March 1st , 2014 by: Marcus Kahyazi
L and D Methamphetamine
Grade 12 Chemistry SCH4U1
For Mrs. Sgouromitis
Many over the counter drugs contain stereoisomers called optical isomers. There are two types of isomer; structural isomers and stereoisomers. Structural isomers do not have similar physical or chemical properties, but have same molecular formulas. Stereoisomers have the same molecular formula, but differ in their three-dimensional arrangements. There are two forms of stereoisomers: geometric and optical isomers. (Appendix A) Geometric isomers are compounds that have the same molecular formulas as one another, but have different geometric formations. There are two features that constitute a geometric isomer. Rigidity, meaning that there is a double bond linking the carbons, and two groups on each side of the double bond.
Optical isomers, or enantiomers, are mirror images that aren't superimposable. (Appendix B) The physical and chemical properties differ. (Appendix C) To be considered an optical isomer, a compound must have four different groups attached to one of its carbons, making this carbon the chiral centre.
Optical isomers can be determined by their interaction with plane polarized light. They are distinguished based on the direction that the polarized light has shifted which determines the name of the compound and its enantiomer. There are two forms of optical isomers, the (+) shape and the (-) shape. The (+) form can be written as R or as D, which stands for dextro or right. The (-) shape can be written as L or as S, which stand for levo or left. When an optical isomer comes into contact of polarized light it bends the light either clockwise or counter clockwise. The (+) form turns it clockwise, while the (-) form turns it counter clockwise. (Appendix D) However, if the polarized...