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Islamic University of Gaza

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Presentation on theme: "Islamic University of Gaza"— Presentation transcript:

1 Islamic University of Gaza
Organic chemistry A Chapter 2 Methane By Prof. Dr. Adel M. Awadallah Islamic University of Gaza

2 Bond Angles in Methane

3 Physical Properties of Methane Colorless gas, Nonpolar (London Forces)
mp = -183, bp = oC Only slightly soluble in water Soluble in organic solvents Source Anaerobic decay of plants {{ Natural gas (97%) }}

4 Reactions of Methane

5 Halogenation (vigorous reaction)F2 > Cl2 > Br2 >>> I2 (no reaction) Control of chlorination Use excess methane and distill Methane bp = oC Methyl chloride bp -24 oC

6 Mechanism of Chlorination

7 Chain Mechanism

8 Inhibitors A substance that slows down or stops a reaction even though present in small amount.

9 Heat of Reaction

10 Energy of Activation The minimum amount of energy that must be provided by a collision for reaction to occur.

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13 Rate of Reaction Assume Ea1 = 5 Kcal andEa2 = 10 Kcal
A chemical reaction is the result of collisions of sufficient energy and proper orientation Rate = probability factor X Collision frequency X energy factor Collision frequency depends on concentration, size and temperature Probability factor depends upon geometry Energy factor depends upon temperature and activation energy (increasing temperature and decreasing Ea increases the rate of reaction) Rate = PZe-Ea/RT Assume Ea1 = 5 Kcal andEa2 = 10 Kcal Rate 1/ rate 2 = 100

14 Distribution of energy

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16 Relative Reactivities of halogens

17 An Alternative Mechanism for Halogenation

18 Energy Calculations

19 Structure of the methyl radical , (planar , sp2 hybridization)

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21 Transition State

22 When Ea is small, TS resembles reactants
When Ea is large, TS resembles products

23 Chlorofluorocarbons and the ozone shield

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