This paper presents the development of a complex fine chemical process involving simultaneous reaction and fractionation. The synthesis of the ethyl eater of pentenoic acid CPA) involves the successive substitution of allyl alcohol (AA) for ethanol (EA) on triethyl orthoacetate (TEOA) followed by an in situ exothermic oxy-Claisen rearrangement of the mixed ortho esters. In this case study scaling-up is carried out from laboratory to production. The emphasis of the work is application of reaction engineering to a problem in reactive distillation. The use of data from automated reactor experiments to determine reaction kinetics is described. The subsequent use of the kinetics in a comprehensive simulation of the reactive distillation for scale-up and to establish safe, optimum production conditions is also described.The three important requirements for this process (i) a high conversion of triethyl orthoacetate to the pentenoic acid ethyl (PAEE) and allyl esters (PAAE), (ii) to achieve a high selectivity for the ethyl ester and (III) to minimise the excess of allyl alcohol used in each batch.At the commencement of the work, the selectivity for the desired ethyl ester was about 50 %, with similar yield of the unwanted allyl ester. At the end of the work, all the stated process requirements were met and the selectivity for the desired product was raised to> 98 % under production conditions.