There was 2 different trials for our PAA production:

-Trial 1 : 

1. Reflux 48g(16 mmol) methyl phenylacetate(45.3ml) and 200ml 2M NaOH for 2h.
2. After the solution cools, acidify it with conc. HCl to reach a PH between 4.0 and 6.0, preferably 5.0.
3. Extract three times with portions of ether equal to half the amount of solution present. The mixture must be stirred until any inorganic precipitate is dissolved.
4. Filter the solution and separate the organic layer.
5. Wash with cold water.
6. Dry over anhydrous sodium sulfate.
7. Distill the ether off. Diethyl ether boils at 34.6°C. Alternatively, leave the ether to evaporate.
8. Recrystallize the residue from water to obtain free crystalline phenylacetic acid.

-Trial 2:

In this trial w proceed with acidification using concentrated hydrochloric acid, then filtration  and recrystallization with cold water

1. Reflux 48g(16 mmol) methyl phenylacetate(~45.3ml) and 200ml 2M NaOH for 2h.
2. After the solution cools, acidify it with conc. HCl (~60mL). The pH value of the solution must be controlled between 4.0 and 6.0, preferably 5.0.
3. Filtrate with a Vacuum filtration using cold water for washing.Purification:
4. Recrystallize the solution by dissolving the filtrate in hot water then letting it cool down at room temperature before freezing overnight.
5. Filter an dry the PAA produced

 RESULTS:

According to the melting point tests, trial 2was the best way used for PAA production with a high yield (86%) and the desired melting point (75-76.6) without purification also, so we can proceed for a large scale production.

There are several methods to identify the presence of phenylacetic acid other then melting point:

Solubility Test: Phenylacetic acid is soluble in hot water, ethanol and diethyl ether

Odor test: Phenylacetic acid has a characteristic odor of honey or horse sweat. If you suspect the presence of phenylacetic acid, you can smell the sample for this distinctive odor.