Refinery - 26-6-2020 at 05:47
It has always fascinated to me that could chemical synthesis be figured out if one knows enough chemistry and molecular reactions? If you give a
compound to a chemist and ask how it could be made, could they tell it by just looking at the structure?
And if, what is needed to learn this skill?
woelen - 26-6-2020 at 06:59
You need to know many different types of reactions and you need the capability to use these reactions in a step by step manner to achieve your goal.
Sometimes it looks straightforward to replace a certain small detail of a big molecule by something else, but in practice this may be very difficult.
It may be necessary to first add (or remove) other groups nearby to make replacement possible and then you need to restore the added (or removed)
parts. You also need to know about side reactions, giving undesirable other products and how to mitigate the risks about that.
All in all, designing a new synthesis can be a daunting task, and you may regard this as a puzzle for which the outcome is not (yet) known. A lot of
experience with this makes the process easier, but still, for complicated molecules, the design can be very complex, involving many steps.
Sometimes, it also can be very difficult to get very simple molecules or ions. A beautiful example is the synthesis of the perbromate ion, BrO4(-).
The bromate ion, BrO3(-), is known already for a very long time. The perbromate ion first was synthesized at the end of the 1960's, by means of
radioactive beta-decay of a certain isotope of selenium:
Se*O4(2-) --> BrO4(-) + e, here Se* is a suitable isotope of selenium.
Lateron, purely chemical synthesis methods were developed, using XeF2 or F2. Still not anything easy. Perbromate salts still are lab curiosities and
not available commercially, like bromates.
Chemorg42 - 26-6-2020 at 07:57
As to what you need to know to start understanding and planning syntheses, I recommend developing a comprehensive understanding of reaction
mechanisms, as well as different types of reactions. After that, you can begin to study individual reactions (and how they can be performed in the
home lab.)
In theory, you could just memorize a bunch of reactions, but if you understand mechanisms, you will have a much better theoretical grounding, which
will help you catch edge cases which would break a reaction.