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I have tried to make sense of the article on fluorine on Wikipedia but I am still very perplexed.

I would like to know generally how reactive the fluorine compound β-(4-Fluorophenyl)-γ-aminobutyric acid; β-(4-Fluorophenyl)-GABA or "Fluorophenibut" would be as it passes through your body. Is fluorine a generally reactive element irrespective of what it is bound to or is it generally stable since it is bound to a carbon atom on an indole ring?

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    $\begingroup$ There is no such thing as generally reactive element. $\endgroup$ – Ivan Neretin Jun 29 '18 at 4:50
  • $\begingroup$ I don't mean generally in all cases.. I mean, how likely it would dissasociate from the carbon and react with other compounds in the body? $\endgroup$ – c73c Jun 29 '18 at 5:32
  • $\begingroup$ Quite totally unlikely. $\endgroup$ – Ivan Neretin Jun 29 '18 at 5:38
  • $\begingroup$ @c73c Differentiate flourine, inorganic flourides and en.wikipedia.org/wiki/Organofluorine_chemistry $\endgroup$ – Karl Jun 29 '18 at 6:41
  • $\begingroup$ I agree with @ivan-neretin, it is very unlikely the fluorine will be lost from this molecule $\endgroup$ – Waylander Jun 29 '18 at 7:06
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Fluorine the element is very reactive, but that doesn't mean its compounds are

Fluorine the gas is a very reactive element because it loves to take electrons from other compounds. But this is irrelevant to whether compounds containing fluorine are reactive. Consider the more common chlorine. Chlorine gas is less reactive than fluorine, but is still very reactive. It is a dangerous and corrosive compound that has been (and probably is still) used as a military weapon. But you encounter very unreactive compounds of chlorine every day. Common salt is a chlorine-containing ionic compound that makes up a significant portion of the electrolytes in your body; PVC is a fairly inert plastic made from a polymer containing chlorine carbon bonds.

The very reactivity of fluorine makes some of its compounds very unreactive. F-C bonds, for example, are very strong and often very unreactive even compared to other carbon-halogen bonds. PTFE (a long carbon chain with all the hydrogens replaced by fluorine) is a very inert polymer that is safe enough to use at the high temperatures achieved in frying pans, for example.

Some fluorine compounds are, however, very biologically active but not because their fluorines are "reactive". Fluoroacetic acid and its salts, for example, are dangerous (and naturally occurring) poisons. But their mechanism of action relies on their stability not their reactivity: they are similar enough to acetic acid that they get involved in the standard citric acid cycle but end up blocking one of the key enzymes to further reactions because the product is too stable.

Whether or not fluorophenibut is "reactive" in the body in the sense you mean is unlikely. It is a neurodepressant similar to gabapentin and pregabalin, though little is known about its safety.

Complicated molecules can't be judged as dangerous, safe or reactive just because of the elements they contain. You need to know the detailed and specific ways they interact with bodily processes. Prozac, for example, is a widely used anti-depressant that contains fluorine. Just because it does doesn't make it reactive or dangerous.

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The carbon-fluorine bond is very strong. The fluorine in a drug molecule is not going to get loose and attack other molecules in your body.

What it will do is park a very strong negative charge at one spot on the drug molecule. That is extremely handy for making a molecule bind to a target. As I understand it, that's why so many drugs include one or more fluorine atoms.

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