[mass]

[Yggdrasil]

Which question, 12 or 13?

[mass]

13 please, I need someone to explain to me rather than give me url.

[Ahmed Abdullah]

For stereo-isomer the connectivity of the atoms are the same but they are arranged differently in the space.
For each chiral center there are two isomers. So, first find out the number of chiral carbon in the compound. Then calculate the possible number of isomers.

[mass]

For stereo-isomer the connectivity of the atoms are the same but they are arranged differently in the space.
For each chiral center there are two isomers. So, first find out the number of chiral carbon in the compound. Then calculate the possible number of isomers.

for the last molecule, are there 2 carbon atoms?

[Ahmed Abdullah]

For stereo-isomer the connectivity of the atoms are the same but they are arranged differently in the space.
For each chiral center there are two isomers. So, first find out the number of chiral carbon in the compound. Then calculate the possible number of isomers.

for the last molecule, are there 2 carbon atoms?

There are 7 carbon in the last molecule. You have to look for chiral carbon not just carbon. A chiral carbon is a carbon atom bonding with four different groups.

the carbon in CH4 or CH2X2 is not chiral
but the carbon in CHXYZ is chiral. So  has two stereo-isomer. It means there are two different compound of the structure CHXYZ.

[mass]

For stereo-isomer the connectivity of the atoms are the same but they are arranged differently in the space.
For each chiral center there are two isomers. So, first find out the number of chiral carbon in the compound. Then calculate the possible number of isomers.

for the last molecule, are there 2 carbon atoms?

There are 7 carbon in the last molecule. You have to look for chiral carbon not just carbon. A chiral carbon is a carbon atom bonding with four different groups.

the carbon in CH4 or CH2X2 is not chiral
but the carbon in CHXYZ is chiral. So  has two stereo-isomer. It means there are two different compound of the structure CHXYZ.

sorry it was a typo, I meant are there 2 chiral carbons in the last molecule.

[sjb]

Yes, I see two chiral carbons in the disubstituted cyclohexane.

So there are how many possible diasteromers?

[mass]

Yes, I see two chiral carbons in the disubstituted cyclohexane.

So there are how many possible diasteromers?

4 right?

[sjb]

Sounds good to me

[english]

Don't be afraid to experiment with it by drawing all possible stereoisomers yourself.

Switch some stereo bonds around! 

[Vik]

i understand that the number of sterioisomers can be found by the formula 2^n (where n is the number of chiral centers in the molecule), but isnt the calcuation for DIAsterioisomers different? Also, is there a formula for calculating the number of structural isomers in a compound?

[movies]

i understand that the number of sterioisomers can be found by the formula 2^n (where n is the number of chiral centers in the molecule), but isnt the calcuation for DIAsterioisomers different? Also, is there a formula for calculating the number of structural isomers in a compound?

Correct!  Diastereomers are stereoisomers that are not enantiomers. 

I don't know of any equation to calculate the number of diastereomers since it depends on the molecule and the nature of the stereocenters.  I think the best way is to draw all of the stereoisomers out and then start pairing off enantiomers and see what you have left.

Note that cis and trans olefin isomers would also be considered diastereomers even if they do not contain an asymmetric center.