Percarbonates

Activation parameters for monoperoxycarbonates (Table 111) indicate a one-bond homolysis reaction. In comparison to di-t-butylperoxyoxalate where multibond homolysis occurs, the rate coefficient for di-f-butyl monoperoxycarbonate is 10 times slower at 45 °C . The rate of decomposition of di-t-butyl diperoxy- 

Kinetic data for thermal decomposition of the related dialkyl peroxydicarbonates are given in Table 112. Variation of the substituent groups R has little effect on the rate coefficients or the activation energy. In addition the activation energies are in the range of those reported for benzoyl peroxides. This suggests a one-bond homolysis reaction. Activation energies for dialkyl peroxydicarbonates with 

R = C6H4 in dimethyl formamide ° and with R = CgHjCHj in benzyl alcohol are 22 and 26,8 kcal.mole , respectively. These rather low values may be indicative of induced decomposition by radicals originating from the solvent or possibly an inversion reaction (c/., section 13.3.4). 

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There are international transport regulations controlling the transport of sodium percarbonate, which assigned it to Class 5.1, oxidizing substances, however, no such compound has ever been commercialized, and sodium carbonate peroxohydrate is treated as nonhazardous. The origin of this item is not known. 

In 1993, the world capacity for sodium peroxoborate hexahydrate (tetrahydrate) was about 900,000 metric tons, of which about one-third was converted to the dehydrated compound (monohydrate). At the then prevailing prices, the total value of this business was about 6 x 10 . The world capacity for sodium carbonate peroxohydrate (percarbonate) was about 60,000 metric tons, valued at about 70 x 10 . ... 

Fig. 1. Bulk polymerization of diethylene glycol bis(aHylcarbonate) at 45°C with initial addition of 3.0% diisopropyl percarbonate. Rates of polymerization as measured by density and catalyst consumption decrease with time at a given temperature (14).

Many proprietary methods have been developed for casting and shaping DADC, especially for lenses. In one method DADC containing 3.5% diisopropyl percarbonate is prepolymerized by warming to a symp of viscosity 40—60 mm /s (=cSt) (15). Polymerization is continued in a lens for 18 h at 90°C followed by annealing at 120°C. 

Scratch resistance of polymer from DADC is improved by novel mixtures of peroxide initiators such as 5% isopropyl percarbonate with 3.5% benzoyl peroxide (16). In order to force completion of polymerization and attain the best scratch resistance in lenses, uv radiation is appHed (17). Eyeglass lenses can be made by prepolymerization in molds followed by removal for final thermal cross-linking (18). 

The DADC monomer has been copolymerized with small amounts of polyfunctional methacryflc or acryflc monomers. For example, 3% triethylene glycol dimethacrylate was used as a flexibiflzing, cross-linking agent with a percarbonate as initiator (26). CR-39 and diethylene glycol diacrylate containing isopropyl percarbonate were irradiated with a mercury lamp to a 92% conversion and then cured at 150°C (27). By a similar two-step process DADC was copolymerized with methyl methacrylate and tetraethylene glycol dimethacrylate (28). 

R can be a variety of stmctures. Z is a leaving group and typically the conjugate base of a weak acid whose piC can range from 5 to 20 (86). The hydrogen peroxide is typically incorporated into the bath by a dding a soHd source of peroxide such as sodium percarbonate or the mono- or tetrahydrate of sodium perborate (86). 

Chloroformates are versatile, synthetic intermediates, based on the affinity of the chlorine atoms for active hydrogen atoms. Chloroformates should be considered as intermediates for syntheses of pesticides, perfumes, dmgs, polymers, dyes, and other chemicals. Some of these products, eg, carbonates, are used as solvents, plastici2ers, or as intermediates for further synthesis. A significant use of chloroformates is for conversion to peroxydicarbonates, which serve as free-radical initiators for the polymeri2ation of vinyl chloride, ethylene, and other unsaturated monomers. The most widely used percarbonate initiators are diisopropyl peroxydicarbonate (IPP), di-2-ethyIhexylperoxydicarbonate (2-EHP), and di-j -butylperoxydicarbonate (SBP). The following Hst includes most of the commercially used percarbonates. 

