( 2 ) Harvey, D., Chalkley, I)., Fuel 34,
Table VI.
Compound SnBra BuSnBrs Bu&Brz BuPSnBr BuaSn
Prepared and Observed Mole Per Cent Compositions of Butyltin Bromide Standards 1 and 2 Composition, Mole Per Cent Std. 1 Std. 2 Prepd. Obsd. Diff. Prepd. Obsd. Diff. 11 3.6 -8.4 18 7.0 -11 13 22 f9.O 11 21 10 40 41 18 18 21 30 +9: 0 28 40 +'12 25 14 -11 15 6.5 -8.5
RESULTS AND DISCUSSION
I n the early phases of the work, poor reproducibility of both the retention time and relative peak height of the first peaks in the chromatograms was evident. Reproducibility was improved considerably by consistently programming the column oven to 280" C., shutting off the controller, opening the oven and permitting it to cool for exactly 15 minutes (during which time the programmer was reset to 50' C,), closing the oven, injecting the next sample when the column oven temperature indicator reached 50' C., and then turning on the programmer. Through this technique, the elution temperatures of sample components were reproduced to within two degrees. The reproducibility of the relative peak heights is reflected by the reproducibility of the peak height calibration factors given in Table 111, where the greatest variation is *1.87,. I t is also to be noted from Table E11 that even though the concentration of the sample components varied from less than 0.1 gram to more than 2 granis per 100 ml. of solution, the calibration factors remained constant. Apparently, with a 3-gram sample diluted to 100 ml., the detector response is linear from as low as 3y0 to as high as 70% sample component concentration. Difficulties were encountered in working with the standard alkyltin bromide mixtures. Recovery data (Table V) show that the Grignard reaction is indeed quantitative and that no loss of sample occurred during other steps in the sample preparation procedure. Xevertheless, drastic differences between the added and observed quantities of all the components excluding the dibutyltin dibromide were noted in Standards 1 and 2 . By converting the weight per cent values to mole per-
+
centages, as in Table VI, the reason for these discrepencies becomes apparent, The molar loss of tin tetrabromide and tetrabutyltin is equaled by the gain of butyltin tribromide and tributyltin bromide. What has occurred is the room temperature reaction of equal molar amounts of tin tetrabromide and tetrabutyltin to form butyltin tribromide and tributyltin bromide prior to reaction with the Grignard reagent. The same redistribution reactions were encountered by Matsuda and Matsuda (5) during attempts to prepare standard solutions of other organotin halides. Standards 3 through 6 xere made to contain minimal amounts of either tin tetrabromide or tetrabutyltin and the agreement between observed and added concentrations is much better, Table V, but even here the observed values for tin tetrabromide and tetrabutyltin are consistently low and the observed values for butgltin tribromide and tributyltin bromide consistently high. Dibutyltin dibromide is the only material that does not take part in this redistribution reaction. The data obtained for this material are than more indicative of the accuracy of the method and the observed values are within lYO of the actual percentage in every case. Apparently, accuracy of the method is a t least as good as the precision with which the calibration factors for the butylmethyltin compounds can be determined. Such factors varied only d ~ 1 . 8 7over ~ a concentration range of 3 to 70%. ACKNOWLEDGMENT
The authors thank R . E. Wyant and J. F. Kircher for their helpful suggestions. LITERATURE CITED
E., Wurnik, M., Chem. Ber. 50, 1549 (1917).
( 1 ) Gruttner, G., Krause,
191 (1955). (3) Ingham, I
