Methyl from decomposition

The mechanism of pyrolysis reactions of biomass was extensively discussed in an earlier study (Demirbas, 2000). Water is formed by dehydration. In the pyrolysis reactions, methanol arises from the breakdown of methyl esters and/or ethers from decomposition of pectin-like plant materials. Methanol also arises from methoxyl groups of uronic acid (Demirbas and Giillii, 1998). Acetic acid is formed in the thermal decomposition of all three main components of wood. When the yield of acetic... 

This experiment showed that some volatile component was formed in the thermal decomposition of tetramethyllead and that this compound consumed a cold lead mirror with formation of a volatile product. If, instead, a zinc mirror was first deposited and allowed to be consumed by the volatile product from decomposition of tetramethyllead, dimethylzinc could be identified as the product. Paneth concluded that free methyl radical was formed in the thermal reaction and could determine its half-life to be 0.006 seconds under the reaction conditions employed. Also, free ethyl radicals could be formed in... 

Benzocvclobutenone was obtained from decomposition of 0-alkyl substituted benzoyl chlorides189. Thus, with 2-propylbenzoyl chloride at 600 °C, the 0-quinonoid ketene intermediate is stabilized by 1,5-hydrogen shift to give the aldehyde (equation 101). In this case, the 0-alkyl contains a /1-hydrogen. However, if the 0-substituent lacks a /1-hydrogen, i.e. it is a methyl group, then the cyclobutenone is obtained (equation 102). 

In marked contrast with all the other experiments, hydrogen atoms abstract the aldehydic hydrogen from acetaldehyde to form the acetyl radical, CHg. CO. The occurrence of this reaction is presumably due to the relatively weak CH bond (82 kcal mole ) (Benson, 1965) and the absence of an efficient addition reaction, in contrast to the olefins. A small amount of methyl radical is also observed and must arise from decomposition of the acetyl radical (reaction 29). 

The pyrolysis of both (E)- and (Z)-isomers of 2-[(3-phenyl-2-propenyl)oxy]phenyl azide gave /rans-disubstituted bicyclic aziridines 1 in good yield with minor amounts of 2/7-1,4-benzoxazi-nes, from decomposition of the intermediate dihydrotriazoles114 115. However, substitution of methyl for a phenyl group on the double bond resulted in loss of diastereoselectivity, since a mixture of both cis- and /ra/ts-isomers in the same ratio were obtained from both (E)- and (Z)-isomers115. The cis stereochemistry was retained when the double bond was part of a cycle (five- or six-membered)115. In the presence of an allylic substituent, the stereochemistry of the aziridine stereocenters relative to the pre-existing stereocenter (substrate-induced diastereoselectivity) was not assessed115. 

Ethylene arises from the ethylidene radical. The decomposition of jec-propyl radical to give a hydrogen atom and propene is taken to be the major source of hydrogen atoms this process is not distinguishable from decomposition of i-butane to a hydrogen atom and a butyl radical followed by decomposition of the latter to a methyl radical and propene. 

As in steam cracking, a large number of by-products is produced. Some of them result from the consecutive reactions of the chlorination of vinyl chloride and of its derivatives obtained by dehydrochlorination (tri-, tetra-, pentachloroethane, perchloro-ethane, di-, trichloroethylene. perchloroethyleneX and the others from the hydrochlorination of vinyl chloride il.l-dichloroethane), while others result from decomposition reactions (acetylene, cokei or conversion of impurities initially present (hydrocarbons such as ethylene, butadiene and benzene, chlorinated derivatives such as chloroprene, methyl and ethyl Chlorides, chloroform, carbon tetrachloride, eta, and hydrogen) ... 

In more recent applications, Takajo and Kambe have reported a new synthesis of perhydropyrimid-ines (90) by a double Mannich reaction (one step is intramolecular) using hydrobenzamide (87) and methyl cyanoacetate (89 equation 15). The reaction is general for other highly acidic methylene compounds including malononitrile, dimethyl malonate and nitroethane. In some cases, the intramolecular Mannich step is slow and side products arising from decomposition of the initial adduct are formed. This phenomenon is temperature dependent, indicating that intermediates in the reaction are formed reversibly. 

In studies on the effect of functional groups in EM (1) derivatives, compounds having 9-oxime (11), (95)-9-amino (9a), 6-O-methyl (16a), (8S)-8-hydroxy (6a), and 11,12-cyclic carbonate (15a) substituents were found to stabilize the lactone ring from decomposition in acidic media [2]. Therefore, further improvement of activity and bioavailability in oral administration has been attempted. 

One side reaction which occurs with TMAH/ heat is the formation of ben-zenecarboxylic acid methyl esters from lignin [103] and from aromatic aldehydes [104,105]. Therefore our study summed all phenolic-containing products and their methylated derivatives (or phenolics ) observed in marine sediments (Figs. 6-8). Phenolic compounds are abundant in herbs, shrubs and trees. Phenolics can be released during degradation of lignin, from decomposition of leaves and are common plant metabolites. 

---