Eine semiempirische Gleichung zur Beschreibung des Lösungsmitteleinflusses auf Statik und Kinetik chemischer Reaktionen. Teil I

A model has been developed for calculating the enthalpy, entropy and free energy change associated with the creation of cavities in a liquid the size of which corresponds to the volume occupied by a solvent molecule. The molar enthalpy change H _cav equals the molar enthalpy of vaporization of the liquid, the free energy change G _cav is given by G _cav=–RT ln (V _m ·p _eq /RT) (V _m =molar volume,p _eq =equilibrium vapor pressure) and is related to the standard free energy of vaporization. This relationship provides an estimate of the free energy of cavity formation required to accomodate a substrate in the liquid. It has been shown, that the free energy of solvation of a substrate can be dissected into different contributions accounting for (1) the concentration dependence of partial molar free energy quantities, (2) the formation of holes in the solvent, (3) the existence of specific, short range solute-solvent interactions and (4) the dielectric polarization of the medium. Application of this concept leads to an equation of the general form G ^S –G ^R =a(DN ^S –DN ^R )+b(AN ^S –AN ^R )+c(G _vp ^oS –G _vp ^oR ), where G represents the free energy of reaction or activation,DN the donor number,AN the acceptor number and G _vp ^o the standard free energy of vaporization of a solventS and a reference solventR, resp.

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Donor—acceptor interactions of substituted benzenes with molecular chlorine and carbon disulfide

CNDO molecular orbital calculations have been performed to analyze donor—acceptor interactions between molecular chlorine and benzene, toluene, mesitylene and hexamethylbenzene and the, as yet, unreported chlorine—hexafluorobenzene and carbon disulfide—benzene pairs. The stabilization energy and the dipole moment and its derivative (?p/?R_CICI) calculated for the benzene—chlorine complex are in good agreement with the estimated experimental values. The trends in the experimental stabilization energies and the Cl-Cl vibrational frequencies with increasing methyl substitution appear to be well reproduced by the calculations. The charge transferred from the benzene donor is polarized toward the outer chlorine atom or sulfur atom. For hexafluorobenzene-chlorine the direction of electronic charge polarization is reversed from that of the benzene and methylbenzene complexes. The calculated results are discussed within the framework of Muliiken's simplified resonance theory for complexes.     

Untersuchung der Temperaturabhängigkeit derg ik -Tensoren von Polyäthyleneinkristallen

Zusammenfassung Es wurden die Kristallitgröße und die Änderungen der parakristallinen Gitterstörungen aus den Linienbreiten des Röntgenweitwinkeldiagramms von lösungskristallisiertem linearem Polyäthylen bei den Temperaturen 15°K, 73°K, 173°K und Zimmertemperatur bestimmt. Es wurde eine Zunahme der Gitterstörungen mit fallender Temperatur gefunden.

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Summary The crystallite size and the paracrystalline distortions in polyethylene single crystals were evaluated by the measurement of the linewidth in the X-ray wide angle diagram at four different temperatures (15°K, 73°K, 173°K and 297°K). An increase of the lattice distortions with decreasing temperature was found.

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Vorgetragen auf der Arbeitssitzung des Fachausschusses Physik der Hochpolymeren in der Frühjahrstagung 1970 des Regionalverbandes Hessen-Mittelrhein-Saar der Deutschen Physikalischen Gesellschaft in Darmstadt, 10.–13. März 1970.     

Die Schmelzdiagramme der Systeme CsN3/Zn(N3)2 und KN3/Zn(N3)2

The phase diagrams of the systems CsN₃/Zn(N₃)₂ and KN₃/Zn(N₃)₂ have been obtained employing the microscopic technique ofL. Kofler andA. Kofler. Within the system CsN₃/Zn(N₃)₂ three eutectics at 148°C, 142°C, and 210°C were found. Besides Cs₂Zn(N₃)₄, melting incongruently in the interval 153°C to 170°C, there exist two further compounds of the most probable composition Cs₃Zn₂(N₃)₇ and CsZn₂(N₃)₅, melting congruently at 170°C and 210°C, resp. In the system KN₃/Zn(N₃)₂ there exist two eutectics at 203°C and 172°C and two compounds, one of them, i.e. K₂Zn(N₃)₄, melting congruently at 206°C, the other one, with composition KZn₃(N₃)₇ or KZn₄(N₃)₉, melting incongruently at 210°C.

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Herrn Professor Dr.Heribert Grubitsch zum 70. Geburtstag gewidmet.     

Über einige Eigenschaften von Zinkphosphiten mit Berücksichtigung ihrer Wasserstoffbrückenbindung

Zinc phosphites ZnPHO₃·2.5 H₂O, Zn₂H₂P₃H₃O₉·H₂O, Zn₃H₄P₅H₅O₁₅·1.5 H₂O, ZnH₂H₂P₂H₂O₆ have been studied at higher temperatures and by X-rays and molecular spectroscopy. Hydrates ZnPHO₃·2.5 H₂O and Zn₂H₂P₃H₃O₉·H₂O, when heated, yield an anhydrous salt. Thermal decomposition of dihydrogen triorthophosphite and tetrahydrogen pentaorthophosphite leads, before oxidation of the anion, to a mixture of zinc phosphite ZnPHO₃ and dihydrogen diorthophosphite ZnH₂P₂H₂O₆ and then after loss of water of constitution dihydrogen diorthophosphite converts to zinc diphosphite ZnP₂H₂O₅. The results of the thermal decomposition study were confirmed by X-ray investigation. Anhydrous zinc dihydrogen triorthophosphite Zn₂H₂P₃H₃O₉ and zinc diphosphite ZnP₂H₂O₅ were hitherto unknown. Infrared spectra confirmed the existence of hydrogen bonding in all the phosphites studied and in the case of zinc phosphite ZnPHO₃·2.5 H₂O exhibited a symmetry decrease of the anion PHO₃ ^2– from the point group C_3v to C_s. In the crystal lattice of ZnPHO₃·2.5 H₂O hydrogen bonding by water molecules participates, with polyorthophosphites hydrogen bonding shares in the production of anions and in the case of their hydrates there is in addition hydrogen bonding by water molecules.

