Methanol Glass Research Articles

A kinetic peculiarity of free valence migration in the solid state as studied through the reaction of methyl radicals with methanol at 77 K

The reaction of methyl radicals with methanol at 77 K has been studied. CH 3 radicals were produced by the photolysis of diphenylamine-CH 3I with UV light in a methanol glass. In the methanol samples the percentage of water or the isotopic composition of methanol were changed. The reaction of CH 3 radicals with methanol obeys the law C = C 0exp(− Kt 1 2 ) in all cases.

Solvation spectra. Part 50.—Spectrophotometric studies of the solvation of nitrate ions in protic and aprotic media

Nitrate ions in aprotic solvents exhibit a single band at ∼1 353 cm–1, in the absence of ion-pair formation. However, in protic solvents, (H2O, MeOH)text-decoration:overlineν3 is split into a doublet (∼1 345 and 1 400 cm–1). This indication of descent in symmetry is interpreted in terms of relatively strong hydrogen-bonding to one or two oxygen atoms only. This effect, which contrasts with the behaviour of perchlorate ions, is interpreted in terms of the high polarisability of the nitrate ion. Application of simple equations for weak interactions in a trigonal-planar system suggests that a single strong hydrogen bond is favoured. This is supported by e.s.r. spectroscopic studies of irradiated aqueous and methanolic glasses containing nitrate ions, which show that the product nitrogen dioxide is not hydrogen bonded to the matrix. Addition of low concentrations of methanol to solutions of tetra-n-butylammonium nitrate in methylene chloride caused shifts and splittings of the text-decoration:overlineν1 and text-decoration:overlineν3 modes indistinguishable from those obtained with bulk methanol. This occured in parallel with changes in the O—H stretching mode indicative of strong 1:1 hydrogen-bonding between methanol and nitrate, thus supporting the concept of strong mono-solvation. Ion-pairing with sodium ions in aprotic solvents results in a comparable splitting of the text-decoration:overlineν3 absorption.Studies of the O—H stretching mode of interacting solvent molecules show that the strength of the hydrogen-bonds to nitrate are comparable to those formed by iodide ions and are far stronger than those formed by perchlorate ions.

Radiation mechanisms. Part VII. Electron-loss and -capture processes in phenylphosphinic acid and related compounds

Exposure of phenylphosphinic acid and related compounds to 60Co γ-rays at 77 K resulted in electron addition to the aromatic ring, since, the characteristic e.s.r. spectra of the alternative phosphoranyl radicals were absent except for that assigned to PhṖH(O)OH radicals. The anions were protonated on annealing, or directly at 77 K in methanolic glasses, to give cyclohexadienyl radicals which exhibited a hyperfine coupling of 22 G to 31P nuclei. However, the aromatic anion of PhPH(O)OH probably undergoes a 1,2-hydrogen atom shift from phosphorus to the ring carbon, the resulting adduct having A(1H) 40 and A(31P) 200 G. This species is unstable and either breaks down to give benzene and ·PO(OH)– radicals, or undergoes a further hydrogen shift to give a normal cyclohexadienyl species.

Radiation mechanisms—VIII. Radiolysis of borohydride ions in aqueous solutions. An E.S.R. study

Radiolysis of frozen aqueous or methanolic glasses containing sodium borohydride gave E.S.R. features characteristic of ·BH 3 − as the major radical product. These radicals were strongly associated with the solvent lattice in contrast with their behaviour in the parent salt. Additional E.S.R. features separated by ca. 200 G are assigned to BH 4, but since this spectrum could never be obtained in the absence of the intense BH 3 − features, this assignment is tentative.

Extinction Coefficients of Maleate and Fumarate Radical Anions and Relative Yield of cis-trans Isomerization in Methanol Glass at 77 K

Abstract The photoisomerization of the γ-rayinduced maleate radical anion (DEM−) to the fumarate radical anion (DEF−) has been studied. The molar extinction coefficients of DEM− and DEF− have been determined to be 2.43×104 1 mol−1 cm−1 and 3.40×104 1 mol−1 cm−1 respectively. The yield of the isomerization from DEM− to DEF− is found to be 0.95.

Radiation mechanisms. Part 4.—Electron spin resonance studies of γ-irradiated trichloronitrosomethane and trichloronitromethane

Trichloronitromethane on exposure to 60Co γ-rays at 77 K gives NO2 radicals by dissociative electron capture. However, in methanol glasses, NO2 is barely detectable, the predominating radical formed by electron capture being ·CCl3. The hole centre formed by this molecule is thought to be CCl3NO+2 with the unpaired electron largely confined to oxygen.

