The Mechanisms of Oxymercuration

The title compound (I) was prepared by Diels-Alder reaction of butadiene-1,1,4,4-d., with ethylene. The considerations which led to the synthesis of I are presented and some examples are then given of how use of I can simplify the study of, and provide new information about, a number of different kinds of problems. In the proton magnetic resonance (n.111.r.) spectra of the products of additions to I , the tertiary protons ~~s~~a l l y appear as clearly defined quartets. Since J J a n ! can be read directly from these spectra, both the stereochemistry of the additions and the conforn~ations of the products call be deduced. Thus, oxymercuration of I is clear!y a traws addition and Na/Hg reduction of the mercury takes place with retention of c o n f i g~~r a t~o~l . \hihe11 the second step is performed in D.0, the oxyn~ercuration-reduction sequence represents a convenient route for the trans addition of DOH to a double bond. Deuteroboration provided a n example of cis addition of DOH to I. Acid-catalyzed hydration of I resulted in scrambling of the d e~~t e r i u~n atoms. The value of Gn,/o~f is small; Gur/on is 600 cal/mole. The position of the double bond in a product resulting from allylic substitution of I is determined by integration of the n.m.r. spectrum. lielative to I, the possibilities are no rearrangement, 50% rearrangement, and 100% rearrangement of the double bond. The first product of allylic substitution by N-bro~nosuccinimide shows IIO rearrangement; therefore, this reaction does 11ot require a "free" radical intermediate. The structure of an adduct formed during allylic acetosylation of I by mercuric acetate (the Treibs reaction) has been determined.

Section: Results a S D Discussionmentioning

confidence: 76%

CYCLOHEXENE-3,3,6,6-d₄ A USEFUL COMPOUND FOR THE STUDY OF MECHANISM AND STRUCTURE

Wolfe¹,

Campbell²

1965

“…I t may be seen (item 1G) that a typical alkyl bis-mercurial does not have PD lower than MRD. Alternatively examination of items 12 and 14 as well as [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] shows that the presence of phenyl groups or of polynuclear aromatization leads to PD values which are less than the h/IRD calculation.…”

Section: -112mentioning

confidence: 99%

“…But it is not realistic for bis-mercurials, which split easily upon acid treatment. Consequently a bond moment for C-Hg in bis-mercurials was devised (20) for all possible values of 4, where 0 = 60" and + is the angle between the radial components of the C-NO2 group moments, here assumed t o be 4.0 D. I t may be seen that this resultant moment for free rotation is the same as that for 4 fixed a t 90'.…”

Section: -112mentioning

confidence: 99%

The Non-Linearity of Bis-Arylmercury Compounds

Horning¹,

Lautenschlaeger²,

Wright³

1963

The measured distortion polarizations of a group of bis-arylmercury co~npounds show that they do not exhibit exalted atom polarizations. The apparent orientation polarization of each is appreciable. Two of them, which are substituted symmetrically with methoxyl or nitro, exhibit moments expected from the rotation which is generated in such substances. By comparison of bis-4-bromophenylmercury202 with the analogue containing the ordinary isotopic mixture of mercury the apparent moments are shown to be unrelated to nuclear asymmetry. The conclusion is unaltered that the appare~lt nlonlerlts of bis-arylmercury compounds are due to effective non-linearity in the C-Hg-C bond.In continuation of our search t o explain the apparently anomalous electric moments of bis-arylmercury compounds (1) we have re-examined and extended the work of Hampson (2), who originally observed the anomalies. Essentially we have arrived a t a conclusion which partakes of Hampson's original explanation as a "flexibility moment", which was later generally endorsed by Sidgwick (3) as not unexpected when mercury is involved.Hampson's opinion that he had measured an orientation polarization of bis-phenylmercury and its symmetrical p-methyl, fluoro, chloro, and bromo analogues was not generally accepted. In particular there were some (4) who tried to attribute the anomaly t o atom polarization, an argument which Coop and Sutton themselves questioned on the basis of the unrealistic force constant which would be required. Finally the question whether diphenylmercury exhibited an abnormally high atom polarization was for the first time put t o the test of experiment (1, 5) and was answered in the negative.Indeed the value obtained by direct measurement of distortion polarization (PD, i.e. PE+*) for diphenylmercury was found to be lower than that expected according to the commonly used methods of calculating molecular refraction (RIIR, i.e. P,) by addition of the constituent atom refraction according to Eisenlohr (6) or of the bond refractions according to Vogel (7). Since the low distortion polarization implies a definite dipole moment which is unexpected among bis-mercurials it is necessary to decide why these distortion polarizations are low. Consequently the distortion polarizations of a series of bis-mercurials have been examined by the method of dielectric constant determination with compressed wafers of randomly oriented powders together with a number of other substances more or less related. The results are sho\vn in Table I, where the differences between PD and an average of MRD by the methods of Eisenlohr and Vogel are shown in the last column.The distortion polarization (PD) of diphenylmercury has been redetermined with a result in good agreement with the 57.1 cc reported previously (1). The low value (negative difference) is reflected in comparable differences for the series of substituted diphenylmercurys, items 2-8 inclusive. On the other hand item 9, dimesitylmercury, shows a distortion polarization which is higher than the aver...

