The effect of structural factors on polymer formation versus cyclization is reported. The reaction of sodium sulfide with either 1,4-dibromobut-2-ene 1 or 1,4-dibromobutane 2 has been carried out in presence of a phase transfer catalyst and it was observed that the former yields polymer, whereas the latter gives cyclic and linear products. Interestingly, trans/cis isomerization takes place during the polymer formation from 1 and a plausible mechanism has also been discussed.