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.
A question I hear a lot from chemists is “how much can I load”. The answer is always “it depends on your separation quality”. At that point I begin asking about the TLC data and purification goals. Purification goal setting should be your first step and the question to answer is – what do I need this purification to achieve? Is the goal high purity, high yield, or some combination. Remember, you will typically sacrifice purity for high yield and yield for high purity so optimization is an important consideration.
Synthetic organic chemistry is the genesis of new pharmaceutical and commercial chemical products. In short, it is based on the idea that two or more carbon-based compounds can be forced to react using heat, or other energy source, to create a new, novel product – but this we already know.
How to choose between normal- and reversed-phase flash column chromatography is an excellent question and one that my readers often ask. Those who use column chromatography know that as long as the reaction products or compounds are fairly non-polar and near neutral pH they will have successful purifications. However, when your mixture's chemical characteristics are more challenging (polar, non-polar, basic, acidic) there are other options that are available to successfully separate pure compounds.
In this post, I will discuss the criteria you can use to guide your choice between normal- or reversed-phase flash chromatography.
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Creative productivity is the ability to find innovative ways to keep projects moving forward, including finding a way around the roadblocks that will inevitably show up as you go. So the real measure of productivity is not in molecules per day, but in your ability to find the synthetic pathway. Instrument manufacturers tend to want to tell you about the latest user-friendly ultra-fast instrument. Faster is nicer, but if you can cut 30 seconds off a column chromatography step, what does it matter when the reaction refluxed overnight and the reaction didn’t work? The thing is, many of the reliable techniques you apply to your organic chemistry work are considered unchangeable. There may be a better way, but that takes time and feels risky. So, you continue on, using what you learned as far back as college chemistry.
