Asymmetric Carbon: Why Treat - Sign as Group?

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In summary: No.In summary, my teacher says that in picture (1) carbon atom is asymmetric carbon atom. I don't know why. I know asymmetric carbon atom are those carbon atoms which are bonded with four different groups/atoms by single bonds. But why would we treat a negative sign as a group or atom? And I also want to ask for whatever reason we are treating negative sign as a different group we must treat + sign in a same way. Hence, carbon atom in (2) should also be asymmetrical.
  • #1
gracy
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chiral.png

My teacher says in picture (1) carbon atom is Asymmetric carbon atom. I don't know why. I know asymmetric carbon atom are those carbon atoms which are bonded with four different groups/atoms by single bonds. But why would we treat a negative sign as a group or atom?
And I also want to ask for whatever reason we are treating negative sign as a different group we must treat + sign in a same way. Hence, carbon atom in (2) should also be asymmetrical. Right?
 
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  • #2
Hi Gracy,
It would help if you would let us know what level class this is for. The explanation level should greatly depend on that.
 
  • #3
Hint: difference in charges means difference in the number of electrons present. They have to "be somewhere".
 
  • #4
Borek said:
They have to "be somewhere".
You mean negative charge isn't present there alone there must be an atom carrying that negative charge?
 
  • #5
No. There is no atom carrying the charge.

The electron ha to be somewhere. For example in a water molecule, in an ammonia molecule, there are electrons that are not accompanied by an atom (it happens that these molecules don't carry a charge, but the idea is exactly the same).

Where do these electrons reside?
 
  • #6
Are these examples you made up or your teacher made up? I don't think these represent any actual molecules that would exist (for example, the nitrogen with only a single chemical bond would be very unstable).

In general, however, it may be useful to consider the geometry of the carbon (i.e. is it trigonal planal, trigonal pyrimidal, tetrahedral, bent, linear, etc).
 
  • #7
Ygggdrasil said:
Are these examples you made up or your teacher made up?
My teacher.
 
  • #8
Borek said:
The electron ha to be somewhere. For example in a water molecule, in an ammonia molecule,
I think there are partial charges in water and ammonia molecules.
 
  • #9
gracy said:
I think there are partial charges in water and ammonia molecules.

We are not talking about dipoles here.

Have you ever heard about a lone pair? An orbital?
 

Related to Asymmetric Carbon: Why Treat - Sign as Group?

1. What is an asymmetric carbon?

An asymmetric carbon, also known as a chiral carbon, is a type of carbon atom that is bonded to four different groups or atoms. This results in the carbon atom having a non-superimposable mirror image, making it optically active.

2. Why is it important to treat asymmetric carbon as a group?

Treating asymmetric carbon as a group is important because it allows us to distinguish between enantiomers, which are molecules that are mirror images of each other and have the same chemical formula but different spatial arrangements. This is crucial in fields such as drug development, where the two enantiomers of a molecule can have different biological effects.

3. What is the significance of the - sign in asymmetric carbon?

The - sign in asymmetric carbon notation represents the direction of the priority of the four groups attached to the carbon atom. The group with the lowest priority is placed at the back of the carbon atom, while the other three groups are arranged in a clockwise or counterclockwise direction, with the highest priority group at the front.

4. How is the priority of groups determined in asymmetric carbon notation?

The priority of groups in asymmetric carbon notation is determined by the Cahn-Ingold-Prelog (CIP) rules, which assign priorities based on the atomic number of the atoms directly attached to the asymmetric carbon. The group with the highest atomic number is given the highest priority, followed by the second-highest, and so on.

5. Can a molecule have more than one asymmetric carbon?

Yes, a molecule can have multiple asymmetric carbons. The number of asymmetric carbons in a molecule determines the number of possible stereoisomers, which are molecules with the same chemical formula but different spatial arrangements. For example, a molecule with two asymmetric carbons can have a maximum of four stereoisomers (2^2 = 4).

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