Chemical Reaction

Archive for ‘ December 2011

12/24/11 - Acyl Imidazolide Formation from Carboxylic Acid

    I apologize for my absence in updating this blog as I have just finished exams and I have now been frantically getting ready for Christmas while working everyday.  The reaction for this christmas eve is one that describes the synthesis of an Acid Imidazolide, which can be used in claisen like reactions due to the fact that the Imidazole acts as a good leaving group. All that is required in this reaction is to react the carboxylic acid with Carbonyl Diiamidazole (CDI), alleviating carbon dioxide and an imidazole molecule.

12/23/11 - Acyl Imidazolide Formation from Acid Chloride

   This reaction is acid imidazolide synthesis from the addition of and acid chloride to an imidazole molecule.

12/17/11 - Metal Reduction of Conjugated 2-Decalones

   As a means to regeochemically select an enolate in a decalone it is quite easy if there is a substitution at the Beta carbon.  All that is needed is a lithium solution with liquid ammonia in the presence of tert-butanol to provide protons.  These reagents create a solution of electrons which radically charge the beta position which then is pushed up to the alpha position and creating the enolate as the other negative charge is located on the oxygen, which is chelated to the lithium metal.

12/16/11 - Cyclopentadiene and Maleic anhydride

   This little snippet of a reaction was taken from an old exam for the course that I am studying for right now.  It involves a diels alder reaction between a cyclopentadiene and Maleic anhydride.  Here the diene is the cyclopentadiene (this molecule goes through diels alder reactions with itself so it is necessary to heat it above 160*C to reverse the reaction) and the dienophile as the Maleic anhydride.  This is the first step where the reaction goes as a 4π+2π endo reaction as a pericyclic reaction.  Then the second step will remove the diester as it also reduces the C=O into alcohols.  Then the final step involves turning the alkene into a 1,2-diiodine when the alkene gets halogenated, and then intramolecularly the alcohol attaches to the other point of halogenation.

12/15/11 - Sharpless Perruthenate Oxidation

   This oxidation reaction is used to turn primary or secondary alcohols into aldehydes or ketones accordingly.  The reactants involved in this reaction are the addition of (Ph3P)2RuCl2 and N-methylmorpholine-N-oxide, or also known as NMO.  What happens here is that the NMO causes the activation of the Perruthenate by oxidizing it, and then the Perruthenate continues to oxidize the alcohol which being bonded to the oxygen of the alcohol.

12/14/11 - Swern Oxidation

     Here is the second oxidation reaction, a more modern method which involves the activation of the DMSO molecule by the oxalyl chloride, which results in the addition of a chloride to the DMSO and then causes the DMSO to add to the alchohol and removing one of the alpha hydrogens.  Turning the alcohol into an aldehyde (or secondary alcohol into a ketone).

12/13/11 - Parekh-Doering Oxidation

     This oxidation reaction is used in many stereospecific molecules to make sure that the stereochemistry is not compromised during the oxidation.  This reaction is used to turn an alcohol into a ketone (secondary OH) or aldehyde (primary OH).  This technology requires the addition of DMSO with pyridine-SO3, which causes the activation of the DMSO, and triethylamine.

New Science

    This TED talk, I hope, should begin to inspire scientists and researchers into starting to think of science as a whole instead of keeping it as a personal feat.  At this day and age, with these wondrous technologies at hand, we should gain our glory from helping build this knowledge instead of sitting and being devoted to increasing the number of journal articles we have published.

12/2/11 - Creation of the Evan's Auxiliary Enolate

    This reaction works much like the selectivity within amide enolate formation, where the enolate forms in the Z formation where the R group of the enolate is eclipsed by the carbonyl.  And this reaction here causes the Evans imide to form the Z enolate selectively due to the lithium metal being an oxophilic agent to both of the carbonyls there, making sure that the bond between the N and the alpha C of the carbonyl doesn't rotate.  Now this molecule is ready to be put to use in an enolate reaction.

12/1/11 - Insertion of an Evan's Auxiliary on an enolizable carbonyl

   When performing reactions requiring specific stereochemical products (ie for biomedical purposes) it is necessary to gain these stereoisomers in very efficient ways.  One method of posing stereochemical controls is to introduce a very bulky group, adding steric interactions with the substrate and the reactant causing the reaction to add in a certain facial attack.  Over the next couple of days I will describe a certain reaction adhering to this method, and I will start here by describing how to create a stereochemically controlling reactant.  Here is the Evan's auxiliary, which adds to a acid chloride (of which we are wanting to enolize in the future) by the addition of a base (to deprotonate the Evan's auxiliary), and this case it is triethylamine.

Paul Crichton. Powered by Blogger.

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I found myself blogging way too much in procrastination, so I felt it in me to create this blog to combine both my love for chemistry and my great skill of wasting time. I feel that scientific knowledge should follow along what wikipedia is producing; an open, free form for anyone to access, and I hope that this blog will bring this knowledge out to anyone who wishes to access it.

If anyone wishes to make a correction in any of my posts, or if they would like something more formally cited, please leave a message in the comments on that post and I will be more than happy to change it.