The Acidic Constituents ok Dkukas 447 diffusion of which is slow compared with the rate of polymer chain growth.4. Employing a model based on this concept, it is calculated that gelation can only occur after these swollen molecules have filled 13-23% of the reaction mixture. Experimental results indicate 25-46% in fair agreement with calculation.

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The unimolecular reactions that give rise to mass spectra are controlled by spatial relationships and energy considerations. Inmolecules that contain a heteroatom, eliminationreactions, involving bond-making as well as breaking, are often prominent, e.g. loss of water from alcohols. The ease of such reactions depends on spatial relationships in the molecule, and the resultant ion intensities in the spectra of geometric isomers can consequently be correlated with differences in geometry and hence furnish a basis for assigning structures. Processes that do not involve bond-making do not have such rigorous geometric requirements, but depend rather on attainment of a transition state defined in terms of a minimum energy content. Common product ions from stereoisomeric hydrocarbons seem often to arise via a common transition state. When this condition holds, the difference between the enthalpies of the isomers is reflected in the relative appearance potentials and-though the cause-and-effect relationship here is less direct and more readily obscured by other factors-relative intensities of the common product derived from the isomers. In both classes of processes, the spectra of stereoisomers can be simplified and made more distinctive by lowering source temperature and ionizing voltage.