“…i\/Ioreover, the stereospecific reaction occurs with inversion if the recent assignment of configurations for 2-methoxy-1,2-diphellyleth~ilmercuric salts is correct (19). In terms of the V\Terner concept of substitutio~l (commonly called Snz) the stereospecific substitution via radicals may seem to be anonlalous in the sense that nucleophilic attraction is absent in the neutral radical.…”

Section: Stereochemical Aspects Of T H E Oxidationmentioning

confidence: 99%

The Mechanism of Organomercurial Oxidation by Mercuric Salts

Robson¹,

Wright²

1960

Self Cite

It has been shown that the oxidation of organomercuric salts by inorganic mercuric salts is inhibited by oxygen, accelerated to sonle extent by acids, and will form esters as products even in the presence of much water. Moreover, the system will polymerize acrylonitrile. These evidences of free radical participation are substantiated by the formation of the same products when pernitrous acid replaces inorganic mercuric salt in the system. Kinetic studies show that radicals are involved in a self-regenerating chain in which active monomeric mercurous salt seems to be the carrier.I t has been shown previously (1) that the oxidation of organomercuric salts in which the anion is nitrato is much more facile than maiiltains for systems in which the salts are acetates. Because of this difference in reactivity we have found it convenie~lt to discuss the nitrato and acetato systems separately. T H E OXIDATION O F ORGANOMERCURIC NITRATESIn the earlier publication (1) it was shown that the reaction of benzylmercuric nitrate with mercuric nitrate in methanol led to benzyl methyl ether and benzyl nitrate. Additional examples have now been sought. Although n-butylmercuric nitrate will not react, cyclohexylmercuric nitrate in methailol contai~ling mercuric nitrate gives an Syo yield of methoxycyclohexane and a 31% yield of cyclohexyl nitrate.Of greater interest is the observation that benzylmercuric nitrate with n~ercuric nitrate in water yields not only benzyl alcohol, benzaldehyde, and benzoic acid but also benzyl nitrate. Similarly cyclohexylmercuric nitrate with mercuric nitrate in water gives not only a 40% yield of cyclohexanol and a trace of forn~ylcyclopentane (to be explained in a forthcomiilg publication) but also a 21% yield of cyclohexyl nitrate. The formation of these nitrate esters in aqueous solution is unusual even though these reaction systems are not entirely homogeneous. T o be sure benzylmercuric chloride has been found (2) to yield benzyl nitrite and nitrate in nitric acid but little water was present in that sq-stem. Certainly cyclohexanol with mercuric nitrate in dilute nitric acid does not form cyc1ohes)il nitrate according to infrared spectral examination. Indeed the formation of appreciable amounts of nitrate esters under conditions where they should be absent or minimal if they were constituents of heteropolar or ionic equilibria indicates strongly that these nitrate esters are formed by a homopolar or free-radical mechanism.