Di-tert-butyl peroxide initiators

Two types of addition to pyrimidine bases appear to exist. The first, the formation of pyrimidine photohydrates, has been the subject of a detailed review.251 Results suggest that two reactive species may be involved in the photohydration of 1,3-dimethyluracil.252 A recent example of this type of addition is to be found in 6-azacytosine (308) which forms a photohydration product (309) analogous to that found in cytosine.253 The second type of addition proceeds via radical intermediates and is illustrated by the addition of propan-2-ol to the trimethylcytosine 310 to give the alcohol 311 and the dihydro derivative 312.254 The same adduct is formed by a di-tert-butyl peroxide-initiated free radical reaction. Numerous other photoreactions involving the formation by hydrogen abstraction of hydroxyalkyl radicals and their subsequent addition to heterocycles have been reported. Systems studied include 3-aminopyrido[4,3-c]us-triazine,255 02,2 -anhydrouri-dine,256 and sym-triazolo[4,3-fe]pyridazine.257 The photoaddition of alcohols to purines is also a well-documented transformation. The stereospecific addition of methanol to the purine 313, for example, is an important step in the synthesis of coformycin.258 These reactions are frequently more... 

A special reaction is the oxidation of l,2-di(carbazol-9-yl)ethane with air at 188°C in the presence of di-terr-butyl peroxide forming l,2-di(carbazol-9-yl)ethene. The same material was obtained from di-tert-butyl peroxide initiated decarbonylation of carbazol-9-ylethanal in the absence of air with air present, 9-methylcarbazole, dicarbazol-9-ylmethane, and polymer resulted." ... 

Independent Variables. Simultaneous synthesis of two polymer networks is a complex process. Many independent variables are available for study and not all could be explored in a limited investigation. The emphasis in the present study centers on those variables whose predominant effect is to influence the relative rates or gelation times of the reactions. Three independent variables were selected (a) the concentration of di-tert-butyl peroxide initiator was changed to vary the rate of polymerization of n-butyl acrylate (b) the epoxy mix was allowed to prereact for different lengths of time before the acrylate mix was added, and (c) the amount of DEGDM added to the acrylate mix was varied to control the gel time of the acrylate without significantly affecting its rate of polymerization. 

For pure di-tert-butyl peroxide, initially y o = 1-0 tid therefore Pa- Stoichiometry gives 5=1+2 1=2. 

Preparation of Poly(vinyl ethyl ether) Using Di-tert-butyl Peroxide Initiator. . 247... 

High molecular weight polymers are produced by an adiabatic bulk polymerisation process ° using di-tert-butyl peroxide (0.02%) and 2,2 -azo-bisdi-isobutyronitrile (0.01%) as initiators and pressurised with N2. Heating to 80-90°C causes an onset of polymerisation and a rapid increase in temperature. After the maximum temperature has been reached the mass is allowed to cool under pressure. A typical current commercial material (Luvican M.170) has a A -value of about 70 (as assessed in a 1% tetrahydrofuran solution). 

The reaction of benzyl radicals wdth several heterocyclic compounds W as more extensively studied by Waters and Watson, " - who generated benzyl radicals by decomposing di-tert-butyl peroxide in boiling toluene. The products of the reaction with acridine, 5-phenyl-acridine, 1 2- and 3 4-benzacridine, and phenazine were studied. Acridine gives a mixture of 9-benzylacridine (17%) (28) and 5,10-dibenzylacridan (18%) (29) but ho biacridan, w hereas anthracene gives a mixture of 9,10-dibenzyl-9,10-dihydroanthracene and 9,9 -dibenzyl-9,9, 10,10 -tetrahydrobianthryl. This indicates that initial addition must occur at the meso-carbon and not at the nitrogen atom. (Similar conclusions were reached on the basis of methylations discussed in Section III,C.) That this is the position of attack is further supported by the fact that the reaction of benzyl radicals with 5-... 

Biesenberger, J. A. et al., Polym. Eng. Sci., 1976, 16, 101-116 The parameters were determined in a batch reactor for thermal runaway polymerisation of styrene, initiated by azoisibutyronitrile, dibenzoyl peroxide or di-tert-butyl peroxide. 

Homolytic cleavage of most a bonds may be achieved if the compound is subjected to a sufficiently high temperature, typically about 200 °C. However, some weak bonds will undergo homolysis at temperatures little above room temperature. Bonds of peroxy and azo compounds fall in this category, and such compounds may be used to initiate a radical process. Di-tert-butyl peroxide, dibenzoyl peroxide... 

In general, there are two distinctively different classes of polymerization (a) addition or chain growth polymerization and (b) condensation or step growth polymerization. In the former, the polymers are synthesized by the addition of one unsaturated unit to another, resulting in the loss of multiple bonds. Some examples of addition polymers are (a) poly(ethylene), (b) poly(vinyl chloride), (c) poly(methyl methacrylate), and (d) poly(butadiene). The polymerization is initiated by a free radical, which is generated from one of several easily decomposed compounds. Examples of free radical initiators include (a) benzoyl peroxide, (b) di-tert-butyl peroxide, and (c) azobiisobutyronitrile. 

Reported are extremely violent to expl reactions when vinyl cyanide is in contact with acids, bases, bromine, polymerization initiators (such as azoisobutyronitrile, dibenzoyl peroxide or di-tert-butyl peroxide),... 

