Dimethylglyoxime, reaction with

The base was being prepared by distilling a mixture of hydroxylamine hydrochloride and sodium hydroxide in methanol under reduced pressure, and a violent explosion occurred towards the end of distillation [1], probably owing to an increase in pressure above 53 mbar. It explodes when heated under atmospheric pressure [2], Traces of hydroxylamine remaining after reaction with acetonitrile to form acetamide oxime caused an explosion during evaporation of solvent. Traces can be removed by treatment with diacetyl monoxime and ammoniacal nickel sulfate, forming nickel dimethylglyoxime [3], An account of an extremely violent explosion towards the end of vacuum distillation had been published previously [4], Anhydrous hydroxylamine is usually stored at 10°C to prevent internal oxidation-reduction reactions which occur at ambient temperature [5], See other REDOX REACTIONS... 

Alkylidenecyclopentene-l,4-diones (cf. 12, 130).2 The cobaltacyclopente-nedione (2) formed on reaction of a cyclobutenedione with 1, when complexed with dimethylglyoxime, reacts with 1-alkynes to form 5-alkylidenecyclopentene-1,4-diones (3). The reaction involves an alkyne-vinylidene rearrangement. Ben-zoquinones are usually formed in minor amounts. 

An additional example of a functional group undergoing reaction at the alpha atom is provided by the reactions of coordinated oximes. The earliest observation on this class of system appears to have been reported by Barker who reacted bis (dimethylglyoxime) nickel with methyl iodide and dimethyl sulfate (3). The formulations suggested for the products are archaic however, the experiments have been repeated and found to be substantially correct (31). The reactions are exemplified in Equation 47. 

The results of acylation reactions with dimethylglyoxime reveal that ligand displacement invariably occurs (Equation 49) (47),... 

The oxygenation of the related Co system BCo(DH)2(NO) where DH = dimethylglyoximate, B = pyridine derivatives, PPh3 and N-methylimidazole, has been studied by Trogler and Marzilli (214). The main difference from the study by Basolo is the observation of a mixture of products. An O-bonded nitrato compound is obtained as the major product in this reaction with the expected nitro species giving less than 50% of the product mixture. The authors were unable to explain the occurrence of the product mixture, or elucidate the mechanism of O-bonded NOa formation. It does seem clear, however, that electrophilic attack by 02 at NO- is the key step in the reaction. In the absence of added bases, the reactivity of the nitrosyl should be diminished with respect to electrophilic attack, and it is found that only nitro products are obtained (214). 

Hydroxylamine (NH2OH) can be determined by its colour reaction with di(2-pyridyl) ketone guanylhydrazone [113]. It can also be determined in an indirect method by its reaction with biacetyl to give dimethylglyoxime, which then reacts with Ni(II) [114]. The FIA technique has been applied in the determination of NH2OH with the use of ferrozine [115]. A review has been given of methods used for the determination of hydrazine [116]. 

The most usual method of spectrophotometric determination of nickel is using the reaction with dimethylglyoxime and an oxidizing agent (bromine, for example) in alkaline solution to form a red soluble complex (445 nm). 

An early example for cobalt-catalysed Mizoroki-Heck-type reactions with aliphatic halides by Branchaud and Detlefsen showed that an intermolecular substitution of styrene (2) could be achieved with [Co(dmgH)2py] (70) (dmgH = dimethylglyoxime monoanion) as catalyst in the presence of visible light. This radical reaction led selechvely to the substitution products when using stoichiometric amounts of Zn (27) and pyridine (31) as additives (Scheme 10.24) [52]. 

A cobaltphosphine complex (ClCo(PPh3)3) reacts with cyclobutenedione to afford a phthaloyl cobalt complex. As shown in eq. (17.33), the ligand is exchanged by adding dimethylglyoxime pyridine, and a quinone is obtained by reaction with acetylene [45,78,79]. 

Figure 33 shows the result of a separation procedure for lead, copper, iron and nickel carried out in this way. Copper is fixed as sulfide on the paper disk, iron and nickel washed into the ring zone and then revealed respectively in individual sectors by reaction with potassium cyanoferrate(II) and dimethylglyoxime. 

The interference of silver in this test for gold can be avoided by precipitation and removal of silver chloride. The concentration of silver ions in a saturated solution of AgCl in 0.1 iV" hydrochloric acid is so low that in one milliliter the reaction with the reagent is no stronger than that of 0.1 y gold. 2 In the presence of chloride, the reactivity of mercury is also decreased and even completely inhibited for small amounts. Palladium salts can be removed by precipitation in acid solution with dimethylglyoxime the yellow crystalline inner complex Pd-dimethylglyoxime is formed. 

The reaction with nickel dimethylglyoxime equilibrium solution (see page 77) can be apphed with excellent results for the detection of alkaline earths and alkalis in ashes. 

The reagent T1(S04)2 is the main oxidant in the reaction with iron(II) in the presence of sulfate ions. Iron(III) inhibits the reaction suggesting participation by Tl(II). An inner-sphere halide bridged mechanism is proposed for the Fe reduction of rrans-[Co(DH)2pyX] where DH is dimethylglyoximate anion and X is the halogen ion. Rate constants for both uncatalyzed and base-catalyzed pathways show an increase in the order... 

Other Complexes. A dissociative mechanism has been established for substitution reactions of low-spin rm/w-[Fe(dmgH)2(L)2] (L=l-methylimidazole, py, CO, or PhCH2NC) in non-aqueous solvents. The rate data are summarized in Table 26. The dimethylglyoxime complexes with L=CO or PhCHjNC are substantially more... 

The reaction of the nickel, copper, or palladium complexes M(LH)a (L= dimethylglyoxime, salicylaldoxime) with diphenylmercury and aluminium powder in refluxing toluene affords the complexes ML2Al2Ph4. Similar complexes of composition QAI2R2X2L2 (QH2=salicylaldoxime R=alkyl X=... 

The well-known reaction of Ni(II) with dimethylglyoxime (H Dm) in alkaline medium under the influence of such oxidants as persulphate and iodine is widely used for the photometric determination of nickel. The red product (RP) of this reaction is used for this purpose. However, the nature of this red compound has not been defined yet. Using of peroxyacids makes it possible to obtain additional data concerning the conditions and mechanism of generation of RP as well as to improve the metrological pai ameters of the method. 

Reaction of Rh2(OCOR)4 with dimethylglyoxime leads to a non-bridged dimer [81]. 

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