Synthetic chlorins

The advanced applications for nitrocellulose plastisol propellants require that they be integrally bonded to the motor case. Successful case bonding for the multiyear storage life of a rocket calls for special adhesives and liners which are completely compatible with these highly plasticized propellants. Best results have been obtained with a combination of an impervious rubber liner and a crosslinked adhesive system with a limited affinity for the plasticizers used in the propellants. Examples of effective liners are silica-filled butyl rubber and chlorinated synthetic rubber. Epoxy polyamides, isocyanate-crosslinked cellulose esters, and combinations of crosslinked phenol-formaldehyde and polyvinyl formal varnishes have proved to be effective adhesives between propellant and impervious liners. Pressure curing of the propellants helps... 

PDCB is a chlorinated synthetic of extreme chronic toxicity and environmental concern. Paradichlorobenzene is an endocrine disrupter and carcinogen. In other words, mothballs are not an option. 

Some of the most important physiological steroids are the adrenocortical hormones, synthesized by the adrenal cortex. Most of these hormones have either a carbonyl group or a hydroxyl group at Cl 1 of the steroid skeleton. The principal adrenocortical hormone is cortisol, used for the treatment of inflammatory diseases of the skin (psoriasis), the joints (rheumatoid arthritis), and the lungs (asthma). Figure 25-10 compares the structure of natural cortisol with two synthetic corticoids fluocinolone acetonide, a fluori-nated synthetic hormone that is more potent than cortisol for treating skin inflammation and beclomethasone, a chlorinated synthetic hormone that is more potent than cortisol for treating asthma. 

In most cases these substances are organochlorinated compound insecticides, also known as chlorinated hydrocarbons, chlorinated organics, chlorinated insecticides, chlorinated synthetics, and organochlorine pesticides (OCPs) (Table 22.1). 

Another chlorin synthetic methodology worth mentioning is the formation of spirochlorin 122 and allylidenechloiin 123 by the reaction of bromovinylporphyrin 121 with tetra-... 

Polyvinylidene chloride Poly-2-chlorobutadiene Polychlorostyrene Polytetrafluoroethylene Polytrifluorochloroethylene Polyvinyl fluoride Chlorinated synthetic rubber Chlorinated paraffins ... 

Organic chemistry demands much from chlorine, both as an oxidizing agent and in substitution, since it often brings many desired properties in an organic compound when substituted for hydrogen, as in one form of synthetic rubber. 

Chlorination of methane provides approximately one third of the annual U S pro duction of chloromethane The reaction of methanol with hydrogen chloride is the major synthetic method for the preparation of chloromethane... 

Chlorine Ammonia, acetylene, alcohols, alkanes, benzene, butadiene, carbon disulflde, dibutyl phthalate, ethers, fluorine, glycerol, hydrocarbons, hydrogen, sodium carbide, flnely divided metals, metal acetylides and carbides, nitrogen compounds, nonmetals, nonmetal hydrides, phosphorus compounds, polychlorobi-phenyl, silicones, steel, sulfldes, synthetic rubber, turpentine... 

Manufacture via this process has been completely replaced by chlorination of butadiene (3) (see Chlorocarbons and chlorohydrocarbons, chloroprene ElASTOT RS, synthetic, POLYCm OROPRENE). 

Gaskets in both dry gas and Hquid chlorine systems are made of mbberi2ed compressed asbestos. Eor wet chlorine gas, mbber or synthetic elastomers are acceptable. PTEE is resistant to both wet and dry chlorine gas and to Hquid chlorine up to 200°C. Tantalum, HasteUoy C, PTEE, PVDE, Monel, and nickel are recommended for membranes, mpture disks, and beUows. 

Since 1960, about 95% of the synthetic ammonia made in the United States has been made from natural gas worldwide the proportion is about 85%. Most of the balance is made from naphtha and other petroleum Hquids. Relatively small amounts of ammonia are made from hydrogen recovered from coke oven and refinery gases, from electrolysis of salt solutions, eg, caustic chlorine production, and by electrolysis of water. In addition there are about 20 ammonia plants worldwide that use coal as a hydrogen source. 

At one time, the only commercial route to 2-chloro-1,3-butadiene (chloroprene), the monomer for neoprene, was from acetylene (see Elastomers, synthetic). In the United States, Du Pont operated two plants in which acetylene was dimeri2ed to vinylacetylene with a cuprous chloride catalyst and the vinyl-acetylene reacted with hydrogen chloride to give 2-chloro-1,3-butadiene. This process was replaced in 1970 with a butadiene-based process in which butadiene is chlorinated and dehydrochlorinated to yield the desired product (see Chlorocarbonsandchlorohydrocarbons). 

Of the estimated 710,000 t consumed in 1990, 25% was used to produce vinyl chloride [75-01-4] monomer (VCM), 14% for vinyl acetate [108-05-4] monomer (VAM), 23% for butanediol, 14% for industrial use, and the balance to produce other products such as acryUc acid, synthetic mbber, chlorinated solvents, and acetylene black. The demand for PVC is expected to decrease as legislation limiting its use in packaging is pending. Consequentiy, VCM consumption will also suffer. 

