Figure Number: 05-00CO Title: Pair of Enantiomers Caption: A molecule that has a nonidentical mirror image, which does not contain a plane of symmetry is said to be chiral. Notes: The most familiar chiral objects are your hands. A plane of symmetry is a plane that cuts a molecule in two halves, each of which is the mirror image of the other.

Figure Number: 05-00-02UN Title: Isomer Flowchart Caption: The relationship between different kinds of isomers. Notes: Constitutional isomers differ in connectivity, and stereoisomers differ in the way their atoms are arranged in space.

Figure Number: 05-00-06 Title: Cis-trans Isomers Caption: Ball-and-stick and Kekulé structures of cis- and trans-2-pentene. Notes: Configurational isomers cannot interconvert because the double bond cannot rotate. Cyclic compounds can also have cis and trans isomers because the cyclic system prevents free rotation about the single bonds.

Figure Number: 05-01 Title: Figure 5.1 Caption: Original and mirror images of a hand and a chair. Notes: A chiral object is not the same as its mirror image—they are nonsuperimposable (i.e., the hand). An achiral object is the same as its mirror image—they are superimposable (i.e., the chair).

Figure Number: 05-01-01UN Title: Molecule with Asymmetric Carbon Caption: A molecule with an asymmetric carbon is chiral. Notes: Carbon atoms which have four different things attached to them are asymmetric, or chiral. They are not superimposable with their mirror images.

Figure Number: 05-01-10UN Title: Chiral and Achiral Molecules Caption: Structures of a chiral molecule, an achiral molecule, and mirror images of the two. Notes: A chiral molecule has a nonsuperimposable mirror image. An achiral molecule has a superimposable mirror image.

Figure Number: 05-01-14UN Title: Stereocenters Caption: Five stereocenters depicted in three molecules. Notes: A stereocenter is an atom at which the interchange of two groups yields two different nonsuperimposable molecules. Asymmetric carbons are stereocenters and so are carbons which hold attached substituents in E or Z isomeric configurations.

Figure Number: 05-01-16UN Title: A Chiral Molecule Caption: A chiral molecule composed of an asymmetric carbon and four different kinds of attached atoms. Notes: To assign an R or S configuration to a stereocenter of a chiral molecule, the Cahn-Ingold-Prelog system is used to assign relative priorities to all of the groups attached to the stereocenter.

Figure Number: 05-01-17UN Title: Determining Configuration Step 1 Caption: The first step in determining the configuration of a stereocenter is to number attached groups in descending order of priority using the Cahn-Ingold-Prelog rules. Notes: The only carbons that can be chiral stereocenters are sp3-hydridized carbons. Chiral centers must have four groups bonded to them. The three groups attached to an sp2-hybridized carbon all lie in a plane, and if a mirror is oriented parallel to this plane, original and mirror images will be identical (superimposable).

Figure Number: 05-01-18UN Title: Determining Configuration Step 2 Caption: The second step in determining the configuration of a chiral stereocenter is to orient the lowest-priority group behind the stereocenter and determine whether the remaining groups are priority-ordered in a clockwise or counterclockwise fashion around the stereocenter. Notes: If groups are ordered around a chiral stereocenter such that the lowest-priority group is behind the stereocenter and the remaining groups are in front of the stereocenter and ordered clockwise around the stereocenter in ascending priority-numbered order (i.e., 1 to 3 for carbon), the chiral stereocenter is assigned an "R" designation. The "R" in R configuration is from rectus, which is latin for "right." Counterclockwise ordering yields an "S" (sinister, or left) designation.

Figure Number: 05-01-19UN Title: Steering-Wheel Analogy to Priority Assignment Caption: Turning a steering wheel clockwise results in a right (rectus, R) turn and turning it counterclockwise results in a left (sinister, S) turn. Notes: The steering-wheel analogy aids in remembering that ordering highest priority groups in front of a chiral stereocenter in a clockwise fashion results in an R configuration, whereas orienting these groups in a counterclockwise fashion yields an S onfiguration.

Figure Number: 05-01-41UN Title: Plane-Polarized Light Caption: Plane-polarized light oscillates only in a single plane. Notes: Plane-polarized light is produced by passing normal light through a polarizer such as a polarized lens or Nicol prism.

Figure Number: 05-01-44UN Title: Achiral Compound in Plane-Polarized Light Caption: An achiral compound does not rotate the plane of polarized light. It is optically inactive. Notes: When plane-polarized light passes through a solution of achiral molecules, the light emerges from the solution with its direction of polarization unchanged, because there is no asymmetry in the molecules.

Figure Number: 05-01-45UN Title: Chiral Compound in Plane-Polarized Light Caption: A chiral compound rotates the plane of polarized light in either a clockwise or counterclockwise direction. Notes: If one enantiomer rotates the plane of polarized light in a clockwise direction, its mirror image will rotate the plane of polarized light by an equal amount but in the opposite direction.

Figure Number: 05-02 Title: Schematic of a Polarimeter Caption: The amount that an optically active compound rotates the plane of polarized light can be measured by a polarimeter. Notes: Because the amount of rotation depends on the wavelength of the light used, the light source for a polarimeter must produce light with a single wavelength.

