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1.
Infrared absorption spectra of co-crystalline CO(2)·C(2)H(2) aerosol particles were modeled using a combination of two methods. Density functional theory was used to model several bulk CO(2)·C(2)H(2) co-crystal structures and to calculate their lattice energies and frequency-dependent dielectric tensors. This was necessary as there currently exists no crystallographic or refractive index data on co-crystalline CO(2)·C(2)H(2)due to its metastability. The discrete dipole approximation was then used to calculate infrared absorption spectra of different model particles using the dielectric tensors calculated using density functional theory. Results from these simulations were compared to the experimental spectrum of co-crystalline CO(2)·C(2)H(2) aerosol particles. The aerosol particles after the decomposition of the co-crystalline phase were studied in Part I. 相似文献
2.
The data for the relative apparent and integral molar enthalpy of solution, L and H
sol
in
, respectively, were critically reviewed, for the magnesium chloride-water system at 25°C. The concentration dependence L(m) and the enthalpy of solution at infinite dilution H
sol
o
were determined calorimetrically at 25°C. Both results are in agreement with most of the small amount of data published previously. From the results of our measurements, and from the most reliable value for H
sol
o
of MgCl2, the concentration dependence H
sol
in
(m) at 25°C was derived, for MgCl2·6H2O. The enthalpy of the hydration
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3.
A. V. Levanov A. R. Gromov E. E. Antipenko V. V. Lunin 《Russian Chemical Bulletin》2000,49(4):642-648
The formation of formic acid in the low-temperature condensation of CO2−H2 and CO−H2O gas mixtures dissociated in electric discharge was investigated. The gas-phase concentrations of H., O., OH., and O2 were measured downstream a microwave discharge in a CO2−H2 mixture. Low-temperature (77 K) condensates formed from CO2−H2 and CO−H2O mixtures were studied by ESR. The formation of formic acid in the CO2−H2 and CO−H2O systems was found to be due to the reactions of H., CO, O., and O2 on the condensate surface. A single mechanism of the formation of formic acid in the CO2−H2 and CO−H2O systems was proposed. 相似文献
4.
The thermal behaviour of Ba[Cu(C2O4)2(H2O)]·5H2O in N2 and in O2 has been examined using thermogravimetry (TG) and differential scanning calorimetry (DSC). The dehydration starts at relatively low temperatures (about 80°C), but continues until the onset of the decomposition (about 280°C). The decomposition takes place in two major stages (onsets 280 and 390°C). The mass of the intermediate after the first stage corresponded to the formation of barium oxalate and copper metal and, after the second stage, to the formation of barium carbonate and copper metal. The enthalpy for the dehydration was found to be 311±30 kJ mol–1 (or 52±5 kJ (mol of H2O)–1). The overall enthalpy change for the decomposition of Ba[Cu(C2O4)2] in N2 was estimated from the combined area of the peaks of the DSC curve as –347 kJ mol–1. The kinetics of the thermal dehydration and decomposition were studied using isothermal TG. The dehydration was strongly deceleratory and the -time curves could be described by the three dimensional diffusion (D3) model. The values of the activation energy and the pre-exponential factor for the dehydration were 125±4 kJ mol–1 and (1.38±0.08)×1015 min–1, respectively. The decomposition was complex, consisting of at least two concurrent processes. The decomposition was analysed in terms of two overlapping deceleratory processes. One process was fast and could be described by the contracting-geometry model withn=5. The other process was slow and could also be described by the contracting-geometry model, but withn=2.The values ofE
a andA were 206±23 kJ mol–1 and (2.2±0.5)×1019 min–1, respectively, for the fast process, and 259±37 kJ mol–1 and (6.3±1.8)×1023 min–1, respectively, for the slow process.Dedicated to Prof. Menachem Steinberg on the occasion of his 65th birthday 相似文献
5.
J.-C. Grivel 《Journal of Thermal Analysis and Calorimetry》2012,109(1):81-88
The thermal decomposition of Ho(III), Er(III), Tm(III) and Yb(III) propionate monohydrates in argon was studied by means of thermogravimetry (TG), differential thermal analysis (DTA), IR-spectroscopy and X-ray diffraction (XRD). Dehydration takes place around 90?°C. It is followed by the decomposition of the anhydrous propionates to Ln2O2CO3 (Ln?=?Ho, Er, Tm or Yb) with the evolution of CO2 and 3-pentanone (C2H5COC2H5) between 300 and 400?°C. The further decomposition of Ln2O2CO3 to the respective sesquioxides Ln2O3 is characterized by an intermediate plateau extending from approximately 500?C700?°C in the TG traces. This stage corresponds to an overall composition of Ln2O2.5(CO3)0.5 but is more probably a mixture of Ln2O2CO3 and Ln2O3. The stability of this intermediate state decreases for the lighter rare-earth (RE) compounds studied. Full conversion to Ln2O3 is achieved at about 1,100?°C. The overall thermal decomposition behaviour of the title compounds is similar to that previously reported for Lu(C2H5CO2)3·H2O. 相似文献
6.
