How do you determine the steric hindrance

Nucleophilic substitution

You're preparing for your next exam and you're ready for the nucleophilic substitution bumped? Would you like to know more about it now? No problem, here we explain how the two of them are to shapeSn1 and Sn2 the nucleophilicsubstitution differ and how they work.

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  • Nucleophilic substitution explained simply
    in the text
  • Nucleophilic Substitution Mechanisms
    in the text
  • Nucleophilic substitution: Sn1 or Sn2 mechanism
    in the text
  • Nucleophilic substitution example alcohol
    in the text

Nucleophilic substitution explained simply

First of all, you probably want to know what's roughly in the nucleophilic substitution expires.

Intervene in this reaction Nucleophile, So a electron-rich particle, a organic molecule R-X with a strong polarized bond at. The more electro-negative part of the attacked bond becomes the nucleophilic substitution cleaved and one forms new bond of the molecule to the attacking nucleophile out.

Nucleophilic Substitution Mechanisms

However, there are several variants the nucleophilic substitution, namely the and the Reaction. The letters stand as abbreviation For "nucleophilic substitution“While the number in the end has to do with the number of reactants involved in the speed-determining step relates. In the case of the So that's just a reaction a particlewhile it is in mechanism 2 reaction partners are.

This step is speed-determining because it is the highest activation energy owns. Let's look at the two different mechanisms of the nucleophilic substitution it is best to do it one at a time.

Nucleophilic substitution Sn1 mechanism

First to the Reaction: In this case the first and also speed-determining Step that X-particle heterolytic from. So there is an intermediate product with an anion and a positively charged carbocation. This carbo-cation is included planar, because in this state it also has its Hybridization of to changed. If you stick to that Hybridization model remember back, you probably also remember that hybridized carbon atoms Bond angle of 120° and are so planar. If you like the wholeHybridization model want to look again, please clickhere.

That this is the speed-determining Step, you can tell by the fact that in the diagram he is the highest activation energy needed. Only in the next step, the one clearly lower activation energy has and also more quickly expires, the real thing takes hold Nucleophile the Carbocation and forms a new bond, which also creates the product of the reaction. That at the speed-determining step only a particle is involved, i.e. only the organic molecule R-X itself, becomes clearer to you when you do that Speed ​​law for this Elemental reaction set up. This looks like this:

So if only the organic molecule R-X is actually involved in the rate-limiting step, then the Reaction speed only then increase, albeit the concentration from Substrate R-Xincreases. However, that also means that the Reaction speed independent is from the Concentration of the nucleophile. Experimental investigations also confirm exactly this suspected mechanism.

Nucleophilic substitution Sn1 stereochemistry

Besides, you should Carbocation in the intermediate take a closer look at nucleophilic substitution. Because, as already said, this is a planar molecule. The nucleophile can therefore from both sides attack the carbocation.