Clathrate formation in the series of systems diisopentyldibutylammonium halide-water

Three clathrate hydrates: (i-C₅H₁₁)₂·(C₄H₉)₂NCl·38H₂O (mp 20.5°C), (i-C₅H₁₁)₂·(C₄H₉)₂NCl·32H₂O (mp 22.2°C), and (i-C₅H₁₁)₂·(C₄H₉)₂NCl·27H₂O (mp 23.8°C) were detected in the system diisopentyldibutylammonium chloride-water. Crystals of all the compounds were isolated, and their composition was determined. The size effect of the halide anions (F^?, Cl^?, and Br^?) on the properties of related compounds was considered.     

The heats of fusion of tetrabutylammonium fluoride ionic clathrate hydrates

Two ionic clathrate hydrates with different structures are formed in the binary system tetrabutylammonium fluoride–water, namely tetragonal structure-I hydrate (TS-I) (n-С₄H₉)₄NF · 32.8H₂O, and cubic superstructure-I hydrate (CSS-I) (n-С₄H₉)₄NF · 29.7H₂O. The heats of fusion (ΔH_f) of these polyhydrates were measured calorimetrically with differential scanning calorimeter. For TS-I polyhydrate ΔH_f = (204.8 ± 2.3) kJ/mol hydrate, for CSS-I hydrate ΔH_f = (177.5 ± 3.1) kJ/mol polyhydrate. The change of water molecules energy state in the water lattices of TS-I and CSS-I polyhydrates are discussed.     

Clathrate hydrates of triisoamylbutylammonium iodide

The phase diagram of the (i-C₅H₁₁)₃C₄H₉NI?H₂O system is reported. Triisoamylbutylammonium iodide forms polyhydrates with hydration numbers of 36 (mp 12.5°C) and 32 (mp 13.2°C) and a dihydrate. Crystals of both polyhdrates have been isolated, and their compositions have been determined.     

Clathrate formation in (i-C5H11)4−k (C4H9) k NF−H2O (k=1,2,3) binary systems

Phase diagrams of some binary aqueous systems with tetraalkylammonium fluorides are examined. The size of the hydrophobic moiety of the guest is consecutively varied in the series (i-C₅H₁₁)_4−k(C₄H₉)_kNF (k=0, 1, 2, 3) by replacing bulky isoamyl radicals with n-butyl radicals. Changes in clathrate formation caused by variations of the sizes and forms of guests are analyzed in the series (i-C₅H₁₁)_k−4(C₄H₉)_kNF−H₂O (k=0, 1, 2, 3, 4). All tetraisoamylammonium fluoride hydrates are more stable than other hydrates of this series. The stability of the compounds increases due to the fact that the isoamyl radicals use the host cavities more effectively than the butyl radicals. In all hydrates of the series, tetragonal structures-I (TS-I), which were earlier thought typical only for hydrates of tetrabutylammonium salts, are formed. Hydrates of the orthorhombic system are formed until three isoamyl radicals have been replaced by butyl radicals. Hydrates with 26–28 water molecules (mp 27.4–34.6°C) are the most stable hydrates of the series, except for i-AmBu₃NF·25.9 H₂O, melting 0.3°C lower than the tetragonal hydrate in the same system. All compounds are defined chemically, and for some of them crystal data are given. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Institute of Physical Chemistry, Polish Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 3, pp. 501–508, May–June, 1995. Translated by L. Smolina     

Clathrate Formation in the Water–Tetraisoamylammonium Propionate System: X-ray Structural Analysis of the Clathrate Hydrate (i-C5H11)4NC2H5CO2·36H2O

In this work X-ray single crystal structural analysis was carried out on the clathrate hydrate of tetraisoamylammonium propionate with the composition (i-C₅H₁₁)₄NC₂H₅CO₂·36H₂O. The hydrate was found to have an orthorhombic structure in space group Cmc2 ₁ with unit cell parameters: a = 21.281(2) Å, b= 12.010(7) Å, c = 24.768(3) Å (150 K). X-ray powder diffraction studies were performed of the hydrate phase, crystallized in the water–(i-C₅H₁₁)₄NC₂H₅CO₂ system in the concentration range of the salt (10–25 wt%) that is the crystallization region of the studied polyhydrate, according to the phase equilibria data. It was found, that in the given concentration region the same hydrate of orthorhombic structure is formed, unit cell parameters, obtained at 20 °C: a = 21.454(13) Å, b = 12.156(4) Å, c = 25.030(14) Å, are in a good agreement with the data of single crystal structural analysis.     

