Double bonds unsaturation assessment

Studies of the reaction of ozone with simplified lipid systems have shown that malonaldehyde can be produced by direct ozonolysis. The use of malonaldehyde assay as an index of lipid peroxidation is therefore invalid in ozone studies. Liposomes formed from egg lecithin and prepared in aqueous media were quite resistant to ozone, but the contribution of polyconcentric spheres to this resistance has not been fully assessed. However, the bilayer configuration, with the susceptible unsaturated fatty acids shielded from ozone by the hydrophilic areas of the molecule, may be resistant. In hexane, where the fatty acid moieties are exposed, ozone reacts stoichiometrically with the double bonds. The experiments with aqueous suspensions of phosphatidylcholine gave no evidence of the formation of lipid peroxides,nor did experiments with films of fatty acids exposed to ozone. ... 

In summary, infrared and Raman stretching frequencies of the C=C double bond are affected by in-plane as well as out-of-plane distortions. For an assessment of how the different distortions affect the stretching frequency of the C=C double bond, the coupling of vibrations cannot be ignored. The general importance of force constants determined experimentally from stretching frequencies or obtained from ab initio calculations for force field calculations of undistorted and distorted saturated and unsaturated carbon compounds can only be mentioned here (9,11). 

Toxicity studies of retinoids have involved assessment of teratogenic potential [104,105] and overall toxic effects [63,64] in adult animals upon treatment with retinoids. In general, it appears that the structural features necessary for teratogenic potency overlap with those features required for anti-cancer activity [105]. These requirements may be summarized as follows (1) An acidic polar terminus is necessary. (2) Conjugation in the three double bonds nearest to the polar terminus must be maintained. Unsaturation of the 7,8 double bond is not indispensable. (3) Substitution of non-polar groups in the terminal ring is required. 

In this case we have, unlike PBT and more like PET, the requirement for abstraction of a hydrogen from an unsaturated carbon during chain scission via the proposed 6-mem bered cyclic intermediate. It is difficult to be certain whether this product will form. The potential for resonance stabilisation of the intermediate is difficult to assess the allyl radical and allyl ions show some resonance characteristics, but it is also known that in the final compound the two double bonds are orthogonal, i.e., there is no interaction between them. Allene is extremely volatile (bp = -34 °C), but it is also quite reactive with water and oxygen and can, under certain circumstances, form a resonance structure with methyl acetylene ... 

Thiocyanogen value Vsl- a-no-jon val-(i)yii. Measure of the number of single double bonds in a substance, for example, an oil. Whereas thiocyanogen is selective in its action, adding on to isolated double bonds only, iodine is not selective and thus a combination of both thiocyanogen and iodine values provides a means of assessing quantitatively the different types of unsaturated components in a material. 

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