Totally degenerate (CH)/sub 9//sup +/ ion 9-barbaralyl cation studied by /sup 13/C labeling and isotopic perturbation by eight deuteriums

Journal Article · Wed Feb 23 00:00:00 EST 1983 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00342a042· OSTI ID:6108215

Engdahl, C; Jonsaell, G; Ahlberg, P

There has been controversy regarding the structure and mechanisms of rearrangement of the totally degenerate (CH)/sub 9//sup +/ carbocation 1 obtained from bicyclo(3.2.2)nona-3,6,8-trien-2-ol (2) in superacid. Ion 1 appears as a sharp singlet in the /sub 1/H NMR spectrum at -135/sup 0/C and rearranges rapidly at -125/sup 0/C to the 1,4-dihomotropylium ion (3). Among others, bicyclo(3.2.2)nona-3,6,8-trienyl cation (4), 9-barbaralyl(tricyclo(3.3.1.o/sup 2/ /sup 8/)nona-3,6-dien-9-yl) cation (5), and the D/sub 3h/ structure (6) have been proposed as structures of ion 1. The present paper presents complete results of studies of /sup 13/C labelled ion 1 and isotopic perturbation by eight deuteriums of /sup 13/C-labeled 1. The ion precursors (3-/sup 13/C)bicyclo(3.2.2)nona-3,6,8-trien-2-ol (10) and (3-/sup 13/C,1,2,4,5,6,7,8,9-/sup 2/H/sub 8/)bicyclo(3.2.2)nona-3,6,8-trien-2-ol (12) have been synthesized. From these alcohols the corresponding ions ((CH)/sub 8//sup 13/CH)/sup +/ (11) and ((CD)/sub 8//sup 13/CH)/sup +/ (13) have been generated in superacid. On the basis of the /sup 13/C NMR spectrum of 11 and its temperature dependence, structure 4 is excluded as candidate for ion 1. Perturbation of the rapid degenerate equilibria of 11 by eight deuteriums as in 13 results in shifts of the /sup 13/C NMR signals relative to those of ion 11. These results exclude 6 as a candidate for the structure of ion 1 but are consistent with structure 5. Ion 5 undergoes a 9-fold degenerate rearrangement (..delta.. G* = 21 kJ mol/sup -1/) presumably via 4 as an intermediate. Ion 5 also undergoes an even faster rearrangement, a 6-fold degenerate rearrangement (..delta.. G* < 16 kJ mol/sup -1/) via divinylcyclopropylcarbinyl-divinylcyclopropylcarbinyl cation mechanism.

• Research Organization: Univ. of Uppsala, Sweden
• OSTI ID: 6108215
• Journal Information: J. Am. Chem. Soc.; (United States), Vol. 105:4
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
DEUTERIUM
ISOTOPE EFFECTS
ALCOHOLS
CARBON 13
LABELLED COMPOUNDS
CARBON ISOTOPES
EVEN-ODD NUCLEI
HYDROGEN ISOTOPES
HYDROXY COMPOUNDS
ISOTOPES
LIGHT NUCLEI
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
STABLE ISOTOPES
400301* - Organic Chemistry- Chemical &amp; Physicochemical Properties- (-1987)