1.2- Dibromoethane hydrolysis

Thermal cyclization of the arylaminomethylenemalonate afforded quinoline 3-carboxylate 630 whose reaction with 1,1-dibromoethane gave oxazolo[5,4,3-(/]quinoline 631. Acid hydrolysis and reaction with N-methylpiperazine gave 632 whose bactericidal activity is superior to that of pipemidic acid (82JAPK57203085) (Scheme 108). 

Biotic and abiotic degradation of 1,2-dibromoethane in surface waters is slow relative to volatilization of the compound to the atmosphere (ERA 1987b). 1,2- Dibromoethane is resistant to hydrolysis (Jaber et al. 1984) the hydrolytic half-life of the compound has been reported to range from 2.5 years (Vogel and Reinhard 1982) to 13.2 years (HSDB 1989). As a result of its hydrolytic stability and the limited biological activity in subsurface soils, 1,2- dibromoethane leached to groundwater is expected to persist for years. 

Sanz Gil and Groth applied several substituted Af-allyl-Af-benzyl-2-bromobenzenes 493 for a similar reaction sequence and trapped the lithiomethyl intermediates 494 by hydrolysis (El = H) or by bromination with 1,2-dibromoethane (El = Br) giving 495 (equation 135) . ... 

As indicated in Table 13.7,1,2-dibromoethane (BrCH2-CH2Br) and 1,1,1-trichloro-ethane (CH3-CC13) are examples in which both hydrolysis and elimination are important. If in such cases the reactions occur by SN2 and E2 mechanisms, respectively, the ratio of the hydrolysis versus elimination products should vary with varying pH and temperature, since the two competing reactions likely exhibit different pH and temperature dependencies. On the other hand, if the reaction mechanisms were more SN1- and El-like, a much less pronounced effect of temperature or pH on product formation would be expected, since the rate-determining step in aqueous solution may be considered to be identical for both reactions ... 

Two alternative approaches to the synthesis of the partially unsaturated ring systems are depicted in Schemes 27 and 28. The addition of sulfide ion to the multiple bonds of (208) in the former is facilitated by the activating effect of the sulfinyl or sulfonyl moiety and reaction occurs rapidly, giving yields of 67-84% (79S47). The second approach illustrates the use of an unsaturated dithiolate ion (76JOC1484). The first dianion (209) is generated from electrochemically reduced carbon disulfide and reacts with 1,2-dibromoethane to give the fused compound (210). Hot base-catalyzed hydrolysis cleaves (210) to form a new dianion which, with 1,2-dibromoethane, affords the product. 

A number of functionalized 1-trimethylsilylcyclopropanes have become readily accessible along this and other routes 86). Among them, the 1-trimethylsilylcyclo-propane carboxaldehyde 156 was obtained from the spiroalkylation of trimethyl-silylacetonitrile 154 upon successive treatment with 1 equivalent of lithium diiso-propylamide (LDA), 1.5 equivalent of 1,2-dibromoethane and finally with a second equivalent of LDA. Subsequent diisobutylaluminum hydride (DIBAH) reduction of 155 followed by hydrolysis of the resulting imine with dilute sulfuric acid gave the aldehyde 156 in high yields, Eq. (49) 86). 

Previously cyclopropane-1,1-dicarboxylic acid had been prepared2-4 by hydrolysis of the corresponding diester. The preparation of 1,1-dicarboalkoxycyclopropanes by a conventional double alkylation of diethyl malonate with 1,2-dibromoethane was severely complicated by the recovery of unreacted diethylmalonate. This required a rather difficult distillation to separate starting material and product. In fact, many commercially offered lots of cyclopropane diester contain extensive amounts of diethyl malonate. Furthermore, preparation of the diacid required a separate and relatively slow saponification of the diester.5... 

Derivatives of 1-methyl-3//-l,4-benzodiazepine-2,5(l/I,4/I)dione (193) were synthesized by ring closure of substituted 2-(A-chloro-acetyl-A-methylaminoJbenzamides with sodium methoxide in methanol.209 Treatment of 193 with lithium aluminum hydride led to reduction of both carbonyl groups.209 The parent tetrahydro system (194) has been prepared by reaction of the tosylate (195) with 1,2-dibromoethane followed by hydrolysis.210 The preparation of 194 by another route had previously been noted.204 Reaction of 194 with formaldehyde or benzaldehyde gave a compound formulated as 196 (R = H or C6H5).210 Hydrolysis of 196 (R = C6H5) with 0.1 N hydrochloric acid gave 194 while 196 (R = H) was not hydrolyzed at this acidity. 

The hydrazone structure was preferred because of the ease with which S,S -dialkylation of N-aryl dithiocarbazates is known to take place and because acid hydrolysis of the product yields 1,3-dithio]sn-2-cne (CCXXIV) and the aryl hydrazine. The hydrazone (CCXXIII, R2=1 3=R.i=1 5 =H, Ri=CfiH5), independently prepared from 2-imino-1,3-dithiolane (CCX X. V ) 374 and phenylhydrazine 254), has the same melting point (94° C) and causes no lowering of the melting point when mixed with the product prepared from N-phenyl dithiocarbazate and 1,2-dibromoethane (m.p. 

In light of these results the reported synthesis 2 of 1,2-dilithioethane 7 in 6-9% yield from 1,2-dichloro- or 1,2-dibromoethane and lithium should be reinvestigated, inasmuch as characterization was only by hydrolysis to yield some ethane. 

Halogenated ethanes are distributed widely in the environment. Dibromoethane has been used as a soil fumigant and fuel additive while a number of chlorinated ethanes find extensive use as solvents. These compounds are common contaminants in groundwater and, consequently, their hydrolysis reactions are of interest. Hydrolysis of dibromoethane yields primarily ethylene glycol through substitution reactions, however, some vinyl bromide is produced through an elimination reaction. 

Table 2.8 compares hydrolysis half-lives with half-lives for reaction with sulfur-based nucleophiles for several halogenated aliphatics. These data show that the environmental half-lives for substrates such as 1-bromohexane and 1,2-dibromoethane can be substantially reduced in the presence of HS and polysulfides. Enhanced degradation of 2-bromopropane and 1,1,1-trichloroethane, as well as chloroform and carbon tetrachloride (results not shown) was not observed, suggesting that steric hindrance significantly impedes reaction with the sulfur based nucleophiles (Haag and Mill, 1988a). 

In the second step, the organolithium reagent is destroyed with an organic halide (e.g., benzyl chloride or 1,2-dibromoethane). It is supposed that the organolithium reagent reacts quantitatively affording LiCl or LiBr and that the residual base (LiOH and lithium alkoxides) does not react. After hydrolysis with an excess of water, the amount of free (residual) base is determined. 

Germanium.— The effect of the nature of univcilent cations M+ (M = Li, Na, K, Cs, or Mc4N) on the rate of alkaline hydrolysis of [GeFJ has been examined. The reaction of hexamethyldigermane with 1,2-dibromoethane, under photochemical conditions, is thought to have an Sb.2 mechanism. ... 

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