Made by:- Sofia MubashirTopic:- 2,3-dichloropentane

“2,3-dichloropentane”

• Stereoisomerism• Optical Isomerism• Optical Activity• Chiral Center• Enantiomers• Fischer Projection• R/S Rotation• Racemization• Method Of Racemization• Resolution

Stereoisomerism

Stereoisomerism is defined as “ isomerism in compounds having equal number of same types of bonds with identical connectivity , but differing in the spatial arrangement of atoms.”

Stereo isomers are divided into two classes Configurational Stereoisomerism Conformational stereoisomerism

non-polarized polarized

Optical activity:-When a substance rotates the plane of plane polarized light.

Plane polarized light:-Light that has been passed through nicol prism or other

polarizing medium so that all of the vibration are in the same plane.

polarimeter – an instrument used to measure optical activity.

light source sample tube

polarizer analyzer

Diastereomers: Stereoisomers • There are many molecules with two or more stereogenic centers that havediastereomers.• Every diastereomer can have a mirror image, which constitutes two stereoisomers.• A molecule with two stereogenic centers will have up to two diastereomers and eachwill have a mirror image. This means there is a maximum total of four stereoisomersfor a molecule with two stereogenic centers.• This observation can be extended to all molecules that have stereogenic centers. Fora given number of stereogenic centers (say n) there will be a maximum of 2nstereo isomers.• A molecule with two stereogenic centers has 22 or 4 stereoisomers.• A molecule with 4 stereogenic centers will have a maximum of 24 or 16stereoisomers.• If a molecule has 9 stereogenic centers, the maximum number of stereoisomers willbe 29 or 512 stereoisomers.• A molecule with 28 stereogenic centers; 228 means 2.684 x 108 stereoisomers (that'smore than 268 million stereoisomers) for one constitutional isomer of a singleempirical formula.

Diastereomers Enantiomers: Mirror-image stereoisomers.Diastereomers: Stereoisomers which are notenantiomers.

I is a stereoisomer of III & IV.II is a stereoisomer of III & IV.I is not a mirror image of III or IV.II is not a mirror image of III or IV.Therefore,I is a diastereomer of III & IV.II is a diastereomer of III & IV.Diastereomers often have similar, but not identical,chemical properties. They have different physicalproperties, and can be separated from one another byordinary physical means.

Fisher Projections + A method of representing stereogenic centers withoutusing wedged or dashed bonds.Horizontal bonds come from the stereogenic centertoward you.Vertical bonds go from the stereogenic center away fromyou.e.g.

R And S Configurations From Fischer Projection:To determine the R,S configuration of each.• interchange pairs of groups around the stereogenic center of one

until both projections are identical.• Since each exchange inverts the configuration anodd number of

exchanges means the configurationswere opposite; an even number means they are the same.

Racemization:“Racemization is the process by which 50 % of an

optically active compound ( dextro or levo) may be converted to its enantiomer.”

Method Of Racemization

Consider an optically active halide. The process of racemization would involve the removal of halide ion from the sp3 carbon. This is possible in a

solvent which can stabilize the carbocation.

Resolution Of Racemic Mixture:“The separation of enantiomers from racemic mixture is called resolution of racemic mixture.Following special methods have been used for separation of enantiomers from racemic mixture:1. Mechanical method2. Biological method3. Chemical method4. Chromatographic method