1- Butene, thermal decomposition

The reaction of 1-butene with 0 , followed by the thermal decomposition of surface intermediates, leads to the formation of butadiene as the main product. Thus, 1-butene appears to be more similar to alkanes than to ethylene or propylene in its reaction with 0 . 

The kinetic preference for cis- over imns-olefin elimination from acyclic compounds is rare. Cope and co-workers 91) reported a slight preference for cis- over irans-2-butene and 2-pentene in the thermal decomposition of the quaternary ammonium hydroxides, and Andr u and co-workers 92,93) found a preponderance of cis- over trons-2-butene in the elimination of hydrogen chloride from 2-chlorobutane over solid catalysts. Neureiter and Bordwell 94) found the formation of cis-2-butene rather than alkene from a-chlorosulfone on treatment with alkali ... 

DIS(B)(42)1892]. Thermal decomposition in 2,3-dimethyl-2-butene gave a mixture of 144 and 145 [81DIS(B)(42)1892] (Scheme 39). Compound 145 might arise from attack of the carbene 139 (R = Ph) on the double bond of the 2,3-dimethyl-2-butene to give an intermediate cyclopropane... 

In oxidation studies it has usually been assumed that thermal decomposition of alkyl hydroperoxides leads to the formation of alcohols. However, carbonyl-forming eliminations of hydroperoxides, usually under the influence of base, are well known. Of more interest, nucleophlic rearrangements, generally acid-catalyzed, have been shown to produce a mixture of carbonyl and alcohol products by fission of the molecule (6). For l-butene-3-hydroperoxide it might have been expected that a rearrangement (Reaction 1) similar to that which occurs with cumene hydroperoxide could produce two molecules of acetaldehyde. 

Decreased deactivation efficiency may also account for changing product ratios, such as increased formation of 3-methylbutene-l. Although Frey found no 3-methylbutene-l in photolysis experiments without added argon, this product was reported by Setser and Rabinovitch in pyrolysis of CH2N2-butene-2 mixtures and is also found to some extent in the thermal decomposition of 1,2-dimethylcyclopropane. It appears, therefore, that the formation of 3-methylbutene-l depends more on reaction conditions than on the electronic state of CH2. 

Conlin and coworkers have prepared (E)- and (Z)-l,l,2,3-tetramethylsilacyclobutanes 5 and have studied the mechanism of their thermal decomposition in order to gain insight into the stereochemistry of the thermal decomposition of silacyclobutanes20. The occurrence of transient 1,4-biradicals like 6 in [2 + 2] fragmentations is accompanied by a loss of the reactant stereochemistry. This can be rationalized by rotational processes in the diradical 6 (6a —> 6b) which compete effectively with the -scission steps yielding the silene 2 and E/Z 2-butene 7 (equation 3). 

Compound 1 exhibits significantly different reactivity than the acyclic analogue. The metallacycle is more stable than the acyclic complex and whereas Cp2Ti"Bu2 decomposes via the expected (3-1I elimination pathway to produce butenes and butane, the thermal decomposition products of 1 are ethylene and 1-butene. In addition, the metallacycle is observed to be significantly more reactive towards CO than Cp2Ti"Bu2 Reaction of 1 with carbon monoxide at —55 °C yields the titanium acyl species, based on infrared data, which then rapidly converts to cyclopentanone at 0 °C (Scheme l).13... 

Unsymmetrically substituted tetra- and penta-n-butyl borazines are obtained by thermal decomposition of dibutylazidoborane 100> with the elimination of butene. Because of the hazards of handling boron azides, this method cannot be recommended. 

Relatively little study has been carried out on the thermal decomposition of ozonides. This is a complicated reaction, which generally leads to a mixture of cleavage products.127 The decomposition of 2-butene ozonide23 34 and of 2,3,3-trimethylbut-l-ene ozonide90 (121) also yields dimeric alkylidene peroxides, e.g., 122. These are thought to be formed via the peroxidic zwitterion. 

The thermal decomposition of 2-azidobenzothiophene in benzene at room temperature in the presence of (Z)- or ( )-2-butene afforded the corresponding aziridine with complete retention of the double bond configuration, supporting the hypothesis of a singlet nitrene intermediate72. However, the yields were low, since 4-cyanothiochromans were the major products. The formation of the aziridines was favored by electron-poor alkenes and by a decrease in the reaction temperature, but partial loss of the alkene configuration is observed 73. In the case of... 

The polymerization initiated by thermal decomposition of hydrogen peroxide has been extended to butenes (1-butene, 2-butene, isobutene) 99). Their molecular weight is below 1000 and their functionality varies between 2 and 4. The weak efficiency (yields < 10 %) of homopolymerization of various monomers initiated by H202 is low and reactivities of the monomers decrease in the series ... 

Thermal decomposition of 1-butene provides a more complex product spectrum than is obtained from either cis- or trans-2-butenes. Between 550° and 760°C in a flow system with nitrogen dilution (3), methane, propylene, butadiene, and ethylene were major products as well as hydrogen, ethane, 1-pentene, 2-pentene, 3-methyl-1-butene, and 1,5-hexa-diene. In studies in a static system (4), cyclohexadienes, benzene, cyclopentene, cyclopentadiene, toluene, orthoxylene, and cyclohexene were observed among the liquid products of the reaction over the temperature range 490°-560°C. 

