There was, however, an alternative technology practiced by Celanese (USA) until 1981 in a plant with a capacity of almost 30000 tonnes per year. In this process, cyclohexanonc was first oxidized to caprolactonc (L$ Scction 10.3.1.2), which was then hydrogenated to 1,6-hexanediol in almost quantitative yield at about 250 “C and 280 bar in the prcsencc of, for example, Raney copper or copper chromite. o-Hydroxycaproic acid or adipic acid can also be used as starting materials for 1,6-hexanediol manufacture (c$ Section 10.1.1). Finally, 1,6-hexanediol was aminated with ammonia at 200°C and 230 bar in the presence of Raney nickel to hexamethylenediamine. The yield approached 90% and the main by-products were hexamethyleneimine and I ,6-aminohexanol: