This document defines alkanes as acyclic saturated hydrocarbons with the general formula CnH2n+2. It discusses the sp3 hybridization of carbon atoms in alkanes, and general methods of preparing alkanes such as the Wurtz reaction and catalytic hydrogenation. The document also outlines some common reactions of alkanes like halogenation and describes the mechanism of halogenation reactions. It compares the reactivity and selectivity of chlorination versus bromination of alkanes.

1. Mr. Amit Z Chaudhari
Dept. of Pharma Chemistry,
L. M. College of Pharmacy,
Ahmedabad - 380009 India
ALKANE

2. C O N T E N T
- Definition
- Structure : sp3 hybridization
- General methods of preparation
• Wurtz reaction
- General reactions :
• Halogenation
- use
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3. D e f i n a t i o n
Acyclic branched or unbranched hydrocarbons having the general
formula Cn H2n+2 and therefore consisting entirely of H atoms and
saturated C atoms
The simplest saturated organic compounds made of C & H only
Synonym: open chain saturated hydrocarbon
acyclic saturated hydrocarbon
Paraffins (have low chemical reactivity)
Gen. formula:
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4. S T R C T U R E
sp3 hybridization of C
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5. S T R C T U R E
sp3 hybridization of C
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6. S T R C T U R E
sp3 hybridization of C
- Methane
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7. P R E P A R A T I O N S
1. Catalytic hydrogenation of alkenes or alkynes
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8. P R E P A R A T I O N S
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2. From alkyl halide
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9. P R E P A R A T I O N S
2. From alkyl halide
Wurtz reaction
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10. P R E P A R A T I O N S
2. From alkyl halide
Wurtz reaction
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11. P R E P A R A T I O N S
3. From carboxylic acid
Duma’s Decarboxylation
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12. P R E P A R A T I O N S
4. From aldehyde and ketones
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13. R E A C T I O N S
1
Halogenation
Nitration
Sulfonation
Oxidation
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14. R E A C T I O N S
1
Cracking or pyrolysis
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15. R E A C T I O N S
1
Cracking
Types
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16. R E A C T I O N S
1
Cracking
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17. R E A C T I O N S
1
Halogenation of alkanes: or
Free radicals chain reactions of alkane :
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18. R E A C T I O N S
1
Halogenation of alkanes:
Mechanism
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19. R E A C T I O N S
1
Halogenation of alkanes:
Mechanism
Step_3 Chain-termination : conversion of free radical to normal
molecule
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20. R E A C T I O N S
2
Halogenation of alkanes:
Transition state
Potential
Energy
Reaction progress
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21. R E A C T I O N S
2
Halogenation of alkanes:
Example
- Chlorination of propane
the rate of abstraction of H atom is-- 3o > 2o > 1o
Isomerization
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22. R E A C T I O N S
2
Halogenation of alkanes:
Ease of abstraction of hydrogen atoms, Energy of activation
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23. R E A C T I O N S
2
Halogenation of alkanes:
Ease of abstraction of hydrogen atoms, Energy of activation
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24. R E A C T I O N S
2
Halogenation of alkanes:
Reactivity and Selectivity [ chlorination vs bromination]
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25. R E A C T I O N S
2
Halogenation of alkanes:
Reactivity and Selectivity [ chlorination vs bromination]
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26. R E A C T I O N S
Halogenation of alkanes:
Reactivity and Selectivity [ chlorination vs bromination]
- Propagation step of chlorination and bromination
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27. R E A C T I O N S
2
Halogenation of alkanes:
Reactivity and Selectivity [ chlorination vs bromination]
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28. R E A C T I O N S
2
Halogenation of alkanes:
Reactivity and Selectivity [ chlorination vs bromination]
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29. U S E
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30. of the topic
End
Reference:
Textbook of org. chem. – Bahl & Bahl
Org. chem. – Mehta & Mehta
Org. chem. – Morrison and Boyd