Stannic chloride

This sequence implies the release of a chloride ion in the ionisation step, and this elimination usually requires the assistance of a molecule of HCl in the solvents used in cationic polymerisation. Also, stannic chloride is not consumed in the overall process. The interactions leading to the active species can therefore be written as  

It can be seen that at equilibrium, the concentration of carbenium ions is independent of the stannic chloride concentration in this scheme. However, if chloride ion exchange can occur between the Lewis acid and HClj, the sequence of equilibria is shifted to the ri t and a dependence is established between carbenium ion concentration and amount of SnCL used  

The existence of the pentachlorostannate anion in well known, but to the best of our knowledge this species has never been characterised in a polymerising system. If we consider its presence in this context as plausible, the concentration of carbenium ions at equilibrium will be determined by the overall relationship  

An alternative mechanism can also be proposed where the initial interaction occurs between the monomer double bond and hydrogen chloride, while the role of stannic chloride consists in providing the driving force for the release of the anion, Q or HCIJ  

as in the preceding scheme, the hydrogen dichloride anion is the relevant species, the equilibrium concentration of (paired) carbenium ions formed will be governed by the same equation, and the rate of polymerisation will also follow the same kinetic laws, assuming that protonation is rate determining. 

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Tin IV) chloride, SnCU, stannic chloride. M.p. — 33" C, b.p. 1I4°C. Colourless fuming liquid (Sn plus CI2) hydrolysed in water but forms SnCl4,5H20 and [SnCl p" from acid solutions, soluble in organic solvents. Used as a mordant. 

Stannic chloride is prepared by treating metallic tin with chlorine Sn + 2C1 SnCl4... 

Both aliphatic and aromatic nitro-compounds can be readily reduced in acid solution to the corresponding primary amine. Thus when a mixture of nitrobenzene and tin is treated with hydrochloric acid, the tin dissolves to give stannous chloride, SnCh, which in these circumstances then reacts with more acid to give stannic chloride, SnCl, and the nascent hydrogen produced from... 

Alkyltin Intermedia.tes, For the most part, organotin stabilizers are produced commercially from the respective alkyl tin chloride intermediates. There are several processes used to manufacture these intermediates. The desired ratio of monoalkyl tin trichloride to dialkyltin dichloride is generally achieved by a redistribution reaction involving a second-step reaction with stannic chloride (tin(IV) chloride). By far, the most easily synthesized alkyltin chloride intermediates are the methyltin chlorides because methyl chloride reacts directiy with tin metal in the presence of a catalyst to form dimethyl tin dichloride cleanly in high yields (21). Coaddition of stannic chloride to the reactor leads directiy to almost any desired mixture of mono- and dimethyl tin chloride intermediates ... 

The other commercially important routes to alkyltin chloride intermediates utilize an indirect method having a tetraalkjitin intermediate. Tetraalkyltins are made by transmetaHation of stannic chloride with a metal alkyl where the metal is typicaHy magnesium or aluminum. Subsequent redistribution reactions with additional stannic chloride yield the desired mixture of monoalkyl tin trichloride and dialkyltin dichloride. Both / -butjitin and / -octjitin intermediates are manufactured by one of these schemes. 

A telomerization reaction of isoprene can be carried out by treatment with 2-chloro-3-pentene, prepared by the addition of dry HCl to 1,3-pentadiene (67). An equimolar amount of isoprene in dichi oromethane reacts with the 2-chloro-3-pentene at 10°C with stannic chloride as catalyst. l-Chloro-3,5-dimethyl-2,6-octadiene is obtained in 80% yield by 1,4-addition. 

Carbonyl Compounds. Cychc ketals and acetals (dioxolanes) are produced from reaction of propylene oxide with ketones and aldehydes, respectively. Suitable catalysts iaclude stannic chloride, quaternary ammonium salts, glycol sulphites, and molybdenum acetyl acetonate or naphthenate (89—91). Lactones come from Ph4Sbl-cataly2ed reaction with ketenes (92). 

Platinum-group metals (qv) form complexes with chelating polymers with various 8-mercaptoquinoline [491-33-8] derivatives (83) (see Chelating agents). Hydroxy-substituted quinolines have been incorporated in phenol—formaldehyde resins (84). Stannic chloride catalyzes the condensation of bis(chloromethyl)benzene with quinoline (85). 

Several modified forms of this synthesis are available. For example, treatment of either isocyanate (28) or urethane (29) derivatives with phosphoryl chloride followed by stannic chloride has been reported to give the substituted isoquinoline [80388-01-8] (158). 

