Hydrogen as a migrating group in some pinacol ­rearrangements: a DFT study

✍ Scribed by William B. Smith

• Book ID: 101288250
• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 74 KB
• Volume: 12
• Category: Article
• ISSN: 0894-3230
• DOI: 10.1002/(sici)1099-1395(199910)12:10<741::aid-poc187>3.0.co;2-6

✦ Synopsis

DFT calculations at the Becke3LYP/6-31G* level were employed to demonstrate that the pinacol rearrangement of ethylene glycol and the 1,1-dimethyl and 1,1,2-trimethyl analogs undergo pinacol rearrangements by a concerted hydrogen-bridged transition structure. No evidence for a bridged intermediate was found. Calculations by two methods on the ethylene glycol system were repeated with the various structures embedded in a solvent cavity with the medium dielectric constant set for water. The ratio of rates for the two methylated glycols was calculated with good agreement with the experimental value. The kinetic isotope effect for the rearrangement of 1,1,2trimethylethylene glycol was calculated (2.8) in fair agreement with the experimental value of 1.6. Sources of error are briefly discussed.