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Which of the following statements about a carbocation is INCORRECT?

1. It is a Lewis acid.
2. It has 6 electrons in its valence shell.
3. It is an electrophile.
4. It is always trigonal planar.

Correct answer: It is always trigonal planar.

Solution

A simple carbocation carbon is sp2 with an empty p-orbital, 6 valence electrons, behaves as a Lewis acid and electrophile - those three statements are correct. However, carbocations are NOT always trigonal planar: bridged (non-classical) carbocations and vinyl/aryl cations adopt other geometries. So the statement that it is 'always trigonal planar' is incorrect.

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