Diallyl decomposition

Many incidents involving explosions have been attributed, not always correctly, to peroxide formation and violent decomposition. Individually indexed incidents are 2-Acetyl-3-methyl-4,5-dihydrothiophen-4-one, 2807 Aluminium dichloride hydride diethyl etherate, Dibenzyl ether, 0061 f 1,3-Butadiene, 1480 f Diallyl ether, 2431 f Diisopropyl ether, 2542... 

SAFETY PROFILE Poison by intraperitoneal route. An irritating poison to skin, eyes, and mucous membranes. Reacts explosively with aniline, diallyl sulfide, and hydrazine hydrate. Explosive reaction with propiononitrale after heating to 105°C for 24 hours. Violent reaction with dibenzoyl peroxide + 4-toluic acid. When heated to decomposition it emits toxic fumes of Br and NOx. See also BROMIDES and NITROGEN MONOXIDE. 

The reactions of allyliron tricarbonyl halides with donor molecules were studied. Triphenylphosphine substituted only one carbonyl, that trans-oriented with respect to the halogen of the form (XIX) [432). The phosphine derivatives of (XX) were not isolated as pure compounds. The complexes were decomposed entirely by dimethyl sulfoxide, giving [(0113)280] jFeX2 [435). Thermal decomposition of C3H5Fe(CO)3X depended on the medium and gave either diallyl, or diallyl ketone, together with propene, allyl ether, Fe(CO)5, and FeX2 [436). 

Cadmium diallyls are also formed immediately on adding boron triallyls to MejCd . Because of the low T decomposition of the allylcadmiums, the reactions must be performed at ca. — 20°C. 

An intramolecular carbenoid addition onto a carbon-carbon double bond provides a possible synthetic route to the pyrrolidine ring. The rho-dium(II) acetate-catalyzed reaction of diazo amide 106 leads to a mixture of diastereomers 107 and 108 (6 1) in 43% yield (88TL1181). The decomposition of AjA-diallyl-a-diazoacetamide catalyzed by Rh2(55-MEPY)4 forms product 109 from an enantioselective intramolecular cyclopropanation (50% yield, 72% e.e.) (94T1665). Spiro-fused ring systems were produced by this route from quinonediazides 110 and 111 under irradiation (83TL4773 86TL2687). 

At room temperature the thiosulfinates (e.g., allicin) convert to variorrs diallyl and allyl sulfides, etc., which may be accelerated by heating. Pnre allicin itself is an unstable oily liquid, lasting less than 20 hours at room temperature (equivalent to say a half-life of a few hours, as has been reported). The decomposition products include various organic sulfides, and it is also been observed that allicin is very reactive with the amino acid cysteine. 

Attempts by Brodnitz et al. in 1971 to determine allicin by gas chromatography-mass spectrometry (GC-MS) provided evidence for an unusual mode of decomposition (70). They indicated that GC caused diallyl thiosulfinate to dehydrate according to the reaction C6HiqS20 -> C gS2 + H2O, affording a 2.4 1 mixture of two compounds, claimed (incorrectly as we shall see below) to be 3-vinyl-4H-l,2-dithiin (10, equation 1) and 3-vinyl-6H-l,2-dithiin (10a, equation 1) (70). Analytical methods for allicin quantitation that rely on GC detection of compounds 10 and 10a are still used (77), even though serious problems exist with this method and more accurate high-performance liquid chromatographic (HPLC) methods have been developed (see below). 

Whereas, the investigations on the influence of other compounds on the rate of decomposition of propylene itself are quite scare. Szwarc (10), Kunugi et al (6) and Robinson Weger (8) have only reported that the rate of decomposition of propylene had a tendency to be accelerated by the addition of small amounts of diallyl, 1-butene and propane in the feed, respectively. 

The initiation reaction is assumed to be the decomposition of diallyl into two allyl radicals. Lossing et al. (16), Ruzicka and Bryce (17) and Akers and Throssell (18) also suggested the same initiation reaction. An allyl radical generated by reaction 1 abstracts hydrogen from the parent molecule to produce propylene as in reaction 2. Existence of the 1,5-hexadienyl radical (II) is supported by Ruzicka and Bryce (17) and James and Troughton ( ). 

Typical experimental results were listed in Table IV. Overall mass balances of the outlet gas to the inlet gas were within 93 - 98 %. The diallyl decomposition (%) was calculated based on the amount of diallyl in the outlet gas to that in the inlet gas. The product distribution was presented as mole % of each to the total products. Main products were cyclopentene, 1-pentene, 1-butene, butadiene, and propylene. The molar ratio of 1-butene... 

Figure 3. Arrhenius plots for decomposition of diallyl in excess ethylene...

From Arrhenius plots, shown in Figure 3, the kinetic parameters for the decomposition rate constant of diallyl were obtained as below ... 

The activation energy obtained in the present experiments, i.e., 55.0 kcal/mole, was higgler than that obtained in the preceeding section of diallyl decomposition with nitrogen dilution, i.e.,... 

Examination of the product distribution vs. residence time curves at four temperature levels, i.e., at 580, 620, 660 and 700 C, revealed that the same mechanism applied in the temperature range investigated. Accordingly, as shown in Figure 4, product distribution versus diallyl decomposition (%) curves were offered for the following discussion. 

From Figure 4, it can be said that all the main products which were listed in Table IV are primary products of the reaction. It is ambiguous experimentally whether or not 1,4-pentadiene and cyclopentadiene are primary products. An interesting fact is that the ratio of the amount of cyclopentene to 1-pentene decreases from about 1.3 at the lower diallyl decomposition percentages to... 

---