is also contemplated that carbon monoxide can be formed in situ by a chemical reaction e g by the decomposition of formic acid into carbon monoxide and water in accordance with the practice of this process the saturated aldehyde non adjacent dihydric alcohol and hydrogen fluoride are fed to the reaction zone at a mol percent of from about 5 to about 35 aldehyde from about 5 to about 35 alcohol and from about 50 to about 90 hydrogen fluoride the reaction product comprising a di alkoxycarboxy hydrocarbylene can be purified using conventional methods the following examples illustrate the process of this invention those familiar with the art will recognize that various modifications are possible a 300 m1 magnetically stirred stainless steel autoclave was charged with 0 4 mol of formaldehyde trioxane 0 2 mol of 1 4 butanediol and 50 grams of hydrogen fluoride the autoclave was pressured to 1000 psig with carbon monoxide the reaction mixture was stirred for 55 minutes during which time the temperature rose from 18 u00b0 to 29 u00b0 c after removal of hydrogen fluoride the crude product was analyzed and found to comprise the same autoclave used in example 1 was charged with 0.