US EPA

8710729 

Journal Article 

A lanthanide induced shift (LIS) investigation of the conformation of cyclohexanones in solution 

Abraham, RJ; Bovill, MJ; Chadwick, DJ; Griffiths, L; Sancassan, F 

1980 

1 

Tetrahedron
ISSN: 0040-4020 

36 

2 

279-285 

English 

10.1016/0040-4020(80)80016-0 

The solution conformations of cyclohexanone 1 and 4-t-butyl cyclohexanone 2 have been obtained by the use of the LIS given by Yb(fod)3. A starting geometry for the substrates was obtained by molecular mechanics calculations. The use of a two-site model for lanthanide-substrate complexing, together with iteration on the 1H and 13C induced shifts allowed the angle of pucker of the cyclohexanone rings to be determined. In contrast, a one-site model gave no acceptable solutions. The cyclohexanone ring is somewhat flatter at the carbonyl end than cyclohexane, the angle of pucker (α) being reduced from 51° to 49° i.e. the dihedral angle (ω12) is reduced trom 56 to 51°. In 4-t-butyl-cyclohexanone the angle of pucker at the carbonyl end is further reduced. The solution conformation of 1 agrees closely with that deduced by MM calculations; interestingly, the conformation of 2 is essentially identical with the geometry found in the crystal. 1980.