Thermochemical Properties of Palladium(II) Chelates Involving Dialkyldithiocarbamates

The standard molar enthalpies of formation of crystalline dialkyldithiocarbamates chelates, [Pd(S₂CNR₂)₂], with R=C₂H₅, n-C₃H₇, n-C₄H₉ and i-C₄H₉, were determined through reaction-solution calorimetry in acetone, at 298.15 K. From the standard molar enthalpies of formation of the gaseous chelates, the homolytic (172.4±3.8, 182.5±3.2,150.9±3.1 and 162.6±3.1 kJ mol⁻¹) and heterolytic (745.0±3.8, 803.7±3.3,834.3±3.1 and 735.2±3.0 kJ mol⁻¹) mean palladium-sulphur bond-dissociation enthalpies were calculated. This revised version was published online in July 2006 with corrections to the Cover Date.     

Humidity controlled calorimetric investigation of the hydration of MgSO4 hydrates

The isothermal heat of hydration of MgSO₄ hydrates was studied by humidity controlled calorimetry. Two hydrates, starkeyite (MgSO₄·4H₂O) and a mixture of MgSO₄ hydrates with summary 1.3 mol H₂O were investigated. The solid-gas reactions were initiated at 30°C and 85% relative humidity. The heat of hydration was determined in a circulation cell in the calorimeter C80 (Setaram). The crystal phases formed after the hydration process were analyzed by thermogravimetry (TG) and X-ray powder diffraction (XRD). Starkeyite reacted with the water vapour to the thermodynamic stable epsomite and the MgSO₄ hydrate mixture with 1.3 mol water to hexahydrite. The hydration heats of starkeyite and the mixture were determined to be −169±3 and −257±5 kJmol⁻¹, respectively.     

Quenching of I(2P½) by R-OH compounds. Influence of the alkyl group on the quenching efficiency

The deactivation of I(²P_½) by R-OH compounds (R = H, C_nH_2n+1) was studied using time-resolved atomic absorption at 206.2 nm. The second-order quenching rate constants determined for H₂O, CH₃OH, C₂H₅OH, n-C₃H₇OH, i-C₃H₇OH, n-C₄H₉OH, i-C₄H₉OH, s-C₄H₉OH, t-C₄H₉OH, are respectively, 2.4 ± 0.3 × 10⁻¹², 5.5 ± 0.8 × 10⁻¹², 8 ± 1 × 10⁻¹², 10 ± 1 × 10⁻¹², 10 ± 1 × 10⁻¹², 11.1 ± 0.9 × 10⁻¹², 9.8 ± 0.9 × 10⁻¹², 7.1 ± 0.7 × 10⁻¹², and 4.1 ± 0.4× 10⁻¹² cm³ molec⁻¹ s⁻¹ at room temperature. It is believed that a quasi-resonant electronic to vibrational energy transfer mechanism accounts for most of the features of the quenching process. The influence of the alkyl group and its role in the total quenching rate is also discussed. © 1997 John Wiley & Sons, Inc.     

Study on ketalization reaction of poly(vinyl alcohol) by ketones. VIII. kinetic study on acetalization and ketalization reactions of poly(vinyl alcohol)

