Question

Both compounds prepared in this experiment must be distinguishable from one another. Determine 3 physical tests that can be done to distinguish the two isomers. Then, write simple procedures to carry out the actual tests using available lab equipment.

compounds: Maleic acid and Fumaric acid

Answer 1

The three physical properties which will be different for the given two isomers are

a) Melting point : It can be determined with the help of electric melting point apparatus in lab. The compound is placed in small capillary and then the melting point is noted for both the isomers individualy.

the melting point of fumaric acid is more than the melting point of maleic acid due to better / effecient close packing in fumaric acid as compared to maleic acid.

b) Solubility : Due to dipole dipole interaction present in maleic acid it is polar and hence is soluble in water. (Like dissolved like, water is also polar). While Fumaric acid does not show such high solubility in water due to absence of dipole -dipole interaction. So we can disntiguish the two by mere dissolving in water.

c) Boilint point: The boiling point of fumaric acid will be higher than maleic acid.

Maleic acid forms interamolecular hydrogen bonds while fumaric acid forms intermolecular hydrogen bonds. Fumaric acid forms a spherical symmetrical sturucture and makes high number of hydrogen bonds which increases its boiling point.