When you have two hydrogens attached come a single carbon, they can have 3 different species of relationships. We contact them “homotopic”, “enantiotopic”, and also “diastereotopic”.

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Table that Contents

1. As soon as Is “Homotopic, Enantiotopic, Diastereotopic” Important?

 Certain reactions directly replace hydrogens with various other atoms. Because that example, cost-free radical chlorination replaces C-H bonds with C-Cl bonds. So expertise these principles assist in knowledge what potential varieties of assets you could achieve from these reactions.

2. Homotopic Atoms

Take a molecule prefer ethane. Let’s label (with color) two different hydrogens, blue and red. Next, let’s change each of this hydrogens subsequently with a different atom. In this example it might be deuterium (D) however really this deserve to be done with any kind of atom or group (except hydrogen the course).

Replace the red H and also the blue H subsequently with D and also compare the molecule that are formed. Ask: just how are these molecules related?

In this situation they space both deuterioethane. Due to the fact that the two molecules space the same, the two hydrogens are said to be “homotopic”. Instead of of either provides rise come the exact same product.

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5. When does the matter?

Two situations:

In free radical chorination – say, of butane – on the 2nd carbon (C-2), substitution the C-H through Cl will result in a mixture the stereocenters. It’s essential to recognize once this can happen. (Most common) – In NMR spectroscopy:homotopic protons have actually the exact same chemistry shiftenantiotopic protons have the same chemical shift in the vast majority of situations. However, if castle are placed in a chiral atmosphere (e.g. A chiral solvent) they will have different chemical shifts.diastereotopic protons have various chemical shifts in all situations

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