Figure Number: 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.

Figure Number: 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.

Figure Number: 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.

Figure Number: 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.

Figure Number: 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.

Figure Number: 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.

Figure Number: 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.

Figure Number: 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.

Figure Number: 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.

Figure Number: 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.

Figure Number: 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.