Question

we were doing acid-base extraction lab. The mixture included a base, an acid and a neutral organic compound. So at the end of lab we have to predict what is the organic compound. this organic compound was one of these:

a) 4-chlorobenzophenone

b) biphenyl

c) trans-stilbene

d) trans-chalcone

in the solubility test, the organic compound dissolve in cold hexane and ethyl acetate. it did not dissolve in water and cold methanol, but it dissolve in hot methanol.

can someone predict what is the organic compound and explain please??

Answer 1

Your compund must be b) Biphenyl

Explanation: Here Solubility test in cold hexane is most important in determining the compound you are dealing with. Out of four compounds, two have C=O group (a and d), so their interaction with non-polar solvent like hexane won't be that effective beacuse of poor dipole-hydrophobic interaction.

Now, out of b) biphenyl and c) trans-stilbene, the trans-stilbene has an extended conjugation as a result it will be more polar than biphenyl and hence, its solubility in heanxe will be poor.

The only reamining compound is biphenyl which has excellent solubility in hexane.

Therefore, your compound is b) Biphenyl

Solvents like ethyl acetate and methanol will dissolve all four compounds. Its won't give us any conclusion.