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Experimental Sectiontion). Each was purified by preparative gas chromatography. Physical constants and spectral data agreed with literature" values. The instrumentation and procedures of chemical ionization mass spectrometry have been described elsewhere. la Methylthiomethyl acetate and methylthiomethyl propionate were prepared by allowing dimethyl sulfoxide to react with acetic anhydride and propionic anhydride, respectively (Pummerer reac-(15) C. Abstract:Rates are reported for some or all of the positions of naphthalene, biphenylene, benzo[b]biphenylene, phenanthrene, chrysene, pyrene, fluoranthene, triphenylene, and perylene for protodetritiation in 96.9 % trifluoroacetic acid-3.1 % perchloric acid at 25" and in 98 % trifluoroacetic acid-2 % carbon tetrachloride at 70'.The results are compared with related results from Eaborn's research group and the two solvent systems are interrelated. The result is an extensive set of quantitative relative reactivities for aromatic substitution on polycyclic aromatic hydrocarbons suitable for testing various molecular orbital methods.romatic substitution reactions and their orientation A for specific positions in aromatic hydrocarbons have long been useful for testing theories of organic chemistry such as resonance theory and molecular orbital methods. Electrophilic hydrogen isotope exchange is an especially simple and convenient type of aromatic substitution and in the form of protodedeuteration or protodetritiation is particularly important because quantitative reactivities can thus be obtained for positions too unreactive for measurement by direct substitution. Such protodetritiations were pioneered by Eaborn's research group, first in mixtures of trifluoroacetic acid with strong mineral acid such as perchloric acid at room temperature4 and subsequently in trifluoroacetic acid alone at 7 O O . j Because of our own interest in applying molecular orbital methods to quantitative reactivities in aromatic substitution, we have applied Eaborn's approach to additional polycyclic aromatic hydrocarbons, first in a mixture of 96.9 trifluoroacetic acid-3.1 % perchloric acid at 25" (I) and subsequently in trifluoroacetic acid at 70" (11). In this paper we summarize the results we have obtained for both solvent systems. These results taken together with the data of Eaborn allow a quantitative correlation of the two solvent systems and provide reactivity data for many individual positions of a wide variety of polycyclic aromatic hydrocarbons.The tritiated hydrocarbons were generally prepared by treatment of the known bromo derivatives with butyllithium followed by quenching of the aryllithium with tritiated water. Most of the kinetic runs were

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The kinetics of high‐intensity electron beam‐induced polymerization of di(2′‐methacryloxyethyl)‐4‐m‐phenylenediurethane during the network formation has been studied up to complete gelation and up to 56% conversion of unsaturation. From experimentally determined gel fractions, rate of disappearance of unsaturation, kinetic chain length, and intensity dependence, it is proposed that the polymerization takes place in a swollen network where the growing chains undergo unimolecular termination, and where gel‐gel reaction is prohibited. The rate expression derived is: In [α(1 − g)0.545] = In α0 − 2.51 kikpt/kt where α is the total unsaturation and g is the gel fraction. The value of kp/kt is found to be 2.1 and that of GR, the free radical yield per 100 eV absorbed, to be 16; these high values are ascribed to the high viscosity of the polymerizing system.