SnCl4 STANNIC CHLORIDE

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... 

B. Reduction of Dinitrodurene.—A solution of 90 g. of dini-trodurene in 1 1. of glacial acetic acid is boiled in a 12-I. flask (Note 6) 700 g. of stannous chloride is dissolved in 800 cc. of concentrated hydrochloric acid and heated to boiling. The heat is removed from the acetic acid solution of the nitro compound, and the stannous chloride solution is poured very carefully (during about ten minutes) into the dinitrodurene solution. The reaction is complete in fifteen minutes, and as the solution cools the stannic chloride compound of the diamine begins to crystallize. The reaction mixture is cooled to io° in an ice-water bath, and the solid is filtered off by suction, washed twice with 50 cc. of 95 per cent ethyl alcohol and twice with 50 cc. of ether, and dried. The filtrates from the tin compound contain very little of the reduction product and may be discarded. The composition of this compound is [G (CH i)4(NH2-HCI)2l2-SnCl4, and it crystallizes from the reaction mixture in fine, glistening plates which are almost colorless. The yield is 145 g. (97 per cent of the theoretical amount). 

The third Mayo plot, (Figure 12), 1/DP against [SnClJ, has a discontinuity at a stannic chloride concentration corresponding approximately to [SnCl4]/[H20] = 1. The rising branch of the curve can be represented by a line of intercept L = 2 x 10"5 and slope S, = 8 x 10-3 1/mole. 

Tater, Gantmakher and Medvedev [43] revived the Hunter-Yohe mechanism with the addition that they supposed it to operate only in polar solvents, the idea being that the zwitterion would thus be stabilised by solvation. The experiments of Colclough and Dainton [36] with the system styrene-stannic chloride-nitrobenzene, and those of Tongworth, Plesch and Rutherford [44] with isobutene-titanium tetrachloride-various alkyl chloride solvents, then showed that in these systems a co-catalyst is required and that therefore the HY-MG mechanism cannot be operative. It has in fact now been abandoned by its originators, who have conceded that in the styrene-SnCl4-EtCl system a co-catalyst is required [45]. 

Example 4. Type C. Category 2. It was found by Norrish and Russell [5] that when isobutene was polymerised by stannic chloride in ethyl chloride at -78 °C the DP of the polymer fell rapidly with increasing water concentration until the ratio [H20]/[SnCl4] was about unity, and remained approximately constant at all higher water concentrations. These results have been analysed and interpreted in detail [6]. It was concluded that the principal chain-breaking agent is a species whose concentration was proportional to... 

After using stannic chloride (SnCl4), immediately clean the syringe by rinsing with dilute hydrochloric acid, water, and then methanol. 

EXERCISE 26. SULFUR MONOCHLORIDE, S2C12 PHOSPHORUS TRICHLORIDE, PClsj STANNIC CHLORIDE, SnCl4... 

A weighed quantity of anhydrous stannic chloride, SnCl4, is treated with six equivalents of water in the form of a concentrated solution of hydrochloric acid. The proportions required are 100 parts of SnCl4 and 41.64 parts of water, corresponding to 60.15 parts of 33 per cent hydrochloric acid of sp. gr. 1.166. 

Why is calcium fluoride, CaF2, a high-melting-point crystalline solid while stannic chloride, SnCl4, is a volatile liquid ... 

In the fabrication of printed circuit boards the sensitizer is applied to the substrate S by immersion of the substrate into the solution for 1-3 mins. Alternatively, the surface of a nonconductor may be sprayed with sensitizer. Addition of aged stannic chloride (SnCl4) solution to the tin sensitizer solution results in an improved sensitizer (17). The improved sensitizer yields a greater number of active centers per unit surface area (greater density) and a more uniform distribution. The density of adsorbed centers, using the conventional and the improved sensitizer, is 1011 and 1012 particles per square centimeter, respectively. The size of adsorbed particles for both types of sensitizers is about 10-15 A in diameter. 

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