Effectively, I am without technical library access. I get old texts, and it is from one such this preparation comes. Principles of Organic Chemistry, T.A. Geissman, W.H. Freeman 1962. Geissman devotes pages 126-130 to eight equilibrium reactions occuring in sulfuric acid mixed with ethanol. I give his section on diethyl sulfate:
At low temperatures, and with excess sulfuric acid, the chief constituent of the mixture is ethyl hydrogen sulfate, EtOSO3H. If the mixture is now heated under reduced pressure to a temperature at which diethyl sulfate, EtOSO2OEt, distils, the removal of the diethyl sulfate shifts the equilibrium EtOSO3H + EtOSO3- <--> EtOSO2OEt + HSO4- to the right, with the result that the overall equation
2EtOH + H2SO4 --> Et2SO4 + 2H2O
represents the result of the process as a preparative operation.
Then, after discussions of diethyl ether and of ethylene, Geissman presents a section called The Formation of Alkyl Sulfates:
Although a great deal of attention has been paid to the reaction of ethanol and sulfuric acid, this has been done primarily because that reaction is a good example of some important fundamental principles. Comparable reactions are shown by other alcohols. For example, dialkyl sulfates other than diethyl sulfate can be prepared in a similar manner. Dimethyl sulfate, (CH3)2SO4, is made by the reaction of methanol and sulfuric acid. Higher dialkyl sulfates (such as di-n-propyl sulfate) become increasingly difficult to prepare in good yield by this method, however, because as the boiling point of the desired dialkyl sulfate becomes higher with increasing molecular weight, the higher temperature required for their removal by distillation allows the side reaction of olefin formation to assume greater prominence, and, eventually, to be the principal reaction.
This, and a brief supporting comment in another text, led me to try it. As far as yields, well, ahem. Half-a-Pint's lab technique is a bit rough around the edges sometimes. Geissman implies fair yields are achievable with ethanol and methanol; but Half-a-Pint has a bunch of syringaldehyde to methylate, and needed some DMS PDQ, so decided to bull ahead with whatever works, and work on the technique and improving the yields later. 2 runs averaged 15%, not good, but I know it's sloppy to use recycled acid. Other details of trying to work out a prep also got in the way: the first run did not have enough excess acid, and lots of dimethyl ether went bye-bye before I noticed nothing much was condensing. Another run got lots of liquid (presumably water) in the KOH trap I was using to protect my vac from sulfuric fumes, had to be stopped before the pump aspirated caustic solution, and so forth, you know. Tell you what, I'll make a clean run and write it up in Chemistry discourse; I've already made ethyl sulfate by this route, so I'll try a clean run on that too.
turning
science fact into
<<science fiction>>
