Encyclopedia > SN1 reaction

  Article Content

SN1 reaction

The SN1 reaction is an organic reaction in chemistry. "SN" stands for substitution nucleophilic and the "1" represents the fact that the rate-determining step[?] take place on the first order, that is it happens with only one molecule. Increasing or decreasing the concentration of that kind of molecule in a closed system[?] changes the rate of the reaction in a direct relationship[?].

The SN1 reaction takes place in two steps:

  1. Changing the carbon centre:
    1. Formation of a carbocation: due to the separates of leaving group (molecule A) from the carbon.
    2. Nucleophilic attack[?]: a nucleophile (molecule B) joins onto the carbon.
  2. Deprotonation: Removal of a proton on the protonated nucleophile by a molecule (sometimes the same species as A) in the solvent, usually protic.

An example reaction:

  1. C(CH3)3Br --> C(CH3)3+ + Br-
  2. C(CH3)3+ + OH- --> C(CH3)3OH

This gives the overall reaction:

C(CH3)3Br + OH- --> C(CH3)3OH + Br-

SN1 occurs where the central carbon atom is surrounded by bulky groups. The rate depends only on the concentration of the substrate.

rate = k[RX]

Nucleophilicity is irrelevant in the determining step's rate, in which only the substrate is crucial.

Because the intermediate cation, R+, is planar, an optically active[?] substrate gives a racemic mixture because nucleophilic attack[?] can occur from either side.

External links

  • Diagrams (http://www.chemhelper.com/sn1): Frostburg State University
  • Excercise (http://www.usm.maine.edu/~newton/Chy251_253/Lectures/Sn1/Sn1FS): the University of Maine

All Wikipedia text is available under the terms of the GNU Free Documentation License

  Search Encyclopedia

Search over one million articles, find something about almost anything!
  Featured Article

... (layers 1 through 3) of the OSI model. It was developed to describe how data passes into and out of public data communications networks. It is connection oriented[?] and ...