Dibutyl tin

Acetylsucrose [63648-81-7] has been prepared in 40% yield by direct acetylation of sucrose using acetic anhydride in pyridine at 40° C (36). The 6-ester has subsequently been obtained in greater than 90% yield, by way of 4,6-cycHc orthoacetate. Other selective methods for the 6-acylated derivatives include the use of alkyl tin reagents such as dibutyl tin oxide (37) and of dibutyl stannolane derivatives (38). Selective acetylation of sucrose by an enzymic process has also been described. Treatment of sucrose with isopropenyl acetate in pyridine in the presence of Lipase P Amano gave, after chromatography, 6-0-acetylsucrose (33%) and 4/6-di-O-acetylsucrose (8%). The latter compound has been obtained in 47% yield by the prolonged treatment (39). 

Cychc carbonates result from polyols by transesterification using organic carbonates (115). Thus sorbitol and diphenylcarbonate in the presence of dibutyl tin oxide at 140—150°C form sorbitol tricarbonate in quantitative yield (116). 

In recent years there has been some substitution of TDI by MDI derivatives. One-shot polyether processes became feasible with the advent of sufficiently powerful catalysts. For many years tertiary amines had been used with both polyesters and the newer polyethers. Examples included alkyl morpholines and triethylamine. Catalysts such as triethylenediamine ( Dabco ) and 4-dimethyla-minopyridine were rather more powerful but not satisfactory on their own. In the late 1950s organo-tin catalysts such as dibutyl tin dilaurate and stannous octoate were found to be powerful catalysts for the chain extension reactions. It was found that by use of varying combinations of a tin catayst with a tertiary amine... 

The pieces of cloth are then plied up and moulded at about 170°C for 30-60 minutes. Whilst flat sheets are moulded in a press at about lOOOlbf/in (7 MPa) pressure, complex shapes may be moulded by rubber bag or similar techniques at much lower pressures ( 15 Ibf/in ) (0.1 MPa) if the correct choice of resin is made. A number of curing catalysts have been used, including triethanolamine, zinc octoate and dibutyl tin diacetate. The laminates are then given a further prolonged curing period in order to develop the most desirable properties. 

A typical condensation system involves the reaction of a silanol-terminated polydimethylsiloxane with a multi-functional organosilicon cross-linking agent such as Si(RO)4 Figure 29.8). Pot life will vary from a few minutes to several hours, depending on the catalysts used and the ambient conditions. Typical catalysts include tin octoate and dibutyl tin dilaurate. 

The polymetallosiloxanes above may in fact be considered as variants of a series of polymetalloxanes which are akin to the silicones but which contain, for example, tin, germanium and titanium instead of silicon. Of the poly-organostannoxanes, dibutyl tin oxide finds use as a stabiliser for PVC and as a silicone cross-linking agent. Polyorganogermanoxanes have also been prepared (Figure 29.13). 

Catalysts such as dibutyl tin dilaurate or tertiary amines are added to promote the urethane reaction and/or subsequent moisture cure. Dimorpholine diethyl ether is particularly effective at promoting moisture cure without promoting allophanate side reactions at the application temperature (which leads to instability in the hot melt pot) [29]. 

Initiation of stannous octoate-catalyzed copolymerization of e-caprolactone with glycerol was used to prepare a series of trifunctional hydroxy-end blocked oligomers, which were then treated with hexane-1,6-diisocyanate to form elastomeric polyesterurethanes with different crosslink densities (49). Initiation of e-caprolactone polymerization with a hydroxypropyl-terminated polydimethylsiloxane in the presence of dibutyl tin dilaurate has been used to prepare a polyester-siloxane block copolymer (Fig. 4) (50). 

Butyl cellosolve stearate Diamyl naphthalene Dibutyl tin laurate Dioctylphthalate Methyl cellosolve oleate Methyl phthalylethylglycola Phenylsalicylate Propylene stearate Stearic acid... 

Diazo aminobenzene Di-t-butyl-p-cresol Dibutyl tin maleate Dibutyl tin oxide Dichlorophene 2,4-Dichiorophenoxy ethyl benzoate... 

The foams can be obtained by the action of a diiscyanate on a polyol and water. The reaction with water forms carbon dioxide and the reaction with polyol forms a urethane polymer. Catalysts play a crucial role in the process. Tin octeate and dibutyl tin dilaurate are preferred catalysts along with tertiary amines. 

Special consideration should be paid to metal complexes such as azomethine pigments (Sec. 2.10). At high temperatures, the yellow copper complex with the chemical constitution 10, incorporated in PVC, will exchange its chelated copper atoms with the metal atoms present in the application medium. Stabilizers containing barium/cadmium or lead produce yellow shades, while dibutyl tin thiogly-colate or other tin compounds produce a brilliant medium red. Color change is slow at low temperatures, but at 160°C the effect is rapid [108],... 

The mechanism for cyclic formation via depolymerization is the same type of transesterification which occurs on polymerization, as outlined in Scheme 3.3. Metal alkoxides such as tetraalkyl titanates or dibutyl tin alkoxides have proven... 

After reaching the desired DP, 40-50 % of the oligomeric melt is transferred to the polymerization vessel. Titanium butoxide (50-150 ppm) or dibutyl tin oxide catalyst (100-250 ppm), or some combinations of the two catalysts, is added to catalyze polymerization at 260-275 °C. A vacuum of <0.15 kPa is applied to remove the condensed water so as to drive the reaction until the polymer reaches an intrinsic viscosity (IV) of 0.7-0.9 dL/g. 

Half-blocked Dllsocyanates. The half-blocked diisocyanates were prepared using conventional methods (2) by adding dropwlse, over a period of one hour, 1 mole of alcohol to 1 mole of diisocyanate and 100 mg dibutyl tin dilaurate in methyl amyl ketone under an inert atmosphere. After the addition of the alcohol, the reaction was heated at 60-80°C for 2 hours. For half-blocked diisocyanates prepared from tertiary alcohols, the heating period was replaced with room temperature stirring for 24-36 hours to prevent undesirable side reactions. 

We have prepared and characterized three linear isosorbide containing polyurethanes with toluene diisocyanate (TDI), 4,4 -diphenylmethane diisocyanate (MDI), and 1,6-hexamethylene diisocyanate (HMDI) P(I-TDI), P(I-MDI), and P(I-HMDI). These polyurethanes have been synthesized as described in the experimental section by solution polymerization of isosorbide with the corresponding diisocyanate in dimethylacetamide using dibutyl-tin dilaurate as the catalyst at 75 C for 24 hours. All polymers have been isolated in quantitative yield by precipitation in methanol or water (5). 

Methods. Reaction with IEM Reactions with IEM were performed in methylene chloride using dibutyl tin dilaurate (ca. 1 wt.%) as catalyst. The reaction mixture with model compound or HBL was reacted at 40°C under dry nitrogen. The reaction product was obtained by precipitation with n-hexane. Detailed experimental and analytical results are given elsewhere (15). 

Unfortunately this ingeneous mechanism remains speculative since there is some doubt as to the identity of some of the labelled compounds. Thus, Mufti and Poller were unable to repeat the preparation of dibutyl tin bis (methyl maleate) but obtained instead dibutylchlorotin methyl maleate (93). Also there was no clear indication of either the chemical purity or the radiochemical purity (see Section 5 c) of the compounds BuaSnY2 (94). 

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