Part 7 : MECHANISM

The following diagram shows the solution to the mechanistic question. Note that all the information applies to a single reaction sequence that has been completely described verbally.  There is no need for extra reagents or extra steps etc. The curly arrows are drawn specifically to match the text in the question. The biggest problem students have is making sure they understand the language of chemistry. Most students have trouble because they can't draw the structures from the IUPAC names. Read the words carefully, and then make the curly arrows tell that same story.  Remember curly arrows go from electron rich to poor and to balance the charges at each step.

mechanism scheme

Since the thermodynamic data shows that the E-isomer has a less exothermic heat of combustion, it tells us the the E-alkene is more stable than the Z-alkene.
Hence, this type of elimination reaction is controlled by the product stability, i.e. the major product is the more stable alkene.

E- and Z-alkenes are examples of geometric isomers.