C. G. Freeman, M. McEwan, R. Claridge, L. F. Phillips
Rate constants for bimolecular and termolecular reactions with Hg(3P0), lifetimes of complexes with Hg(3P0), and lower limits for dissociation energies of complexes with Hg(3P0), have been determined for ethylamine, n-propylamine, isopropylamine, n-butylamine, sec-butylamine, isobutylamine and tert-butylamine. These results, when supplemented by previous values for the quantum efficiencies of mercury-sensitized luminescence, allow us to assess the relative importance of Hg(3P0) in the sensitized decompositions of amines.
{"title":"Phase-shift studies of Hg(3 P 0) reactions. Part 3.?Complexes of Hg(3 P 0) with some primary amines","authors":"C. G. Freeman, M. McEwan, R. Claridge, L. F. Phillips","doi":"10.1039/tf9716703247","DOIUrl":"https://doi.org/10.1039/tf9716703247","url":null,"abstract":"Rate constants for bimolecular and termolecular reactions with Hg(3P0), lifetimes of complexes with Hg(3P0), and lower limits for dissociation energies of complexes with Hg(3P0), have been determined for ethylamine, n-propylamine, isopropylamine, n-butylamine, sec-butylamine, isobutylamine and tert-butylamine. These results, when supplemented by previous values for the quantum efficiencies of mercury-sensitized luminescence, allow us to assess the relative importance of Hg(3P0) in the sensitized decompositions of amines.","PeriodicalId":23290,"journal":{"name":"Transactions of The Faraday Society","volume":"67 1","pages":"3247"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1039/tf9716703247","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"57632545","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The kinetics of the oxidation of α-hydroxyisobutyric acid by aquomanganese(III) ions have been investigated in aqueous perchlorate media using conventional and stopped-flow spectrophotometry. The acidity range is more restricted than that used for the oxidation of other organic substrates by MnIIIaq as the MnII added to maintain the ionic strength at µ= 4.00 and to suppress the formation of MnIV has a small effect on the rate at [HClO4]⩽ 1.0 M. The rate-determining step involves the decomposition of an intermediate complex, Mn3+(CH3)2COHCOOHaq, and the overall energy E and entropy ΔS* of activation are compared with E and ΔS* for other organic substrates oxidized by MnIIIaq: the high reactivity of α-hydroxyisobutyric acid arises from the high positive ΔS* derived from chelation. A value is estimated for the protonation constant of α-hydroxyisobutyric acid.
采用常规和停流分光光度法研究了高氯酸水溶液中α-羟基异丁酸被水锰离子氧化的动力学。酸度范围更受到的限制比用于其他有机底物的氧化MnIIIaq MnII添加到维护的离子强度µ= 4.00和抑制MnIV的形成有一个小对速率的影响(高氯酸)⩽1.0 m的分解速率决定步骤涉及到一个中间复杂,Mn3 + (CH3) 2 cohcoohaq,和整体能量E和熵Δ*的激活与E和ΔMnIIIaq S *其他有机底物氧化:α-羟基异丁酸的高反应活性来源于螯合产生的高正电荷ΔS*。对α-羟基异丁酸的质子化常数进行了估计。
{"title":"Kinetics of oxidation of α-hydroxyisobutyric acid by aquomanganese (III) ions in aqueous perchlorate media","authors":"C. F. Wells, C. Barnes","doi":"10.1039/TF9716703297","DOIUrl":"https://doi.org/10.1039/TF9716703297","url":null,"abstract":"The kinetics of the oxidation of α-hydroxyisobutyric acid by aquomanganese(III) ions have been investigated in aqueous perchlorate media using conventional and stopped-flow spectrophotometry. The acidity range is more restricted than that used for the oxidation of other organic substrates by MnIIIaq as the MnII added to maintain the ionic strength at µ= 4.00 and to suppress the formation of MnIV has a small effect on the rate at [HClO4]⩽ 1.0 M. The rate-determining step involves the decomposition of an intermediate complex, Mn3+(CH3)2COHCOOHaq, and the overall energy E and entropy ΔS* of activation are compared with E and ΔS* for other organic substrates oxidized by MnIIIaq: the high reactivity of α-hydroxyisobutyric acid arises from the high positive ΔS* derived from chelation. A value is estimated for the protonation constant of α-hydroxyisobutyric acid.","PeriodicalId":23290,"journal":{"name":"Transactions of The Faraday Society","volume":"67 1","pages":"3297-3305"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1039/TF9716703297","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"57632653","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Assuming an oriented molecular layer to behave optically as a homogeneous, uniaxial medium with its optic axis normal to the interface, such a system is treated theoretically to yield equations relevant to both specular reflectance and ellipsometric spectroscopy. Explicit expressions are derived for the empirical quantities (relating them to the optical constants of the media and other system parameters) which are both reasonably simple and correct to second-order terms in the film thickness. From ellipsometric measurements alone, it is not possible to distinguish between very thin uniaxial and isotropic films. However, data for a very thin non-absorbing uniaxial film on an absorbing substrate (e.g., a metal), if analyzed on the assumption of film isotropy, lead to an apparent absorption index for the film of the magnitude of the absorption index found for semi-conductors. A similar result is predicted for specular reflectance measurements, except that in that case the apparent optical constants of the film depend on the angle of incidence.
