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Chapter 9
Reactions of Alkanes

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09-00-00
Title
Vitamin C and Vitamin E
Caption
Potential maps of vitamins C and E.
Notes
Vitamin C and vitamin E are free-radical scavengers which protect the body from the damaging effects of free radicals.
Keywords
vitamin, C, E, radical, scavengers
09-00-02UN
Title
Petroleum Distillation
Caption
Schematic of an apparatus used for separating petroleum into fractions by distillation.
Notes
Asphalt, grease, heating oil, kerosene, gasoline, and liquified petroleum gas (LPG) are a few of the fractions produced by petroleum distillation.
Keywords
petroleum, distillation, schematic, apparatus
09-00-13UN
Title
Relative Stabilities of Alkyl Radicals Measured with Chlorine
Caption
Relative rates of alkyl radical formation by chlorine atom (radical) at room temperature.
Notes
More stable alkyl radicals are formed faster: tertiary > secondary > primary > methyl.
Keywords
relative, stability, stable, alkyl, radicals, rates, formation, chlorine
09-00-23UN
Title
Relative Stabilities of Alkyl Radicals Measured with Bromine
Caption
Relative rates of alkyl radical formation by bromine atom.
Notes
Stabilities of alkyl radicals measured with bromine parallel stabilities measured with chlorine: tertiary > secondary > primary > methyl. However, the reactivity differences in the series are much more pronounced with bromine than with chlorine because bromine is more stable (less reactive) than chlorine. Less reactive species are more selective in carrying out chemical reactions, yielding bigger differences in speeds of faster and slower reactions compared to more reactive species.
Keywords
relative, stabilities, alkyl, radicals, bromine, selectivity
09-00-26UN
Title
Reaction Enthalpies for Abstraction of Hydrogen by Chlorine and Bromine
Caption
Reaction enthalpies for formation of primary, secondary, and tertiary alkyl radicals using chlorine atom and bromine atom. Values are calculated in both kcal/mol and kJ/mol.
Notes
While the value of the reaction enthalpy for abstraction of a hydrogen by a chlorine or bromine atom drops as the stability of the alkyl radical formed increases for both chlorine and bromine abstractions, the chlorine abstractions are exothermic, and the bromine abstractions are endothermic.
Keywords
reaction, enthalpies, chlorine, bromine, abstraction, hydrogen
09-01a,b
Title
Figure 9.1
Caption
Reaction coordinate diagrams for the abstraction of primary, secondary, and tertiary hydrogens by chlorine and bromine atoms.
Notes
Since the chlorine abstractions are exothermic, their transition states resemble reactants, and their relative stabilities do not fully reflect the relative stabilities of the product alkyl radicals. The bromine abstractions are endothermic, so the bromine-abstraction transition states resemble product alkyl radicals. Thus, the relative stabilities of the bromine-abstraction transition states resemble the relative stabilities of the alkyl radical products. Thus, the activation energies (and relative speeds) of bromine-abstraction reactions more closely reflect alkyl radical stabilities than do the activation energies of chlorine-abstraction reactions.
Keywords
reaction coordinate, diagrams, abstraction, hydrogens, chlorine, bromine, figure, 9.1
09-01-02UN
Title
Halogenation Reaction Enthalpies
Caption
Calculation of reaction enthalpies for the chain-propagating steps of free-radical halogenations of methane.
Notes
Fluorinations are violently exothermic, chlorinations and brominations are exothermic, and iodinations do not occur because they are endothermic.
Keywords
halogenation, reaction, enthalpies, calculation, chain-propagating, halogenations
09-01-03UN
Title
Halogen Molecules
Caption
Space-filling models of diatomic halogen molecules.
Notes
As the halogen atoms grow in size, they form longer, weaker bonds with carbon atoms and other halogen atoms.
Keywords
space-filling, diatomic, halogen, molecules
09-01-13
Title
Stereochemistry of Radical Substitution Reactions
Caption
If a reactant does not have an asymmetric carbon, and a radical substitution reaction forms a product with an asymmetric carbon, a mixture of enantiomers is produced.
Notes
In a radical substitution reaction, a radical intermediate is produced which can abstract atoms to form a new bond from either of two possible orientations, giving rise to either of two possible enantiomers.
Keywords
stereochemistry, radical, substitution, asymmetric, enantiomers
09-01-14UN
Title
Radical Intermediate
Caption
A radical intermediate reacting with molecular bromine.
Notes
The radical intermediate has a prochiral carbon. It can abstract a bromine atom from either its top face or its bottom face, giving rise to one of two possible enantiomers with equal probability.
Keywords
radical, intermediate, bromine, enantiomers
09-01-27.1
Title
Vitamin C and Vitamin E
Caption
Potential maps and structures of vitamin C and vitamin E.
Notes
Vitamin C and vitamin E are free-radical scavengers.
Keywords
vitamin, C, E, potential, map

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