Hyperfine coupling constants in muonium adducts of the carbonyl bond

Cox, S. F. J.; Geeson, D.A.; Rhodes, Christopher J.; Roduner, Emil; Scott, Christopher A.; Symons, Martyn C. R.

doi:10.1007/bf02394983

Cited by 24 publications

(12 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This coupling showed a positive temperature dependence, implying that its sign was positive, as with the carbonyl adducts studied in this way. 1 However, extension to an aliphatic series of thiocarbonyl compounds gave results which are in complete contrast with this, since each compound gave rise to a single radical with a large muon hyperfine coupling of ca. 50 G (reduced value, see Table l), with no precession signals in the low frequency region as observed in the case of Ph2CS.…”

mentioning

confidence: 89%

“…This is reminiscent of results for alkyl radic?ls (3-substituted with sulphur substituents, such as MeSCH2CH2, in which low CJ-proton couplings are observed. This is interpreted in terms of a preference for conformation (1) in which the MeS group eclipses the carbon 2p orbital.5 One explanation for this is that hyperconjugation6 involving the C-S bond is more effective than for the P-C-H bonds in these alkyl radicals. The positive temperature dependences of these (3-proton couplings .…”

mentioning

confidence: 99%

See 1 more Smart Citation

Muonium containing thiyl radicals: R₂C(Mu)–S˙

Rhodes¹,

Symons²,

Roduner³

1988

J. Chem. Soc., Chem. Commun.

View full text Add to dashboard Cite

Sulphur centred radicals of the type R2C(Mu)-S-have been observed by the ySR technique, during the irradiation of a number of thiocarbonyl compounds with positive muons; such thiyl radicals, RS., have never been detected by e.s.r. spectroscopy in the liquid phase.We have recently observed a number of adducts of the light hydrogen isotope, muonium, with carbonyl compounds1 by the transverse-field pSR technique. These adducts are R2COMu radicals, in which the muonium atom is bonded to the oxygen parbonyl atom. Corresponding proton derived radicals, R2COH, are well known, and comparisons of the data reveal interesting isotope effects. A logical extension of this work was a stvdy of C=S adducts, which were expected to be of the type R2CSMu. This aim was realised for thiobenzophenone in diethyl ether, which gave a radical with a small [7 G (G = 10-4 T)] coupling-constant, as expected for the

show abstract

mentioning

confidence: 89%

mentioning

confidence: 99%

Muonium containing thiyl radicals: R₂C(Mu)–S˙

Rhodes¹,

Symons²,

Roduner³

1988

J. Chem. Soc., Chem. Commun.

View full text Add to dashboard Cite

show abstract

“…The C=O compound most often studied by TF-μSR is acetone, which yields the "muoxy-iso-propyl" radical, Me 2 C • OMu, by addition to the oxygen atom of the C=O group [58][59][60][61][62][63][64][65][66][67][68][69] . Assuming that the relative order of bond energies for species X-Mu is approximately the same as those for X-H, it might reasonably be concluded that the driving force for this is the formation of an O-Mu bond, which should be 80 kJ mol -1 stronger than a C-Mu bond.…”

Section: Muonium Adducts Of C=o C=s C=n N=n and No 2 Compoundsmentioning

confidence: 99%

Muonium–the Second Radioisotope of Hydrogen: A Remarkable and Unique Radiotracer in the Chemical, Materials, Biological and Environmental Sciences