{"title":"Specular reflectance and ellipsometric spectroscopy of oriented molecular layers","authors":"M. Dignam, M. Moskovits, R. W. Stobie","doi":"10.1039/TF9716703306","DOIUrl":"https://doi.org/10.1039/TF9716703306","url":null,"abstract":"Assuming an oriented molecular layer to behave optically as a homogeneous, uniaxial medium with its optic axis normal to the interface, such a system is treated theoretically to yield equations relevant to both specular reflectance and ellipsometric spectroscopy. Explicit expressions are derived for the empirical quantities (relating them to the optical constants of the media and other system parameters) which are both reasonably simple and correct to second-order terms in the film thickness. From ellipsometric measurements alone, it is not possible to distinguish between very thin uniaxial and isotropic films. However, data for a very thin non-absorbing uniaxial film on an absorbing substrate (e.g., a metal), if analyzed on the assumption of film isotropy, lead to an apparent absorption index for the film of the magnitude of the absorption index found for semi-conductors. A similar result is predicted for specular reflectance measurements, except that in that case the apparent optical constants of the film depend on the angle of incidence.","PeriodicalId":23290,"journal":{"name":"Transactions of The Faraday Society","volume":"67 1","pages":"3306-3317"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1039/TF9716703306","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"57632695","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The gas-phase pyrolysis of 1,2-dichloropropane has been studied at temperatures from 393 to 470°C and initial pressures from 0.2 to 26.0 Torr. In a 1-1. silica reaction vessel of low surface/volume ratio, the products are the four monochloropropenes and hydrogen chloride. Above 440°C the product ratios show only a small dependence on temperature and the relative amounts of the various isomers at 457°C are (expressed as percentage of the total chloropropenes), 3-chloropropene 63.6%, cis-1-chloropropene 22.9 %, trans-1-chloropropene 12.7 %, 2-chloropropene 0.8 %. The overall reaction is closely represented by the pressure change which leads to the overall rate-constant log10k(s–1)=(13.78 ±0.21)–(54 760 ±440)/4.576 T. Arrhenius parameters have been derived for each of the chloropropene products from the above expression and the product ratios at various temperatures (extrapolated to zero time). Additions of small amounts of nitric oxide and propene had virtually no effect upon the overall rate. The reaction has also been studied at low temperatures (300–380°C) and in various packed reaction vessels. The product ratios (extrapolated to zero time and corrected for the concurrent homogeneous reaction at the higher temperatures) show increased proportions of 2-chloropropene and cis-1-chloropropene and also formation of propene which can constitute up to 15 mol % of the total organic products. The results are consistent with four parallel unimolecular reactions occurring homogeneously at high temperatures. The heterogeneous reactions are more complicated although similarities are noted with the elimination reactions of other alkyl halides at glass surfaces.
