Carboxyl group

  Carboxyl group or carboxy group -COOH or CO₂H is a functional group present in amino acids and carboxylic acids. Its structure is composed of one carbon atom attached to an oxygen atom by double bond and to a hydroxyl group by a single bond. It is often mentioned that a carboxyl group is a carbonyl group bonded to a hydroxyl group. The carboxyl group has one valence electron in its carbon atom, making it possible to be a part in a larger molecule by bonding through it. Carboxyl groups can only occur at the end of a carbon chain, because the carbon must make 3 bonds (O double bond and single bond to hydroxyl group) in addition to its connection to the R group.

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Carboxyl groups will often lend their H+ into solution and therefore will act as acids. This is the case with carboxylic acids, such as is the case when acetate lends its H+ into solution to become acetic acid.

See also

• Amino acid
• Carboxylic acid

References

• Entry from the Encyclopedia of Astrobiology, Astronomy, and Spaceflight.
• Highbeam Encyclopedia.