4hydroxyphenylacetamide

4-hydroxyphenyl, also called para-hydroxyphenyl (p-hydroxyphenyl), denotes a phenyl ring bearing a hydroxyl group at the para (4) position relative to a reference substituent. It is a common substituent in organic chemistry and is often described as a hydroxyphenyl moiety.

In chemical structures, 4-hydroxyphenyl is found in a variety of compounds, including p-hydroxybenzaldehyde, p-hydroxyacetophenone, and the family of 4-hydroxycinnamic acids such as p-coumaric acid. The hydroxyl group at the 4-position confers phenolic character, affecting properties such as acidity, hydrogen bonding, and redox behavior. The motif can influence solubility, UV absorbance, and reactivity in further functionalization.

Biochemically, the 4-hydroxyphenyl group is a defining feature of 4-hydroxyphenylalanine, the amino acid known as tyrosine, in which the para-hydroxyphenyl ring is attached to the amino acid backbone. Tyrosine plays roles in protein synthesis and the biosynthesis of catecholamines and melanin. Hydroxyphenyl motifs also occur in plant phenolics and polyphenols, such as tyrosol and hydroxytyrosol, which contribute to antioxidant activity and plant defense.

Applications of compounds bearing the 4-hydroxyphenyl group span pharmaceuticals, dyes, and polymers. The presence of the 4-hydroxyphenyl moiety can influence biological activity, chemical reactivity, and material properties, making it a recurring motif in research and development across chemistry and biochemistry.