{"title":"Gas-phase pyrolysis of 1,2-dichloropropane","authors":"K. A. Holbrook, J. S. Palmer","doi":"10.1039/TF9716700080","DOIUrl":"https://doi.org/10.1039/TF9716700080","url":null,"abstract":"The gas-phase pyrolysis of 1,2-dichloropropane has been studied at temperatures from 393 to 470°C and initial pressures from 0.2 to 26.0 Torr. In a 1-1. silica reaction vessel of low surface/volume ratio, the products are the four monochloropropenes and hydrogen chloride. Above 440°C the product ratios show only a small dependence on temperature and the relative amounts of the various isomers at 457°C are (expressed as percentage of the total chloropropenes), 3-chloropropene 63.6%, cis-1-chloropropene 22.9 %, trans-1-chloropropene 12.7 %, 2-chloropropene 0.8 %. The overall reaction is closely represented by the pressure change which leads to the overall rate-constant log10k(s–1)=(13.78 ±0.21)–(54 760 ±440)/4.576 T. Arrhenius parameters have been derived for each of the chloropropene products from the above expression and the product ratios at various temperatures (extrapolated to zero time). Additions of small amounts of nitric oxide and propene had virtually no effect upon the overall rate. The reaction has also been studied at low temperatures (300–380°C) and in various packed reaction vessels. The product ratios (extrapolated to zero time and corrected for the concurrent homogeneous reaction at the higher temperatures) show increased proportions of 2-chloropropene and cis-1-chloropropene and also formation of propene which can constitute up to 15 mol % of the total organic products. The results are consistent with four parallel unimolecular reactions occurring homogeneously at high temperatures. The heterogeneous reactions are more complicated although similarities are noted with the elimination reactions of other alkyl halides at glass surfaces.","PeriodicalId":23290,"journal":{"name":"Transactions of The Faraday Society","volume":"67 1","pages":"80-87"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1039/TF9716700080","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"57612884","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. K. Mohanty, T. S. Sarma, S. Subramanian, J. C. Ahluwalia
Integral heats of solution of Bu4NBr in aqueous binary solvent mixtures (containing 0.0 to 0.30 mol fraction of consolvent) of t-butanol, acetone, dioxan and ethylene glycol were determined at 15, 25, and 35°C. Integral heats of solution of NaBPh4 in the same aqueous binary solvents containing 20 % by volume (about 0.05 mol fraction) of cosolvent were also determined at 15, 25 and 35°C. Corresponding excess partial molal heat capacities Δtext-decoration:overlineC°p were derived at 20 and 30°C. The partial molal enthalpies Δtext-decoration:overlineH°s of Bu4 NBr increased (sharply in aqueous t-butanol up to 0.06 mol fraction) with the addition of increasing amount of cosolvent to water till the maximum value was attained at 0.1–0.3 mol fraction of cosolvent. The endothermicity maxima Δtext-decoration:overlineH°smax were in the decreasing order of t-butanol > acetone > ethylene glycol > dioxan. text-decoration:overlineH°smax decreased with increasing temperatures in all aqueous binary solvents. text-decoration:overlineC°p results indicate that addition of small amounts of t-butanol and acetone stabilize the water structure, the maximum stabilization occurring around 0.04 mol fraction of acetone and t-butanol. Further addition of t-butanol to 0.06 mol fraction results in complete collapse of the water structure, whereas further addition of acetone results in gradual breakdown of the water structure which continues up to 0.3 mol fraction of acetone. Dioxan and ethylene glycol seem to have net structure breaking influence on the water structure.
{"title":"Partial molal enthalpies, excess partial molal heat capacities and structural effects of Bu4NBr and NaBPh4 in aqueous binary solvent mixtures","authors":"R. K. Mohanty, T. S. Sarma, S. Subramanian, J. C. Ahluwalia","doi":"10.1039/TF9716700305","DOIUrl":"https://doi.org/10.1039/TF9716700305","url":null,"abstract":"Integral heats of solution of Bu4NBr in aqueous binary solvent mixtures (containing 0.0 to 0.30 mol fraction of consolvent) of t-butanol, acetone, dioxan and ethylene glycol were determined at 15, 25, and 35°C. Integral heats of solution of NaBPh4 in the same aqueous binary solvents containing 20 % by volume (about 0.05 mol fraction) of cosolvent were also determined at 15, 25 and 35°C. Corresponding excess partial molal heat capacities Δtext-decoration:overlineC°p were derived at 20 and 30°C. The partial molal enthalpies Δtext-decoration:overlineH°s of Bu4 NBr increased (sharply in aqueous t-butanol up to 0.06 mol fraction) with the addition of increasing amount of cosolvent to water till the maximum value was attained at 0.1–0.3 mol fraction of cosolvent. The endothermicity maxima Δtext-decoration:overlineH°smax were in the decreasing order of t-butanol > acetone > ethylene glycol > dioxan. text-decoration:overlineH°smax decreased with increasing temperatures in all aqueous binary solvents. text-decoration:overlineC°p results indicate that addition of small amounts of t-butanol and acetone stabilize the water structure, the maximum stabilization occurring around 0.04 mol fraction of acetone and t-butanol. Further addition of t-butanol to 0.06 mol fraction results in complete collapse of the water structure, whereas further addition of acetone results in gradual breakdown of the water structure which continues up to 0.3 mol fraction of acetone. Dioxan and ethylene glycol seem to have net structure breaking influence on the water structure.","PeriodicalId":23290,"journal":{"name":"Transactions of The Faraday Society","volume":"67 1","pages":"305-315"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1039/TF9716700305","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"57613871","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The sorption, permeation and diffusion of water in a series of polyalkylmethacrylates has been studied for a number of temperatures in the range 298–353 K. In each case the diffusion coefficient decreased as the concentration of sorbed water was increased. The heat and the entropy of dilution decreased with concentration and the activation energy for diffusion increased. Polymethylmethacrylate was the exception in that both the heat of dilution and the activation energy for diffusion were independent of concentration. The results are consistent with significant clustering of the water molecules in the polymer matrix. A comparison is made with a random polycondensation model for the association of water through hydrogen-bond formation.