Slobodin et al. [39] confirmed that thermal decomposition of EPR (equimolar ratio) began at 170 °C and ceased at 360 C. A total 93.66% condensate products, 5.2% gas and 1.14% carbonaceous residue were obtained, mainly at 235 °C. The composition of the gaseous portion, determined by GLC was ethane-ethylene 1.25%, propane 0.81%, propylene 0.98%, butane-butylene 0.99% and butadiene 0.99% by wt. of EPR. The liquid products were separated into five fractions with boiling ranges of 100 C, 100-150 C, 150-200 °C, 200-250 °C, and >250 °C. The fractionation yielded pentane, 1-pentene, 2-methylbutane, 2-methyl-l-butene, 2-methyl-2-butene, isoprene and piperylene of C5 hydrocarbon and hexane, 1-hexane, 2-methylpentane of Cg hydrocarbons. Based on these data, the thermal degradation was proposed to proceed via a free-radical mechanism. A free radical CH3... 

Thermal decomposition of l,2-dibutyl-l,2-bis (dimethylamino)diborane-(4) at 200°-230°C was found by Noth and Fritz to yield 1-butene and butyl-(dimethylamino)borane, the reaction postulated being... 

Vapor-deposited carbon atoms have been known to reduce epoxides to alkenes but with low stereoselectivity, whereas chemically generated carbon atoms, by thermal decomposition of S-tetrazolediazo-nium chloride (2), deoxygenate cis- and franr-2-butene oxide with a high degree of retention of stereochemistry. ... 

The photolysis or pyrolysis of diazoesters is the only source of carboalkoxy-carbenes and although numerous examples can be found in the literature concerning the reactivity of these carbenes, very little information is available on the kinetics of the decomposition. The photolysis of methyldiazoacetate yields carbo-methoxycarbene which adds stereospecifically to 2-butene. The quantum yield of the photolysis of ethyldiazoacetate has been determined in various solvents at different wavelengths (Table 12) . Thermal decomposition occurs above 150 °C although the presence of catalysts greatly accelerate the decomposition . Carboalkoxycarbenes are very selective with respect to insertion reactions, due to... 

The thermal desulfonylation of episulfones is highly stereospecific e.g., cis-2,3-dimethyl-thiirane-1,1-dioxide gives cw-2-butene , and trans- and cw-2,3-diphenyl thiirane 1,1-dioxides give trans and cis stilbenes, respectively . This result is remarkable in that the Woodward-Hoffman symmetry selection rules for inter-molecular cycloadditions (and their reversals) appear to exclude a concerted thermal decomposition of thiirane-l,l-dioxides . ... 

The homogeneous, gas phase, thermal decomposition of thiiranes, ethylene episulfide, propylene episulfide, and 2-butene episulfide sheds additional light on the mechanism of the S + olefin reactions. Below ca, 250 °C the decomposition products are sulfur and the olefin. The rate of olefin formation is first order in episulfide concentration, and the reaction features an activation energy which is considerably lower than the... 

Complexes 29 and 30 are decomposed photochemically to give the products expected as the latter stage of an olefin metathesis reaction, namely ethene from 29, propene from 30, and both ethene and propene from 31, but their thermal decomposition at 80°C gives cyclopropane and propene from 29, and butenes from 30 and 31 (Ephritikhine 1976, 1977 Adam 1980). 

Strongly basic catalysts can be prepared by impregnating CsNaX and CsNaY with cesium acetate followed by thermal decomposition of the acetate into the oxide (60-62). The cataljrtic activity for the dehydrogenation of isopropyl alcohol to acetone increased an order of magnitude by loading Cs onto CsY. The isomerization of 1-butene proceeds over these catalysts at 273 K. Various evidences including (133) Cs nmr indicate that the active species is nanophase cesium oxide occluded in the supercage of the zeolites. 

The thermal decomposition of propylene involves a series of primary and secondary reactions leading to a complex mixture of products. Studies showed that the distribution of pyrolysis products varies considerably with the pyrolysis conditions and the type of reactor used. There is agreement among the studies on propylene pyrolysis that the three major products of pyrolysis are methane, ethylene, and hydrogen. However, there is disagreement on the types and amounts of minor or secondary product species. Ethane, butenes, acetylene, methylacetylene, allene, and heavier aromatic components are reported in different studies, Laidler and Wojciechowski (1960), Kallend, et al. (1967), Amano and Uchiyama (1963), Sakakibara (1964), Sims, et al. (1971), Kunugi, et al. (1970), Mellouttee, et al. (1969), conducted at different conversion and temperature levels. Carbon was also reported as a product in the early work of Hurd and Eilers (1943) and in the more recent work of Sims, et al. (1971). 

Thermal decomposition of quaternary ammonium hydroxides is different because elimination occurs preferentially to form the least substituted double bond. Thermal decomposition of scc-butyltrimethylammonium hydroxide, for example, gives 1-butene as the major product. 

---