Thread: Why are catalysts so specific?

wherever i go looking for explanations they always say catalysts are

HIGHLY SPECIFIC

but it never explains

WHY

I don't think they are to be honest, though I suppose it depends what you mean by specific. Lots of catalysts will catalyse several different reactions that are fairly different from one another, so I wouldn't really say a catalyst is necessairly specific to one reaction if thats what you mean.

If you are talking about a catalyst being specific in that it always produces the same end product, then that is obviously a very desirable quality, but its something that can only be achieved through a lot of trial and error, it isn't something inherently true of any active catalyst. Some catalysts are more specific than others.

I would also add that it depends on substrate. The same catalyst can give different results based on the substrate. For example, we have been working with phase transfer catalyzed alkylation in my lab using cinchona catalysts. Usually cinchonadine gives one enantiomer and cinchonine gives the other, but occasionally we come across a substrate where both catalysts give the same enantiomer. Enzymes in the body however show much greater selectivity and specificity.

Thaiv kind of mentioned this right at the end... Enzymes can be catalysts, and they have specific binding/active sites that accept only specific types of substrate. Perhaps this is what you've been encountering.

Highly Specific simply means they are picky


A catalyst will usually only catalyse ONE chemical



for example enzymes are catalysts and Protease will only ever catalyse Protiens

It's not generally true that catalysts are specific. Sulfuric acid could catalyze many types of reactions that require acid catalysts.

Going the other way, a reaction that requires an acid catalyst doesn't have to use sulfuric acid, it would be catalyzed by any (preferably strong) acid.