5. Steriochemistry

Question 1

The three-dimensional structure of molecules.

Answer 1

Steriochemistry

Question 2

A large molecule composed of smaller monomer units covalently bonded to each other in a repeating pattern.

Answer 2

Polymer

Question 3

Small organic compounds that can be covalently bonded to each other (polymerized) in a repeating pattern.

Answer 3

Monomer

Question 4

Two different compounds that have the same molecular formula.

Answer 4

Isomer

Question 5

Two isomers that differ only in the way the atoms are oriented in space.

Answer 5

Stereoisomer

Question 6

Two compounds that have the same molecular formula, but differ in the way the atoms are connected to each other.

Answer 6

Constitutional (Structural) Isomer

Question 7

A particular three-dimensional arrangement of atoms.

Answer 7

Configuration

Question 8

A molecule that is superimposable upon its mirror image. An achiral molecule is not chiral.

Answer 8

Achiral Molecule

Question 9

A molecule that is not superimposable upon its mirror image.

Answer 9

Chiral Molecule

Question 10

Stereoisomers that are mirror images but are not superimposable upon each other. They have the exact opposite R,S designation at every stereogenic center.

Answer 10

Enantiomers

Question 11

A site in a molecule at which the interchange of two groups forms a stereoisomer.

Answer 11

Stereogenic (Chiral, Asymmetric) Center

Question 12

A mirror plane that cuts a molecule in half, so that one half of the molecule is the mirror reflection of the other half.

Answer 12

Plane of Symmetry

Question 13

The system of designating a stereogenic center as either R or S according to the arrangement of the four groups attached to the center.

Answer 13

Cahn-Ingold-Prelog System of Nomenclature

Question 14

Stereoisomers that are not mirror images of each other. They have the same R,S designation for at least one stereogenic center and the opposite R,S designation for at least one of the other stereogenic centers.

Answer 14

Diastereomers

Question 15

An achiral compound that contains two or more tetrahedral stereogenic centers.

Answer 15

Meso Compound

Question 16

Light that has an electric vector that oscillates in a single plane.

Answer 16

Plane-Polarized (Polarized) Light

Question 17

An instrument that measures the degree that a compound rotates plane-polarized light.

Answer 17

Polarimeter

Question 18

Not able to rotate the plane of plane-polarized light as it passes through a solution of a compound.

Answer 18

Optically Inactive

Question 19

The angle that a sample of an optically active compound rotates plane-polarized light. The angle is denoted by the symbol α and is measured in degrees (°).

Answer 19

Observed Rotation

Question 20

Able to rotate the plane of plane-polarized light as it passes through a solution of a compound.

Answer 20

Optically Active

Question 21

Rotating plane-polarized light in the clockwise direction. The rotation is labeled d or (+).

Answer 21

Dextrorotatory

Question 22

Rotating plane-polarized light in the counterclockwise direction. The rotation is labeled l or (−).

Answer 22

Levorotatory

Question 23

An optically inactive equal mixture of two enantiomers

Answer 23

Racemic Mixture

Question 24

A standardized physical constant for the amount that a chiral compound rotates plane-polarized light. It is denoted by the symbol [α] and defined using a specific sample tube length (l in dm), concentration (c in g/mL), temperature (25 °C), and wavelength (589 nm). [α] = α/(l × c)

Answer 24

Specific Rotation

Question 25

A measurement of how much one enantiomer is present in excess of the racemic mixture. Known as ee = % of one enantiomer − % of the other enantiomer.

Answer 25

Enantiomeric Excess (Optical Purity)