Synthesis of E and Z Isomers of Α-Phenylcinnamic Acid

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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. CompoundLiteratureActual
Crude (E)-α-phenylcinnamic acid3054Aromatic =C-H (stretch)5053Aromatic =C-H (stretch)
2616-3054Carboxylic acid O-H (stretch)2498-3053Carboxylic acid O-H (stretch)
1676Carbonyl C=O (stretch)1670Carbonyl C=O (stretch)
1599&1493Benzene C=C (aromatic stretch)1597&1493Benzene C=C (aromatic stretch)
1293Carboxylic acid C-O (stretch)1267Carboxylic acid C-O (stretch)
788Alkene =C-H bending (stretch)786-845Alkene =C-H bending (stretch) Pure (E)-α-phenylcinnamic acid3054Aromatic =C-H (stretch)5053Aromatic =C-H (stretch)
2616-3054Carboxylic acid O-H (stretch)2516-2951Carboxylic acid O-H (stretch)
1676Carbonyl C=O (stretch)1673Carbonyl C=O (stretch)
1599&1493Benzene C=C (aromatic stretch)1573&1493Benzene C=C (aromatic stretch)
1293Carboxylic acid C-O (stretch)1271Carboxylic acid C-O (stretch)
788Alkene =C-H bending (stretch)788-843Tri-substituted alkene =C-H bending (stretch) Crude (Z)-α-phenylcinnamic acid3053Aromatic =C-H (stretch)3056Aromatic =C-H (stretch)
2630-3053Carboxylic acid O-H (stretch)2470-2561Carboxylic acid O-H (stretch)
1675Carbonyl C=O (stretch)1669Carbonyl C=O (stretch)
1616&1493Benzene C=C (aromatic stretch)1616&1491Benzene C=C (aromatic stretch)
1272Carboxylic acid C-O (stretch)1291Carboxylic acid C-O (stretch)
787Alkene =C-H bending (stretch)789Alkene =C-H bending...
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