P-dithianes

Disodium 1,2 ethanedithiol, 39, 23 Disodium monohydrogen phosphate dodecahydrate, 34, 83, 37, 74 Distillation, steam, of p dithiane,... 

Di- -propylcarbinol, 380 Di- -propylcyclopropene, 224 Disiamylborane, 57-59, 201, 262 Disodium phenanthrene, 350-351 Dispiro[5.1.5.0]tridecane, 1021 p-Dithiane, 1070-1071 5,5 -Dithiobis(2-nitrobenzoic acid), 351... 

NHs and H2S also undergo addition to ethylene oxide in the presence of NaX, but the initial addition products rapidly condense to produce heterocyclic molecules. At 340°, ethylene oxide and NHs produced piperazine, morpholine, and p-dioxane. Byproducts included ethylene and acetaldehyde, the latter arising from an isomerization reaction. HsS reacts with ethylene oxide at 200° to produce p-dithiane, p-thioxane, and p-dioxane, along with byproduct acetaldehyde. These transformations are summarized in the accompanying diagram. 

Crown thioether chemistry dates from 1886, when Mansfeld reported the synthesis of 9S3 [40]. To determine whether ring sizes greater than six could be prepared ( ) he allowed ethylene bromide to react with sodium sulfide. From this reaction he isolated a product that differed in properties from p-dithiane he suggested it might be 9S3 (Table 4). A similar procedure with 1,3-dibromopropane led to a compound tentatively proposed to be 12S3. 

In 1920 Ray published the first of a series of papers on 9S3 [41, 42, 43]. He reported that preparation of ethanedithiol (by reaction of ethylene bromide with potassium hydrosulfide) leaves behind 9S3 after distillation (Table 4). In contemporaneous work Bennett [44] and coworkers [45] used mixed melting point and cryoscopic molecular weight determination to show that Ray s product was in fact p-dithiane, not 9S3. In a similarly convincing fashion they also disproved Mansfeld s earlier claim for 9S3. Tucker and Reid [46] were also unable to repeat Ray s work. 

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