Bài giảng Organic chemistry - Chapter 9: Alkyl Halides - Phan Nam
ORGANIC CHEMISTRY
Dr Nam T. S. Phan
Faculty of Chemical Engineering
HCMC University of Technology
Office: room 211, B2 Building
Phone: 38647256 ext. 5681
Email: [email protected].vn
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Chapter 9: ALKYL HALIDES
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NOMENCLATURE OF ALKYL
HALIDES
Common names: alkylhalide (chloride, bromide…)
IUPAC names: halogeno + alkane (chloro, bromo…)
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Alkyl & halogen substituents are considered of
equal rank
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PREPARATION OF ALKYL HALIDES
Alkyl halides from alcohols
Only in acidic conditions
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Alkyl halides from alkenes
More stable
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Alkyl halides from alkanes
Chlorination is much less selective
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REACTIONS OF ALKYL HALIDES
Very
reactive
Very
unreactive
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With the same R
NUCLEOPHILIC SUBSTITUTION
REACTIONS
SN1 vs SN2 – depending on alkyl structure,
nucleophile concentration & reactivity, and solvent
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Stereochemistry of SN2 reactions
• The nucleophile attacks from the back side / the side
directly opposite the leaving group
• This attacks causes an inversion of configuration
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Stereochemistry of SN1 reactions
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However, few SN1 reactions occur with
complete racemization
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Factors affecting the rates of
SN1 & SN2
1. The structure of the substrate
2. The concentration & reactivity of
the nucleophile
3. The reaction solvent
4. The nature of the leaving group
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Affects of substrate structure
Steric
hindrance
Steric effect in the SN2 reaction
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Affects of nucleophile concentration
& strength
1) Neither the concentration nor the
structure of the nucleophile affects the
rates of SN1 reactions since the
nucleophile does not participate in the
rate-determining step
2) The rates of SN2 reactions depend on
both the concentration and the structure
of the nucleophile
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