Cacodyl radical

Robert Wilhelm Bunsen, 1811-1899, German chemist who investigated the cacodyl radical, the geysers of Iceland, and the chemical action of light. Inventor of the Bunsen battery, the grease-spot photometer, ice and vapor calorimeters, the thermoregulator, the constant-level water-bath, and the filter pump. 

The cacodyl radical [(CH3)2As] also appeared to Bunsen to be a stable superatom that could be exchanged amongst other radicals. Many cacodyl compounds are explosive as well as spontaneously flammable. One of these, cacodyl cyanide [(CH3)2AsCN], exploded during Bunsen s exploratory studies, and he lost his right eye. ... 

The search was now on to identify different radicals. Dumas found the methyl radical. Robert Wilhelm Bunsen investigated compounds of the cacodyl radical (a smelly, toxic, sometimes explosive set of compounds containing arsenic) and isolated what appeared to be a free radical. It was actually a compound made of two radicals joined together, but it supported the idea that radicals were stable, isolatable entities, which could be treated like organic elements. Bunsen did not carry this work further because an explosion of cacodyl cyanide cost him an eye and several weeks of illness (and thereafter he steered clear of organic chemistry in general). He did go on to have a successful career in other chemical endeavors, inventing for instance a gas burner called the Bunsen burner, which is still standard laboratory equipment. 

The Radical Theory, based on the views of Lavoisier and Berzelius, and extended by Liebig, was supported by the classical researches of Bunsen on the cacodyl radical. Robert Wilhelm Bunsen (Gottingen, 31 March 1811-Heidelberg, 16 August 1899), the son of a professor of modern languages and... 

Cabannes factor analy chem An equational factor to correct for the depolarization effect of the horizontal components of scattered light during the determination of molecular weight by optical methods. ko banz. fak-tor cacodyl orgchem (CH3)2As A radical found in, for example, cacodylic acid, (CH3)2A-sOOH. kak-3 dil ... 

Miscellaneous radicals, for example, cacodyl (CHi) As—. celebrated on account of the investigations by Bunsen (1838). 

Intramolecular electron transfer leading to a bromouracil radical anion is supposed to take place upon irradiation of the duplex d(GCABrUGC)2 in sodium cacodylate buffer at pH 7.0437. The resulting uracilyl-5-yl radical can abstract the adjacent C-l hydrogen of the adenosine radical cation. Adenine is then released by hydrolytic cleavage of the A-glycosidic bond. 

Cacodyl was later found to be tetramethyldiarsine (251), with the weakness of the arsenic-arsenic bond accounting for its high reactivity. But before this became known, cacodyl was believed to be a free radical hence the -yl in the name. This belief contributed both to research on the theory of radicals, and, more importantly, to the further development of organometallic chemistry. 

Cacodyl, prepared originally by Bunsen, was claimed by him to be a free radical. The formula of the radical would be As(CHs)2. He had actually prepared (CHs) 2AsAs(CH3) 2. Cacodyl is discussed again on p. 102 where Franldand concludes tl t it is a compound rather than a radical, though he does not modify its formula,—O.T.B.]... 

Frankland here aigucs tiiat if cacodyl and zinc alkyls are radicals, they should form the same number of oxides as there are states of oxidation for the free metal. However, the highest oxide predicted by this view can never be prepared. Frankland therefore proposes that these so-called radicals are, in fact, stable compounds, and correspond without further combination to the lowest oxidation state of the metals.—O.T.B.]... 

All the inhibitions reported so far indicate that there is no known specific inhibitor for the manganese superoxide dismutase. The enzyme from B. stearothermophilus was found to be inhibited by cacodylate (Thornalley et al., 1982) however, the inhibition could only be observed in the xanthine/xanthine oxidase assay and not in the pulse radiolysis assay. No evidence was obtained that cacodylate could be competing with the enzyme for because little or no inhibition was observed when the copper/zinc rather than the manganese enzyme was assayed in the presence of cacodylate. Further investigations revealed that the inhibitory effect is due to a cacodylate anion radical produced by the interaction of hydroxyl radicals (generated by the xanthine/xanthine oxidase reaction) and cacodylate anions. A radical of pamoic acid (4,4 -methylenebis-(3-... 

R represents hydrogen atoms, or aliphatic or aromatic organic radicals and X represents an electronegative atom or radical (F, Cl, Br, I, OH, etc.). Arsenous acid is an example of the most oxidized member of Category I, in which one finds, as derivatives, tetraalkyl arsonium compounds, cacodyl derivatives, and esters of arsenous acids. Arsenic acid is an example of the most oxidized members of Category II, and trimethyl arsine oxide (CHjjjAsO is an example of one of the lowest oxidation states. The practically nontoxic compound arsenobetaine is the main form of arsenic in most species of fish and crustaceans (Edmonds and Francesconi 1988). 

It is a wonderful irony to note that there is indeed a truly stable (actually, persistent ) cacodyl free radical. Some 20 years ago it was discovered that mild heating of the compound [(CH3)3Si)2CH]2As— As[CH(Si CH3 3)2]2 produces two As[CH(Si CH3 3)2]2 radicals that are stable and observable for indefinite periods in solution at 25°C. The trick here is the group of four huge [( CH3 3Si)2CH] groups that hinder recombination of the radicals and formation of the weak As— As bond. 

Most speculative radicals of the nineteenth century, like benzoyl, cacodyl, ethyl or acetyl (some of which later turned into formal-descriptive rests or functional groups ) had no chance to become real entities, or better, to be given an empirically adequate description. The Gomberg radical, in contrast, became more than just some strange movement behind the curtain. 

Later analyses showed that the substance had this formula, and Bunsen adopted the proposal of Berzelius that it should be named Kakodyloxyd (cacodyl oxide), from KaKa>8rj9y stinking, and regarded as the oxide of a radical cacodyl C4Hi2As2 = Kd (Berzelius, with reasons, used Kk). By the action of concentrated acids on cacodyl oxide, Bunsen prepared the chloride, iodide, and fluoride of cacodyl, and the cyanide, diese schone aber beispiellos giftige Verbindung by the same method, but more conveniently by distilling cacodyl oxide and mercuric cyanide. He also prepared cacodyl sulphide and selenide. 

In cacodyl the mere conception of a radical is converted into reality. It has the character of a metal in forming halogen and double halogen compounds. The... 

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