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Chapter 5
Stereochemistry

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.
Keywords	enantiomers,chiral

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.
Keywords	stereoisomer, isomer, flowchart, constitutional, connectivity

05-00-06

Title	Cis-trans Isomers
Caption	Ball-and-stick and KekulŽ 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.
Keywords	configurational, isomers, 2-pentene, ball-and-stick, KekulŽ

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 imageÑthey are nonsuperimposable (i.e., the hand). An achiral object is the same as its mirror imageÑthey are superimposable (i.e., the chair).
Keywords	mirror, image, hand, chair, chiral, achiral, superimposable, nonsuperimposable, figure, 5.1

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.
Keywords	molecule, asymmetric, carbon, chiral, superimposable

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.
Keywords	chiral, achiral, molecules, nonsuperimposable, mirror, image, superimposable

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.
Keywords	stereocenters, interchange, asymmetric, nonsuperimposable

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.
Keywords	chiral, molecule, asymmetric, R, S, configuration, stereocenter, Cahn-Ingold-Prelog, priorities

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).
Keywords	chirality, centers, determining, configuration, step, 1, chiral, stereocenter, Cahn-Ingold-Prelog

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.
Keywords	R, configration, determining, configuration, step, 2, priority, clockwise, counterclockwise, rectus, sinister, S

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.
Keywords	steering-wheel, analogy, priority, assignment, clockwise, counterclockwise, R, S

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.
Keywords	plane-polarized, light, polarized

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.
Keywords	propagation, rotate, light, achiral, plane-polarized

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.
Keywords	propagation, rotate, light, chiral, plane-polarized

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.
Keywords	polarimeter, schematic, rotation, optically active

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%.
Keywords	enantiomeric, excess, formula, optical, isomeric, purity

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.
Keywords	stereoisomers, diastereomers, erythro, threo, enantiomers

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.
Keywords	ball-and-stick, 3-chloro-2-butanol, isomers, erythro, threo, enantiomers, diastereomers

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.
Keywords	3-bromo-2-butanol, isomers, erythro, threo, enantiomers, diastereomers

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.
Keywords	1-bromo-3-methylcyclobutane, enantiomers, plane, symmetry, cis, trans

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.
Keywords	cyclic, meso, compounds, cis, isomer, trans

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.
Keywords	3-bromo-2-butanol, isomers, named, perspective, Fischer

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.
Keywords	receptor, binding, site, schematic enantiomer

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.
Keywords	thalidomide, teratogen, d, l, isomer

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.
Keywords	amine, inversion, lone, pair, flipping

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.
Keywords	racemic, mixture, enantiomers, mechanism, addition, 1-butene, 2-butene, 2-bromobutane

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.
Keywords	carbocation,Br,racemic

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.
Keywords	bromonium, potential, map, cis-2-butene, anti

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.
Keywords	end-of-chapter, problem, 75

Title	Table 5.1 Physical Properties of the Stereoisomers of Tartaric Acid
Caption
Notes
Keywords

Title	Table 5.2 Stereochemistry of Alkene Addition Reactions
Caption
Notes
Keywords

Chapter 5 Stereochemistry

Chapter 5
Stereochemistry