Electronic effects of icosahedral carboranes: kinetic evidence for interaction between boron atom and nucleophile in the solvolysis of (o-carboranyl)benzyl tosylates
✍ Scribed by Yasuyuki Endo; Yoshiyuki Taoda
- Publisher
- Elsevier Science
- Year
- 2001
- Tongue
- French
- Weight
- 113 KB
- Volume
- 42
- Category
- Article
- ISSN
- 0040-4039
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✦ Synopsis
Solvolysis of (o-, m-and p-carboranyl)benzyl toluene-p-sulfonates substituted at the second carbon atom with a phenyl group bearing a range of substituents at the para position has been performed. The rates of hydrolysis of m-and p-carboranyl derivatives measured linearly with increasing electron-releasing character of the substituent group (z=-0.23, z=-0.35), which indicates that these carboranes transmit electronic effects, and the substituents affect the stability of the neighboring carbocation. In contrast, the rate of hydrolysis of o-carboranyl derivatives showed a linear decrease with increasing electron-releasing character of the substituent (z=+1.12), which indicates that the interaction between the B(3) atom of the o-carborane cage and the nucleophile controls this particular reaction.