{"title":"Diffusion and association of water in some polyalkylmethacrylates. Part 1.—Equilibrium sorption and steady state permeation","authors":"J. A. Barrie, D. Machin","doi":"10.1039/TF9716700244","DOIUrl":"https://doi.org/10.1039/TF9716700244","url":null,"abstract":"The sorption, permeation and diffusion of water in a series of polyalkylmethacrylates has been studied for a number of temperatures in the range 298–353 K. In each case the diffusion coefficient decreased as the concentration of sorbed water was increased. The heat and the entropy of dilution decreased with concentration and the activation energy for diffusion increased. Polymethylmethacrylate was the exception in that both the heat of dilution and the activation energy for diffusion were independent of concentration. The results are consistent with significant clustering of the water molecules in the polymer matrix. A comparison is made with a random polycondensation model for the association of water through hydrogen-bond formation.","PeriodicalId":23290,"journal":{"name":"Transactions of The Faraday Society","volume":"67 1","pages":"244-256"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1039/TF9716700244","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"57614087","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The degrees of association of n-pentyl lithium and n-octyl lithium in benzene at 30°C have been measured using the method of vapour pressure lowering. The value from n-pentyl lithium is 6.00 ± 0.09 [degrees of freedom (D.F.)]= 13]; the value for n-octyl lithium is 5.953 ± 0.016 (D.F. = 9). It is argued that the two compounds exist predominantly as hexamers in solution.
{"title":"Degrees of association of n-pentyl lithium and n-octyl lithium in benzene","authors":"D. Margerison, J. D. Pont","doi":"10.1039/TF9716700353","DOIUrl":"https://doi.org/10.1039/TF9716700353","url":null,"abstract":"The degrees of association of n-pentyl lithium and n-octyl lithium in benzene at 30°C have been measured using the method of vapour pressure lowering. The value from n-pentyl lithium is 6.00 ± 0.09 [degrees of freedom (D.F.)]= 13]; the value for n-octyl lithium is 5.953 ± 0.016 (D.F. = 9). It is argued that the two compounds exist predominantly as hexamers in solution.","PeriodicalId":23290,"journal":{"name":"Transactions of The Faraday Society","volume":"67 1","pages":"353-359"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1039/TF9716700353","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"57614313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The nature of oxygen adsorbed on slightly reduced TiO2 has been investigated using oxygen enriched with 17O2. On anatase, the oxygen adsorbs as O–2 with a hyperfine splitting Axx about g3 of 77 G; no structure could be resolved for Ayy and Azz. On rutile, oxygen adsorbs as O–2 on two sites of different thermal stability; (I) with g1= 2.030, g2= 2.008, g3= 2.004 and Axx= 76 G, and (II) with g1= 2.020, g2= 2.009, g3= 2.003 and Axx= 72 G. The evidence indicates that O–2 exists in a largely ionic form on TiO2 and other oxides. A symmetrical line at g= 2.003 which appears on some anatase samples after oxygen adsorption is attributed to the localization of a conduction electron by the adsorbed oxygen.
