Organic Chemistry Help: Symmetric diols from the Pinacol reaction

Some of your professors will try to sneak this one in on you during an exam:  Your professor will ask you to synthesize the symmetric diol shown below and you will either not know how or you will come up with a convoluted, difficult or wrong answer. JUST REMEMBER: Symmetric diols came from the Pinacol reaction.

While not obvious, there is a very simple way to create a symmetric diol using the Pinacol reaction.  Using a number of reducing agents, ketones and aldehydes can be coupled with themselves to form a symmetric diol, as shown below:

The reaction is also called the Pinacol Coupling Reaction and can be used on most aldehydes and ketones, but not on acid halides or carboxylic acids.  Now to address the original synthetic problem above:

The first step is reaction of the reaction of ethyl lithium with ethanal to form 2-butanol.  This is then oxidized to 2-butanone using Jones’ oxidation.  Now, under Pinacol Coupling conditions, 2-butanone is then reacted with itself using magnesium to form the final product. 

Take Home Message:  Symmetric 1,2 diols came from the Pinacol reaction.           

For more organic chemistry help, go to organic chemistry

Dr. Michael Pa got a bachelors degree in chemistry from Binghamton University, a masters degree in organic chemistry from the University of Arizona and a Ph.D. in organic chemistry from the University of Arizona. His research focus was on novel pain killers which were more potent than morphine but designed to have fewer side effects. There may even be a patent or two that came out of it. Prior to all of this, he was a chemist at Procter and Gamble. After all of that, he (briefly) worked as a post-doctoral assistant at Syracuse University, working on novel organic light-emitting diodes (OLEDs). In between, he did NOT compete at the 1996 Olympics, make the Atlanta Braves opening day roster, or become the head coach of the Indiana Pacers, as he had intended. #fail During this entire time, he always loved helping students, especially if they were struggling with organic chemistry. In 2006, Dr. Pa founded in order to make learning organic chemistry fast and easy. 14 years and about 60,000 students later we are still helping students to learn organic chemistry one reaction at a time at

2 thoughts on “Organic Chemistry Help: Symmetric diols from the Pinacol reaction”

  1. Hello Dear
    please send me books about INORGANIC CHEM.& Books about symmetric in Inorganic chem.
    Thanks a lot

Comments are closed.