{ stereoisomers

Isomer :compounds have the same structural formula but

Different in spatial configuration are known stereoisomers

The number of possible isomer of compound depends upon

The number of asymmetrical carbon atom Chiral center.

Asymmetric carbon - 4 different things are attached to it.

Cl

| I =2n

I - C - F

|

Br

You must have at least one asymmetric carbon to have stereoisomers.

EXAMPLE

CHO

HO H

C

CH OH2

CH OH2

H

CHO

HO

CHO

H

C

CH OH2

OH

CH OH2

H

CHO

OH

glyceraldehyde

D- glyceraldehydeL-glyceraldehyde

Types of isomer in glucose1- D and L form

Pairs of stereoisomers

Designated by D- or L- at the start of the name.

They are mirror images that can’t be overlapped.

If you don’t believe it,

give it a try!

2- and forms (anomer )

The -OH group that forms can be above or below the ring resulting in

two forms - anomers

Mutarotation : change in specific rotation of optically active solution

without any change in other properties

3- Epimer

What is an Epimer?

a. In a compound with more than one chiral carbon, only one of

the carbons differ in the epimer from the original

1. C #2 Epimer

2. C #3 Epimer

3. C #4 Epimer

EXAMPLE

4- Pyranose and furanose ring structure

furanose : is a collective term for carbohydrates that have a chemical

structure that includes a five-membered ring system consisting of four

carbon atoms and one oxygen atom. The name derives from its

similarity to the oxygen heterocycle furan, but the furanose ring does

not have double bonds.

Pyranose : any cyclic hemiacetal form of monosaccharide having a six-membered ring

5- optical activity

Dextrorotatory :compound that rotate the light to the right is

Called dextrorotatory (d or +)

Levorotatory :compound that rotate the light to the left is

Called dextrorotatory (L or - )

Racemic :no optical activity (when equal amount of dextrorotatory

and levorotatory are present )

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