1,1-dichloroethane, hydrolysis

Nucleophilic substitution is one of a variety of mechanisms by which living systems detoxify halogenated organic compounds introduced into the environment Enzymes that catalyze these reactions are known as haloalkane dehalogenases The hydrolysis of 1 2 dichloroethane to 2 chloroethanol for example is a biological nude ophilic substitution catalyzed by a dehalogenase... 

Hydrolysis. Heating 1,2-dichloroethane with excess water at 60°C in a nitrogen atmosphere produces some hydrogen chloride. The rate of evolution is dependent on the temperature and volume of the aqueous phase. Hydrolysis at 160—175°C and 1.5 MPa (15 atm) in the presence of an acid... 

The chemistry of side reactions and by-products may also offer opportunities for increasing the inherent safety of a process. For example, a process involving a caustic hydrolysis step uses ethylene dichloride (EDC 1,2-dichloroethane) as a solvent. Under the reaction conditions a side reaction between sodium hydroxide and EDC produces small but hazardous quantities of vinyl chloride ... 

The degradation of 1,2-dichloroethane by Pseudomonas sp. strain DCAl was initiated not by hydrolysis, but by monooxygenation with the direct formation of 1,2-dichloroethanol that spontaneously decomposed to chloroacetaldehyde (Hage and Hartmans 1999). 

Inter- and intramolecular hetero-Diels-Alder cycloaddition reactions in a series of functionalized 2-(lH)-pyrazinones have been studied in detail by the groups of Van der Eycken and Kappe (Scheme 6.95) [195-197]. In the intramolecular series, cycloaddition of alkenyl-tethered 2-(lH)-pyrazinones required 1-2 days under conventional thermal conditions involving chlorobenzene as solvent under reflux conditions (132 °C). Switching to 1,2-dichloroethane doped with the ionic liquid l-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6) and sealed-vessel microwave technology, the same transformations were completed within 8-18 min at a reaction temperature of 190 °C (Scheme 6.95 a) [195]. Without isolating the primary imidoyl chloride cycloadducts, rapid hydrolysis was achieved by the addition of small amounts of water and subjecting the reaction mixture to further microwave irradia-... 

Chemical/Physical. A glass bulb containing air and 1,1-dichloroethane degraded outdoors to carbon dioxide and HCl. The half-life for this reaction was 17 wk (Pearson and McConnell, 1975). Hydrolysis of 1,1-dichloroethane under alkaline conditions yielded vinyl chloride, acetaldehyde, and HCl (Kollig, 1993). The reported hydrolysis half-life at 25 °C and pH 7 is 61.3 yr (Jeffers et al., 1989). 

Hydrolysis of 1,2-dichloroethane under alkaline and neutral conditions yielded vinyl chloride and ethylene glycol, respectively, with 2-chloroethanol, and ethylene oxide forming as the intermediates under neutral conditions (Ellington et al, 1988 Jeffers et al, 1989 Kollig, 1993). The reported hydrolysis half-life in distilled water at 25 °C and pH 7 is 72.0 yr (Jeffers et al, 1989), but in a 0.05 M phosphate buffer solution the hydrolysis half-life is 37 yr (Barbash and Reinhard, 1989). Based on a measured hydrolysis rate constant of 1.8 x 10 at 25 °C and pH 7, the half-life is 71.5 yr (Jeffers and Wolfe, 1996). 

Figure 12-1 The active site structure of haloalkane dehalogenase from Xanthobacter autotrophicus with a molecule of bound dichloroethane. See Pries et al.13 The arrows illustrate the initial nucleophilic displacement. The D260 - H289 pair is essential for the subsequent hydrolysis of the intermediate ester formed in the initial step.

While ot,3-unsaturated aldehydes react exclusively with triotganoaluminums in the 1,2-mode, the identical reaction of the corresponding chiral a,3-unsaturated acetals (5), obtained from (RJi)-(+)-N V V V -tetramethyltartaric acid amides, is solvent dependent." For example, in 1,2-dichloroethane, preferential y-addition (Sn2 ) occurs (5 giving 7 Scheme 2), while in dichloromethane, preferential a-addition occurs (5 giving 8 Scheme 2). Subsequent hydrolysis of (7) affords the -substituted aldehydes in high enantiomeric purity (Scheme 2) thus the acetals (5) serve as effective surrogates for —CH=CH—CHO (+CH2CH2CHO). 

When 2,4-dioxopyrido[l,2-a]pyrimidines 391 were treated dropwise in acetonitrile with tetrachlorosilane in 1,2-dichloroethane in the presence of sodium iodide at room temperature, 2-acetamido-3,4-dihydro-2//-pyridopyrimidin-4-ones 396 were obtained after work-up [92MJ24 93IJC(B)637]. In the first step iodotrichlorosilane was formed, and 1,2-addition of iodotrichlorosilane to a 2-carbonyl group of pyridopyrimidine 391 led to the formation of a-iodosilyl esters 392, which reacted with acetonitrile. After the rearrangement of adduct 393 and a further reaction with a second mole of iodotrichlorosilane, the hydrolysis of disylylated intermediates 395 yielded 2-acetamido-3,4-dihydro-2//-pyridopyrimidin-4-ones 396 (see Scheme 24). 

The MEMED technique has been used to study the hydrolysis of aliphatic acid chlorides in a water/l,2-dichloroethane (DCE) solvent system [3]. It was shown unambiguously that the reaction proceeds via an interfacial process and shows saturation kinetics as the concentration of acid chloride in the DCE increases the data were well fitted to a model based on a pre-equilibrium involving Langmuir adsorption at the interface. First-order rate constants for interfacial solvolysis of CH3(CH2) COCl were 300 150(n = 2), 200 100(n = 3) and 120 60 s-1( = 8). 

Vorbruggen s strategy, involving a Friedel-Crafts catalyzed silyl Hilbert-Johnson procedure, offered an alternative approach to the synthesis of 5-azacytidines.23 Utilizing these conditions, a related analog, 1-O-acetyl-2,3,5-tri-O-benzoyl-p-D-ribofuranose (14) was reacted with 2,4-bis(trimethylsilyloxy)-6-azauracil (15) and SnCl4 in 1,2-dichloroethane on a 10-kg scale. After hydrolysis of the reactive intermediate, 93% of recrystallized 6-azauridine-2,3, 5 -tri-(9-benzoate(16) was obtained. 

Meth-Cohn and co-workers have observed that the treatment of 1,2-bis (N-methylanilino)-l,2-dichloroethanes, obtained by the dimerisation of the Vilsmeier reagents prepared from iV-methylformanilides in POCI3 using a tertiary amine, with an eletrophilic species yielded isatins in 11 to 79% after hydrolysis. The best yields were observed when bromine was used as the electrophilic species60 (Scheme 18). 

A1C13 > stoichiometric amount 1,2-Dichloroethane as solvent Batch reactor Hydrolysis at the end of reaction Destruction of the catalyst Zeolite catalyst No solvent Continuous reactor No water Periodic catalyst Regeneration... 

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