Neutral aqueous salt solutions react slowly with tin when oxygen is present but oxidizing salt solutions, such as potassium peroxysulfate, ferric chloride and sulfate, and aluminum and stannic chlorides dissolve tin. Nonaqueous organic solvents, lubricating oils, and gasoline have Httle effect. 

Of the large volume of tin compounds reported in the Hterature, possibly only ca 100 are commercially important. The most commercially significant inorganic compounds include stannic chloride, stannic oxide, potassium staimate, sodium staimate, staimous chloride, stannous fluoride, stannous fluoroborate, stannous oxide, stannous pyrophosphate, stannous sulfate, stannous 2-ethyUiexanoate, and stannous oxalate. Also important are organotins of the dimethyl tin, dibutyltin, tributyltin, dioctyltin, triphenyl tin, and tricyclohexyltin families. 

Halides. The tin haUdes of the greatest commercial importance are stannous chloride, stannic chloride, and stannous fluoride. Tin hahdes of less commercial importance are stannic bromide [7789-67-5], stannic iodide [7790-47-8], stannous bromide [10031-24-0], and stannous iodide [10294-70-9] ( ) ... 

Anhydrous stannous chloride, a water-soluble white soHd, is the most economical source of stannous tin and is especially important in redox and plating reactions. Preparation of the anhydrous salt may be by direct reaction of chlorine and molten tin, heating tin in hydrogen chloride gas, or reducing stannic chloride solution with tin metal, followed by dehydration. It is soluble in a number of organic solvents (g/100 g solvent at 23°C) acetone 42.7, ethyl alcohol 54.4, methyl isobutyl carbinol 10.45, isopropyl alcohol 9.61, methyl ethyl ketone 9.43 isoamyl acetate 3.76, diethyl ether 0.49, and mineral spirits 0.03 it is insoluble in petroleum naphtha and xylene (2). 

Stannous Chloride Dihydrate. A white crystalline soHd, stannous chloride dihydrate is prepared either by treatment of granulated tin with hydrochloric acid followed by evaporation and crystallisation or by reduction of a stannic chloride solution with a cathode or tin metal followed by crystallisation. It is soluble in methanol, ethyl acetate, glacial acetic acid, sodium hydroxide solution, and dilute or concentrated hydrochloric acid. It is soluble in less than its own weight of water, but with much water it forms an insoluble basic salt. 

Stannic Chloride. Stannic chloride is available commercially as anhydrous stannic chloride, SnCl (tin(IV) chloride) stannic chloride pentahydrate, SnCl 5H20 and in proprietary solutions for special appHcations. Anhydrous stannic chloride, a colorless Aiming Hquid, fumes only in moist air, with the subsequent hydrolysis producing finely divided hydrated tin oxide or basic chloride. It is soluble in water, carbon tetrachloride, benzene, toluene, kerosene, gasoline, methanol, and many other organic solvents. With water, it forms a number of hydrates, of which the most important is the pentahydrate. Although stannic chloride is an almost perfect electrical insulator, traces of water make it a weak conductor. 

Stannic chloride is made by the direct chlorination of tin at 110—115°C. Any stannous chloride formed in the process is separated from the stannic chloride by volatilization and subsequently chlorinated to stannic chloride. The latter is inert to steel in the absence of moisture and is shipped in plain steel dmms of special design. Because prolonged contact with the skin causes bums, goggles and protective clothing should be used in the handling of stannic chloride. Stannic chloride, like stannous chloride, also forms many complexes (3). 

Stannic chloride is also used widely as a catalyst in Eriedel-Crafts acylation, alkylation and cycHzation reactions, esterifications, halogenations, and curing and other polymerization reactions. Minor uses are as a stabilizer for colors in soap (19), as a mordant in the dyeing of silks, in the manufacture of blueprint and other sensitized paper, and as an antistatic agent for synthetic fibers (see Dyes, application and evaluation Antistatic agents). 

Stannic Chloride Pentahydrate. Stannic chloride pentahydrate [10026-06-9] is a white, crystalline, deHquescent soHd that is soluble in water or methanol and stable at 19—56°C. It is used in place of the anhydrous chloride where anhydrous conditions are not mandatory. It is easier to handle than the fuming anhydrous Hquid form. The pentahydrate is prepared by dissolving stannic chloride in hot water, thereby forming the pentahydrate at a temperature above the melting point and crystallizing by cooling. The cake is broken into small lumps for packaging. 

