CIS-TRANS ISOMERISM ON RING

– Example :

 

 

 

 

 

 

 

 

 

 

CIS-TRANS ISOMERISM ON C=C

–  Example : CH₃CH-CHCH₃

 

 

 

 

 

cis-isomer–trans-isomer-1–2-dichloroethene

 

– Diastereomers different in physical properties

 

 

 

 

 

 

 

 

HOW TO IDENTIFY CIS-TRANS ISOMER

–  Restricted rotation of carbon-carbon bonds due to:

*  C=C

*  Cyclic (ring) structure

–  Two different atoms or groups of atoms attached to each of C atom which form double bond or cyclic               structure

 

 

 

 

 

 

 

TYPE OF DIASTEREOMEDS

–  Molucules with two or more chiral centers

–  Cis-trans (geometric) isomer

* C=C (alkene)

* Disubtituted cycloalkane

 

 

 

 

 

 

 

 

 

 

 

 

OPTICALLY ACTIVITY OF ENANTIOMERS

– Two enantiomers have identical physical properties

* Melting, boiling point, and solubility

– They are differ in their behavior toward plane-polarized light

– Separate enantiomers rotate the plane of plane-polarized light equal amount but in opposite direction

– Separate enantiomers are said to optically active

 

 

 

 

 

 

 

 

 

 

 

 

Polarimeter…

• Main part :

1. light source
2. Polarizer
3. Sample tube
4. Analyzer
5. Scale for measuring degrees of rotation

 

OPTICAL ACTIVITY

* The ability of a chiral compound to rotate the plane-polarized light

* Compound that change (rotate) the plane o polarized light – optically active

* Compound that does not change the plane polarized light – optically inactive

 

 

 

STEREOISOMERISM

– Compound which have their atoms connected in same order but differ in arrangement in space

– Same molecular formula and structural formula

 

 

DIFFERNCES AMONG CONSTITUTIONAL ISOMERS

-IUPAC names

– Physical properties

* Separable by physical techniques such as distillation

– Chemical properties

* Give different product

 

Difference in type of functional group…

-Also called functional group isomerism.

-Example: