The invention relates to a process to separate butadiene dimers from a mixture comprising butadiene dimers and alkyl-3-pentenoate and/or isomers thereof wherein the butadiene dimers are separated from said mixture by distillation in the presence of an alcohol and in that the distillation is effected at a bottom temperature of between 80 and 200.degree. C. Examples of frequent occurring butadiene dimers are 4-vinylcyclohexene and 1,3,7-octatriene. Examples of the alcohol are monohydroxy aliphatic alcohols.