{"title":"Identification of oxygen species adsorbed on reduced titanium dioxide","authors":"C. Naccache, P. Mériaudeau, M. Che, A. J. Tench","doi":"10.1039/TF9716700506","DOIUrl":"https://doi.org/10.1039/TF9716700506","url":null,"abstract":"The nature of oxygen adsorbed on slightly reduced TiO2 has been investigated using oxygen enriched with 17O2. On anatase, the oxygen adsorbs as O–2 with a hyperfine splitting Axx about g3 of 77 G; no structure could be resolved for Ayy and Azz. On rutile, oxygen adsorbs as O–2 on two sites of different thermal stability; (I) with g1= 2.030, g2= 2.008, g3= 2.004 and Axx= 76 G, and (II) with g1= 2.020, g2= 2.009, g3= 2.003 and Axx= 72 G. The evidence indicates that O–2 exists in a largely ionic form on TiO2 and other oxides. A symmetrical line at g= 2.003 which appears on some anatase samples after oxygen adsorption is attributed to the localization of a conduction electron by the adsorbed oxygen.","PeriodicalId":23290,"journal":{"name":"Transactions of The Faraday Society","volume":"67 1","pages":"506-512"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1039/TF9716700506","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"57614834","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Processes of solid phase transition, fusion and decomposition in several nitramines (and a nitrosamine) have been investigated using differential scanning calorimetry. The following values (kcal mol–1) for the enthalpy changes, ΔH(TK) are reported: N-picryl-N-methylnitramine (tetryl), ΔHf(400.5)= 6.18±0.07, –ΔHd(445)= 94±2; 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX)ΔHf(478.5)= 8.52 ± 0.07, –ΔHd(483)= 136 ± 2; 1,3,5,7-tetranitro-1,3,5,7-tetra-azacyclooctane, (HMX), ΔHt,β→δ(ca. 460)= 2.35±0.20, –ΔHd(ca. 540)= 166±9; 1,7-diacetoxy-2,4,6-trinitro-2,4,6-triazaheptane (BSX), ΔHf(422.5)= 9.2 ±0.4, –ΔHd(ca. 500)= 124± 12; 1,5-endomethylene-3,7-dinitro-1,3,5,7-tetra-azacyclooctane (DPT), –ΔHd(ca. 471)= 35 ± 6; 1,3-dinitro-1,3-diazacyclopentane (DDCP), ΔHf(403)≃ 6.0; 1,3-dinitro-1,3-diazacyclohexane(DDCHX), ΔHt(343)= 3.7 ± 0.3, ΔHf(353)= 0.70 ±0.02; 1,3-dinitro-1,3-diazacycloheptane (DDCHP), ΔHt(370)≃ 5.6, ΔHf(376)≃ 0.95; 1,3,5-trinitroso-1,3,5-triazacyclohexane (TNOHX), ΔHt(365)= 4.25±0.15, ΔHf(376)= 0.90±0.03. The depression of the melting point of tetryl caused by pre-heating the solids is used together with literature data ((i) relating the melting point depression with the amount of gas produced during decomposition, and (ii) for the amount of gas produced on complete decomposition) to calculate first-order rate constants for decomposition in the region of the solid→liquid transition. The results indicate a “premonitory” effect at temperatures below the melting point. With the exception of RDX (apparent Ea= 45.2±0.4 kcal mol–1) the apparent activation energies for de-composition of the nitramines tend to be unrealistically high. DDCHX, DDCHP and TNOHX show plastic crystal behaviour and may be classified as “globular” molecules; the absence of this type of behaviour with DDCP and RDX is discussed in terms of factors affecting molecular rotation in the solid state.