Frost RL Palmer SJ 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(4):1255-1260
The mineral nesquehonite Mg(OH)(HCO(3))·2H(2)O has been analysed by a combination of infrared (IR) and infrared emission spectroscopy (IES). Both techniques show OH vibrations, both stretching and deformation modes. IES proves the OH units are stable up to 450°C. The strong IR band at 934 cm(-1) is evidence for MgOH deformation modes supporting the concept of HCO(3)(-) units in the molecular structure. Infrared bands at 1027, 1052 and 1098 cm(-1) are attributed to the symmetric stretching modes of HCO(3)(-) and CO(3)(2-) units. Infrared bands at 1419, 1439, 1511, and 1528 cm(-1) are assigned to the antisymmetric stretching modes of CO(3)(2-) and HCO(3)(-) units. IES supported by thermoanalytical results defines the thermal stability of nesquehonite. IES defines the changes in the molecular structure of nesquehonite with temperature. The results of IR and IES supports the concept that the formula of nesquehonite is better defined as Mg(OH)(HCO(3))·2H(2)O. 相似文献
7.
《Journal of organometallic chemistry》1989,378(3):457-468
Hydrocarboxylation of isoprene catalyzed by iodocarbonylrhodium derivatives is described. Either 4-methyl-3-pentenoic (pyroterebic) acid or its lactone derivative (γ,γ-dimethyl-γ-butyrolactone) can be selectively produced in high yield depending on the experimental conditions. Spectroscopic evidence indicates the possible participation of H+ ··· Rh(CO)2I2− tight ion pairs and/or cis-Rh(CO)2(H2O)I in the catalysis. The identification of these two new species is based on spectroscopic investigation of the interconversion reactions between solvent-separated [H3O]+[Rh(CO)2X2]− ions and [Rh(CO)2X]2 (X = Cl, I). 相似文献
8.
J.-C. Grivel 《Journal of Thermal Analysis and Calorimetry》2014,115(2):1253-1264
The thermal decomposition of Dy(III), Tb(III), Gd(III), Eu(III), and Sm(III) propionate monohydrates was studied in argon by means of simultaneous differential thermal analysis and thermogravimetry, infrared-spectroscopy, X-ray diffraction, and optical microscopy. After dehydration, which takes place below 120 °C, all salts decompose into dioxycarbonates with simultaneous release of CO2 and C2H5COC2H5 (3-pentanone) between 250 and 460 °C. However, whereas the anhydrous Dy-, Tb-, and Gd-propionates appear to transform into RE2O2CO3 (rare earth [RE] = Dy, Tb, Gd) in a single step, an intermediate stage involving a RE2O(C2H5CO2)4 composition was evidenced in the case of the Eu- and Sm-propionates. For all compounds, further decomposition of RE2O2CO3 into the corresponding sesquioxides (RE2O3) is accompanied by the release of CO2. The thermal decomposition of Dy- and Tb-propionates occurs entirely in the solid state. In contrast the dehydrated Gd-, Eu-, and Sm-propionates melt at increasingly higher temperatures. Evidence for recrystallization was found in conjunction with the onset of decomposition of these three propionates. 相似文献
9.
10.
