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Bicyclo[3.2.0]hepta-1,4,6-triene: synthesis, thermal rearrangement, and anion formation


D'Amore, Michael Brian (1972) Bicyclo[3.2.0]hepta-1,4,6-triene: synthesis, thermal rearrangement, and anion formation. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/HJ5M-D411.


In order to determine the properties of the bicycloheptatrienyl anion (Ia) (predicted to be conjugatively stabilized by Hückel Molecular Orbital Theory) the neutral precursor, bicyclo[3. 2. 0] hepta-1, 4, 6-triene (I) was prepared by the following route.

Reaction of I with potassium-t-butoxide, potassium, or lithium dicyclohexylamide gave anion Ia in very low yield. Reprotonation of I was found to occur solely at the 1 or 5 position to give triene II, isolated as to its dimers.

A study of the acidity of I and of other conjugated hydrocarbons by means of ion cyclotron resonance spectroscopy resulted in determination of the following order of relative acidities:

H2S ˃ C5H6 ˃ CH3NO2 ˃ 1, 4- C5H8 ˃ I ˃ C2H5OH ˃ H2O; cyclo-C7H8 ˃ C2 H5OH; фCH3 ˃ CH3OH

In addition, limits for the proton affinities of the conjugate bases were determined:

350 kcal/mole ˂ PA(C5 H5-) ˂ 360 kcal/mole

362 kcal/mole ˂ PA(C5H7-, Ia, cyclo-C7H7-) ˂ 377 kcal/mole PA(фCH2-) ˂ 385 kcal/mole

Gas phase kinetics of the trans-XVIII to I transformation gave the following activation parameters: Ea = 43.0 kcal/mole, log A = 15.53 and ∆Sǂ (220°) = 9.6 cu. The results were interpreted as indicating initial 1,2 bond cleavage to give the 1,3-diradical which closed to I. Similar studies on cis-XVIII gave results consistent with a surface component to the reaction (Ea = 22.7 kcal/mole; log A = 9.23, ∆Sǂ (119°) = -18.9 eu).

The low pressure (0.01 to 1 torr) pyrolysis of trans-XVIII gave in addition to I, fulvenallene (LV), ethynylcyclopentadiene (LVI) and heptafulvalene (LVII). The relative ratios of the C7H6 isomers were found to be dependent upon temperature and pressure, higher relative pressure and lower temperatures favoring formation of I. The results were found to be consistent with the intermediacy of vibrationally excited I and subsequent reaction to give LV and LVI.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Chemistry
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Bergman, Robert G.
Thesis Committee:
  • Unknown, Unknown
Defense Date:5 November 1971
Funding AgencyGrant Number
Department of Health, Education and WelfareUNSPECIFIED
Record Number:CaltechTHESIS:04042016-112239738
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9646
Deposited On:06 Apr 2016 17:40
Last Modified:09 Nov 2022 19:20

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