Hydrogen chloride and the aqueous solution, muriatic acid, find appHcation in many industries. In general, anhydrous HCl is consumed for its chlorine value, whereas aqueous hydrochloric acid is often utilized as a nonoxidizing acid. The latter is used in metal cleaning operations, chemical manufacturing, petroleum well activation, and in the production of food and synthetic mbber. 

The cumene oxidation route is the lea ding commercial process of synthetic phenol production, accounting for more than 95% of phenol produced in the world. The remainder of synthetic phenol is produced by the toluene oxidation route via benzoic acid. Other processes including benzene via cyclohexane, benzene sulfonation, benzene chlorination, and benzene oxychl orin ation have also been used in the manufacture of phenol. A Hst of U.S. phenol production plants and their estimated capacities in 1994 are shown in Table 2, and worldwide plants and capacities are shown in Table 3. 

The first synthetic pyrogaHol plant using hydrolysis of chlorinated cyclohexanol (2,2,6,6-tetrachlorocyclohexanone) was built by BFC Chemicals, Inc. (Muskegon, Michigan) and has been producing pyrogaHol for the carbamate insecticide Beniocarb since 1982 (8,19). SocifitH Fransaise Hoechst offers pyrogaHol for sale in the United States (American Hoechst Corp.), and Japan is also a source of this chemical. 

Methylphenol. y -Cresol is produced synthetically from toluene. Toluene is chlorinated and the resulting chlorotoluene is hydrolyzed to a mixture of methylphenols. Purification by distillation gives a mixture of 3-methylphenol and 4-methylphenol since they have nearly identical boiling points. Reaction of this mixture with isobutylene under acid catalysis forms 2,6-di-/ f2 -butyl-4-methylphenol and 2,4-di-/ f2 -butyl-5-methylphenol, which can then be separated by fractional distillation and debutylated to give the corresponding 3- and 4-methylphenols. A mixture of 3- and 4-methylphenols is also derived from petroleum cmde and coal tars. 

The anodic oxidation of hydroquiaone ethers to quiaone ketals yields synthetically useful iatermediates that can be hydroly2ed to quiaones at the desired stage of a sequence (76). The yields of iatermediate diacetal are 83% for chlorine and 75% for bromine. 

Magnesium oxide is a typical acid scavenger for chlorinated mbbers. Compounds containing zinc oxide or magnesium oxide may tend to swell upon immersion in water. These inorganic salts have some water solubiHty and osmotic pressure causes the vulcanizates to imbibe water to equalize pressure (8,9). As such, vulcanizates tend to sweU more in fresh (distilled) water than in salt water. To minimize water sweU, insoluble salts such as lead oxides can be substituted. Because of the health concerns associated with lead, there is much mbber industry interest in other acid acceptors, such as synthetic... 

Natural mbber comes generally from southeast Asia. Synthetic mbbers are produced from monomers obtained from the cracking and refining of petroleum (qv). The most common monomers are styrene, butadiene, isobutylene, isoprene, ethylene, propylene, and acrylonitrile. There are numerous others for specialty elastomers which include acryUcs, chlorosulfonated polyethylene, chlorinated polyethylene, epichlorohydrin, ethylene—acryUc, ethylene octene mbber, ethylene—propylene mbber, fluoroelastomers, polynorbomene, polysulftdes, siUcone, thermoplastic elastomers, urethanes, and ethylene—vinyl acetate. 

Butyl and Halobutyl Rubber. Butyl mbber is made by the polymerization of isobutylene a small amount of isoprene is added to provide sites for curing. It is designated HR because of these monomers. Halogenation of butyl mbber with bromine or chlorine increases the reaction rate for vulcanization and laminates or blends of halobutyl are feasible for production of mbber goods. It is estimated that of the - 100 million kg of butyl (UR) and halobutyl (HIIR) mbber in North America, over 90% is used in tire apphcations. The halogenated polymer is used in the innerliner of tubeless tires. Butyl mbber is used to make innertubes and curing bladders. The two major suppHers of butyl and halobutyl polymers in North America are Exxon and Bayer (see ELASTOLffiRS,SYNTHETIC-BUTYLrubber). 

Chlorosulfonated Polyethylene. This elastomer is made by the simultaneous chlorination and chlorosulfonation of polyethylene in an inert solvent. The resulting polymer is an odorless, colorless chip that is mixed and processed on conventional mbber equipment. The polymer typically contains 20-40% chlorine and 1% sulfur groups (see ElASTOL RS, SYNTHETIC-Cm OROSULFONATEDPOLYETHYLENE) (8). 

The reactive intermediate, (C2H3)2NCH2CH2C1 HCl, which is used to produce cationic starch, is made by the reaction of (C2H3)2NCH2CH20H with thionyl chloride. A synthetic sweetener (qv), sucralose [56038-13-2] is made by the reaction of sucrose or an acetate thereof with thionyl chloride to replace three hydroxy groups by chlorines (187,188). 

Miscellaneous. In ore flotation, sodium sulfite functions as a selective depressant. In textile processing, sodium sulfite is used as a bleach for wood (qv) and polyamide fibers and as an antichlor after the use of chlorine bleach. Synthetic appHcations of sodium sulfite include production of sodium thiosulfite by addition of sulfur and the introduction of sulfonate groups into dyestuffs and other organic products. Sodium sulfite is useful as a scavenger for formaldehyde in aminoplast—wood compositions, and as a buffer in chrome tanning of leather. 

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