Chapter 7

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CHAPTER 8 ELIMINATION REACTIONS
Nucleophilic substitution reaction is not the only possible reaction for alkyl halides and other substrates with a good
leaving group. These substrates could also undergo elimination reaction. In an
elimination
reaction, a small molecule
(XY) is removed from two adjacent atoms of the reactant, and a multiple bond is formed in the product:
Figure 8.0a General equation of elimination reaction
For elimination reaction of alkyl halides, the major product alkene is produced together with the small HX (X is halogen)
molecule, which is the side inorganic product. Such reaction with removal of a proton and a halide ion is called
dehydrohalogenation
. Dehydrohalogenation is a commonly applied method for the synthesis of alkene.
Figure 8.0b Dehydrohalogenation of alkyl halide
In the discussions of elimination reaction, the carbon atom that bonded to the leaving group (halogen for alkyl halide)
is called the
alpha (
α
) carbon
atom, and the carbon atom adjacent to
α
-carbon is called the
beta (
β
) carbon
atom. In
dehydrohalogenation, it is the hydrogen atom on
β
-carbon that is eliminated together with halogen, as HX, therefore the
reaction is often called as