The kninetics of acid-catalyzed acetalization and ketalization of poly(vinyl alcohol) (PVA) were systematically studied in completely homogeneous media with carefully selected solvents. Thus the acetalization reaction was run in water with six aldehydes [R₁CHO (R₁ = H, CH₃, C₂H₅, n-C₃H₇, i-C₃H₇, ClCH₂)], whereas the ketalization in dimethylslfoxide with 11 ketones [R₂CH₃CO (R₂ = CH₃, C₂H₅, n-C₃H₇, i-C₃H₇, n-C₄H₉, i-C₄H₉, tert-C₄H₉, C₆H₅CH₂, C₆H₅CH₂CH₂), cyclopentanone, and cyclohexanone]. The latter was difficult to proceed in aqueous media. Both reactions were reversible and bimolecular and, despite the use of different solvents, gave similar heats of reaction (7.5 kcal/mol) and activation energies (ca. 15 kcal/mol) except for the case of formaldehyde and chloroacetaldehyde; however the equilibrium constants at 25°C showed that the acetalization is thermodynamically much more favored than the ketalization (ca. 5000 vs. 0.01–0.9), probably because of steric hindrance of the ketone substrate. The rate constants of hydrolysis (reverse reactions) for the poly(vinyl acetal) and poly(vinyl ketal) followed the Hammett-Taft equation to give a single p* (=3.60) that is very close to that for the hydrolysis of diethyl acetal and ketal. From these and other data, it was concluded that the polymer hydrolysis, as well as PVA acetalization and ketalization, are all electrophilic reaction where the formation of hemiacetal or hemiketal is the rate-determining step. © 1996 John Wiley & Sons, Inc.     

Tin(IV) complexes of schiff bases derived from pentane-2,4-dione or 2-hydroxy-1-naphthaldehyde

The 1∶2 molar reactions of tin(IV) chloride with the Schiff bases, CH₃C(OH):CHC(CH₃):NR and 2 HOC₁₀H₆CH:NR′ (where R=C₂H₅,n-C₃H₇ orn-C₄H₉ and R′=C₆H₅, C₂H₅,n-C₄H₉ ort-C₄H₉) have resulted in the synthesis of SnCl₄·(SBH)₂ type derivatives (whereSBH represents the Schiff base molecule). These have been characterized by elemental analysis, conductivity measurements and IR spectral studies.     

Thermodynamic data for hydrogen bonding of thiols with Lewis bases in carbon tetrachloride. Weak association by the PMR method

Data for 30 hydrogen bonding pairs taken from the alkanethiols, i-C₃H₇SH, nC₃H₉SH and t-C₄H₉SH, and 16 bases have been obtained by a PMR method. Representative data for i-C₃H₇SH at 304 ± 2°K are (base, 10²K in M^?1, –ΔH° in kcal/mole): (CH₂)₄S, 3·1, 0·8; (CH₃)₂S, 3·0, 0·9; (CH₃)₂S₂, 3·7, 0·5; (CH₃)₂CO, 4·7, 0·9; CH₃COOC₂H₅, 5·7, 1·1; (CH₂)₄O, 6·1, 1·0; HCON(CH₃)₂, 12, 0·9; (CH₃ O)₂ SO, 12, 0·9; (C₂ H₅O)₃PO, 6·5, 1·0; CH₃ (CH₃ O)₂PO, 18, 1·0; ((CH₃)₂N)₂ CO, 5·9, 1·1; CH₃ CN, 13, 0·6. In essence, the problems and errors involved in obtaining equilibrium data for weak complexes stem from the limited concentration rangethat is accessible. This leads to large uncertainties in the quantities K, ΔH° and ΔS°. Structural effects on hydrogen bonding at the sulfur site, both as Lewis acid or base, are discussed. Two erroneous PMR methods in the literature used for assessing the strength of hydrogen bonds are pointed out.     

The effect of carboxylate anions on the formation of clathrate hydrates of tetrabutylammcnium carboxylates

The solid-liquid phase diagrams of binary mixtures of water with tetrabutylammonium carboxylate having an unsaturated alkyl group in the carboxylate anion ((n-C₄H₉)₄NOOCR; R=C₂H₃–C₉H₁₇) were examined in order to confirm the formation of clathrate-like hydrates. The results are summarized as follows: (1) the formation of a clathrate-like hydrate is newly confirmed for all the 13 carboxylates examined; (2) these hydrates are classified into three groups I, II, and III on the basis of the hydration numbers; (3) the group I hydrates, which are formed by the carboxylates with R=C₂ and R=C₃, have hydration numbers around 30 and are the most stable hydrates among those examined in this study; (4) the group II hydrates, with hydration numbers around 39, are formed by all the carboxylates with R=C₄ and C₅ including sorbate and are less stable than the group I hydrates; (5) the group III hydrates, with hydration numbers around 30 like the group I hydrates, are formed by carboxylates with long alkyl chains such as 2-octenoate and 2-decenoate and are generally unstable.     

