1 ,2-Dichloro-1 ,2-Dibromoethan

Fig. 3 Chart illustrating the superconducting transition temperatures as a function of solvent and anion in the KL-(BEDT-TTF)M(CF3)4(l,l,2-trihaloethane) (M = Cu, Ag and Au) series. 1120 is 1,1,2-trichoroethane, lBrl2Cl is l-bromo-l,2-dichloroethane, llC12Bris 1,1-dichloro-2-bromoethane, lC112Br is 1-chloro-1,2-dibromoethane and 112Bris 1,1,2-tribromoethane...

DDD Dichloro(chlorophenyl)-bis Ethane DDE Dichlorodiphenyldichloroethylene Dichlorobenzene, 1,2 Dichlorobenzene, 1,3 Dichlorobenzene, 1,4 Hexachlorobenzene Polychlorinated Benzenes Polychlorinated Biphenyls PCBs Aroclor Ring-Substituted Aromatics Tetrachlorobenzene Trichlorobenzene, 1,2,4 Saturated Alkyl Halides Bromodichloromethane Bromoform Tribromomethane Butyl Chloride Chlorobutane Carbon Tetrachloride Carbon Tetrafluoride Chloroform Trichloromethane Chloromethane Methyl Chloride Dibromochloromethane Dibromoethane, 1,2 Ethylene Dibromide Dibromomethane... 

Some details concerning the synthesis of pyrroles from ketoximes and 1,2-dichloro- or 1,2-dibromoethanes in the KOH/DMSO system are described in a patent (82MIP1). The reaction proceeds smoothly and at a fairly high rate at 90-120°C. It is recommended that ketoxime, 1,2-dihaloethane, and KOH be taken in a molar ratio of 1 (2-3) (7-10) and the process carried out at 100°C for 2.5-6 hr. The preferable ketoxime/ DMSO volume ratio is 1 10. 

CBZ COD Cp Cy DABCO dba DBE DBN DBU DCC DCE DDQ DEA DEAD Dibal-H Diphos-4 DMAP DME 0 II Carbobenzoxy = —COCH2Ph 1,5-Cyclooctadienyl Cyclopentadienyl Cyclohexyl 1.4- Diazabicyclo[2.2.2]octane Dibenzylidene acetone 1.2- Dibromoethane = BrCH2CH2Br 1,8-Diazabicyclo[5.4.0]undec-7-ene 1.5- Diazabicyclo[4.3.0]non-5-ene 1.3- Dicyclohexylcarbodiimide = C6H,3—N=C=N—C6H13 1.2- Dichloroethane = CICH2CH2CI 2.3- Dichloro-5,6-dicyano-1,4-benzoquinone Diethylamine = HN(CH2CH3)2 Diethylazodicarboxylate Diisobutylaluminum hydride 1.4- b s-(Diphenylphosphino)butane 4-Dimethylaminopyridine Dimethoxyethane 0... 

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. 

An important Pd(II)-generation step in Pd(II)-catalyzed reactions is the elimination of heteroatom groups such as Cl, Br, OAc and OH at )3-position to Pd, and Pd(JI) species are generated after the elimination. Elimination of heteroatom groups is faster than that of hydrogen. No reoxidant is required for this efficient catalytic reaction. Based on this reaction, 1,2-dichloro- and dibromoethane derivatives [10], a-halo ketones such as chloroacetone and desyl chloride are used for Pd(II) generation [11,12]. 

Cyclobutenes. Ethereal cis-1,4-dichloro-l,2-diphenyl-1-butene added to pure sublimed Mg, 1,2-dibromoethane added as activator, and the product isolated after 19 hrs. 1,2-diphenyl-1-cyclobutene. Y 86%. — This synthesis is sensitive to the structure of the dichloride and to experimental conditions. F. e. s. M. S. Newman and G. Kaugars, J. Org. Ghem. 30, 3295 (1965). 

Addition methods were used for the determination of m-saturated compounds and olefins. The methods are based on the additions of bromine to unsaturated bonds, and the waves for the brominated compounds corresponding to the reduction of o, j8-dibromides (involving elimination) are measured. Their heights are proportional to the concentration of the unsaturated compound. Thus vinylchloride and 1,2-dichloroethylene were transformed into l-chloro-l,2-dibromoethane and l,2-dichloro-l,2-dibromoethane, by the action of a 3 M solution of bromine in methanol saturated with sodium bromide. The excess of bromine was removed with ammonia and the polarographic analysis was performed with sodium sulphite or lithium chloride as a supporting electrolyte. On the other hand, acetylene, vinyl-chloride, 1,2-dichloroethylene and 1,1,2-trichloroethylene were determined ) after a 24 hr reaction with bromine in glacial acetic acid (1 1). The excess bromine was removed with a stream of nitrogen or carbon dioxide. An aliquot portion is diluted (1 10) with a 3 M solution of sodium acetate in 80 per cent acetic acid and after deaeration the curve is recorded. 

These terms can be clarified by looking at some specific examples. In the following ro-tamers of ) cso-l,2-dichloro-l,2-dibromoethane, the only achirotopic site in rotamer A is the point of inversion in the middle of the structure. Every atom is in a locally chiral environment, and so is chirotopic. For rotamer B, all points in the mirror plane (a plane perpendicular to the page of fhe paper) are achirotopic. All other points in these conformers are chirotopic, existing at sites of no symmefry. In other words, all other points in these conformers feel a chiral environment, even though the molecule is achiral. 

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