Matrix proton ENDOR studies of the overlap of trapped electron wavefunctions with first solvation shell molecules in methanol glass at 77 K

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Electron paramagnetic resonance studies of spin trapping of the primary neutral radicals formed in γ-irradiated methanol

The primary neutral radicals in γ-irradiated liquid methanol at 194°K have been spin trapped with phenyl- t-butyl nitrone. The principal primary radicals are CH 2OH and CH 3O. In contrast to earlier work, these radicals are formed with an initial ratio of CH 2OH/CH 3O ≈ 1.5 which agrees with gas phase mass spectrometric results. H atoms are also spin trapped although their apparent yield is several times lower than that of the other radicals. In methanol glass at 77°K only CH 2OH becomes spin trapped upon warming.

Kinetic studies of photobleaching of trapped electrons in protiated and deuterated methanol and ethanol glasses at 77.deg.K

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKinetic studies of photobleaching of trapped electrons in protiated and deuterated methanol and ethanol glasses at 77.deg.KTadamasa Shida and Masashi ImamuraCite this: J. Phys. Chem. 1974, 78, 3, 232–234Publication Date (Print):January 1, 1974Publication History Published online1 May 2002Published inissue 1 January 1974https://doi.org/10.1021/j100596a007RIGHTS & PERMISSIONSArticle Views38Altmetric-Citations13LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (362 KB) Get e-Alerts

Hydrogen atom abstraction by methyl radicals in methanol glasses at 67-77.deg.K

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHydrogen atom abstraction by methyl radicals in methanol glasses at 67-77.deg.KAlan Campion and Ffrancon WilliamsCite this: J. Am. Chem. Soc. 1972, 94, 22, 7633–7637Publication Date (Print):November 1, 1972Publication History Published online1 May 2002Published inissue 1 November 1972https://doi.org/10.1021/ja00777a004RIGHTS & PERMISSIONSArticle Views93Altmetric-Citations55LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (606 KB) Get e-Alerts Get e-Alerts

Unstable intermediates. Part 117.—Electron spin resonance studies of dimeric (σ*) radicals of type R3X—XR3with a three electron X—X bond, when X is phosphorus or arsenic

Seven hyperfine components separated by about 450 G were observed in the e.s.r. spectrum of γ-irradiated triethylarsine at 77 K. This is indicative of two equivalent interacting arsenic atoms, and an analysis of the hyperfine tensor components suggests that the species is the dimer cation (R3As—AsR3)+ with a σ2, σ*1 structure as in VK centres. Similar species are formed in γ-irradiated trialkyl phosphines, but are not formed from phosphonium or arsonium salts, nor from the phosphines or arsines in methanol glasses. Irradiation of Me2PS—PSMe2 gave a similar di-phosphorus radical.

Electronic Spectra of Trapped Electrons in Organic Glasses at 4°K

The optical absorption spectra of trapped electrons were observed in γ-irradiated ethylene glycol–water, methanol, 10M NaOH, and MTHF at 4°K. The prominent infrared absorption bands were observed in ethylene glycol–water and ethanol glasses, while the bands in methanol, 10M NaOH, and MTHF glasses were similar in shape, slightly red shifted, to the bands for the radiolysis at 77°K. When the glasses were warmed to 77°K, the bands changed irreversibly into those for the radiolysis at 77°K, reducing the absorption intensity. The spectral changes at the intermediate temperatures between 4°K and 77°K were recorded for ethylene glycol–water and methanol cases. The results are interpreted by the molecular reorientation model proposed in the previous paper [T. Higashimura, M. Noda, T. Warashina, and H. Yoshida, J. Chem. Phys. 53, 1152 (1970)].

Mössbauer study of the glass transition in methanol

A Mössbauer investigation of the temperature dependence of the recoil free fraction of FeCl 2 doped methanol glasses is reported. The recoil free fraction shows a sharp decrease near the glass transition temperature T g. This decrease is assigned to the transition from a rigid glass to the supercooled state at or slightly above T g. The recovery of the recoil free fraction is associated with crystallization of the supercooled liquid.

