Octa-l,3,5,7-tetraene

Chemical Abstracts would name this as 8-phenyl-7-azabicyclo[4.2.01-octa-l,3,5,7-tetraene, which is unnecessarily complicated. Use of a replacement modification of a fusion name presents difficulties although the corresponding carbocycle should, in accord with IUPAC Rules, be named cyclobutabenzene, it is almost exclusively referred to in the literature as benzocyclobutene. Thus the name 2-phenyl-1-azacyclobuta benzene would be strictly correct, but 2-phenyl-1-azabenzocyclobutene is more in line with current usage. The fusion name based on azete avoids this problem. 

Using a relative rate method, rate constants for the gas-phase reactions of O3 with 1- and 3-methylcyclopentene, 1-, 3- and 4-methylcyclohexene, 1-methylcycloheptene, cw-cyclooctene, 1- and 3-methylcyclooctene, cycloocta-1,3- and 1,5-diene, and cyclo-octa-l,3,5,7-tetraene have been measured at 296 2 K and atmospheric pressure. The rate constants obtained (in units of 10-18 cm3 molecule-1 s-1) are as follows 1-methylcyclopentene, 832 24 3-methylcyclopentene, 334 12 1-methylcyclohex-ene, 146 10 3-methylcyclohexene, 55.3 2.6 4-methylcyclohexene, 73.1 3.6 1-methylcycloheptene, 930 24 d.s-cyclooclcnc, 386 23 1-methylcyclooctene, 1420 100 3-methylcyclooctene, 139 9 d.v.d.v-cycloocta-1,3-diene, 20.0 1.4 cycloocta- 1,5-diene, 152 10 and cycloocta-l,3,5,7-tetraene, 2.60 0.19 the indicated errors are two least-squares standard deviations and do not include the uncertainties in the rate constants for the reference alkenes (propene, but-l-ene, d.s-but-2-ene, trans-but-2-ene, 2-methylbut-2-ene, and terpinolene). These rate data were compared with the few available literature data, and the effects of methyl substitution have been discussed.50... 

DFT investigation of the eight-electron electrocyclization reactions of 1,8-disubsti-tuted (3Z,5Z)-octa-l,3,5,7-tetraenes has found that these reactions proceed via a Mobius helical aromatic transition state. It was also found that outward substituents were preferred to inward ones, regardless of the electronic nature of the substituents, and that torquoelectronic effects are overridden by secondary orbital, electrostatic,... 

Bicyclo[3.3.0]octa-l,3,5,7-tetraene (2), trivially called pentalene [26, 27], is the second member in the series of fully unsaturated oligoquinanes. Huckel MO theory predicts that this planar hydrocarbon with its 8 r-electron system should be an antiaromatic species [25]. 2-Methylpentalene (37) has been generated by a retro-Diels-Alder reaction and deposited as a film at —196 °C on a NaCl or quartz plate for its spectroscopic characterization. It rapidly dimerized upon warming the cold plates to temperatures above —140 °C [26]. Only two stable derivatives of pentalene not complexed to a metal [29], the hexaphenyl- (38) [30] and 2,4,7-tri-tert-butylpentalene (39) [31], have hitherto been reported (Figure 4). 

Evans DF (1961) Magnetic perturhations of singlet-triplet transitions. Part VI. Octa-l,3,5,7-tetraene. J Chem Soc 2566-... 

Ethyl 2ff-pyran-2-carboxylate (32) 6-Ethoxy-2tf-pyran-2-carboxaldehyde (33) (Z -6-Oxo-2,4-hexadienoic acid (Sda) ( ,Z)-6-Oxo-2,4-hexadienoic acid (34b) (Z, )-6-Oxo-2,4-bexadienoic acid (34c) ( JS)-6-Oxo-2,4-hexadienoic acid (34d) 4-Caifaoxyinethylbut-2-eii-l,4-olide (muconolactone) (37) Bicyclo[S.1.0]octa-2,4-diene (41) (Z Octa-l,3.5,7-tetraene (42) ... 

Figure 13.23 Ring current in the Mobius transition state of the electrocyclic reaction of octa-l,3,5,7-tetraene to cycloocta-1,3,5-triene. For details see Figure 13.21. Note that the basis orbitals (atomic orbitals that are involved in the reaction) can be written with arbitrary phase. The number of antibonding overlaps (sign inversion) will...

DFT calculations of the transition structure for the [ 8a] electrocyclic conversion of (3Z,5Z)-octa-l,3,5,7-tetraene provide support for this rule. 

Andres J, Berski S, Domingo LR, Gonzalez-Navarrete P (2012) Nature of the ring-closure process along the rearrangement of octa-l,3,5,7-tetraene to cycloocta-l,3,5-triene from the perspective of the electron localization function and catastrophe theory. J Comput Chem 33 748-756... 

For the following compounds Chem. Abstr. incomprehensibly uses the von Baeyer names bicyclo[4.2.0]octa-l,3,5,7-tetraene and lif-bicyclo[4.1.0] hepta-l,3,5-triene that totally disregard the aromatic character of these compounds. 

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