File:A problem in optical isomerism (1917) (14596153858).jpg

Identifier: probleminoptical00palm (find matches)
Title: A problem in optical isomerism
Year: 1917 (1910s)
Authors: Palmer, Charles Shattuck
Subjects: Optical isomers Isomerism Theses
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Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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tivity exists in certain organic compounds. It was soon noted that optically active substances may be divided into two classes: those in which the rotatory power depends solely on the crystalline form, and those in which the property is derived from tne molecular structure the itself, and is retained in/liquid or even tne gaseous state. Itis this latter kind which is included in the field of opticalisomerism. Pasteur showed that in many substances the molecular struc-ture which causes optical activity is connected with the crystal- 2 line form. In his work on the tartaric acids he snowed that theacid which rotates the plane of polarized light to tne leftpossesses a crystalline iorm which is the mirror-image of the op- ■Mfant Hoff, The Arrangement of Atoms in bpace1; Cohen, Or-ganic Chemistry ior Advanced Students; Eantzscn, The Ele-ments of Stereo-Chemistry; Stewart, Stereochemistry; V;ede-kind, Stereochemie; Werner, lehrbuch der Stereochemie. ^Pasteur,C.R., £6,535; 27,401; 55,180.
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posite rotating acid. Such crystals are known as enantiomorphous.( See j:ig. 1). The Asymmetric Carbon Atom According to the Vant Eoff-Le Bel hypothesis the fourvalences of the carbon atom are directed outward toward the fourcorners ox a regular tetrahedron. An asymmetric carbon atom isone in which the four groups attached to it are different chem-ically or structurally. Two arrangements which are mirror imagesof each other are then possible. (See Fig* 2). If the stereo-chemical model of a substance possesses a plane of symmetry, thatis, if it can be divided into two halves which are mirror-imagesof each other, the molecule is inactive. If there is no plane ofsymmetry, activity is possible. (See fig. 3). Besides the dextro- and laevo-rotatory forms there may exista racemic form by addition of the two active xorms to each other.The racemic form may be resolved into its active constituents bysuitable methods. If more than one asymmetric carbon atom ispresent inactive, unresolvable (mesoprobleminoptical00palm

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