Synthesis of E and Z Isomers of Α-Phenylcinnamic Acid

Introduction:
This experiment focuses on carrying out a Perkin Reaction to synthesize (E) and (Z) isomers of α-phenylcinnamic acid. This was accomplished by refluxing benzaldehyde, phenylacetic acid, acetic anhydride and triethylamine as a base. The chemical equation of a Perkin Reaction can be seen below. The reaction mechanism for the synthesis of α-phenylcinnamic acid is shown below:

Results:
Theoretical Yield

Therefore, phenylacetic acid is the limiting reagent.

Table 1. Literature and actual IR values of (E) and (Z) isomers of α-phenylcinnamic acid.
Compound Literature Actual
Crude (E)-α-phenylcinnamic acid 3054 Aromatic =C-H (stretch) 5053 Aromatic =C-H (stretch) 2616-3054 Carboxylic acid O-H (stretch) 2498-3053 Carboxylic acid O-H (stretch) 1676 Carbonyl C=O (stretch) 1670 Carbonyl C=O (stretch) 1599&1493 Benzene C=C (aromatic stretch) 1597&1493 Benzene C=C (aromatic stretch) 1293 Carboxylic acid C-O (stretch) 1267 Carboxylic acid C-O (stretch) 788 Alkene =C-H bending (stretch) 786-845 Alkene =C-H bending (stretch)
Pure (E)-α-phenylcinnamic acid 3054 Aromatic =C-H (stretch) 5053 Aromatic =C-H (stretch) 2616-3054 Carboxylic acid O-H (stretch) 2516-2951 Carboxylic acid O-H (stretch) 1676 Carbonyl C=O (stretch) 1673 Carbonyl C=O (stretch) 1599&1493 Benzene C=C (aromatic stretch) 1573&1493 Benzene C=C (aromatic stretch) 1293 Carboxylic acid C-O (stretch) 1271 Carboxylic acid C-O (stretch) 788 Alkene =C-H bending (stretch) 788-843 Tri-substituted alkene =C-H bending (stretch)
Crude (Z)-α-phenylcinnamic acid 3053 Aromatic =C-H (stretch) 3056 Aromatic =C-H (stretch) 2630-3053 Carboxylic acid O-H (stretch) 2470-2561 Carboxylic acid O-H (stretch) 1675 Carbonyl C=O (stretch) 1669 Carbonyl C=O (stretch) 1616&1493 Benzene C=C (aromatic stretch) 1616&1491 Benzene C=C (aromatic stretch) 1272 Carboxylic acid C-O (stretch) 1291 Carboxylic acid C-O (stretch) 787 Alkene =C-H bending (stretch) 789 Alkene =C-H bending