Electrophilic Addition Uni Year 1 Worksheet

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1
Year
Organic Tutorial
st
Trinity 2011
Electrophilic Addition to C=C and C≡C
This includes both polar and radical reactions, but do the polar ones first. It excludes
nucleophilic addition to C=C-C=O (Michael additions) for the moment
Reading: Sykes will cover all of the topics listed below, some Primers are also suggested. Read
and learn the general chemistry (preparation and properties, bonding, shape etc,) of alkenes
and alkynes. See Meakins, OUP Primer no. 35, Chapters 5 and 6. [There will be much more on
alkenes than on alkynes – why?]
Read and learn some simple aromatic chemistry; mechanisms of halogenation. nitration,
sulfonation, Friedel- Crafts reactions; orientation of electrophilic substitution on PhX. See
Sainsbury, Aromatic Chemistry, OUP Primer no. 4.
Notes and Questions:
a) Summary on not more than 6 sides. In your summary, consider the mechanisms (with
evidence to support them, especially for the trans addition of bromine to C=C),
stereochemistry, effects of substituents on the rate of reaction and on mechanism, etc; any
selectivity shown, with reasons; uses of these reactions in synthesis.
The following reagents must be included:
Halogen
KMnO
2
4
H-Hal
OsO
4
H
/catalyst (various)
O
2
3
also hydration; hydroxylation, the Wittig reaction; epoxidation; hydroboration (followed by
oxidation with alkaline H
O
); radical addition of Hal
, H-Hal.
2
2
2
This should outline the possible mechanisms and the evidence on which they are based, in
particular the evidence for inversion during S
2 reactions. Consider the effects of changes in
N
solvent, nucleophile, leaving group as well as in substrate structure – include a range of nearby
functional groups, such as α-haloketones and α-haloethers. Discuss stereochemical effects and
rate differences etc. Include S
i and neighbouring group effects with examples of both.
N
b) Check that you can do the easy problems on this subject in Hornby and Peach ‘Foundations
of Organic Chemistry: worked examples’, OUP Primer no. 87, chapter 4, Q 1-7.
c) Learn the general chemistry of alcohols, alkyl halides, vinyl halides etc. See Meakins,
Functional Groups: characteristics and interconversions.
d) Do the problems attached. These are particularly important. For additional problems with
answers and explanations, see Chapter 2 of Stereochemistry at a glance.
1. Draw the mechanisms and the structures of the products of each of the following reactions?
a) 2-methyl pent-1-ene + HBr, dark
 
1
 

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