Summary Sterculia foetida oil has been found to contain 71.8% of sterculic acid and minor proportions of oleic, linoleic, and saturated acids. The saturated component consists mostly of myristic and palmitic acids. The oil consists of traces of tristearin (0.8%) and a major quantity of tristerculin (31.4%) together with different amounts of the glycerides of the type GS2U, GSU2, and GU3 of other fatty acids.
The dielectric properties of three ethyl esters (of the c 1 6 , c 1 8 and Czz fatty acids) are reported. Like the methyl esters, these compounds possess at least two regions of dielectric absorption. In the lower frequency absorption the simple expression for the relaxation time in terms of the oscillation frequency of the molecule and an energy barrier requires modifications to fit the results. The magnitude of this absorption depends on the thermal history of the sample and the significance of this is discussed in relation to the types of imperfections which can occur in the crystal.Dielectric absorption in the microwave region has been studied in these ethyl esters, and also in four other esters and an n-primary bromide. In a series of esters the magnitude of this absorption decreases as the dipole moves in from one end of the molecule. Possible mechanisms for this absorption are discussed.
The changes in the infrared absorption spectra accompanying the chlorination of unmasticated deproteinized natural rubber dissolved in carbon tetrachloride, with phenyl iododichloride, are reported. The 6% chlorine content product shows, in general, decreased absorption in the 8–11 μ region. The spectrum of 6% chlorine content product is markedly different from that of fully chlorinated rubber. The 19% chlorine content product is intermediate to that of 6–51% and shows some of the characteristics of fully chlorinated rubber, while retaining part of the characteristic absorption of natural rubber. The spectrum of the fully chlorinated product is similar to that of hydrochlorinated rubber and chlorinated rubber obtained by the gaseous chlorine reaction.
The changes in the infra-red absorption spectra of rubber following cyclization are reported. The spectra of cyclized rubber prepared by the action of sulphuric acid on stabilized Hevea latex have shown that cyclization starts even at room temperature. The spectral changes were more pronounced when the reaction was carried out a t 80°C. From a comparison of the spectra of cyclized rubber with that of 1,Z-dimethyl-cyclohex-1-ene, it is inferred that cyclized rubber contain> substituted cyclohexene type rings. Absorption a t 13.17 p appeared to be characteristic of cyclized rubber.The changes in the infra-red absorption spectra of cyclized rubber, following additive chlorination are also discussed. Chlorinated cyclized rubber showed absorptions, characteristic of cyclized rubber and chlorinated rubber. ZUSAMMENFASSUNG:Die hderungen in der UR-Absorption von Kautschuk nach Cyklisierung werden beschrieben. Die Spektren von cyklisiertem Kautschuk, der bei Einwirkung von Schwefelsaure auf stabilisierten Hevea Milchsaft dargestellt wutde, zeigen, daB Cyklisierung aucli bei Zmmertemperatur stattfindet. Die Spektralanderungen werden noch deutlicher wenn die Reaktion bei 80" C durchgefiihrt wird. Ein Vergleich der Spektren von cyklisiertem Kautschuk und 1,2-Dimethyl-Cyclohexen-l deutet an, daB der cyklisierte Kautschuk substituierte Cyclohexen-Ring-Systeme enthalt. Eine Absorption hei 13,17 p war charakteristisch fur cyclisierten Kautschuk.Die hderungen in den UR-Absorption-Spektren von cyklisiertem Kautschuk nach Chloraddition werden ebenfalls diskutiert. Cyklisierter Kautschuk zeigt nach Chlorierung charakteristische Absorption von beiden, chloriertem und cyklisiertem Kautschuk.
In the infrared absorption spectra of solutions of natural rubber in carbon tetrachloride, two new absorptions are observed, one at 6.52 μ and another at 8.2 μ. These bands disappear when films from the solution are examined. Possible origins of these bands are discussed and it is suggested that the absorption at 6.52 μ may be due to a perturbed double bond in a loose complex formed between rubber and carbon tetrachloride. The infrared absorption spectrum of rubber aged in solution also shows these absorptions. However, in the film from aged rubber the 8.2 μ absorption is found to persist. Chemical evidence for the loss in unsaturation is advanced.
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