Question

I'm trying to work on a separation scheme for 50% 1,2,4,5-tetrachlorobenzene, 40% o-toulic acid, and 10% 1,4-dibromobenzene. I could really use your advice ASAP, thank you! Using crystalllization and acid-base extraction, I need to sperate and purify at least 2 of the 3 compounds listed. The following reagents are available: 1M NaOH, 6M NaOH, 1M HCl, 6M HCl, 1M NaHCO3, saturated sodium chloride, diethyl ether, 95% ethanol, methanol, isopropyl alcohol, actone, hexane, toulene, methylene choride, and granular anhydrous sodium sulfate.

Answer 1

separation scheme for 50% 1,2,4,5-tetrachlorobenzene, 40% o-toulic acid, and 10% 1,4-dibromobenzene :

1. CH3-C6H4-COOH + NaOH --------> H2O + CH3-C6H4-COONa

CH3-C6H4-COOH + NaHCO3 ---> CH3-C6H4-COONa + H2O(l) + CO2(g)

The aqueous NaOH or NaHCO3 will react with o-toluic acid to form the sodium salt of acid, while the 1,2,4,5-tetrachlorobenzene and 1,4-dibromobenzene remain in the organic layer.

the aqueous layer was then separate out and precipitated out using HCl. this will give us o-toluic acid.

2. 1,2,4,5-tetrachlorobenzene and 1,4-dibromobenzene are insoluble in water. hence, The separation of p-dibromobenzene from 1,2,4,5-tetrachlorobenzene would most likely require fractional distillation at reduced pressure.

Boiling point of p-dibromobenzene is around 220 ^oC.

Boiling point of p-dibromobenzene is around 245 ^oC.