How many stereoisomers are possible for

a. a ketoheptose? b. an aldoheptose? c. a ketotriose?

Stereoisomers are the isomers that have the “same molecular formula and bonds but differ in the orientation of their atoms.”

The formula to calculate the number of stereoisomers is given as follows:

Number of stereoisomers = 2ⁿ

Where:

A number of chiral centers present in the given compound are given by “n” and are represented by the sign of *.

Ketoheptose structure has a total of four chiral carbon (attach to all four different groups); thus,the value of n = 4

Putting the value of n in the formula of the number of stereoisomers :

Number of stereoisomers = 2ⁿ

= 2⁴

= 16

ThereforeKetoheptose has 16 possible stereoisomers.

The four chiral carbon (represented by *) of Ketoheptose is shown as follows:

Ketoheptose Chiral carbon

Aldoheptose structure has a total of five chiral carbon (attach to all four different groups); thus,the value of n = 5

Putting the value of n in the formula of the number of stereoisomers :

Number of stereoisomers = 2ⁿ

= 2⁵

= 32

Thereforealdoheptose has 35 possible stereoisomers.

The five chiral carbon (represented by *) of aldoheptose is shown as follows:

Aldoheptose Chiral carbon

Ketotriose structure has no chiral carbon (no carbon attach to all four different groups); thus,the value of n = 0

Putting the value of n in the formula of the number of stereoisomers :

Number of stereoisomers = 2ⁿ

= 2⁰

= 0

ThereforeKetotriose has no possible stereoisomers.

The structure of Ketotriose having no chiral center is shown as follows:

Ketotriose with no chiral carbon