is multistep synthesis?
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.
are multistep synthesis problems
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.
an acceptable answer to these problems?
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.
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.
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
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).