Base-catalyzed isomerization of phenylpropenes

✍ Scribed by M. Hassan; A. R. O. Abdel Nour; A. M. Satti; K. S. Kirollos

• Publisher: John Wiley and Sons
• Year: 1982
• Tongue: English
• Weight: 258 KB
• Volume: 14
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550140403

✦ Synopsis

The prototropic rearrangement of 3-phenyl-1 -propenes to the corresponding l-phenyl-I-propenes was investigated in basic media utilizing 0.1M sodium ethoxide in absolute ethanol at 81°C. I t was found that the effect of substituents on the rate of such isomerizations follows the order: p -N 0 2 > a-CI > m-CI > rn-F > p-Br > o-CH:j > m-CH3 > rn-CH(CH:j)P > p-CH-(CH:1)2 p-C(CH:& > o-OCH:{. This is consistent with first-order kinetics and "HSk" mechanism. Quantitative treatment in terms of Hammett's equation showed a straight line, with a slope ( p value) of +2.25. An increase in the strength of the base was also found to cause an increase in the rate of isomerization.