O-Alkylation of thiotetronic acids gives a mixture of 2- and 4-position enol ether products. Comparison of the physical data revealed that UV spectroscopy was the most reliable method of distinguishing between these related ethers. We have determined that 4-position ethers have a distinct absorption between 235-240 nm, while 2-position ethers have two absorbance peaks, one between 205-220 nm and the other between 305-310 nm. This report describes the synthesis and unambiguous characterization of 2- and 4-methoxy-3,5-dimethylthiotetronic acids. The UV absorption properties of several other pairs of thiotetronic acid ethers confirm that these differences are general features that provide a simple method for distinguishing between 2- and 4-substituted isomers.

中文翻译：

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2-和4-烷氧基硫代强酸的合成及光谱鉴别。

硫代蔗糖酸的O-烷基化生成2位和4位烯醇醚产物的混合物。物理数据的比较表明，紫外光谱是区分这些相关醚的最可靠方法。我们已经确定4位醚在235-240 nm之间有明显的吸收，而2位​​醚有两个吸收峰，一个在205-220 nm之间，另一个在305-310 nm之间。该报告描述了2-和4-甲氧基-3,5-二甲基硫代反酸的合成和明确的表征。其他几对硫代磺酸醚的紫外线吸收特性证实，这些差异是一般特征，可为区分2和4个取代的异构体提供简单的方法。