The bane of organic synthesis for most chemists is purification rather than synthesis. Synthetic reaction mixtures are rarely devoid of impurities so some type of purification is necessary. Most often flash chromatography is used but for many chemists, it is less well understood than their chemical reaction and provides some level of anxiety.
In this post, I will summarize the five most important steps to creating a successful flash chromatography method and thus the anxiety associated with it.
Continue reading 5 Steps to successful flash chromatography
I have recently posted on how solvent choice influences the separation of hard to resolve compounds using normal-phase flash chromatography. As a chemist with an inquiring mind, I thought I would expand my research beyond normal-phase and see what happens in reversed-phase.
In this post, I share my results.
Continue reading How does solvent choice impact reversed-phase flash chromatography separations?
The challenges organic, medicinal, and natural product chemists face are many: from designing reactions, to optimizing synthesis, work-up / extraction, and purification / isolation of the desired compound or compounds. Among those issues related to purification / isolation is the common problem of separating compounds with similar chemistry that either co-elute or separate poorly.
In this post I will discuss some tips on how to “resolve” this issue (yes, pun intended).
Continue reading How can I modify my flash chromatography method to separate chemically similar compounds?
With most chromatographic purifications, only two solvents are needed to adequately separate compounds from each other. Unfortunately, there are instances where the separation is either poor or cannot be accomplished with “normal” elution conditions such as those with ionic or very polar organic molecules.
In this post I offer some solutions to this issue.
Continue reading Ionizable compound purification using reversed-phase flash column chromatography
Many microwave assisted organic synthesis (MAOS) reactions use polar solvents such as alcohols, DMF, DMSO, because they absorb and transfer microwave energy very efficiently. However, the downside of using polar, microwave absorbing solvents is that they can interfere with the flash chromatography that follows it injected directly onto a flash cartridge.
In this post, I discuss why dry loading can be advantageous when purifying polar-solvated reaction mixtures.
Continue reading When should I use dry loading instead of liquid loading with flash column chromatography?
Increasingly, organic and medicinal chemistry labs use mass-directed flash chromatography to isolate synthesized compounds. Mass-directed flash chromatography benefits are many, including collecting only the targeted molecule(s) in the reaction mixture. This approach simplifies compound purification since you know what you have made and it’s associated mass.
However, there are mass detection nuances that can be challenging. One of these is to know when an acid should be added to the mass detector’s make-up solvent to protonate targeted molecules. In this post, I will provide some insight on this topic.
Continue reading When should I add acid to my detector make-up solvent when using mass-directed flash chromatography?