Cupric Salts

Metallic Derivatives, (a) Cuprous Acetylide. CujCg. Prepare an ammoniacal solution of cuprous chloride by first adding dilute ammonia to 2-3 ml. of dilute copper sulphate solution until the initial precipitate just redissolves and a clear deep-blue solution is obtained now add an aqueous solution of hydroxylamine hydrochloride drop by drop with shaking until the solution becomes first green and then completely colourless, the cupric salt being thus reduced to the cuprous derivative. 

Several variations of the chemical method are in use. In the one described below, a freshly prepared Fehling s solution is standardised by titrating it directly against a standard solution of pure anhydrous glucose when the end-point is reached, I. e., when the cupric salt in the Fehling s solution is completely reduced to cuprous oxide, the supernatant solution becomes completely decolorised. Some difficulty is often experienced at first in determining the end-point of the reaction, but with practice accurate results can be obtained. The titrations should be performed in daylight whenever possible, unless a Special indicator is used (see under Methylene-blue, p. 463). 

Oxidation of benzoin with concentrated nitric acid or by catalytic amounts of cupric salts in acetic acid solution, which are regenerated continuously by ammonium nitrate, yields the diketone benzil ... 

Uncatalyzed addition of hydrochloric acid is accompanied by replacement of one hydroxyl group, giving high yields of 2,4-dichloro-2-buten-l-ol (58) with mercuric or cupric salt catalysts, addition occurs without substitution (59,60). 

The most suitable oxidizing agent is potassium ferricyanide, but ferric chloride, hydrogen peroxide ia the presence of ferrous salts, ammonium persulfate, lead dioxide, lead tetraacetate or chromate, or silver and cupric salts may be useful. Water mixed, eg, with methanol, dimethylformamide, or glycol ethers, is employed as reaction medium. 

In a similar procedure, the atomizer test, which depends on the behavior of an advancing rather than a receding contact angle, a fine mist of water is apphed to the metal surface and the spreading of water is observed. On a clean surface, water spreads to a uniform film. With oleic acid as the test soil, the atomizer test can detect the presence of 10 mg of soil per cm, less than a monomolecular layer (115). For steel that is to be electroplated, the copper dip test is often employed. Steel is dipped into a cupric salt solution and the eveimess of the resulting metallic copper deposit is noted. 

Chemical Designations - Synonyms Acetic Acid Cupric Salt Crystallized Verdigris Cupric Acetate Monohydrate Neutral Verdigris Chemical Formula Cu(C2H302)2 H20. 

The acetylide anion 3 is likely to form an alkynyl-copper complex by reaction with the cupric salt. By electron transfer the copper-II ion is reduced, while the acetylenic ligands dimerize to yield the -acetylene 2 ... 

Cupri-. cupric, copper(II). -azetst, n. cupric acetate, copper(II) acetate, -carbonat, n. cupric carbonate, copper(II) carbonate, -chlorid, n. cupric chloride, copper(II) chloride. -hydroxyd, n. cupric hydroxide, cop-per(II) hydroxide. -ion, n. cupric ion, copper(II) ion. -ozalat, n. cupric oxalate, copper(II) oxalate, -oxyd, n. cupric oxide, copper(II) oxide. -salz, n. cupric salt, copper(II) salt, -suifat, n. cupric sulfate. copper(II) sulfate, -sulfid, n. cupric sulfide, copper(II) sulfide, -verbihdung, /. cupric compound, copper(II) compound, -wein-saure, /. cupritartaric acid. 

Kupferoxyd, n. cupric oxide, copper(II) oxide, -ammoniak, n. ammoniacal copper oxide, cu-prammonium. -ammoniakkunstseide, -am-moniakzellulose, /. cuprammonium rayon, -hydrat, n. cupric hydroxide, copper(II) hydroxide. -salz, n. cupric salt, copper(II) salt. 

Returning now to Beckwith s data we shall consider them on the basis of our discussion of aryl radical formation by electron transfer (Secs. 8.6, 10.5, and 10.6). It may appear surprising in Table 10-9 that Meijs and Beckwith (1986) carried out chloro- and bromo-de-diazoniations only with cupric salts. The authors point out, however, that they identified tiny amounts of cuprous impurities, and that relatively large concentrations of CunHlg2 are necessary for the second step in Scheme 10-80. 

The oxidative dimerization of the anion of methyl phenyl sulfone (from a Grignard reagent) in ethereal solution in the presence of cupric chloride in 5% yield has been reported47. Despite the reported48 poor stability of the a-sulfonyl C-centered radicals, Julia and coworkers49 provoked the dimerization (in 13 to 56% yields) of the lithiated carbanion of alkyl phenyl sulfones using cupric salts as oxidants. The best results are obtained with cupric triflates in THF-isobutyronitrile medium (56% yield for R = H). For allyl phenyl sulfones the coupling in the 3-3 mode is predominant. 

