Process for the production of unsaturated ethers, in particular isopropenyl methyl ether (IPM), by pyrolysis of a ketal-containing or acetal-containing mixture, in particular dimethoxypropane (DMP), in the liquid phase in the presence of an organic carboxylic acid, according to the following reaction scheme: ##STR1## wherein R.sub.1 =H or alkyl with 1-8 C atoms; R.sub.2 =H, CH.sub.3 --, C.sub.2 H.sub.5 --, or Cl--; R.sub.3 =alkyl with 1-8 C atoms; R.sub.4 =H, CH.sub.3 --, C.sub.2 H.sub.5 --, or C.sub.3 H.sub.7 --, and R.sub.1 and R.sub.4 may be joined to form a 5-, 6-, or 7-membered ring. DMP is produced by the process from acetone and methanol by reaction in an acidic heterogeneous ion exchanger, the product being isolated by extraction with aqueous alkaline solution. In particular the process involves combining the IPM reaction product with the DMP reaction product, which permits the execution of a stable recycling process in which the methanol-containing streams of the IPM and DMP stages can be simultaneously extracted. The product may be isolated by the process by simple distillation of IPM from a mixture containing IPM, DMP and acetone.