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Hydroxybromierung und Methoxybromierung von (Z)-Cycloocten

In addition totrans-2-bromocyclooctanol andtrans-1,2-dibromocyclooctane,cis-4-bromocyclooctanol,cis-1,4-dibromocyclooctane,trans-1,4-dibromocyclooctane, and (Z)-5-bromocyclooctene are obtained, when (Z)-cyclooctene is treated with N-bromosuccinimide in the presence of water. Similarly the methoxybromination of (Z)-cyclooctene gives transanular products.     

Interaction of dextran sulfates with positively and negatively charged silver bromide hydrosols

Summary The effects of dextran sulfates of different molecular weights and charge densities on the stability of positively and negatively charged silver bromide solsin statu nascendi have been studied by means of light scattering.The plots of scattering intensities of a positively charged sol against the concentration of the added dextran sulfates show one pronounced maximum, the position which is independent on the molecular weight of the polyelectrolyte used. The maximum shifts to lower polyion concentrations with dilution of the sol.The effect of polyanions on the stability of silver bromide sols of the same sign of charge were investigated as a function of molecular weight of the polymers, the sol concentration, the charge and the concentration of counterions, and the addition of methanol. Destabilization only occurred if sufficient amount of indifferent electrolyte was present in the system. However, the concentration of counterions necessary to produce a flocculation maximum was lower in the presence of the polyelectrolytes than in their absence. The results obtained were compared with the data on sols containing nonionic dextrans reported earlier.

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Zusammenfassung Der Einfluß der Dextransulfate von verschiedenen Molekulargewichten und Ladungsdichten auf die Stabilität der positiv und negativ geladenen Silberbromid-Solein statu nascendi wurden durch Lichtstreuung untersucht. Wenn die Intensitäten der Lichtstreuung eines positiv geladenen Silberbromid-Sols gegen die Konzentration der zugesetzten DextranSulfate aufgetragen werden, tritt ein ausgeprägtes Maximum auf, dessen Lage von dem Molekulargewicht des angewandten Polyelektrolyten unabhängig ist. Bei Verdünnung des Sols wird das Maximum zur niedrigeren Konzentration des Polyanions verschoben.Der Einfluß der Polyanionen auf die Stabilität der Silberbromid-Sole mit gleichem Ladungsvorzeichen wurde in Abhängigkeit von dem Molekulargewicht des zugesetzten Dextransulfats, der Solkonzentration, der Ladung und Konzentration der Gegenionen und dem Zusatz von Methylalkohol untersucht. Destabilisierung wird nur in Anwesenheit einer genügenden Menge von Neutralelektrolyten in den untersuchten Systemen beobachtet. Die Konzentration der Gegenionen, die ein Flockungsmaximum verursachen, ist immer niedriger als die kritische Koagulationsmenge derselben Ionen für das gleiche Sol in Abwesenheit von Makroionen. Die Resultate wurden mit den Wechselwirkungen der Silberbromid-Sole mit nichtionogenen Dextranen verglichen, und der Mechanismus der Flockung durch Polyelektrolyte wurde diskutiert.

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5 figures and 1 table

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Supported by the NSF Grant GP 42331 X.

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A part of the Ph.D. Thesis by David Lindsay.     

Reactions of tetrahydro-as-triazine-3(2H)-thiories with α, β-difunctional compounds

The results of allowing tetrahydro-as-triazine-3(2H)-thiones to react with various α,β-diiunctional compounds, such as, α-bromoethyl p-toluenesulfonate, chloroacetaldehyde, α-bromophenylacet-uldehyde, phenaeyl bromide, chloroacetonitrile, α-bromophenylaeelonitrile, and α-cyanobenzyl p-toluenesulfonate are discussed. These condensations give either a 5H-thiazolo[3,2-b]-as-triazine or a 2H-thiazolo[2,3-c]-as-triazine.     

A 13C- and 195Pt-NMR. Study of the Complexes trans-PtCl2 (amine) (CH2CH2)

¹³C- and ¹⁹⁵Pt-NMR. spectra for the complexes trans-PtCl₂(amine)(CH₂?CH₂) have been measured. For amine = (S)-N-methyl-α-methylbenzylamine the two diastereomers present may be distinguished from the values ³J(Pt,C). The ¹⁹⁵Pt-chemical shift is shown to be sensitive to subtle differences stemming from intramolecular non-bonded interactions.     

Mechanism of the oxidation of cycloheptanone by chloramine-T

The oxidation kinetics of cycloheptanone by chloramine-T in alkaline media has been investigated. A mechanism involving the formation of an intermediate by the interaction between the enolic anion of cycloheptanone and chloramine-T in a slow step followed by its interaction with another molecule of chloramine-T in a fast step leading to products has been proposed. The scheme satisfactorily accords with the observed stoichiometry, negligible influence of ionic strength and a positive dielectric effect. Various rate parameters have been computed and 1.2-cycloheptanedione identified as the end product.With 2 Figures