Hydroxy group

Source: Wikipedia, the free encyclopedia.
This article is about the hydroxy functional group. For the Hydroxyl radical, see Hydroxyl radical.
covalent chemical bonds
.

In

anion HO−, called hydroxide, and the neutral radical HO·, known as the hydroxyl radical
, consist of an unbonded hydroxy group.

According to IUPAC definitions, the term hydroxyl refers to the hydroxyl radical (·OH) only, while the functional group −OH is called a hydroxy group.[1]

Properties

Sulfuric acid contains two hydroxy groups.

Water, alcohols,

carboxylic acids, and many other hydroxy-containing compounds can be readily deprotonated due to a large difference between the electronegativity of oxygen (3.5) and that of hydrogen (2.1). Hydroxy-containing compounds engage in intermolecular hydrogen bonding increasing the electrostatic attraction between molecules and thus to higher boiling and melting points than found for compounds that lack this functional group. Organic compounds, which are often poorly soluble in water, become water-soluble when they contain two or more hydroxy groups, as illustrated by sugars and amino acid.[citation needed
]

Occurrence

The hydroxy group is pervasive in chemistry and biochemistry. Many inorganic compounds contain hydroxyl groups, including sulfuric acid, the chemical compound produced on the largest scale industrially.[2]

Hydroxy groups participate in the dehydration reactions that link simple biological molecules into long chains. The joining of a

triacylglycerol removes the −OH from the carboxy end of the fatty acid. The joining of two aldehyde sugars to form a disaccharide removes the −OH from the carboxy group at the aldehyde end of one sugar. The creation of a peptide bond to link two amino acids to make a protein removes the −OH from the carboxy group of one amino acid.[3]

Hydroxyl radical

Main article: Hydroxyl radical

Hydroxyl radicals are highly reactive and undergo chemical reactions that make them short-lived. When biological systems are exposed to hydroxyl radicals, they can cause damage to cells, including those in humans, where they can react with DNA, lipids, and proteins.[4]

Planetary observations

Airglow of the Earth

The Earth's night sky is illuminated by diffuse light, called airglow, that is produced by radiative transitions of atoms and molecules.[5] Among the most intense such features observed in the Earth's night sky is a group of infrared transitions at wavelengths between 700 nanometers and 900 nanometers. In 1950, Aden Meinel showed that these were transitions of the hydroxyl molecule, OH.[6]

Surface of the Moon

In 2009, India's

Deep Impact probe each detected evidence of water by evidence of hydroxyl fragments on the Moon. As reported by Richard Kerr, "A spectrometer [the Moon Mineralogy Mapper, also known as "M3"] detected an infrared absorption at a wavelength of 3.0 micrometers that only water or hydroxyl—a hydrogen and an oxygen bound together—could have created."[7] NASA also reported in 2009 that the LCROSS probe revealed an ultraviolet emission spectrum consistent with hydroxyl presence.[8]

On 26 October 2020,

Clavius (crater), obtained by the Stratospheric Observatory for Infrared Astronomy (SOFIA).[9] The SOFIA Faint Object infrared Camera for the SOFIA Telescope (FORCAST) detected emission bands at a wavelength of 6.1 micrometers that are present in water but not in hydroxyl. The abundance of water on the Moon's surface was inferred to be equivalent to the contents of a 12-ounce bottle of water per cubic meter of lunar soil.[10]

The Chang'e 5 probe, which landed on the Moon on 1 December 2020, carried a mineralogical spectrometer that could measure infrared reflectance spectra of lunar rock and regolith. The reflectance spectrum of a rock sample at a wavelength of 2.85 micrometers indicated localized water/hydroxyl concentrations as high as 180 parts per million.[11]

Atmosphere of Venus

The Venus Express orbiter collected Venus science data from April 2006 until December 2014. In 2008, Piccioni, et al. reported measurements of night-side airglow emission in the atmosphere of Venus made with the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on Venus Express. They attributed emission bands in wavelength ranges of 1.40 - 1.49 micrometers and 2.6 - 3.14 micrometers to vibrational transitions of OH.[12] This was the first evidence for OH in the atmosphere of any planet other than Earth's.[12]

Atmosphere of Mars

In 2013, OH near-infrared spectra were observed in the night glow in the polar winter atmosphere of Mars by use of the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM).[13]

Exoplanets

In 2021, evidence for OH in the dayside atmosphere of the exoplanet

ultra-hot Jupiters
and it is likely that any water in their atmospheres is present as dissociated ions.

See also

Wikimedia Commons has media related to Hydroxyl group.

References

  1. doi:10.1351/goldbook.A00204
    . Retrieved 23 March 2015.
  2. ^ "Research Report 2012 – 2013" (PDF). Ludwig Maximilians Universität München Fakultät für Chemie und Pharmazie. 12. Archived from the original (PDF) on Dec 7, 2022.
  3. ^ "Peptide Bond - an overview". ScienceDirect Topics. Archived from the original on 2022-10-20. Retrieved 2022-10-20.
  4. PMID 22798706
    .
  5. S2CID 120677542. Archived
    from the original on Oct 5, 2023.
  6. doi:10.1086/145296. Archived
    from the original on Oct 24, 2022.
  7. ^ Kerr RA (24 September 2009). "A Whiff of Water Found on the Moon". Science. Archived from the original on Dec 8, 2023. Retrieved 2016-06-01.
  8. ^ Dino J (13 November 2009). "LCROSS Impact Data Indicates Water on Moon". NASA. Archived from the original on 2009-11-15. Retrieved 2009-11-14.
  9. S2CID 228954129
    .
  10. ^ Chou F, Hawkes A (26 October 2020). "NASA's SOFIA Discovers Water on Sunlit Surface of Moon". NASA. Retrieved 2020-10-26.
  11. PMID 34995111
    .
  12. ^
    ISSN 0004-6361
    .
  13. doi:10.1016/j.icarus.2013.05.035
    .
  14. S2CID 232110452
    .
  15. S2CID 239616465
    .

Further

External links

Look up hydroxy group in Wiktionary, the free dictionary.
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