Chem 351 Fall 2007 MT Mechanism

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 (that means they don't know their nomenclature well enough). Read the words carefully, and then make the curly arrows tell that same story. There is NO need for extra steps. Remember curly arrows go from electron rich to poor and to balance the formal charges at each step - errors on formal charges were common.

mechanism

If you struggled with this part of the question, first draw the compounds whose names were provided, then think about the types of reactions (e.g. acid / base) and try to fill in the structures in the gaps, then finally add the required curly arrows to account for all the bonding changes.

via primary carbocation

1-phenylpropene reaction

Common errors:

could not draw the correct structures of the alkene starting materials or the product ether
could not draw sulfuric acid correctly and worse, didn't know the molecular formula of sulfuric acid
drawing structures that break valence rules
drawing a carbocation that was not tertiary (read the question)
incorrect formal charges (extra or missing)
incorrect, vague or backwards curly arrows
showing extra steps not described in the question (so in effect answering a different question)

b. Did not read the question and did not use part a as the basis of working out part b.

c. Could not draw the starting material correctly given the name. Did not read the question and did not use part a as the basis of working out part c.