Sec-butoxy

A modified equation for the calculation of retention indices of mixed tetraalkoxysilanes from the retention indices of the symmetrical counterparts has been compared with earlier equations371. These methods have been extended to compounds which also contained branched alkoxy groups (isopropoxy, isobutoxy and sec-butoxy)371,420. The best agreement between experimental and calculated values for retention indices was obtained with Apiezon M stationary phase420. With cyanosilicone EX-60 stationary phases, good agreement in retention indices was obtained only for tetraalkoxysilanes that contain isobutoxy groups. 

In general, there is a fair correlation between increasing stability of the carbon radical formed and increasing ease of j3-cleavage [112] loss of an ethyl group from the f-amyloxy radical is about four times faster than loss of ethyl from the less-hindered sec-butoxy radical [35,107], both at 100°C. 

The same authors studied the synthesis of 2-alkoxy-5-n-propyl- or 2-alkoxy-5-sec-butylphenyl methylcarbamates as active intermediates for insecticides [218]. This involved phosgenation of the substituted phenol, followed by aminolysis of the formed chloroformate with monomethylamine. As already discussed, methylcarbamates can also be synthesized by reacting the appropriate phenol with methyl isocyanate. Thus, 2-isopropoxy-5-sec-butylphenyl chloroformate was synthesized by treating 2-isopropoxy-5-sec-butylphenol with phosgene. The product was reacted with monomethylamine to obtain the desired 2-isopropoxy-5-sec-butylphenyl methylcarbamate. Similarly, 2-sec-butoxy-5-sec-butylphenyl methylcarbamate, 2-iso-propoxy-5-n-propylphenyl methylcarbamate, and 2-sec-butoxy-5-n-propylphenyl methylcarbamate were also synthesized. 

Table 82 gives the retention indices for AI values of tetraiso-propoxy-, tetraisobutoxy-, tetra n-propoxy and tetra-sec-butoxy silanes. For comparison, the data for corresponding normal tetraalkoxysilanes, taken from the work of Ellrdn et al 02 also given. The retention indices of the branched compounds are considerably lower than those of the normal compounds, which was to be expected because of their lower boiling points. The marked difference between the AI values of normal and branched compounds reflects the increased shielding of the polar Si-0 and C-0 bonds in the latter, which increases their activity on the polar XE-60 stationary phase. 

The best agreement between experimental and calculated values was obtained for Apiezon M retention indices, the mean deviation being about 3 index units. Thus, it appears that the method used gives an at least approximately correct value for the correction term for the type of compound studied. For 5 of the 28 compounds, the deviation is 6 index units or more. All of these compounds contain sec.-butoxy groups. This deviation is considerably greater than the error in the retention index measurement, and it is concluded that equation (2) is less suited for the calculation of Apiezon M retention indices of mixed tetraalkoxysilanes with sec.-butoxy groups, than for those with isopropoxy or isobutoxy groups. 

As the calculated values for sec,-butoxysilanes are always too high, it is obvious that a better agreement should be attained by using smaller k d values for the combinations methoxy-sec,-butoxy and ethoxy-sec,-butoxy respectively. 

Obtained by reaction of ethyl 4-sec-butoxy-2-hydroxy-6-methylbenzoate with sodium methylsulfinylmethide [5586] according to [5587],... 

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