[prncess23]

Hello,

Ok, so i know that in order for a carbon to be a stereocenter, it has to have 4 different things attached to it. So, a carbon with a double bond can NEVER be a stereocenter because it will only have 3 things attached to it...at most...right? And that if a carbon is chiral its mirror image is NOT superimposeable.

So....i am confused with determining how many isomers 1,4-pentadien-3-ol has and citric acid.  But first, i need to determine how many stereocenters it has so i can use the 2ⁿ rule.

structures are below:

1,4-pentadien-3-ol


Citric Acid

[Borek]

Do you see a carbon with four different groups attached in any of these compounds?

[prncess23]

Do you see a carbon with four different groups attached in any of these compounds?

1,4-pentadien-3-ol, i see that carbon 3 with the OH group attached.

citric acid...the three carbons in the middle of the molecule, between the double bonds have 4 things attached, but the 2 H's are the same...so...that molecule is achiral right...b/c its mirror image CAN be superimposed upon itself...and b/c it has a internal plane of symmetry???

[Borek]

1,4-pentadien-3-ol, i see that carbon 3 with the OH group attached.

List and compare all three groups attached.

[prncess23]

1,4-pentadien-3-ol, i see that carbon 3 with the OH group attached.

List and compare all three groups attached.

but in order for it to be a stereocenter, the carbon needs to have 4 different groups attached...NOT 3....

[prncess23]

1,4-pentadien-3-ol, i see that carbon 3 with the OH group attached.

List and compare all three groups attached.

but in order for it to be a stereocenter, the carbon needs to have 4 different groups attached...NOT 3....

groups:
CH
CH
OH
H

[Borek]

List and compare all three groups attached.

but in order for it to be a stereocenter, the carbon needs to have 4 different groups attached...NOT 3....

Sorry. Let's call it a typo. I was thinking about other three groups (apart from -OH that you have already named).

groups:
CH
CH
OH
H

CH are wrong, it is not only the closest atom that counts.

Try to compare these groups.

[wanderlust]

Neither of these two compounds has a stereocenter.  If you're having troubles try watching this series of youtube videos they might be helpful http://www.youtube.com/watch?v=NxIOrK6wF70