Hydro-dealkylation

Kinetic studies have shown that thermal hydro-dealkylation is a first-order reaction with respect to the aromatics, and a half-order reaction in relation to hydrogen. 

The process flowsheet of the hydro-dealkylation (HDA) of toluene to benzene is the ubiquitous example used in the pedagogy of the process design. Moreover, it has been studied extensively in the open literature [1,7]. Luyben et al. [7] have developed a plantwide control structure for the HDA process using their nine step approach to control structure synthesis Fisher et al. [19] provide a control structure development for the HDA process using a hierarchical approach. Stephanopoulos [47] also presents a control structure for the HDA process. These flowsheets provide a basis by which the outcome of the proposed methodology can be compared. 

Phenacetin Analgesic NH-COCH3 9 O-CHsCHg 0-Dealkylation, N-hydro-xylation and arene oxide formation Glutathione conjugates 0-Dealkylation (Cunninghamella elegans) [97]... 

These are generally metabolised in the hepatic endoplasmic reticulum, the initial reaction being N-dealkylation, with subsequent hydrolysis. An exception to this is prilocaine, where the initial step is hydrolysis, forming o-toluidine. This is further metabolised to 4- and 6-hydro toluidine. The latter is believed to be responsible for the methaemoglobinaemia which may follow high doses. The amidelinked local anaesthetics are extensively protein-bound (between 55% and 95%) particularly to ol-acid glycoprotein. 

Reversal of Friedel—Crafts Alkylation Hydro-de-alkylation or Dealkylation... 

In the light of the ease of dealkylation of di-fcr butyl esters of quinquevalent phosphorus acids, either thermally or under acid catalysis, the reaction between di- er -butyl hydro-genphosphonate and 4-(diethoxymethyl)benzaldehyde has been employed to yield, after deprotection of the para substituent, the (a-hydroxybenzyl)phosphonic diester 169, useful for classical development at the aldehyde group ... 

The metabolism of chloro-S-triazines in soil involves reactions of dealkylation, deamination, hydroxylation, and ring cleavage [171]. Dealkylation of chloro -triazines does not remove their toxidly, which has been, instead, attributed to the release by chemical hydrolysis of active chknine [172]. In a study on the effects of atrazine and its degradation products on phototrophic microorganisms, the most toxic degradation product was deethylated atrazine, vdiidi was 2 to 7 times more effective towards cyanobacteria than deisopropylated atrazine. On the contrary, diamino and hydro atrazine were non-toxic [173]. 

The presence of a P-C substituent limits the pathway of biotransformation of ephedrine to p-hydro-xylation, N-dealkylation, and deamination. Dealkylation and subsequent deamination is the major route of metabolism of ephedrine in most species, excluding the rat (Williams et al. 1973). 

---