A stannic chloride pentahydrate—ammonium bifluoride formulation for fireproofing wool is commercially available and used in New Zealand and AustraHa (20) (see Elal retardants for textiles). 

Stannic Oxide. Stannic oxide tin(IV) oxide, white crystals, mol wt 150.69, mp > 1600° C, sp gr 6.9, is insoluble in water, methanol, or acids but slowly dissolves in hot, concentrated alkaH solutions. In nature, it occurs as the mineral cassiterite. It is prepared industrially by blowing hot air over molten tin, by atomizing tin with high pressure steam and burning the finely divided metal, or by calcination of the hydrated oxide. Other methods of preparation include treating stannic chloride at high temperature with steam, treatment of granular tin at room temperature with nitric acid, or neutralization of stannic chloride with a base. 

Transparent electroconductive coatings of stannic oxide are deposited on nonconductive substrates for electrical and strengthening appHcations. However, the agents used to deposit the oxide film are actually stannic chloride. More recently, some organotin compounds have been employed. 

A variant of the Wurtz reaction is the preparation of tetrabutyltin from activated magnesium chips, butyl chloride, and stannic chloride in a hydrocarbon mixture. Only a small amount of tetrahydrofuran is required for the reaction to proceed in high yield (86). 

Bis(trineophyltin) oxide [60268-17-4] is prepared from the chloride in the normal manner. The chloride can either be prepared directiy from the reaction of three moles of neophylmagnesium chloride and stannic chloride or by the butyl transfer reaction between butyltrineophyltin and stannic chloride. The hydroxide derivative initially formed on hydrolysis of the chloride is readily dehydrated to the bis(oxide) at ca 100°C. 

Prepa.ra.tlon, Diorganotin dichlorides are the usual precursors for all other diorganotin compounds three primary methods of manufacture are practiced. Dibutyltin dichloride is manufactured by Kocheshkov redistribution from cmde tetrabutyltin and stannic chloride and usually is cataly2ed with a few tenths of a percent aluminum trichloride ... 

The reaction of higher alkyl chlorides with tin metal at 235°C is not practical because of the thermal decomposition which occurs before the products can be removed from the reaction zone. The reaction temperature necessary for the formation of dimethyl tin dichloride can be lowered considerably by the use of certain catalysts. Quaternary ammonium and phosphonium iodides allow the reaction to proceed in good yield at 150—160°C (109). An improvement in the process involves the use of amine—stannic chloride complexes or mixtures of stannic chloride and a quaternary ammonium or phosphonium compound (110). Use of these catalysts is claimed to yield dimethyl tin dichloride containing less than 0.1 wt % trimethyl tin chloride. Catalyzed direct reactions under pressure are used commercially to manufacture dimethyl tin dichloride. 

Hydrogen haHde addition to vinyl chloride in general yields the 1,1-adduct (50—52). The reactions of HCl and hydrogen iodide [10034-85-2], HI, with vinyl chloride proceed by an ionic mechanism, while the addition of hydrogen bromide [10035-10-6], HBr, involves a chain reaction in which a bromine atom [10097-32-2] is the chain carrier (52). In the absence of a transition-metal catalyst or antioxidants, HBr forms the 1,2-adduct with vinyl chloride (52). HF reacts with vinyl chloride in the presence of stannic chloride [7646-78-8], SnCl, to form 1,1-difluoroethane [75-37-6] (53). 

A typical cationic polymeriza tion is conducted with highly purified monomer free of moisture and residual alcohol, both of which act as inhibitors, in a suitably dry unreactive solvent such as toluene with a Eriedel-Crafts catalyst, eg, boron triduoride, aluminum trichloride, and stannic chloride. Usually low temperatures (—40 to —70°C) are favored in order to prevent chain-transfer or sidereactions. 

Carbon tetrachloride readily dissolves stannic chloride, SnCl, but not ferric chloride, FeCl. Carbon tetrachloride forms a large number of binary and several ternary azeotropic mixtures a partial Hst of the former is shown in Table 3. 

The epoxidation is generally conducted in two steps (/) the polyol is added to epichlorohydrin in the presence of a Lewis acid catalyst (stannic chloride, boron triduoride) to produce the chlorohydrin intermediate, and (2) the intermediate is dehydrohalogenated with sodium hydroxide to yield the aliphatic glycidyl ether. A prominent side-reaction is the conversion of aliphatic hydroxyl groups (formed by the initial reaction) into chloromethyl groups by epichlorohydrin. The aliphatic glycidyl ether resins are used as flexibilizers for aromatic resins and as reactive diluents to reduce viscosities in resin systems. 

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