Cyclo Butanes

Thermal decomposition of unsubstituted 3,4,5,6-tetrahydropyridazine at 439 °C in the gas phase proceeds 55% via tetramethylene and 45% via a stereospecific alkene forming pathway. The thermal decomposition of labelled c/s-3,4,5,6-tetrahydropyridazine-3,4- f2 affords cfs-ethylene-l,2- f2, trans-ethylene-l,2-if2, c/s-cyclobutane-l,2- f2 and trans-cyclo-butane-1,2- /2 (Scheme 57) (79JA3663, 80JA3863). 

Einc dagegen nur bescheidene Ausbeute erbringt die reduktive Cyclisierung von 1,4-Dibrom-butan zu Cyclo-butan [an Hg in DMF/(C4H9)4NC104 25% d.Th.]4. 

Hexafluorothioacetone, 50, 83 Hexamethylbicyclo[1.1.0]butane, from 1,3-dibromohexamethyl-cyclo butane and sodium-potassium alloy, 51, 58 Hexamethylphosphoramide, 50,... 

Cyclobutylcaxbinol, welches durch Wasserstoff katalytisch zu Cyclo-butan dehydroxymethyliert werden konnte. 

Pajenkamp, H. t)ber die Herstellung und das RAMAN-Spektrum des Cyclo-butans. Z. Elektrochem. angew. physik. Chem. 52, 104 (1948). 

Both cis- and frana-butene-2 are formed from each of the dimethyl-cyclobutanes. They are not however formed in equilibrium amounts. Further, more a -butene-2 than the equilibrium amoimt is formed in the decomposition of cis-l,2-dimethylcyclobutane. The fact that the cis- and [Pg.174]

Krief, A. Synthesis and Synthetic Applications of 1-Metallo-l-Selenocyclopropanes and -cyclo-butanes and Related 1-Metallo-l-silyl-cyclopropanes. 135, 1-75 (1986). 

Figure 3. Calculated (a) and experimental (b) H-NMR spectra of cyclo butane protons of 4 at 400 MHz.

What is the point group for each of the following substituted cyclo-butanes Assume that C4H8 itself has DAh symmetry and that replacing an H by X or Y changes no other structure parameters. 

Property Structural element Cyclopropane Aziridine Oxirane Cyclo butane... 

I, 2-dimethylcyclopropane 5.5 kJmol-13. The third difference is likewise unavailable and, indeed, there are fewer calorimetric data for cyclobutane derivatives than for cyclopropane derivatives. Assuming (admittedly, falsely) substituent effects on cyclopropanes and cyclobutanes are identical, the difference is 5.5 kj mol-1. Should substituent effects on cyclobutanes be simulated by those of cyclohexanes, the difference is now 7.8 2.6 kJmol. The last thermochemical quantity may be estimated as the difference of the enthalpies of formation of the isomeric o- and p-xylene, 1.1 1.4 kJmol-1. For all of the results to be consistent, then 6A//ls pr + 45 = 200 kJmol-1 and so A7/isoprs = 25 kJmol-1. In that the methylation enthalpies of ethylene, benzene and cyclopropane are so similar (cf Sections II. A and III. A), the methylation of cyclo butane enthalpy cannot be too different. But the resulting ca 25 k J mol-1 for A J/lsoprs seems untenable. We are confused. 

Our enthalpy of formation archive lacks data for the corresponding cyclobutene/cyclo-butane derivatives. Nonetheless, the enthalpy of hydrogenation22 of both 1-methyl-cyclobutene and methylenecyclobutane in the same solvent (AcOH) has been reported. Because the same product, methylcyclobutane, is formed, it is not unreasonable to assume that the difference of the enthalpies of hydrogenation of the two olefins roughly equals the difference of the enthalpies of formation of the olefins66. It is thus found that the... 

Methyl-2-benzyliden-A3-oxazolinon-(5) dimerisiert sich schon bei Tageslicht, schneller beim Bestrahlen mit einer UV-Lampe zum Cyclo-butan 123 62k Die grofie Reaktivitat der exocyclischen C=C-Doppelbin-... 

Gajewsld and Shih S2> synthesized l,2-bis(dideuteriomethylene)cyclo-butane and found it rearranged at 275 °C to a mixture of tetradeuterio-1,2-dimethylenecyclobutanes containing 26—31% of the total protium on exocyclic methylene groups. 

CyclopropanecarboxaUehytte. Dehydration of a mixture of cis- and froni-cyclo-butane-l,2-diol (I) with boron trifluoride n-butyl etherate at 230° yields cyclopropane-carboxaldehyde (2) in 65-80% yield. Dehydration of (I) with p-toluenesulfonic acid gives (2) in somewhat lower yields (66%)- ... 

This substrate, along with the corresponding substrate 6, which has a cyclo-butanation rate of 1.2 x 10 , have been proposed as sensitive cation radical probes, for detecting the presence of cation radical intermediates in various reactions [74]. An interesting example is the reaction of tetracyanoethylene (TCNE) with electron rich alkenes, a reaction for which an electron transfer mechanism had been considered (Scheme 39) [75],... 

Poly-methylenes, Cycle ParaflSns.—The names tetra-methylene or cyclo butane, hexa-methylene or cycle hexane, etc., are analogous to tri-methlyene or cyclo propane. For the homologous series the names poly-methylenes or cyclo parafi s are used. 

Irradiation of 2,2,4,4-tetramethylcyclobutane-I,3-dione in pentane, cyclohexane or dichloro-methane resulted in rapid evolution of carbon monoxide (0 = 0.30) and formation of 2,2,3,3-tetramethylcyclopropanone (1). The reaction was easily monitored by infrared spectroscopy, the photolysis was terminated when the characteristic carbonyl doublet of the cyclo-propanone (1823 and 1843 cm ) reached a constant intensity (10-20% conversion of cyclo-butane-1,3-dione). 

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