Rhodes

2012

Science Progress

View full text Add to dashboard Cite

Muonium (Mu), may be regarded as a radioactive hydrogen atom with a positive muon as its nucleus, and is formed in a range of media which are irradiated with positive muons. This exotic atom can be considered as a second radioisotope of hydrogen, along with tritium. Addition of this light atom (with a mass 1/9th that of a normal hydrogen, protium, atom) to unsaturated organic molecules forms free radicals, in which the muon serves as a radioactive and magnetic probe of their kinetic and structural properties. Suitable examples are chosen to illustrate the very large functionality of organic radicals which have been measured using muons and various methods of μSR, where μ stands for muon, S for spin and R may refer to rotation, resonance or relaxation. The principal techniques illustrated are transverse-field muon spin rotation (TF-μSR), avoided level crossing muon spin resonance (ALC-μSR) and longitudinal-field muon spin relaxation (LF-μSRx). Structural studies of radicals, the determination of mechanisms for radical formation, the measurement of radical stabilisation energies, the determination of the kinetics of reactions of free muonium atoms and of free radicals have all been accomplished using TF-μSR methods. It is further shown that TF-μSR is most useful in measuring radical reaction rates in non-aqueous media, to provide information of relevance to cell membrane damage and repair. Muonium may further be used as a mechanistic probe since it determines a true pattern of H-atom reactivity in molecules, against which results from similar radiolysed materials may be compared. [In many solid materials that are exposed to ionising radiation, apparent H-atom adduct radicals are detected but which originate from charge-neutralisation of positive holes (radical cations) and ejected electrons, without free H-atoms being formed. DNA is the superlative example of this. Free H-atoms normally feature in the province of radiolysed aqueous media]. The applications of ALC-μSR and LF-μSRx in studying the reorientation of reactive radicals on reactive surfaces forms the substantive proportion of the review: considered specifically are radicals sorbed in zeolites, in clays and in porous silica, in porous carbons and on ice-surfaces, in connection with their role as intermediates in catalytic systems, particularly hydrocarbon cracking and oxidation processes, and in atmospheric aerosol chemistry. The formation of muonium and other muon species in cation-exchanged zeolite-X samples are also considered, according to the evidence of longitudinal field repolarisation measurements. Finally, mention is given of the use of μSR techniques for studying radicals in the gas-phase.

show abstract

“…The C᎐ ᎐ O compound most often studied by MuSR is acetone, which yields the "muoxy-isopropyl" radical, Me 2 C ؒ -OMu, by addition to the oxygen atom of the C᎐ ᎐ O group. [55][56][57][58][59][60][61][62][63][64][65][66] Assuming that the relative order of bond energies for species X-Mu is approximately the same as that for X-H, it might reasonably be concluded that the driving force for this is the formation of an O-Mu bond, which might be 80 kJ mol Ϫ1 stronger than a C-Mu bond. Compared with most of the radicals so far considered, the muon coupling is very small, in the region of 2.8 G, its precise value depending both on solvation effects and temperature.…”

Section: Muonium Adducts Of C᎐ ᎐ O C᎐ ᎐ S C᎐ ᎐ N N᎐ ᎐ N and No 2 Comp...mentioning

confidence: 99%

Muonium—the second radioisotope of hydrogen—and its contribution to free radical chemistry

Rhodes

2002

J. Chem. Soc., Perkin Trans. 2

View full text Add to dashboard Cite

Hyperfine coupling constants in muonium adducts of the carbonyl bond

Cited by 24 publications

References 10 publications

Muonium containing thiyl radicals: R₂C(Mu)–S˙

Muonium containing thiyl radicals: R₂C(Mu)–S˙

Muonium–the Second Radioisotope of Hydrogen: A Remarkable and Unique Radiotracer in the Chemical, Materials, Biological and Environmental Sciences

Muonium—the second radioisotope of hydrogen—and its contribution to free radical chemistry

Contact Info

Product

Resources

About

Hyperfine coupling constants in muonium adducts of the carbonyl bond

Cited by 24 publications

References 10 publications

Muonium containing thiyl radicals: R2C(Mu)–S˙

Muonium containing thiyl radicals: R2C(Mu)–S˙

Muonium–the Second Radioisotope of Hydrogen: A Remarkable and Unique Radiotracer in the Chemical, Materials, Biological and Environmental Sciences

Muonium—the second radioisotope of hydrogen—and its contribution to free radical chemistry

Contact Info

Product

Resources

About

Muonium containing thiyl radicals: R₂C(Mu)–S˙

Muonium containing thiyl radicals: R₂C(Mu)–S˙