As was noted by Jones (ref. 12) the success of a metal bromide as a catalyst for alkylaromatic autoxidations depends on the ability of the metal to transfer rapidly and efficiently oxidizing power from various autoxidation intermediates onto bromide ion in a manner which generates Br-. The fact that no free bromine is observable in this system is consistent with rapid reaction of intermediate bromine atoms with the substrate. Inhibition of the reaction by cupric salts can be explained by the rapid removal of Br2 or ArCH2- via one-electron oxidation by Cu (Fig. 10). 

Terminal alkynes can be coupled by heating with stoichiometric amounts of cupric salts in pyridine or a similar base. This reaction, which produces symmetrical diynes... 

When the alkyl group is one oxidizable to COOH (19-11), cupric salts are oxidizing agents, and the OH group is found in a position ortho to that occupied by the alkyl group.This reaction is used industrially to convert toluene to phenol. 

Several studies have been made of oxidations of ketols by Cu(II). Simple cupric salts deposit cuprous oxide, but this has been overcome by using a citrate complex of Cu(II) or a 1 1 (mole) pyridine-water mixture. A recent detailed account is that of Wiberg and Nigh ° , who found the stoichiometry and rate law for the oxidation of a-hydroxyacetophenone by Cu(II) acetate to be, respectively,... 

Additional acceleration of acylation can be obtained by inclusion of cupric salts, which coordinate at the pyridine nitrogen. This modification is useful for the preparation of highly hindered esters.122 Pyridine-2-thiol esters can be prepared by reaction of the carboxylic acid with 2,2 -dipyridyl disulfide and triphenylphosphine123 or directly from the acid and 2-pyridyl thiochloroformate.124... 

Iodinations can be carried out by mixtures of iodine and various oxidants such as periodic acid,26 I205,27 N02,28 and Ce(NH3)2(N03)6.29 A mixture of a cuprous iodide and a cupric salt can also effect iodination.30... 

Carboxylic acids are oxidized by lead tetraacetate. Decarboxylation occurs and the product may be an alkene, alkane or acetate ester, or under modified conditions a halide. A free radical mechanism operates and the product composition depends on the fate of the radical intermediate.267 The reaction is catalyzed by cupric salts, which function by oxidizing the intermediate radical to a carbocation (Step 3b in the mechanism). Cu(II) is more reactive than Pb(OAc)4 in this step. 

The oxidation of butanone-2, catalyzed by complexes of pyridine with cupric salts, appeared to be similar in its main features [191]. Butanone-2 catalytically oxidizes to acetic acid and acetaldehyde. The reaction proceeds through the enolization of ketone. Pyridine catalyzes the enolization of ketone. Enole is oxidized by complexes of Cu(II) with pyridine. The complexes Cu(II).Py with n = 2,3 are the most reactive. Similar results were provided by the study of butanone-2 catalytic oxidation with o-phenanthroline complexes, where Fe(III) and Mn(II) were used as catalysts [192-194],... 

The oxidation of ethylene to acetaldehyde by dioxygen catalyzed by palladium and cupric salts found important technological application. The systematic study of this process was started by Smidt [245] and Moiseev [246]. The process includes the following stoichiometric stages [247,248] ... 

A suspension process using redox initiation in a water medium was developed. The redox system is a combination of persulfatesulfite. Often ferrous or cupric salts were added as a catalyst for the redox reaction. Polymerizations were run in water at low temperature (20-25°C) and low pressure (65-85 psi). Monomer to monomer-plus-water weight ratios of 0.20 to 0.25 were used. Good agitation was required to keep an adequate monomer concentration in the aqueous phase. Yields ofup to 100% were obtained with polymer inherent viscosities of0.4 to 1.5 dl/g in C6F5C1. Reactions were run on both a 1-gal and a 100-gal scale. 

The mechanism of the Kharasch-Sosnovsky reaction remains unclear. The generally accepted version, as proposed by Kochi and co-workers (94-96) and later improved by Beckwith and Zavitsos (97), is illustrated in Scheme 8. Cuprous ion reduces the perbenzoate to Cu(II)OBz (Bz = benzoyl) and free /-BuO radical. The radical abstracts an allylic hydrogen atom generating an allyl radical that combines with the cupric salt to form an allylcopper(III) species. Reductive elimination with... 

In 1965, Denney et al. (98) reported the reaction of a number of alkenes with ferf-butyl hydroperoxide (TBHP) and cupric salts of chiral acids. The use of ethyl camphorate copper complex 144 in the allylic oxidation of cyclopentene provides, upon reduction of the camphorate ester, the allylic alcohol in low yield and low selectivity, Eq. 82. The initial publication only provided the observed rotation of cyclopentenol, but comparison to subsequent literature values (99) reveals that this reaction proceeds in 12% ee and 43% yield (based on the metal complex). 

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