Q: “I am in organic chemistry 2 and I am trying to learn how to predict the products.”

One of the most challenging, but ultimately the main goal, of organic chemistry is to take an abundant, cheap starting reactants and transform it into a biologically active or synthetically useful product.  In the two semesters of organic chemistry, you will learn reactions that will produce all of the functional groups that give molecules these useful properties. But as a chemist, it is very importantly to accurately predict how and in what yield these reactions will produce you desired products.

The stakes seem higher when you are given less than 2 hours to complete several multi-step synthesis problems that often ask to identify not only reagents but the mechanism of each step of the reaction.  We here at StudyOrgo have compiled advice and guidance for learning to tackle these problems.

1. Relax!
2. Understand that each step in a synthesis reactions can be broken down into two basic types of reactions;
   1. Change in the carbon-carbon skeleton: Take a look at the starting material and the final product. Count the carbons, is there a difference in number?  If so, then you will need a carbon-carbon bond breaking or addition reaction.  There are only a few examples of these reactions so that instantly narrows down reactions you have to focus on.
   2. Change in the identity or location of a functional group: This is the most common synthesis question. Remember, that the pathways from one functional group to another are limited.  Set up a reaction roadmap or use included with your StudyOrgo membership to help you memorize what reactions can be used to get you to your final functional group.
3. There are often times MANY routes to get to a final product. ALL OF THEM ARE CORRECT, if in fact the route is possible.
   1. HINT: Professors will only ask you to use reactions they have covered in class. Make a list and indicate what the reaction does to help you memorize the products.
4. Sound out the problem. Often time students have a viable synthesis approach, but get held up at one or two places and just leave the entire question blank. Remember, it is multistep, which means there are many places to get points!  Draw out what you know.  Worst-case scenario: you get partial credit.  Best case scenario: you realize what reaction is next and get full points!!
5. Practice, practice, practice! Make sure to perform all of your practice problems assigned to you for each chapter.  It takes a lot of time and effort, but likely these examples will be used by your professor.  Also, the more examples you see the less surprises will be on the exam!
6. Sign up with StudyOrgo for help! The Editors at StudyOrgo have spent numerous hours reviewing and preparing the material in the most crystal-clear and “get-to-the-point” manner as possible. We provide quick descriptions and in-depth mechanism explanations. Many of our reaction have multiple examples, so you can learn and then quiz yourself in our website! For the student on-the-go, we have also developed a mobile app (iOS and Android) provides all the functionality of the website! All of these benefits are included in your StudyOrgo membership!

Many students taking Orgo 1 have commented there are a few types of reactions the professors save to the end of the semester and cover quickly and “gloss” over or sometimes skip all together in the interest of time.  However, in Orgo 2, you will be responsible for all of the reactions necessary for multi-step synthesis (starting product known to get to unknown final product) and retrosynthesis (product known to get to unknown starting material) reactions.  We at StudyOrgo don’t want you to get stuck on trying to cram for exams by studying reactions that were poorly covered in your class.  In this article, we focus on epoxide formation and epoxide ring-opening reactions because of their usefulness in synthesis and industrial application.

Epoxide Formation

In order to form an epoxide, a electron-rich reagent is required, such as an alkene.  Formation of the epoxide occurs in the presence of a peroxide reactant, such as MCPBA or DET.  The choice of reagent depends on the stereo-specificity desired from the reaction.  MCPBA is used to add the epoxide symmetricaly across the double bond, so that substituents that are cis- or trans- remain in this configuration.  The Sharpless asymmetric addition allows the researcher to choose a stereoisomer of DET, referred to as (+) and (-).  This reagent allows for the attack of the peroxide intermediate on only one face of the alkene, allowing for the production of nearly pure enantiomeric excess product, generally >98%!

Ring-opening Reactions

Many of you have probably hear of epoxy-glue, which is a very strong binding agent.  The process usually involves mixing two reagents and you must quickly apply the mixture to the broken items before the expoxy hardens.  One tube will contain the resin, or epoxide, while the other contains the “hardening” agent, which is the nucleophile that will attack the epoxide.  In a ring-opening reaction, a molecule such as TETA, which contains 4 amino groups, will attack 4 equivalents of oxirane to produce a complex polymer, which is the basis for a strong glue.  Changing the size and complexity of the epoxide can allow for flexibility of strength, thermostability and rigidity!

We here at StudyOrgo have devoted countless hours to preparing complex reaction mechanisms in simple and easy-to-understand manner to help you maximize your studying.  Sign up with StudyOrgo for detailed explanations of epoxide reaction mechanisms and other essential Orgo 2 reactions today!