T h e heats of combustion, melting points, heats of fusion, boiling points, refractive indices and in four cases the densities have been determined on selected samples of the cyclanes with 4 to 9 C-atoms; some hitherto unknown transition points were discovered and the heats of transition measured. T h e heats of vaporisation a t 25" are estimated. Results of the measurements are discussed.a. Calibrafion of fhe fhermocouple. T h e measuring thermocouple of the micro-calorimeter 1 ) was calibrated in order to determine the absolute values of melting and transition points. This was done with the aid of some substances, the melting and transition points of which were accurately known from the literature:Melting and transition phenomena 2). Na,SO, . 10 H,O, transition point + 32.38 t-0.01' C 3 ) 4 ) Cyclohexane, 1.-87.08 k 0.05 5 ) ' 3)Toluene melting., -94.99 i-0.02
)Cyclopentane, lower trans.,, -150.77 i-0.05Na,SO, . 10 H,O Schuchardt "pro Analyse mit Garantieschein" was crystallised four times from water: cyclohexane and cyclopentane were selected samples of this investigation. The toluene sample was purified by Mulder l o ) , its AT amounting to 0.02" c.
The series of the normal saturated fatty acids and their methyl esters with 5 to 20 carbon chain atoms was synthesized and careful purified, mainly by fractional distillation of the methyl esters in columns with up to 58 theoretical plates.
The purity was checked with the aid of melting curves determined in a microcalorimeter and proved to be 96.6% or better.
Refractive indices were determined and can be represented by
with an accuracy of 5 units in the fifth decimal place (c = number of carbon chain atoms).
Densities, accurate to 1 unit in the fourth decimal place, can be represented by
Boiling points can be given by
b.pt. 20 mm
for the methyl esters (c> 5), accurate to 0.1 °.
From our data, combined with literature values, the molecular refractivity of the CH2 group in an aliphatic chain calculated according to Lorentz‐Lorenz. was determined at 4.64 at room temperature.
In addition, melting and transition points, and heats of fusion and transition were determined.
Im Laufe der letzten Jahre ist besonders von drei Seiten Tatsachenmaterial zusammengebracht worden zugunsten der Sachse-Mohrschen Theorie') des nicht-flachen Baus der Cycloparaffine mit mehr als funf Kohlenstoffatomen und ihrer Derivate. Wir mochten diese drei Gruppen von Untersuchungen hier kurz erwahnen, um zu zeigen, da13 unsere Kenntnisse auf diesem Gebiete noch immcr ziemlich gering, recht cinseitig und fragmentarisch sind und -entgegen der oft geaul3erten Meinung -ein exakter Beweis fiir die Richtigkeit dieser Theorie noch immer nicht gebracht worden ist.A. Boeseken und Mitarbeiter. Das abweichende Verhalten von Cyclohexan-cis-l,2-diol in Vergleich mit Cyclopentan-cis-l,2-diol gegenuber Borsaurelosung fuhrte B o es e ke n und v a n Giffen2), offenbar ohne da13 sie von den Arbeiten von Sachse und von Mohr Kenntnis hatten, zur Annahme einer gewissen ,,Souplesse" im Cyclohexanring. Etwas spater fand D erx3), da13 Cycloheptan-cis-l,2-diol sich sowohl gegenuber 'Borsaurelosung als gegenuber Aceton in unerwarteter
In order to be able to study the injluence of the position of substituents in the aromatic nuclei of compounds of the tetraphenylethane type on the possibility of dissociation, several of these substances were synthesized.It was found that the presence of four ortho-methyl groups per diphenylmethyl in this series is an essential condition for the occurrence of dissociation upon heating in solvents like benzene, toluene, and naphthalene.Preliminary investigations of the diphenylmethyl radicals showed 2 ) that a classification into three groups is possible: Group I. Radicals in which the aromatic nuclei have no substituents in the ortho positions. These radicals, in solution and in an atmosphere OE an inactive gas, form a dimeric compound, a tetraphenylethane. This ethane does not again dissociate upon heating in a solvent like benzene, xylene or naphthalene, which is ascertained from the fact that the solution remains colourless upon heating, and from the inactivity with respect to oxygen. Radicals in which both the hydrogen atoms in the ortho positions of the aromatic nuclei are substituted give colourless ethanes which are reversibly dissociable upon heating.Radicals in which the hydrogen atoms in the ortho and in one or both para positiom of the aromatic nuclei are substituted.In the case of these radicals a colourless dimeric compound can sometimes be isolated, in other cases a disproportionality reduces the yield of ethane to give a methane and products poorer in hydrogen. I) Seventh communication: W. T h. N a u t a and D. M u I d e r, Rec. trav. chirn.
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