P. Melnikov V. A. Nascimento L. Z. Z. Consolo A. F. Silva 《Journal of Thermal Analysis and Calorimetry》2013,111(1):115-119
The thermal decomposition of yttrium nitrate hexahydrate Y(NO3)3·6H2O is a complex condensation process generating a tetramer arrangement Y4O4(NO3)4 formed by alternating yttrium and oxygen atoms. The anions NO3 ? attach themselves to the yttrium atoms. The tetramer gradually loses N2O5 and, through the formation of Y4O5(NO3)2, is transformed into yttrium oxide. The bond lengths and bond angles of intermediate oxynitrates calculated using the molecular mechanics method rendered data compatible with the results of X-ray diffraction for related compounds. 相似文献
11.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1982,38(4):399-408
Infrared spectra of h5- and d5-pyridinium salts Py+H ⋯ A− (A−= SbCl−6, ClO−4, BF−4, J−, Br−, Cl−) and their N-deuterated analogues have been measured in organic aprotic solvents in the region of 1650-400 cm−1 and assignments proposed for internal fundamental modes of the pyridinium ions. Notable differences of in-plane δNH and out-of plane γNH deformation mode frequencies in i.r. spectra of the salts in solution and in solid state have been established. In particular, the γNH mode frequencies in solution are 40–80 cm−1 higher than those in solid state. In the series of the salts studied the γNH mode frequencies change from 903 to 1080 cm−1 depending upon the H-bonding strength. A strong vibrational coupling γNH↔-ν5 (γCH) has been shown to occur in h5-pyridinium salts and a γND↔v10b (γCH) coupling in their N-deuterated analogues. Isotopic shifts and changes of the bandwidths of the v14, v19b and v8b internal modes show that these modes are strongly mixed with the in-plane deformation mode δNH in h5- and d5-pyridinium salts. 相似文献
12.
13.
Molecular geometries of H2S···ICF3 and H2O···ICF3 characterised by broadband rotational spectroscopy
The rotational spectra of three isotopologues of H(2)S···ICF(3) and four isotopologues of H(2)O···ICF(3) are measured from 7-18 GHz by chirped-pulse Fourier transform microwave spectroscopy. The rotational constant, B(0), centrifugal distortion constants, D(J) and D(JK), and nuclear quadrupole coupling constant of (127)I, χ(aa)(I), are precisely determined for H(2)S···ICF(3) and H(2)O···ICF(3) by fitting observed transitions to the Hamiltonians appropriate to symmetric tops. The measured rotational constants allow determination of the molecular geometries. The C(2) axis of H(2)O/H(2)S intersects the C(3) axis of the CF(3)I sub-unit at the oxygen atom. The lengths of halogen bonds identified between iodine and sulphur, r(S···I), and iodine and oxygen, r(O···I), are determined to be 3.5589(2) ? and 3.0517(18) ? respectively. The angle, φ, between the local C(2) axis of the H(2)S/H(2)O sub-unit and the C(3) axis of CF(3)I is found to be 93.7(2)° in H(2)S···ICF(3) and 34.4(20)° in H(2)O···ICF(3). The observed symmetric top spectra imply nearly free internal rotation of the C(2) axis of the hydrogen sulphide/water unit about the C(3) axis of CF(3)I in each of these complexes. Additional transitions of H(2)(16)O···ICF(3), D(2)(16)O···ICF(3) and H(2)(18)O···ICF(3) can be assigned only using asymmetric top Hamiltonians, suggesting that the effective rigid-rotor fits employed do not completely represent the internal dynamics of H(2)O···ICF(3). 相似文献
14.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1976,32(8):1471-1476
The solvent shift method of BELLAMY is re-examined, particularly as a tool for the identification of vibrations that include and are coupled to carbonyl, all of which show solvent sensitivity. For α,β-unsaturated ketones, it is shown that s-cis and s-trans conformers are readily distinguished by plots of νCC vs. νCO. The nature of this coupling is discussed and it is concluded that, in so far as coupling occurs, νCO and νCC take on the character of out-of-phase and in-phase modes respectively. In either conformer, the in-phase (νCC) mode gains in relative intensity as the frequencies converge. While s-cis conformers couple more, conjugation is unaffected by this; the true index of conjugation is neither νCO nor νCC but mean frequency νm. The whole of the solvent effect appears to be relayed by carbonyl: even a highly polar carbon double bond is insensitive to solvent unless so coupled. 相似文献
15.
M. Harcharras A. Ennaciri N. Khay K. Brouzi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6):1247-1254
The thermal dehydration of Mg 2 P 2 O 7 ·; 6H 2 O were studied, in the range 25-800°;C, by thermogravimetric analysis (TG-DSC), x-ray diffraction, and infrared spectroscopy. According to the TG-DSC curves, the dehydration of this salt takes place in two stages. The results of thermal analysis, x-ray patterns, and infrared spectra of this compound heated at different temperatures showed that, after dehydration, Mg 2 P 2 O 7 ·; 6H 2 O decomposes into dihydrate Mg 2 P 2 O 7 ·; 2H 2 O diphosphate then to an amorphous Mg 2 P 2 O 7 product which crystallises at 665°;C to give anhydrous diphosphate f Mg 2 P 2 O 7 . The j H enthalpy of the dehydration of Mg 2 P 2 O 7 ·; 6H 2 O and of the formation of f Mg 2 P 2 O 7 have been calculated from thermogravimetric data. The infrared spectroscopic study of Mg 2 P 2 O 7 ·; 6H 2 O and of its heated products, reveals the existence of the characteristic bands of the P 2 O 7 group ( x as POP and x s POP) and showed that the POP angle is bent in these salts. In these compounds, the POP angle values are estimated using the Lazarev's relationship. 相似文献
16.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1987,43(3):395-400
The i.r. and Raman spectra of CuCl2·2H2O and K2CuCl4·2H2O and of deuterated samples of these compounds are presented in the range 50–1700 cm−1 at liquid helium, liquid nitrogen, and ambient temperatures. The spectra obtained are discussed and compared with the literature data in terms of both bonding structure of the water molecules and vibrational modes, assignment, intermolecular coupling, and combination bands of the H2O, HDO, and D2O librations. The i.r. and Raman bands of the librational modes of CuCl2·2H2O are very broad even at liquid helium temperature indicating orientational disorder of the water molecules. 相似文献
17.
