4-Hydroxybenzaldehyde

4‑Hydroxy­benzaldehyde (para‑hydroxy­benzaldehyde) is an organic compound with the formula C₆H₄OH(CHO).^[4][5] Along with 2-hydroxybenzaldehyde and 3-hydroxybenzaldehyde, it is one of the three isomers of hydroxybenzaldehyde.

4-Hydroxybenzaldehyde

Names
Preferred IUPAC name 4-Hydroxybenzaldehyde
Other names p-Hydroxybenzaldehyde, 4-formylphenol[1]
Identifiers
CAS Number	123-08-0 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:17597 Y
ChEMBL	ChEMBL14193 Y
ChemSpider	123 Y
DrugBank	DB03560 Y
ECHA InfoCard	100.004.182
KEGG	C00633 Y
PubChem CID	126
UNII	O1738X3Y38 Y
CompTox Dashboard (EPA)	DTXSID8059552
InChI InChI=1S/C7H6O2/c8-5-6-1-3-7(9)4-2-6/h1-5,9H Y Key: RGHHSNMVTDWUBI-UHFFFAOYSA-N Y InChI=1/C7H6O2/c8-5-6-1-3-7(9)4-2-6/h1-5,9H Key: RGHHSNMVTDWUBI-UHFFFAOYAN
SMILES O=Cc1ccc(O)cc1
Properties
Chemical formula	C7H6O2
Molar mass	122.123 g·mol−1
Appearance	yellow to tan powder
Density	1.129 g/cm3 (130 °C)[1]
Melting point	116 °C (241 °F; 389 K)[1]
Boiling point	310 to 311 °C (590 to 592 °F; 583 to 584 K)
Solubility in water	12.9 g/L[2]
Acidity (pKa)	7.61 (25 °C)[3]
Magnetic susceptibility (χ)	−78.0·10−6 cm3/mol
Refractive index (nD)	1.57051 (130 °C)[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Synthesis, reactions, uses

4-Hydroxybenzaldehyde is prepared by reaction of phenol with chloroform, which gives isomeric hydroxybenzal chlorides. Hydrolysis of the C-Cl bonds gives the aldehyde.^[5]

4-Hydroxybenzaldehyde is a precursor to 4-hydroxyphenylglycine, a precursor to penicillins. In the Dakin oxidation, 4-hydroxybenzaldehyde reacts with hydrogen peroxide in base to form hydroquinone.

Metabolism and occurrence

p-Hydroxybenzaldehyde dehydrogenase is an enzyme found in carrots (Daucus carota).^[6]

4-Hydroxybenzaldehyde is found in the orchids Gastrodia elata,^[7] Galeola faberi,^[8] and the Vanilla orchids.

See also

• Salicylaldehyde (2-hydroxybenzaldehyde)