[Elrojo]

Hi all

I was wondering in terms of fischer projections what the chiral centre of haloperidol is and then what the r and s structures look like.  I postulated that the chiral centre is the C=O carbon, not sure of the number off the top of my head.  and i'm a bit sketchy on the R and S rules.  From memory they are determined on the position of the functional groups, but i've never been able to get a good explanation.

Hope you can help me
 Cheers

[dexangeles]

hint: what is a chirality center?

[Elrojo]

isnt a chiral centre a carbon atom (im sure it doesnt have to be carbon) that has 4 diffrenet substrates, so when you rotate it , it will not superimpose.  But that doesnt help me here Ad Majorem Dei Gloriam.  Unless im getting something wrong.  In which case i dont see it

[Froggirl]

Well you yourself said it!   The C=O carbon would only have 3 different thing attached to the carbon as the carbonyl takes out 2 of the possible 4 bonds. This means that it is definately not a chiral centre as you need 4 different substituents attached to one atom.

The only other possible contender would be the circled carbon in the diagram below but if you look carefully you'll see that its attached to the heteroring in a symmetrial fashion. This means that this atom is also achiral.

The long and the short of it is that halperdiol is achiral in my opinion  

[Froggirl]

As for the R and S rules the way I used to remember it is:

1. First step is to rotate the chiral centre in your mind so that the lowest priority (usually a H) is facing backwards.

2. Next order the 3 groups left in order of priority (according to periodic number).

3. Lastly count from 1-3 noting whether you go clockwise or anticlockwise.

Clockwise = R
Anticlockwise = S

The way I remember it is if you were driving in the car to turn Right you would turn the steering wheel clockwise! (ie. Right = clockwise).

[dexangeles]

yup a C=O cannot be a chirality center