Nidhuban Deb 《Journal of Thermal Analysis and Calorimetry》2013,114(1):261-267
Strontium(II)diaquatris(oxalato)lanthanate(III)unidecahydrate, Sr3[La(C2O4)3(H2O)2]2·11H2O, has been synthesized and characterized by elemental, IR and electronic spectral studies. Thermal studies (TG, DTG and DTA) in air showed that all the crystal and coordinated water molecules are removed at ca. 225 °C. The final end product at 1,000 °C was shown to be a mixture of mainly SrCO3, Sr3La4O9 and La2Sr2O5 along with oxides and carbides of both the metal, through the formation of an intermediate mixture of likely SrC2O4 and La2(C2O4)2.8 at 282 °C, and SrCO3 and La2O(CO3)2 at 540 °C. The multi-step dehydration and decomposition of the compound has been explored from the DSC study in nitrogen up to 670 °C, and the evaluated kinetic parameters are discussed. 相似文献
18.
The thermal dehydration and decomposition of Cd(BF4)2·6H2O were studied by means of DTA, TG, DSC and X-ray diffraction methods and the end products of the thermal decomposition were identified. The results of thermal analysis show that the compound is fused first, then it is dehydrated until Cd(BF4)2·3H2O is obtained, which has not been described in the literature so far. The enthalpy of phase transition is H
ph.tr.=115.6 kJ mol–1 Separation of the compound is difficult since it is highly hygroscopic. Then, dehydration and decomposition take place simultaneously until CdF2 is obtained which is proved by X-ray diffraction. On further increasing the temperature, CdF2 is oxidized to CdO and the characteristic curve assumes a linear character.Based on TG data, kinetic analyses were carried out separately for both parts of the curve: first until formation of the trihydrate and then — until formation of CdF2. The formal kinetic parameters are as follows:for the first phase:E
*=45.3 kJ mol–1; rate equationF=2/3; correlation coefficient 0.9858 for the second phase:E
*=230.1 kJ mol–1; rate equationF=(1–)2/3[1-(1–)1/3]–1; correlation coefficient 0.9982. 相似文献
19.
Tuikka M Niskanen M Hirva P Rissanen K Valkonen A Haukka M 《Chemical communications (Cambridge, England)》2011,47(12):3427-3429
A new type of concerted halogen bond-hydrogen bond interaction was found in the solid state structure of [RuI(2)(H(2)dcbpy)(CO)(2)]···I(2)···(MeOH)···I(2)···[RuI(2)(H(2)dcbpy)(CO)(2)]. The iodine atoms of the two I(2) molecules interact simultaneously with each other and with the OH group of methanol of crystallization. The interaction was characterized by single crystal X-ray measurements and by computational charge density analysis based on DFT calculations. 相似文献
20.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1977,33(3-4):315-322
The i.r. and Raman spectra of NaPF6·H2O and partially deuterated NaPF6·H2O have been obtained. All of the fundamental modes of the PF−6-ion have been located and the rule of mutual exclusion applies for these modes. In the Raman spectra, the number of components observed for each fundamental PF−6-mode is consistent with the number of site group components predicted. The hydrogen bonds in NaPF6·H2O are very weak and the hydrogen bond energy is of the order of 1.7 kcal/mole. The frequencies of the nine fundamental modes of the H2O, D2O and HDO molecules have been converted to harmonic values. It is shown that if the HOH valence angle is varied, and the effective harmonic force field of the water molecules calculated for each assumed value, an estimated value of this angle in NaPF6·H2O can be obtained. The librational modes of the water molecules have been located and are assigned to rocking and wagging modes. 相似文献
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