Hydroxyl Group Definition in Chemistry

The hydroxyl functional group is an oxygen-containing group based on an alcohol or OH group.
The hydroxyl functional group is an oxygen-containing group based on an alcohol or OH group. Ben Mills
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Anne Marie Helmenstine, Ph.D.
Anne Marie Helmenstine, Ph.D.
Chemistry Expert
  • Ph.D., Biomedical Sciences, University of Tennessee at Knoxville
  • B.A., Physics and Mathematics, Hastings College
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
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Updated on November 05, 2018

The hydroxyl group is a functional group consisting of a hydrogen atom covalently bonded to an oxygen atom. The hydroxyl group is denoted by -OH in chemical structures and has a valence charge of -1. The hydroxyl radical is very reactive, so it quickly reacts with other chemical species. Hydroxyl radicals can cause DNA and cell damage.

Hydroxyl Versus Hydroxy

The terms "hydroxyl" and "hydroxy" tend to be used interchangeably, but they don't technically mean the same thing. The term hydroxyl means the radical OH. The functional group -OH is more properly called a hydroxy group. Further, the [OH-] anion, which is called hydroxide, consists of a hydroxy group.

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Helmenstine, Anne Marie, Ph.D. "Hydroxyl Group Definition in Chemistry." ThoughtCo, Aug. 25, 2020, thoughtco.com/definition-of-hydroxyl-group-608739. Helmenstine, Anne Marie, Ph.D. (2020, August 25). Hydroxyl Group Definition in Chemistry. Retrieved from https://www.thoughtco.com/definition-of-hydroxyl-group-608739 Helmenstine, Anne Marie, Ph.D. "Hydroxyl Group Definition in Chemistry." ThoughtCo. https://www.thoughtco.com/definition-of-hydroxyl-group-608739 (accessed June 8, 2023).
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