{"title":"Thermal decomposition and phase transitions in solid nitramines","authors":"P. G. Hall","doi":"10.1039/TF9716700556","DOIUrl":"https://doi.org/10.1039/TF9716700556","url":null,"abstract":"Processes of solid phase transition, fusion and decomposition in several nitramines (and a nitrosamine) have been investigated using differential scanning calorimetry. The following values (kcal mol–1) for the enthalpy changes, ΔH(TK) are reported: N-picryl-N-methylnitramine (tetryl), ΔHf(400.5)= 6.18±0.07, –ΔHd(445)= 94±2; 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX)ΔHf(478.5)= 8.52 ± 0.07, –ΔHd(483)= 136 ± 2; 1,3,5,7-tetranitro-1,3,5,7-tetra-azacyclooctane, (HMX), ΔHt,β→δ(ca. 460)= 2.35±0.20, –ΔHd(ca. 540)= 166±9; 1,7-diacetoxy-2,4,6-trinitro-2,4,6-triazaheptane (BSX), ΔHf(422.5)= 9.2 ±0.4, –ΔHd(ca. 500)= 124± 12; 1,5-endomethylene-3,7-dinitro-1,3,5,7-tetra-azacyclooctane (DPT), –ΔHd(ca. 471)= 35 ± 6; 1,3-dinitro-1,3-diazacyclopentane (DDCP), ΔHf(403)≃ 6.0; 1,3-dinitro-1,3-diazacyclohexane(DDCHX), ΔHt(343)= 3.7 ± 0.3, ΔHf(353)= 0.70 ±0.02; 1,3-dinitro-1,3-diazacycloheptane (DDCHP), ΔHt(370)≃ 5.6, ΔHf(376)≃ 0.95; 1,3,5-trinitroso-1,3,5-triazacyclohexane (TNOHX), ΔHt(365)= 4.25±0.15, ΔHf(376)= 0.90±0.03. The depression of the melting point of tetryl caused by pre-heating the solids is used together with literature data ((i) relating the melting point depression with the amount of gas produced during decomposition, and (ii) for the amount of gas produced on complete decomposition) to calculate first-order rate constants for decomposition in the region of the solid→liquid transition. The results indicate a “premonitory” effect at temperatures below the melting point. With the exception of RDX (apparent Ea= 45.2±0.4 kcal mol–1) the apparent activation energies for de-composition of the nitramines tend to be unrealistically high. DDCHX, DDCHP and TNOHX show plastic crystal behaviour and may be classified as “globular” molecules; the absence of this type of behaviour with DDCP and RDX is discussed in terms of factors affecting molecular rotation in the solid state.","PeriodicalId":23290,"journal":{"name":"Transactions of The Faraday Society","volume":"67 1","pages":"556-562"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1039/TF9716700556","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"57614881","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The rate of recombination of hydrogen atoms in fuel-rich hydrogen/oxygen/nitrogen flames containing metal additives has been measured using the lithium/lithium hydroxide method to monitor hydrogen atom concentrations. It is found that the rate of the recombination reaction is accelerated by the addition of alkaline earth metals. The preferred mechanism for catalysis is via the cycle of reactions: MOH + H →MO + H2(7), MO + H2O(+X)→M(OH)2(+X)(8), M(OH)2+ H⇌MOH + H2O (–5), and the rate of the catalyzed recombination is given by the expression [graphic omitted] Values of k7 and lower limits of k8 have been determined for calcium, strontium and barium at 1570 K and 1800 K. The upper limit for the catalysis to be effective is about 2000 K. This is determined by the increase of K5 with temperature.
采用锂/氢氧化锂法监测氢原子浓度，测定了含金属添加剂的富燃料氢/氧/氮火焰中氢原子的复合速率。结果表明，碱土金属的加入加快了复合反应的速度。优选的催化机理是通过反应循环:MOH + H→MO + H2(7)， MO + H2O(+X)→M(OH)2(+X)(8)， M(OH)2+ H + MOH + H2O(-5)，催化重组的速率由式给出[图略]在1570 K和1800 K下测定了钙、锶和钡的k7值和k8下限。有效催化的上限约为2000k。这是由K5随温度的增加决定的。
{"title":"Catalysis of radical-recombination reactions in flames by alkaline earth metals","authors":"D. Cotton, D. R. Jenkins","doi":"10.1039/TF9716700730","DOIUrl":"https://doi.org/10.1039/TF9716700730","url":null,"abstract":"The rate of recombination of hydrogen atoms in fuel-rich hydrogen/oxygen/nitrogen flames containing metal additives has been measured using the lithium/lithium hydroxide method to monitor hydrogen atom concentrations. It is found that the rate of the recombination reaction is accelerated by the addition of alkaline earth metals. The preferred mechanism for catalysis is via the cycle of reactions: MOH + H →MO + H2(7), MO + H2O(+X)→M(OH)2(+X)(8), M(OH)2+ H⇌MOH + H2O (–5), and the rate of the catalyzed recombination is given by the expression [graphic omitted] Values of k7 and lower limits of k8 have been determined for calcium, strontium and barium at 1570 K and 1800 K. The upper limit for the catalysis to be effective is about 2000 K. This is determined by the increase of K5 with temperature.","PeriodicalId":23290,"journal":{"name":"Transactions of The Faraday Society","volume":"67 1","pages":"730-739"},"PeriodicalIF":0.0,"publicationDate":"1971-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1039/TF9716700730","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"57616231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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