Zwitterion

In chemistry, a zwitterion (/ˈtsvɪtəˌrən/ TSVIT-ə-ry-ən; from German Zwitter [ˈtsvɪtɐ] 'hermaphrodite'), also called an inner salt or dipolar ion,[1] is a molecule that contains an equal number of positively and negatively charged functional groups.[2] With amino acids, for example, in solution a chemical equilibrium will be established between the "parent" molecule and the zwitterion.

Betaines are zwitterions that cannot isomerize to an all-neutral form, such as when the positive charge is located on a quaternary ammonium group. Similarly, a molecule containing a phosphonium group and a carboxylate group cannot isomerize.

  1. ^ "Zwitterion". Chemistry LibreTexts. 2015-11-03. Archived from the original on 2023-06-21. Retrieved 2022-02-11.
  2. ^ Skoog, Douglas A.; West, Donald M.; Holler, F. James; Crouch, Stanley R. (2004). Fundamentals of Analytical Chemistry (8th ed.). Thomson/Brooks/Cole. pp. 231, 385, 419, 460. ISBN 0-03-035523-0.
    Fundamentals of Analytical Chemistry (9th ed.). 2013. pp. 415–416. ISBN 978-1-285-60719-1.