The past week I’ve kept looking into the paraldehyde depolymerization, although it’s now out of personal interest than intended usefulness.
The article “Paraldehyde as an Acetaldehyde Precursor in Asymmetric Michael Reactions Promoted by Site‐Isolated Incompatible Catalysts” is an extension of previous work by the authors to perform Micheal reactions using paraldehyde as a source of acetaldehyde. They have a two-step process: convert paraldehyde to acetaldehyde, and then react acetaldehyde with trans-β-nitrostyrene (see below)
Each step requires a different catalyst: an acidic catalyst to break up the paraldehyde (as we saw last week) and a basic catalyst for the addition. Most times, adding acid and base together gives you a neutralization reaction (which is what happened when they added a homogenous acid and heterogeneous base catalyst). By isolating a heterogeneous acid catalyst from the heterogeneous base catalyst with liquid permeable membranes (read: tea bags), they were able to both create acetaldehyde in situ and create the Micheal addition product. Fan et al. did carry out the reaction in dichloromethane, and fund the bets results were in an anhydrous and deoxygenated atmosphere, achieving 91% conversion! The acid catalyst they used is a sulfonic acid on resin but they don’t specify further.
This paper interested me because it seems to directly relate to some of my goals, and offers a unique solution for solving the paraldehyde problem. Scientifically, it seems sound. As a paper, there are stylistic decisions I take issue with. The authors commonly used first person, referred to themselves through “to our delight,” “as expected,” and often started sentences with “it.” Maybe the article being labelled as “Communication” has to something to do with the informality, but the author was very lax with some of the fundamental lessons I got for scientific writing. Don’t include yourself, don’t include your feelings, and if you’re starting with it, you’re not specific enough (have you noticed how hard I’m trying to avoid using it right now?). With the other articles following these conventions, it was almost jarring to see those asides.
Putting that behind us, another article I’ve read is “Characteristics of Chemical Heat Pump through Kinetic Analysis of Paraldehyde Depolymerization.” If you recall from my last literature corner, there was a paper by that did not cite any source for using Amberlyst 15E as the acidic catalyst. If you don’t cite prior material, you should explain the logic for choosing that particular catalyst (even if it’s to say it performed best compared to others). One of the primary takeaways in this paper is that overall, increasing the temperature pushes the equilibrium towards acetaldehyde. The one step that is exothermic and benefits from colder temperatures is the adsorption of the paraldehyde onto the catalyst surface, but in comparison to changes seen in the occur constants, the negative effect is out-competed, especially in high concentrations of paraldehyde. Additionally, having less acetaldehyde increases the depolymerization rate of paraldehyde, but that seems obvious given this is an equilibrium reaction.
Last article is about the McDonald’s Monopoly game, and how someone was able to rig it to make a lot of money. Not only that, but other contests as well such as an M&M grey candy contest, all to being in the right place at the right time and being willing to abuse that power. It’s an interesting read, definitely something you should spend some time on.
I didn’t realize how often I’ll read an article where I’ll later realize that I can’t include it here, or how some of the lessons I learn will offer too much insight into what I’m doing at work. So please bare with me if the details seem sparse or if there’s only a few articles.