Facile synthesis of new polyolefinic ruthenium(0) complexes from ruthenium(II) precursors

The new ruthenium(II) complex [(C₈H₁₀)RuCl₂]_n (1) (C₈H₁₀ = 1,3,5-cyclooctatriene; n ⩾ 2) has been obtained from the reaction of RuCl₃·xH₂O with 1,3,5,7-cyclooctatetraene in refluxing ethanol. Reduction of [(C₈H₁₀)RuCl₂]_n and [(C₇H₈)RuCl₂]₂ (2) (C₇H₈ = 1,3,5-cyclooctatriene) by Na/Hg amalgam in the presence of isoprene (C₅H₈) gives the novel ruthenium(O) complexes [(η⁶-C₈H₁₀)Ru(η⁴-C₅H₈)] (3) and [(η⁶-C₇H₈)Ru(η⁴-C₅H₈)] (4). [(η⁶-C₇H₈Ru(η⁴-C₅H₈)] reacts with CO and HBF₄ to give [(η⁶-C₇H₈)Ru(η³-C₅H₉)(CO)][BF₄] (C₅H₉ = trans-1,2-dimethylallyl (5a); 1,1-dimethylallyl (5b)).     

The Cubic Superstructure-I of Tetrabutylammonium Fluoride (C4H9)4NF·29.7H2O Clathrate Hydrate

The crystal structure of (C₄H₉)₄NF·29.7H₂O clathrate hydrate (ionic clathrate) determined by X-Ray analysis is reported. The structure is cubic, I $\overline 4 3dThe crystal structure of (C₄H₉)₄NF·29.7H₂O clathrate hydrate (ionic clathrate) determined by X-Ray analysis is reported. The structure is cubic, I , a = 24.375(3) ? (150 K). Its idealized water framework is analogous to that of cubic structure-I of gas hydrates but with eight-fold unit cell, that is a superstructure of cubic structure-I. This is the last structure found in the binary system (C₄H₉)₄NF–H₂O which was not characterized by X-ray analysis earlier. The structure features of the compound under investigation and others existing in H₂O–(C₄H₉)₄NF binary system are discussed.     

Quenching of *UF6 (A state) by alkanes

The removal of *UF₆ (A state) molecules by selected alkanes has been investigated at 25°C. The following rate constants (units of 10¹¹ l/mol·sec) were evaluated: iso-C₄F₁₀, 0.0432 ± 0.0115; n-C₄F₁₀, 0.0764 ± 0.020; C₂F₆, 0.0192 ± 0.0052; CH₄, 0.0612 ± 0.0061; C₂H₆, 3.78 ± 0.60; C₃H₈, 5.08 ± 0.60; n-C₄H₁₀, 5.05 ± 0.78; iso-C₄H₁₀, 4.17 ± 1.15; neo-C₅H₁₂, 6.59 ± 0.93; CF₃? CH₃, 0.0385 ± 0.0056; CF₂H? CF₂H, 0.0729 ± 0.0074; and CF₂H? CFH₂, 0.149 ± 0.015. The perfluoro-alkane quenching of *UF₆ proceeds via a physical mechanism. The other alkane quenching reactions are consistent with a chemical mechanism also contributing in varying degrees which may involve removal of two hydrogens from the alkane.     

