Organic Chemistry Chapter 5 Vocabulary

Front 1

stereochemistry

Back 1

is the study of the structure and chemistry of stereoisomers.

Front 2

constitutional isomers (structural isomers)

Back 2

are connected differently; they differ in their bonding sequence.

Front 3

stereoisomers

Back 3

differ only in how their atoms are oriented in space.

Front 4

chiral

Back 4

Different from its mirror image.

Front 5

achiral

Back 5

Not chiral

Front 6

superimposable

Back 6

Identical in all respects. The three-dimensional positions of all atoms coincide when the molecules are placed on top of each other.

Front 7

enantiomers

Back 7

A pair of nonsuperimposable mirror-image molecules: mirror-image isomers.

Front 8

asymmetric carbon atom (chiral carbon atom)

Back 8

A carbon atom that is bonded to four different groups.

Front 9

chirality center

Back 9

The IUPAC term for an atom holding a set of ligands in a spatial arrangement that is not superimposable on its mirror image. Asymmetric carbon atoms are the most common chirality centers.

Front 10

stereocenter

Back 10

An atom that gives rise to stereoisomers when its groups are interchanged. Asymmetric carbon atoms and double-bonded carbons in cis-trans alkenes are the most common stereocenters.

Front 11

stereocenter (stereogenic atom)

Back 11

An atom that gives rise to stereoisomers when its groups are interchanged. Asymmetric carbon atoms and double-bonded carbons in cis-trans alkenes are the most common stereocenters.

Front 12

internal mirror plane

Back 12

A plane of symmetry through the middle of a molecule, dividing the molecule into two mirror-image halves. A molecule with an internal mirror plane of symmetry cannot be chiral.

Front 13

configurations

Back 13

The two possible spatial arrangements around a chirality center or other stereo-center.

Front 14

Cahn–Ingold–Prelog convention

Back 14

The accepted method for designating the absolute configuration of a chirality center (usually an asymmetric carbon) as either (R) or (S).

Front 15

polarimeter

Back 15

An instrument that measures the rotation of plane-polarized light by an optically active compound.

Front 16

plane-polarized light

Back 16

Light composed of waves that vibrate in only one plane.

Front 17

optical activity

Back 17

Rotation of the plane of polarized light.

Front 18

optically active

Back 18

Capable of rotating the plane of polarized light.

Front 19

optical isomers

Back 19

Compounds with identical properties except for the direction in which they rotate polarized light. (

Front 20

polarimeter

Back 20

An instrument that measures the rotation of plane-polarized light by an optically active compound.

Front 21

dextrorotatory, or (d)

Back 21

Rotating the plane of polarized light clockwise.

Front 22

levorotatory

Back 22

(l) Rotating the plane of polarized light counterclockwise.

Front 23

specific rotation

Back 23

A measure of a compound's ability to rotate the plane of polarized light, given by where c is concentration in g mL and l is length of sample cell (path length) in decimeters.

Front 24

chiral probe

Back 24

A molecule or an object that is chiral and can use its own chirality to differentiate between mirror images. (

Front 25

racemic mixture

Back 25

A mixture of equal quantities of enantiomers, such that the mixture is optically inactive.

Front 26

optical purity (o.p.)

Back 26

The specific rotation of a mixture of two enantiomers, expressed as a percentage of the specific rotation of one of the pure enantiomers. Similar to enantiomeric excess.

Front 27

enantiomeric excess (e.e.)

Back 27

The excess of one enantiomer in a mixture of enantiomers expressed as a percentage of the mixture. Similar to optical purity.

Front 28

Fischer projection

Back 28

A method for drawing an asymmetric carbon atom as a cross. The carbon chain is kept along the vertical, with the IUPAC numbering from top to bottom. Vertical bonds project away from the viewer, and horizontal bonds project toward the viewer.

Front 29

diastereomers

Back 29

Stereoisomers that are not mirror images.

Front 30

cis-trans isomers

Back 30

Isomers that differ in their cis-trans arrangement on a ring or double bond. Cis-trans isomers are a subclass of diastereomers. (p. 287) cis: Having similar groups on the same side of a double bond or a ring. trans: Having similar groups on opposite sides of a double bond or a ring. Z: Having the higher-priority groups on the same side of a double bond. E: Having the higher-priority groups on opposite sides of a double bond.

Front 31

meso compound

Back 31

An achiral compound that contains chirality centers (usually asymmetric carbon atoms). Originally, an achiral compound that has chiral diastereomers.

Front 32

absolute configuration

Back 32

The detailed stereochemical picture of a molecule, including how the atoms are arranged in space. Alternatively, the (R) or (S) configuration at each asymmetric carbon atom. (

Front 33

relative configuration

Back 33

The experimentally determined relationship between the configurations of two molecules, even though the absolute configuration of either may not be known.

Front 34

resolution

Back 34

The process of separating a racemic mixture into the pure enantiomers. Resolution requires a chiral resolving agent.

Front 35

resolving agent

Back 35

A chiral compound (or chiral material on a chromatographic column) used for separating enantiomers.