5hydroksylgruppen

The 5-hydroxyl group, often written as a 5-hydroxy or 5-OH group, is a hydroxyl substituent attached at the fifth position of a ring system in organic molecules. It is defined by IUPAC naming conventions, where the ring or fused-ring system is numbered to give the lowest locants for substituents, and the hydroxyl group is specified as being at position 5.

In terms of chemical behavior, the 5-hydroxyl group is a phenolic or alcohol functional group. As a phenol-type OH, it can donate a proton, making the molecule slightly acidic and capable of forming phenoxide ions under basic conditions. The group participates in hydrogen bonding and can influence the molecule’s polarity, solubility, and UV-visible absorbance. It can undergo typical transformations such as esterification, ether formation, or oxidation to quinones, and its presence can affect the electronic distribution of the ring, guiding electrophilic aromatic substitution.

Occurrence and significance vary with the molecular context. The 5-hydroxyl group appears in various natural products and bioactive compounds, where its position can influence biological activity, solubility, and metabolic pathways. In medicinal chemistry and biochemistry, hydroxyl groups at defined positions often serve as anchors for further modification or as sites of enzymatic action.

A notable example is 5-hydroxytryptophan (5-HTP), a precursor to the neurotransmitter serotonin. The 5-hydroxyl group in such compounds is a key structural feature that contributes to their chemical reactivity and biological function.