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  • The C-Cl bond in the halogenoalkane starts to lengthen and weaken
  • The chloride ion is eventually detached from the carbon atom and a flat carbocation forms. This is the rate determining step.
  • The hydroxide ion could attack from the left-hand side, leading to inversion of the configuration of the carbon skeleton; or
  • attack could come from the right, leading to retention of configuration.
  • The use of a chiral halogenoalkane in this reaction leads to  production of a racemic mixture if the amount of attack from each side is equal. The hindrance caused by the departing cloride ion gives about 40% attack from the right and 60% from the left, however.

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