What is multistep synthesis?

Multistep synthesis is the process of taking a readily available compounds (ones you can buy) and converting them into desired products using known reactions. Multistep syntheses require more than one step, and so one or more intermediate compounds are formed along the way.

What are multistep synthesis problems

Typical multistep synthesis problems give a starting material and a product and instruct you to devise a route that takes the starting material into the product. For example, you might be asked to convert starting material W into product Z using reagents you've learned.

What's an acceptable answer to these problems?

The way to answer these problems is to show the reagents that convert the starting material into the intermediate compounds, and, finally, into the product. For example, if you were asked to convert compound W into compound Z, you might convert W into an intermediate compound (X), which could in turn be reacted to form another intermediate compound (Y), which could be reacted once more to form the product (Z). Note that no mechanisms (arrow-pushing) are shown for the individual reaction steps, just the reagents and any intermediate compounds formed along the way.

Six tips for working through multistep synthesis problems:

Multistep syntheses problems can be very challenging. So here are six tips that can aid you in solving these types of problems.

1. Know the reactions.
   
   This is the basic requirement. No matter how smart you are, you don't stand a chance on synthesis questions unless you know the reactions. Memorize the reagents, use flash cards, use whatever techniques you find most helpful, but get the reactions down cold. Since organic chemistry is a cumulative course, you can't afford to forget any reactions that have been previously covered, so never throw your stack of old flash cards away, but rather keep adding to the pile (the deck will be thick by the end of the course). Often, textbooks have end-of-chapter reaction summaries that can be helpful in making up flash cards.
   
   
   
   
2. Compare the carbon skeletons.
   
   Compare the carbon skeleton of the starting material to the product. Were any carbons lost or added? If so, can you identify where they were added or lost? A carbon count of the reactant and the product doesn't take long, but can help you determine what kind of reactions you are dealing with.
   
   Take the following simple example. The red portion of the molecule identifies where the likely carbon skeleton of the reactant is found in the product. Doing this allows you to clearly see what portion needs to be added or lost during your synthesis (it may seem trivial in this obvious example, but it can be a quite helpful to organize your thoughts in tougher problems).