Malic acid is 2-hydroxybutanedioic acid.
When malic acid is strongly heated it loses the elements of water (H and OH)
from adjacent carbon atoms to yield maleic and fumaric acids.
2HOOC(OH)HC-CH2COOH
H2O
+ 2HOOCHC=CHCOOH
Why do we not show two different acids as products?
The two acids are geometric isomers.
Maleic acid is cis-butendioic acid ; fumaric acid is trans-butendioic acid.
You will find more on these acids in the cis-trans section.