The first free radical initiated copolymerization was described by Brubakerl) in a patent. A variety of peroxides and hydroperoxides, as well as, 02, were used as initiators. Olefins that were copolymerized with CO included ethylene, propylene, butadiene, CH2=CHX (X—Cl, OAc, CN) and tetrafluoroethylene. A similar procedure was also used to form terpolymers which incorporated CO, C2H4 and a second olefin such as propylene, isobutylene, butadiene, vinyl acetate, tetrafluoroethylene and diethyl maleate. In a subsequent paper, Brubaker 2), Coffman and Hoehn described in detail their procedure for the free radical initiated copolymerization of CO and C2H4. Di(tert-butyl)peroxide was the typical initiator. Combined gas pressures of up to 103 MPa (= 15,000 psi) and reaction temperatures of 120—165 °C were employed. Copolymers of molecular weight up to 8000 were obtained. The percentage of CO present in the C2H4—CO copolymer was dependent on several factors which included reaction temperature, pressure and composition of reaction mixture. Close to 50 mol % incorporation of CO in the copolymer may be achieved by using a monomer mixture that is >70 mol% CO. Other related procedures for the free radical... 

Initiators. Free radical polymerization initiated by azoisobutyronitrile, benzoyl peroxide, or di-tert-butyl peroxide may be explosive.4... 

Li and coworkers published addition reactions of ethers, sulfides, or tertiary amines 40 to p-dicarbonyl compounds 39 (Fig. 8) [96]. Fe2(CO)9 proved to be the catalyst of choice and di-tert-butyl peroxide the optimal oxidant. a-Functionalized p-dicarbonyl compounds 41 were isolated in 52-98% yield. Although the details of the catalytic cycle remain unclear, it seems to be likely that the peroxide is reductively cleaved by the Fe(0) catalyst leading to an Fe(I) complex and a ferf-butoxyl radical, which abstracts the a-hydrogen atom of 40. Addition of the resulting radical to the free enol form of 39 or the corresponding iron enolate of 39 may subsequently occur. It remains unclear, however, whether the main catalytic reaction proceeds on an Fe(0)-Fe(I) oxidation stage or whether further oxidation of initially formed Fe(I) rather leads to an Fe(II) catalyst. This cannot be excluded,... 

Example The gas-phase thermal decomposition of one mole of di-tert-butyl peroxide, in a constant volume apparatus, yields two moles of acetone and one mole of ethane. If life reaction obeys first-order kinetics, develop expression the rate-constant as a function of time, initial pressure and total pressure. 

Figure 6.7-14 Infrared absorbance spectra, recorded during the thermal decomposition of di-tert butyl peroxide in -heptane at 160 °C and 100 bar i reaction time. The initial peroxide concentration is 0.1 mol L . ...

A very dangerous fire hazard when exposed to heat or flame can react with oxidizing materials. Explosive in the form of vapor when exposed to heat or flame. The monomer may undergo spontaneous, explosive polymerization. Reacts in air to form a heat-sensitive explosive product (explodes on evaporation at 60°C). May ignite on contact with benzoyl peroxide. Potentially violent reaction with the polymerization initiators azoisobutyronitrile, dibenzoyl peroxide, di-tert-butyl peroxide, propionaldehyde. To fight fire, use foam, CO2, dry chemical. When heated to decomposition it emits acrid smoke and irritating fumes. See also ESTERS. 

ClSiMes. Other A -bromo amides have also been used. Allylic chlorination has been carried out, with A -chlorosuccinimide, tert-butyl hypochlorite, or with NaC10/CeCl3 7 H20. With any reagent an initiator is needed this is usually AIBN (1), a peroxide, such as di-tert-butyl peroxide or benzoyl peroxide or, less often, uv light. 

Aldehydes, both aliphatic and aromatic, can be decarbonylated" by heating with a rhodium catalyst" " or other catalysts, such as paHadium." RhCl(Ph3P)3 is often called Wilkinson s catalystIn an older reaction, aliphatic (but not aromatic) aldehydes are decarbonylated by heating with di-tert-butyl peroxide or other peroxides," usually in a solution containing a hydrogen donor, such as a thiol. The reaction has also been initiated with light, and thermally (without an initiator) by heating at 500°C. 

Elastomers must be crosslinked to hold their final form. The crosslinking reaction takes place through generation of free radicals that promote bonding at sites of unsaturation. The most common crosslinking agents for this include reactive peroxides, such as dicumyl peroxide, diacetyl peroxide, di-tert butyl peroxide, and others. Since each has a different temperature at which thermal decomposition initiates, curing conditions vary with the peroxide type. 

A number of studies have attempted to model this process stage by stage and to determine the values of some kinetic constants. Thus, in112 the researchers investigated the initial stage of isothermal bulk copolymerization of styrene with polybutadiene in the presence of di-tert-butyl peroxide. 

An attempt has been made (56) to understand the role of the structural factor when MAH was grafted to heterophase PP. The latter was a mixture of highly crystalline homopolypropylene, which made the matrix and copolymers dispersed in the PP matrix similar to rubber particles. During fractionation of the heterophase PP, three fractions were separated PP ( 50 wt%), EPR with irregular distribution of ethylene units ( 43 wt%), and ethylene-propylene block copolymer (EPM) ( 2 wt%). Peroxide initiators were DTBP (di-tert-butyl peroxide), S =... 

Scheme 7.38 Free radical copolymerization of various alicyclic monomers initiated by (1) azoisobutyronitrile (AIBN) in THF, and (2) di-tert-butyl peroxide (DTBP) in propylene glycol monomethylether acetate, and used in the synthesis of the alicyclic polymer resist materials for ArF lithography, pioneered at the University of Texas at Austin in 1995. Note that although only 2,3-enchainment of the cyclic olefins is shown above the scheme, 2,7-enchainement is also possible, as reported by Gaylord and co-workers. ...

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