Self-association of thiols. The baggy fit problem in weak complexes

The PMR technique has been used to obtain thermodynamic data for hydrogen bonding of alkanethiols (RSH) in 1:1 dimers in carbon tetrachloride. At ca. 303°K these are (R, 10⁴K(M^?1), ?ΔH°(kcal/mole), ?ΔS°(eu)): n-C₃H₇, 51 ± 5, 0.9 ± 0.15, 13 ± 1; i-C₃H₇, 50 ± 10, 0.8 ± 0.3, 13 ± 1; n-C₄H₉, 35 ± 2, 0.8 ± 0.15, 14 ± 1; t-C₄H₉, 14 ± 4, 1.1 ± 0.7, 16 ± 2; C₆H₁₁, 1.3 ± 2, 0.7 ± 0.3, 15 ± 1. Alkanethiol self-association is weak, and although an exact expression [Eqn. (5)] reproduces spectral data precisely, the fit is sufficiently ‘loose’ or ‘baggy’ so that values of K, ΔH° and ΔS° are uncertain. The methodology of the treatment of self-association data and their errors is examined and Deranleau's useful approach is extended. The impossibility of obtaining reliable data for very weak (< 10 %) or very strong (> 90 %) associations by techniques equivalent to ours is emphasized. The possibility of cyclic thiol dimers is discussed. It is suggested that the PMR method cannot give trustworthy self-association data for aryl or arylalkylthiols because of the relatively large anisotropy effects introduced into the dilution shift.     

Formation of (C x H2x+1)4NBr·nH2O (x = 1–3) hydrate

The phase diagram of the binary system tetramethylammonium bromide-water was studied by the differential thermal analysis. In the stable region two phases, ice and the salt itself, were detected, and in the metastable region, three tetramethylammonium bromide hydrates (bromide-water, 1 : 4, mp 68.8°C, 1 : 5, mp 36.0°C, 1 : 7.5, mp ?19.5°C) were found. Formation of (C _x H_2x+1)₄NBr·nH₂O (x = 1–3, n = 4, 5, 7.5) hydrates was revealed.     

Primary photochemical processes in the photolysis of alkyl nitrites at 366 NM and 23°c in the presence of 15NO

The alkyl nitrites, C₂H₅ONO, n-C₃H₇ONO, n-C₄H₉ONO, and i-C₄H₉ONO were photolyzed at 23°C in the presence of ¹⁵NO at 366-nm incident radiation. The quantum yields of the corresponding isotopically-enriched alkyl nitrites were measured by mass spectrometry. The results indicated that only part of the absorption leads to photodecomposition. The remainder forms an electronically excited state which isotopically exchanges with ¹⁵NO. The indicated reactions of the electronically excited state RONO*, are where k₃/k₂ = 0.50 ± 0.10, 0.62 ± 0.20, 0.42 ± 0.06, and 0.24 ± 0.03 torr, and that k_2a/k₂ = 1.0, 1.0, 0.64 ± 0.04, and 0.56 ± 0.03, respectively, for C₂H₅ONO, n-C₃H₇ONO, n-C₄H₉ONO, and i-C₄H₉ONO.     

Modification of PVC. XXVI. Syntheses and photocrosslinking of polysulfide pendant poly(vinyl chloride)

Poly(vinyl chloride) pendant with polysulfide (PS–PVC) having various degrees of substitution, various S substituents, and various numbers of atoms in the sulfur chain has been synthesized by the reaction of poly(vinyl chloride) with a thiol, sulfur, and triethylamine in dimethylformamide at 30°C for 0.4–5 hr. The photocrosslinking reaction has been investigated under ultraviolet irradiation at 250–450 mμ. The photocrosslinking reaction of PS–PVC is influenced by the degree of substitution, the nature of the S substituent, and the number of atoms in the sulfur chain. The degree of photocrosslinking r increased in the order, n-C₄H₉? < n-C₈H₁₇? < C₆H₅CH₂? < i-C₃H₇? < t-C₄H₉? . On the photocrosslinking of PS–PVC having two different S substituents, r increases in the similar order for aliphatic substituents and in the order NO₂C₆H₄? < ClC₆H₄? < C₆H₅CH₂? < CH₃C₆H₄? < t-C₄H₉C₆H₄? < C₆H₅? for the aromatic substituents. Further, r increases markedly with the increase of sulfur chain number for all PS–PVC. The chemical structure of the crosslinks and the crosslinking mechanism are discussed on the basis of the results.