Exp048-rpg32report

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 * Doing the mechanism of imine formation is fine but use an example of alkyne addition to an aldehyde to compare with what we did in class, not E-2 or even SN2.

The first step of the Ugi reaction consists of reacting an amine and a aldehyde to form an imine. In several experiments, namely Exp048, Exp51, and Exp58, this reaction was studied using [|tert-butylamine] as the amine and [|piperonal] as the aldehyde. The way this reaction works is similar to many of the reactions we have studied. It involves a nucleophile attacking an electrophile. In this case the result is a nucleophilic addition. Here is an example where an alkyne reacts with an aldehyde:



Acetylide reacts with the aldehyde as an addition reaction resulting in an alcohol. This reaction is similar to the reaction that takes place for the formation of an imine. Here is the mechanism for the imine formation:

The methyl groups tend to get in the way of the reaction. In this case, the reaction is not altered, but the rate at which the reaction occurs is slowed. From Exp048 the reaction rate was determined to be 8.0*10^-3 [1/M*min]. When compared to the same reaction but using veratraldehyde for the aldehyde and 5-methylfurfurylamine as the amine the reaction with t-butalamine happened 14 times slower! It is not quite clear however, if the decrease in the reaction rate is strictly due to steric hinderance but the visual representation certainly makes it appear as though it would cause problems.