Figure Number: 05-02-05UN Title: Enantiomeric Excess Formula Caption: Calculation of enantiomeric excess for a compound with an optical purity of 40%. Notes: Optical purity and isomeric purity are not the same. A 50/50 mixture of two enantiomers has a 50% isomeric purity, but a zero optical purity or enantiomeric excess. To convert from enantiomeric excess to isomeric purity, divide the percent enantiomeric excess by two and add the result to 50%.

Figure Number: 05-02-07UN-A Title: Erythro and Threo Diastereomers Caption: Erythro enantiomers are diastereomers of threo enantiomers. Notes: Diastereomers are stereoisomers which are not mirror images of one another. Erythro enantiomers are stereoisomers with two adjacent chirality centers, which have two similar groups on the same side of the carbon chain, and threo enantiomers have the two similar groups on opposite sides of the carbon chain.

Figure Number: 05-02-07UN-B Title: Ball-and-Stick Models of 3-Chloro-2-butanol Caption: Ball-and-stick models of the four isomers of 3-chloro-2-butanol. Notes: 3-Chloro-2-butanol has two erythro enantiomers and two threo enantiomers. Each of the two erythro isomers is a diastereomer of each of the two threo isomers.

Figure Number: 05-02-07UN-C Title: Isomers of 3-Bromo-2-butanol Caption: Eclipsed conformations of 3-bromo-2-butanol make it easy to see which isomers are threo and which are erythro. Notes: 3-Bromo-2-butanol has two erythro enantiomers and two threo enantiomers. Each of the two erythro isomers is a diastereomer of each of the two threo isomers.

Figure Number: 05-02-11UN Title: Cis- and Trans-1-bromo-3-methylcyclobutane Caption: cis- and trans-1-Bromo-3-methylcyclobutane do not have enantiomers because they have a plane of symmetry. Notes: These compounds do not contain any chiral centers. The cis isomer and the trans isomer are the only stereoisomers of this compound.

Figure Number: 05-02-24UN Title: Cyclic Meso Compounds Caption: In the case of cyclic compounds, the cis isomer will be the meso compound. Notes: The trans isomer for cyclic compounds will be a pair of enantiomers.

Figure Number: 05-02-46UN Title: 3-Bromo-2-butanol Isomers Caption: Named perspective formulas and Fischer projections of the isomers of 3-bromo-2-butanol. Notes: The first two structures on the left are enantiomers of each other. The last two structures on the right are also enantiomers. Each of the structures in the left pair is a diastereomer of each of the structures in the right pair.

Figure Number: 05-03 Title: Receptor Binding Sites Caption: Schematic diagram showing why only one enantiomer is bound by a receptor. Notes: One enantiomer fits into the binding site and the other does not.

Figure Number: 05-03-002UN Title: Thalidomide Caption: Structural formula and ball-and-stick model of thalidomide showing chiral carbon. Notes: The l isomer of thalidomide is a severe teratogen, whereas the d isomer is only a mild teratogen.

Figure Number: 05-03-014UN Title: Amine Inversion Caption: Depiction of amine lone pair flipping from right to left side of an amine molecule during an amine inversion. Notes: Amine inversion occurs when the lone pair of electrons in the yellow p orbital jumps to the opposite side of the nitrogen atom, reversing the relative sizes of the two lobes of this orbital and flipping the substituents bonded to the nitrogen atom to the opposite side of the nitrogen atom.

Figure Number: 05-03-021UN Title: Mechanism of Addition of HBr to 1-Butene and 2-Butene Caption: Carbocation intermediates are flat and planar allowing for the nucleophile to attack the top or bottom, yielding both enantiomers of 2-bromobutane as products. Notes: A mixture of equal amounts of a pair of enantiomers is called a racemic mixture, a racemic modification, or a racemate.

Figure Number: 05-03-031UN Title: Stereoisomer w/Br Ion Caption: The carbocation intermediate is flat and planar which allows for the Br ion to attack the top or bottom. Notes: The product is a racemic mixture, containing both R and S enantiomers.

Figure Number: 05-03-051UN Title: Bromonium Ion Potential Map Caption: Electrostatic potential map of the bromonium ion intermediate in the reaction of cis-2-butene with bromine. Notes: The bromine blocks one side of the intermediate from attack by bromide ion, forcing the second bromine to add anti to the first bromine.

Figure Number: 05-03-109P75 Title: End-of-Chapter Problem 75 Caption: Enantiomers of 1,2-dimethylaziridine. Notes: Enantiomers of 1,2-dimethylaziridine do not undergo amine inversion because the three-membered ring cannot easily achieve the 120-degree angle around nitrogen necessary for it to form the flat transition state required for inversion.

Figure Number: Title: Table 5.1  Physical Properties of the Stereoisomers of Tartaric Acid Caption: Notes:

Figure Number: Title: Table 5.2  Stereochemistry of Alkene Addition Reactions Caption: Notes: