The Vinyl System

In this chapter, thermodynamic data of a series of unsaturated hydroperoxides and methylhydroperoxide are calculated for the first time. Vinyl, allyl, and ethynyl are here considered. 

We first justify the use of the density functional calculation method (B3LYP/6-3JlG(d,p) coupled with isodesmic reactions through a number of comparisons with higher level calculations and recent experimental data. 

Enthalpies of formation, entropies, and heat capacities are then calculated for these hydro-and methyl-peroxides as well as for the corresponding peroxy radicals. These calculations require computation of a number of unsaturated ethers and alcohols enthalpies, because these values are needed as reference species. 

Finally the calculated hydroperoxide enthalpies are utilized to determine internal rotations and bond energies such as R—OOH, RO—OH, ROO—H. these are compared with the corresponding methylperoxides, R OOCH3, RO—OCH3, ROO—CH3. 

There is a substantial number of computational chemistry or evaluation studies on peroxy and hydroperoxy alkyl radicals [2, 8, 9, 85, 10]. Bozzelli and co-workers [86, 87, 88, 89] have 

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This is in agreement with the results of Bennett and Zedler (12) they have pointed out that conventional urethane, vinyl and epoxy systems show widely divergent release rates. Whereas the vinyl system lost TBTO at a rate of 1-2 yg/cm2/day and polyurethane at 25 yg/cm2/day, the epoxy system virtually lost no tin. 

PE, RIE and IM resistances for an extensive list of commercial photoresists are included as well for comparison with the vinyl systems and amongst themselves. Although the exact com-osition of these systems is not public information, the generic type of base resin or polymer binder is generally known. In addition, the photoactive components are all known to be aromatic azides or azo-compounds. 

The smaller stabilizations of the vinyl cations 19-21 compared to the alkyl cations in Table 2 is attributed to the a-aryl or alkyl substituents having a greater stabilizing effect on the vinylic systems. 

The similarity between the two reaction categories is shown by the work of Beltrame et al. (1967b) on the reaction of 1,1 -bis(p-nitrophenyl)-2-haloethylenes with ethoxide ion. The vinylic system is a vinylog of the nitrohalobenzenes which are usually studied in SNAr reactions. The activation parameters and the effect of substituents in the two systems were found to be comparable. 

The molecular structures of three >/3-pentadienyl complexes having W, S, and U configurations, respectively, are shown in Fig. 5. Apart from showing the short uncoordinated C=C bond of the vinyl system a common feature is the unsymmetrical bonding of the fj3-allyl group with the longest M—C bond to the atom which bears the vinyl substituent (149). 

There are three sets in the vinyl system, AMX, each set consisting of one proton. 

Biocides. The attack of fungi on the several components of a vinyl formulation may manifest itself as an unsightly growth looking much like dirt or may result in the formation of discolored areas (yellow, pink, blue, clear) on the finished goods. Outdoor exposure, indoor exposure in humid atmosphere, soil burial or contact, and electrical insulation compounds are typical areas where biocide addition is indicated. Since most commercial biocides are heavy metal derivatives, care must be taken to assess their effect on heat and light stability and compatibility with the vinyl system in which they are used. 

As a general rule, the effect on rate due to fi substitution with alkyl or aryl groups in the vinyl system is very small even when the presence of a bulky a-group would lead to an expected rate increase due to steric relief upon ionization. This effect is likely to be counterbalanced by... 

Oxygen, nitrogen and carbon atoms can equally well participate in the vinyl system. Table 2 provides a survey of some synthetically useful rearrangements of this type. In all cases the formation of the alkene is regioselective and in most cases it is stereospecific as well, according to the principles outlined above. The distinction between boat and chair transition states depends on the precise conformation of the reacting system, and this factor can be somewhat manipulated experimentally. 

Conventional Photoresists. PE rate ratio values for several positive photoresists are also included in this study (see Table II), because several of these novolac resin containing formulations also function as positive e-beam and x-ray resists. Generally speaking, these formulations are more dry-process compatible than most of the vinyl systems (see also ref.2). This is due primarily to the aromatic nature of the novolak resins in the photoresists. Thus, the photoresist PE rate ratio data is close in value to those of the aromatic vinyl and negative behaving polymers. 

The spectrum of the vinylic system of styrene consists of three sets—each a doublet of doublets representing a single proton. The X proton (56.80) is coupled trans across the double bond to the M proton (/XM = 18 Hz) and cis across the double bond to the A proton (Jxa = 11 Hz). The M proton (8 5.82) is coupled trans across the double bond to the X proton (/MX = 18 Hz)... 

At 60 MHz, the spectrum of the vinylic system of styrene becomes a borderline ABX system, but with some imagination the structure can be resolved by recognizing that the ABX spectrum can be regarded as though it were a first-order AMX spectrum—which it is at 300 MHz. Again, it must be emphasized that the order of a spectrum depends partly on the sophistication of available instrumentation. At the extreme, an ABC spectrum—a very low Ai> J ratio for all of the sets— may not be resolvable with available instrumentation. 

Chapter 6 presents estimations of thermochemical properties of intermediates, transition states and products important to destruction of the aromatic ring in the phenyl radical + O2 reaction system. We have employed both DFT and high-level ab initio methods to analyze the substituent effects on a number of chemical reactions and processes involving alkyl and peroxyl radicals. Partially based on the results obtained in the vinyl system, high-pressure-limit kinetic parameters are obtained using canonical Transition State Theory. An elementary reaction mechanism is constructed to model experimental data obtained in a combustor at 1 atm, and in high-pressure turbine systems (5-20 atm), as well as in supercritical water [31]. 

The C=C—OOH bond strength increases even further above that of the vinyl systems to ca. 100 kcal mol This corresponds with the increase in the C=COO— H bond compared to vinyl and alkyl systems. We observe a difference of 7 kcal mol with an additional carbon on the non hydroperoxide sp carbon. The R—OOH bond energy increases from 94 C=C—OOH) to 101.58 (CC=C—OOH) kcal mol. ... 

We show that the vinyl system is a good model for the phenyl system which it itself used as model for the dibenzofuranyl system. The high-level calculations on the smaller vinyl system can be used to calibrate ab initio and Density Functional Theory calculations on the phenyl and the dibenzofuranyl system. 

The investigation of the vinyl system consisted in the calculation of thermochemical properties of a series of peroxides and peroxy species using DFT combined with isodesmic reactions. We showed that the vinyl radical for which high-level calculations can be performed is a good model for the phenyl. The accuracy of the DFT method, which is the primary method for this work, was checked through a number of comparisons with high-level calculations. At this point, it is worthwhile mentioning the importance of the vinyl + O2 reaction system ... 

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