Organic Chemistry

107 How to write organic reactions

107.0.1 Writing General Chemistry Reactions

In organic chemistry, a reaction may be written precisely as it is for general chemistry if
only a basic amount of information is needed. For example, when a haloalkane is turned
into an alkene, the reaction may be written:

CH 3 CH 2 CH 2 Br + H 2 SO 4 + H 2 O --> CH 3 CHCH 2 + HBr + H 2 SO 4 + H 2 O

Unfortunately, this method of notation does not tell anyone very much about the reaction,
and it takes expertise to know exactly what is going on. A new student to organic chemistry
probably would not notice that the product molecule contains one site of unsaturation due
to a double bond between carbon atoms number one and number two. Because it is so
general, this notation is good for general chemistry, but organic chemistry requires more
precision.

For most students, common practices in writing organic reactions will be different than used
in general chemistry.

107.0.2 Differences in Organic Chemistry Notation

Organic chemistry reactions are oftennotwritten asbalancedequations. This is because
many organic chemists - who are just as lazy as anyone else - tend to be more interested
in theorganic productof a reaction than in anything else going on in the reaction. Side
products are often ignored, and just as often catalysts and solution notation may be highly
abbreviated or left out altogether. As you gain familiarity with organic chemistry you will
come to understand just what may be abbreviated or left out, but in the beginning this can
be a source of frustration.

Another difference is that modified Lewis drawings of molecules are often used instead of
molecular formulas. This makes sense due to the fact that organic molecules are often rather
large in size and complicated in structure, so that they can be more easily understood in the
form of a drawing as opposed to a word-formula. A two-dimensional drawing reveals some
of the three-dimensional shape of the molecule, but when necessary even three-dimensional
drawings are used to depict reactants and products.