TBTA

About 50 g of pure tributyltin acrylate (TBTA) was dissolved in 1 liter hexane. Evaporation of 20 ml of this solution yielded a solid residue, weighing 0.9796 g. 

Each of the above liquid residues was tritrated against standard sodium hydroxide, using phenolphthalein as indicator. Identical titer values were obtained the same titer value was also given by the original solid residue of unreacted TBTA (0-1). Such an observation of identical titer Values should be expected if the conversion of TBTA, by reaction with sodium chloride, is solj.ly to TBTCl. However, any side reaction leading to TBT hydroxide or TBTO will result in lower titer values since these tin compounds, unlike TBTA or TBTCl cannot be titrated like weak acids. Clearly, the side reactions are not noticeable in these experiments. Hydrolysis is not competitive under the conditions of this study, probably because chloride concentration never drops below 10-1 whereas hydroxide concentration is always below 10 s. (It was noticed that the pH of the aqueous layer in each case had risen from 6.5 to 9.0.)... 

After complete conversion, 0.9796 g TBTA (0-1) is expected to yield 0.8830 g TBTCl (0-2). Based on this, the fraction of TBTA remaining unreacted in each case is calculated, and from that the equilibrium constant, K (Table I). 

TABLE I. Interfacial Reaction1 Between TBTA and NaCl and Equilibrium Constant, K. 

Sample NaCl, wt% Time, h Residue2, R Unreacted % TBTA K... 

TABLE II. Interfacial Reaction Between TBTA and NaCl1. 

Concentration of NaCl solution = 4%, Volume of hexane solution = 200 ml, Concentration of TBTA = 51.4700 g/liter, area of contact = 180 cm2 in all cases all samples collected at the end of 7 days. 20n evaporation of 40 ml hexane solution. 

IR Spectroscopy. Samples of the hexane layer (8-4, 4-4, 2-4, 1-4), after evaporation of the solvent, gave IR spectra of mixtures of TBTC1 and TBTA. The amount of TBTA depended on the concentration of sodium chloride solution and its volume, as evidenced by the intensity of the broad peak at 1650 cm-1. 

The precipitates were collected in sintered glass crucibles, washed with alcohol, and dried in vacuum. The weight of silver chloride was 0.3488 g. Authentic samples of TBTC1 (M T Chemicals), when gravimetrically analyzed under identical conditions, gave an assay of 95%. Thus the conversion from TBTA to TBTC1 is 94% in sample 4-4. 

For the reaction product of TBTA/hexane and NaCl/H20. ZM = 326 3M = 291... 

Shen et al. [95] reported the first instance of SFC coupled to ICP-MS for tetraalkyltin speciation. The mobile phase used was C02. Tetramethyltin (TMT), tetrabutyltin (TBT), thetraphenyltin (TPT), tributyltin acetate (TBTA), and dibutyltin diacetate (DBTDA) were all resolved. C02 was also used as the auxiliary gas flow for ICP-MS. The Sn signal was optimized by adjusting the C02 flow and the rf forward power. The compounds were found to interact poorly with the stationary phase thus only TBT and TPT could be separated. No organic modifiers were added, however. Further organotin speciation studies by the same group... 

Esterification of Protected Peptides with TBTA General Procedure - ... 

Solns of the protected peptides (5-10%) in CHCI3/TFE/TBTA (7 2 1) were kept at rt until TLC probes indicated completion of the esterification (usually 1 h). The products were then precipitated by addition of iPr20 or MTBE, if necessary in a 1 1 mixture with hexane. 

TBTA = tris[(l-benzyl-l//-l,2,3-triazol-4-yl)methyl]amine... 

It is observed that, the reactivity of the photoinitiators is in the following order TBTA-3, TBTA-1 > TBTA-2 > TBTA-4. This reactivity order is presumably due to the stability of the intermediates formed in the reaction pathway. The more stable the intermediates formed during photolysis, the more prone the photoinitiator to initiate... 

Scheme 10.3 CuAAC-accelerating ligands of choice tris(l,2,3-triazolyl)methyl amine (TBTA), water-soluble analogues 11, sulfonated bathophenanthroline 12, tris(benzimidazole)methyl amine (TBiA) 13, and hybrid ligand 14.

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