Treatment of 2-methylthiirane with t-butyl hydroperoxide at 150 °C in a sealed vessel gave very low yields of allyl disulfide, 2-propenethiol and thioacetone. The allyl derivatives may be derived from abstraction of a hydrogen atom from the methyl group followed by ring opening to the allylthio radical. Percarbonate derivatives of 2-hydroxymethylthiirane decompose via a free radical pathway to tar. Acrylate esters of 2-hydroxymethylthiirane undergo free radical polymerization through the double bond. 

SODIUM PENTACHLOROPHENATE SODIUM PERCARBONATE SODIUM PERCARBONATE... 

Chemical Designations - Synonyms Diisopropyl percarbonate Diisopropyl peroxydicarbonate Isopropyl peroxydicarbonate Peroxydicarbonic acid, bis (1-methylethyl) ester Peroxydicarbonic acid, diisopropyl ester Chemical Formula C3H7OOCOOCOOC3H7. 

World production expressed as 100% H2O2 approached 1.9 million tonnes in 1994 of which half was in Europe and one-fifth in the USA. The earliest and still the largest industrial use for H2O2 is as a bleach for textiles, paper pulp, straw, leather, oils and fats, etc. Domestic use as a hair bleach and a mild disinfectant has diminished somewhat. Hydrogen peroxide is also extensively used to manufacture chemicals, notably sodium perborate (p. 206) and percarbonate, which are major constituents of most domestic detergents at least in the UK and Europe. Normal formulations include 15-25% of such peroxoacid salts, though the practice is much less widespread in the USA, and the concentrations, when included at all, are usually less than 10%. 

Perammons. See under Parammons in this Vol Percarbonates. Salts of the hypothetical per-carbonic acid, H2C206, contg the CjO radical, some of which are expl. Guided by analogy with persulfates, Constant and von Hansen (Refs 1 ... 

Noie According to Mellor (Ref 2, p 86), A. Bach claimed that percarbonic acid can exist in cold ethereal so In. When such a so In was treated with an ale KOH soln, a bluish-white ppt of K per-carbonate was formed. Of the percarbonates, the K salt is the easiest to prepare and is available commercially (see below)... 

K percarbonate is sparingly sol in ale it dissolves in ice cold w almost without decompn, but at RT and higher, it decomps with the evolution of H2... 

A percarbonate possesses, according to Daniel (Ref 1), some expl properties because it can be detonated if a sufficiently powerful detonator is used. According to Mellor (Ref 2, p 86), a violent reaction took place when a soln of 0.5g of solid phosphoric acid, some ether, and a few drops of w were added to 2g of K percarbonate. It was used by Turpin in Fr in expl mixts, ie, Pyrodialytes (qv) (Ref 1)... 

K percarbonate is highly toxic, and a strong irritant to tissue. It is also a fire risk in contact with organic materials (Refs 4 5)... 

Oxygen bleaches such as sodium carbonate peroxide (also called sodium percarbonate), sodium peroxide, or sodium perborate are made by reacting molecules with hydrogen peroxide. When the result is added to water, the hydrogen peroxide is released. 

Dimethyl peroxide Diethyl peroxide Di-t-butyl-di-peroxyphthalate Difuroyl peroxide Dibenzoyl peroxide Dimeric ethylidene peroxide Dimeric acetone peroxide Dimeric cyclohexanone peroxide Diozonide of phorone Dimethyl ketone peroxide Ethyl hydroperoxide Ethylene ozonide Hydroxymethyl methyl peroxide Hydroxymethyl hydroperoxide 1-Hydroxyethyl ethyl peroxide 1 -Hydroperoxy-1 -acetoxycyclodecan-6-one Isopropyl percarbonate Isopropyl hydroperoxide Methyl ethyl ketone peroxide Methyl hydroperoxide Methyl ethyl peroxide Monoperoxy succinic acid Nonanoyl peroxide (75% hydrocarbon solution) 1-Naphthoyl peroxide Oxalic acid ester of t-butyl hydroperoxide Ozonide of maleic anhydride Phenylhydrazone hydroperoxide Polymeric butadiene peroxide Polymeric isoprene peroxide Polymeric dimethylbutadiene peroxide Polymeric peroxides of methacrylic acid esters and styrene... 

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