The radiation chemistry of liquid and glassy methanol

The methods of pulse radiolysis, low temperature optical and electron spin resonance spectroscopy and chemical analysis of stable products have been applied to an investigation of theγ-radiolysis of liquid and glassy methanol. Processes induced by generation of presumed intermediates by photoionization of solutes have been studied using the same techniques. Electrons are trapped in glassy methanol afterγ-irradiation at 77 K with a yieldG(e¯t)= 2.7 ± 0.3 and on warming are rendered mobile, ultimately forming an amount of hydrogen equal to1/2G(e¯t). In contrast, illumination of the irradiated sample at 77 K with visible light decomposes the trapped electron, forming hydrogen and CH2OH or CH2O-in yield equal toG(e¯t). The solvated electron in liquid methanol also reacts with the solvent, at a rate faster than the corresponding reaction in water. The addition of sodium methoxide to liquid methanol results in a marked increase in both the yield and lifetime of the solvated electron observed after 0.2μs irradiation pulse. The optical absorptions and decay parameters of CH2OH and CH2O-in liquid methanol were obtained; the ultraviolet absorption observed in irradiated methanol glass after removal of the trapped electrons by photo-bleaching is probably due to these two species. Solutions of methanol glass containing silver perchlorate exhibit complex optical and e. s. r. spectra, which provide evidence for several different species, but a complete analysis has not been possible. The radicals expected from the initial ionization event are considered. The results of this work together with published data are used to predict the reaction of the free radicals CH3O. , CH2OH, CH2O-, H. ande¯sor e¯tin the systems of interest and the relevance of these reactions to some aspects of the radiation chemistry of methanol is discussed.

The radiolysis of alcohols at low temperature—I. The precursors of hydrogen in glassy methanol

Using various electron and hydrogen atom scavengers the γ-irradiation yields of different hydrogen precursors in glassy photobleached methanol were determined: the yields of the trapped electrons, of the independently formed hydrogen atoms, of the hot hydrogen atoms and of the ‘molecularly’ formed hydrogen are 2·3, about 0·5, about 1·1 and about 0·3 respectively. Some conclusions about the separation of electrons from their conjugated ions are drawn from the comparison of these yields with those for liquid methanol. In acid methanol glass G(H 2) is larger by 0·5 than in neutral glass. A possible explanation is offered, namely, that a low excited state of methanol is decomposed by the influence of the electric field of the ions. When the irradiated methanol glass is warmed in the dark—thermally bleached—the yields of hydrogen and glycol are smaller but the reasons for this are not quite clear. Also the crystalline methanol gives questionable results. A few remarks on the process of electron trapping are added.

Processes in γ-irradiated methanol glass

The first page of this article is displayed as the abstract.

The radiation chemistry of low temperature methanolic glasses

A study has been made of the visible, u.v. and e.s.r. spectra produced when glassy methanol at 77 °K is irradiated with cobalt-60 y-rays and of the effects on these of: (i) various additives including 2-methyl-pent-1-ene, sodium hydroxide, sulphuric acid, carbon tetrachloride, benzyl chloride, ferric chloride and naphthalene; (ii) subsequent illumination with either u.v. light or visible light (546 and 578 nm); and (iii) subsequent warming. The data are consistent with a mechanism the major features of which are CH 3 OH gl —vw-> e t - + CH 3 OH (-> CH 3 OH 2 + . CH 2 OH) where e t - is an electron trapped in the glassy matrix, e t - can migrate perceptibly but slowly through the glass at temperatures > 100 °K and can be photo-detached from the matrix by + red or u.v. light, in both cases ultimately reacting with CH 3 OH 2 . The radical • CH 2 OH becomes mobile at temperatures not less than 106 °K and reacts bimolecularly to form glycol or formaldehyde. It is decomposed by u.v. light, but reaches a stationary concentration owing to the reaction sequence • CH 2 OH + hv 1 -> H 2 + CHO; CHO + hv 2 -> CO + H*; H* + CH 3 OH-> H 2 + •CH 2 OH. Solutes may compete with the electron trapping process and also react with electrons rendered mobile by the action of heat or light on trapped electrons.

Reaction between Methanol and Boron-containing Glasses

ADVERTISEMENT RETURN TO ISSUEPREVArticleReaction between Methanol and Boron-containing GlassesRaymond P. PorterCite this: J. Phys. Chem. 1957, 61, 9, 1260Publication Date (Print):September 1, 1957Publication History Published online1 May 2002Published inissue 1 September 1957https://doi.org/10.1021/j150555a034RIGHTS & PERMISSIONSArticle Views141Altmetric-Citations14LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (145 KB) Get e-Alerts