maleic acid

A summary of the most common chemical descriptors (InChI Key and SMILES codes) for maleic acid are summarized together with 3D and 2D structures and relevant physico-chemical properties.

What is maleic acid?

The molecule maleic acid presents a molecular formula of C4H4O4 and its IUPAC name is (Z)-but-2-enedioic acid.

3D structure

Cartesian coordinates

Geometry of maleic acid in x, y and z coordinates (Å units) to copy/paste elsewhere. Generated with Open Babel software.

2D drawing


maleic acid VZCYOOQTPOCHFL-UPHRSURJSA-N chemical compound 2D structure molecule svg
maleic acid


Molecule descriptors

IUPAC namemaleic acid
InChI codeInChI=1S/C4H4O4/c5-3(6)1-2-4(7)8/h1-2H,(H,5,6)(H,7,8)/b2-1-

Physico-Chemical properties

IUPAC name(Z)-but-2-enedioic acid
Molecular formulaC4H4O4
Molecular weight116.07
Melting point (ºC)
Boiling point (ºC)
Density (g/cm3)
Molar refractivity
Topological polar surface area74.6

LogP and topological polar surface area (TPSA) values were estimated using Open Babel software.

The n-octanol/water partition coeficient (Kow) data is applied in toxicology and drug research. Kow values are used, to guess the environmental fate of persistent organic pollutants. High partition coefficients values, tend to accumulate in the fatty tissue of organisms. Molecules with a log(Kow) (or LogP) greater than 5 are considered to bioaccumulate.

TPSA values are the sum of the surface area over all polar atoms or molecules, mainly oxygen and nitrogen, also including hydrogen atoms.

In medicinal chemistry, TPSA is used to assess the ability of a drug to permeabilise cells.

For molecules to penetrate the blood-brain barrier (and act on receptors in the central nervous system), TPSA values below 90 Å2 are required. Thus, molecules with a polar surface area greater than 140 Å2 tend to be poorly permeable to cell membranes.