Bruice - Chimica Organica

Chapter 4 159

erythro enantiomers

the pair of enantiomers with similar groups on two asymmetric centers on the same

side when drawn in a Fischer projection.

isomers

isomers that result from not being able to rotate about a carbon–carbon double

(cis–trans isomers)

bond.

Fischer projection

a method of representing the spatial arrangement of groups bonded to an asymmet-

ric center. The asymmetric center is the point of intersection of two perpendicular

lines; the horizontal lines represent bonds that project out of the plane of the paper

toward the viewer, and the vertical lines represent bonds that project back from the

plane of the paper away from the viewer.

isomers

nonidentical compounds with the same molecular formula.

levorotatory

the enantiomer that rotates the plane of polarization of plane-polarized light in a

counterclockwise direction

meso compound

a compound that possesses asymmetric centers and a plane of symmetry; it is achi-

ral, because it has a plane of symmetry.

observed rotation

the amount of rotation observed in a polarimeter.

optically active

rotates the plane of polarization of plane-polarized light.

optically inactive

does not rotate the plane of polarization of plane-polarized light.

optical purity

the amount of excess of one enantiomer present in a mixture of a pair of

(enantiomeric excess)

enantiomers.

perspective formula

a method of representing the spatial arrangement of groups bonded to an asym-

metric center. Two adjacent bonds are drawn in the plane of the paper; a solid

wedge depicts a bond that projects out of the plane of the paper toward the viewer,

and a hatched wedge depicts a bond that projects back from the paper away from

the viewer.

plane-polarized light

light that oscillates in a single plane.

plane of symmetry

an imaginary plane that bisects a molecule so that the two halves are a pair of mir-

ror images.

polarimeter

an instrument that measures the rotation of the plane of polarization of plane-polarized light.

racemic mixture (racemic)

a mixture of equal amounts of a pair of enantiomers.

configuration

after assigning relative priorities to the four groups bonded to an asymmetric cen-

ter, if the lowest priority group is on a vertical axis in a Fischer projection (or

pointing away from the viewer in a perspective formula), the arrow drawn from the

highest priority group to the next highest priority group and then to the next high-

est priority group is clockwise.