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Thermochemical and X‐ray Crystallographic Investigations of Some (CH) 10 Hydrocarbons: Basketene, Nenitzescu’s Hydrocarbon, and Snoutene
Author(s) -
Verevkin Sergei P.,
Kümmerlin Martin,
Hickl Ernst,
Beckhaus HansDieter,
Rüchardt Christoph,
Kozhushkov Sergei I.,
Haag Rainer,
Boese Roland,
BenetBucholz Jordi,
Nordhoff Karsten,
Meijere Armin de
Publication year - 2002
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200207)2002:14<2280::aid-ejoc2280>3.0.co;2-r
Subject(s) - chemistry , isomerization , enthalpy , hydrocarbon , standard enthalpy of formation , differential scanning calorimetry , calorimetry , standard enthalpy change of formation , crystallography , thermodynamics , organic chemistry , catalysis , physics
The enthalpies of formation [Δ H 0 f (g)] of pentacyclo[4.4.0.0 2,5 .0 3,8 .0 4,7 ]dec‐9‐ene ( 9 , basketene) and pentacyclo[4.4.0.0 2,4 .0 3,8 .0 5,7 ]dec‐9‐ene ( 14 , snoutene) have been determined by measurement of their heats of combustion in a microcalorimeter as 110.2 ± 0.5 kcal·mol −1 and 78.4 ± 0.3 kcal·mol −1 , respectively. These values and the strain energies ( SE s) [ SE ( 9 ) = 110.3 kcal·mol −1 , SE ( 14 ) = 78.4 kcal·mol −1 ] derived from them were compared with values obtained from MM2/MM3 calculations. The enthalpy of isomerization of 9 to tricyclo[4.2.2.0 2,5 ]deca‐3,7,9‐triene ( 8 , Nenitzescu’s hydrocarbon) was measured by differential scanning calorimetry (DSC) as −20.7 ± 0.3 kcal·mol −1 (384.1 K), corresponding to a strain energy SE ( 8 ) of 44.6 kcal·mol −1 . The enthalpy of activation for this rearrangement was also determined from the DSC measurements to be 28.6 ± 0.1 kcal·mol −1 . The obtained strain energies and the derived heats of isomerization to 9,10‐dihydronaphthalene ( 7 ) did not correlate in any way either with the activation energies of the thermal isomerizations of these (CH) 10 hydrocarbons or with the structural features determined experimentally for basketene ( 9 ) and computationally (DFT at the B3LYP/6‐311+G* level) for snoutene ( 14 ). Compounds 8 , 9 , 10 , and 14 exhibited solid‐state phase transitions in a narrow temperature range (−55 to −70 °C), whereas the melting points or rearrangement temperatures varied to a much greater extent (in the 0−126 °C range). Compound 9 formed intermediate plastic phases, 8 had a plastic and a disordered phase, while 10 and 14 both formed phases intermediate between plastic and disordered. Crystal structure determinations based on disordered models could be carried out for 10 and 14 . Basketene 9 could be crystallized from solution directly into the ordered phase at low temperatures (−178 °C). The obtained molecular geometry contrasted with results from an older gas‐phase diffraction study, but agreed very well with DFT calculations. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)