Results from the NAUTILUS three stage chemical evolution model. The solid blue and red lines represent the time evolution of the CH₃OH and CH₃CCH abundances, respectively. The blue and red dashed horizontal lines indicate the minimum and maximum observed abundances for CH₃OH and CH₃CCH, respectively, in AFGL 2591. The dotted black line indicates the minimum and maximum observed abundances in IRAS 20126. The left panel shows the shock stage and the right panels show the post shock stage for three different temperatures.