Acetyl thermal decomposition

The thermal decomposition of diacyl peroxides has been the most frequently employed process for the generation of alkyl radicals. The rate and products of the unimolecular decomposition of acetyl peroxide have been the subject of many studies. Acetyl peroxide decomposes at a convenient rate at 70-80°C both in the solution and in the gas... 

The methoxy group of methyl acetate formed during the thermal decomposition of acetyl peroxide appears as an emission, whereas methyl chloride shows enhanced absorption. Consider the reaction sequence in equation (40). 

Thermal decomposition of 143 gave Af-acetyl-3-acetoxyindole, and subsequent hydrolysis with aqueous sodium hydroxide provided indigos in 86-96% yield. 

Trimesitylplumbyllithium, generated by reaction of hexamesityldiplumbane with lithium, reacts with acyl chlorides to afford isolable air-stable acylplumbanes in modest yields (Equation (127)). Under ultraviolet irradiation as well as thermal decomposition, the benzoylplumbane reacted with methanol to afford methyl benzoate (Equation (128)).156 The simpler acetyl- and benzoyl-triphenylplumbane were only detected as transient species in solution, the acetyltriphenylplumbane decomposing at 50 °C to give acetophenone.157... 

In this section, several typical CINPD spectra will be shown. These spectra can be explained by Kaptain s rules. Typical net absorptive and emissive CINDP signals were observed during the thermal decomposition of acetyl peroxide (AP) in hexachloroacetone at 110 °C as shown in Fig. 4-8. Here, enhanced absorptive signals were observed for CH3CI and CH4 and emissive ones for CH3COOCH3 and CH3-CH3. 

Fig. 4-8. 60 MHz H-CIDNP spectrum of the thermal decomposition of acetyl peroxide in hexachloroacetone. (Reproduced from Ref. [8] by permission from Kluwer Academic Publishers)...

Problem 4.1. Prove the enhanced absorptive CIDNP observed for CH3CI and CH4 during the thermal decomposition of acetyl peroxide (AP) in hexachloroacetone. 

The thermal decomposition of acetyl iodide was studied by Jones . The reaction follows approximately first-order kinetics and the stoichiometry is... 

The thermal decomposition of chloroformates has been further studied (refs. 834, 842, 865, 995) Lennon and Stimson have reported on the pyrolysis of trimethyl acetyl chloride and bromide Dakubu and Maccoll have investigated the elimination of hydrogen chloride from gaseous monochloroketones, and Frey et have reported on the thermal decomposition of 3-chloro-3-methyldiazi-rine. 

The participation of free radicals in the thermal decomposition of acetone has been proved by Patat and Sachsse by the para-ortho technique. Talrose et al identified methyl and acetyl radicals by mass spectrometry. 

The thermal decomposition has been discussed (Section IV,E,1). Imidazole forms quaternary salts with methylmercury(II)." l-Acetyl-3-alkylimi-dazolium salts can be dequaternized by hydroxide ion ° or primary amines to the 1-alkylimidazole. 

Polyacetals form a different subclass of compounds with oxygen in the backbone chain. In this group are included polymers that contain the group -0-C(R2)-0- and can be formed from the polymerization of aldehydes or ketones. A typical example of a polymer from this class is paraformaldehyde or polyformaldehyde or polyoxymethylene (CH20)n. Polyoxymethylene can be prepared by anionic catalysis from formaldehyde in an inert solvent. Acetylation of the -OH end groups of the polymeric chain is common since it improves the thermal stability of the polymer. Some results reported in literature regarding thermal decomposition of these polymers are indicated in Table 9.2.1 [1]. 

Tetracarbonylalkyl derivatives of cobalt(I) have low stability. As early as 1964 it had been noted that ketones are formed in the thermal decomposition of CoR(CO)4 (R = Me, Et) presumably involving a binuclear intermediate or an intermolecular mechanism. The mechanism of acetone formation was studied for other cobalt systems that are more easily handled, namely, Co(>/ -C5H5)Me2(PMe3) and Co2(ti -CsH )2Me2(fi2-CO)2 . Upon carbonylation, in the former case, the transient carbonyl derivative Co()j -C5H5)Me2(CO) was observed spectroscopically, whereupon it underwent carbon monoxide insertion to give an acetyl-methyl complex, followed by reductive elimination of acetone ... 

The thermal decomposition of manganese(II) acetate tetrahydrate [40] commenced with the loss of water in two stages. Hydrolysis with acetic acid evolution was detected at 393 K. The decomposition resembled that of cobalt(II) acetate [41] in that both yield metal acetyl acetate and metal acetate hydroxide (e.g. Mn(CH3COO)2.0H) intermediates. The product from reaction in N2 or H2 was MnO and in air Mn304 was obtained. 

Cork products can also emit considerable amounts of the aldehyde furfural (2-furancarboxaldehyde) with surface-specific emission rates SER, > 1,000 pg m - h [57], whereby the release of the furfural generally corresponds with that of acetic acid. The cause for the formation of furfural is the thermal decomposition of the hemicelluloses contained in the cork at temperatures above 150 °C, while acetic acid is formed by the separation of acetyl groups. Further by-products identified in the thermal treatment of natural cork were formic acid and hydroxymethylfurfural [58]. 

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