Wich is the most corrosive acid/alkali

Probably

the mixture (FSO₃H-SbF₅) known as magic acid

and the cyclohexane pka =52 (Heathcock) as base

 

 

as single isolable compoud

Corrosive cyclohexane? Are you sure?

base C₆H₅^- Na+ (for example) I said ----> (C₆H₆) pKa=52

 

Heathcock Chemistry book

base C₆H₅^- Na+ (for example) I said ----> (C₆H₆) pKa=52

 

Heathcock Chemistry book

 

That isn't cyclohexane though, is it. In fact it's not even close, since the molecular formula for cyclohexane is C₆H₁₂.

 

What you've written down could be any number of chemicals. Not only that, but I sincerely doubt that what you've drawn has a pKa of 52. LDA, an incredibly strong superbase and one that would be much stronger than whatever you've drawn, only has a pKa of 36. I suggest you reread your text book or get a new one.

Those might be very strong acids + bases but that's not what's asked for.

The question of how corrosive something is depends on what you are trying to corrode.

 

I can get a glass beaker, fill it with hydrochloric acid and put some steel in it and watch the metal dissolve.

Or I can get a copper beaker, fill it with hydrofluoric acid and put a glass marble in it and watch the glass dissolve.

 

Which acid is more corrosive?

It depends.

 

Incidentally, if we ignore the cyclohexane/ benzene cock-up, he still has a point. Phenyllithium or phenylsodium is still a stronger base than LDA.

Alkyl lithium reagents can have pKa values of 50 or more.

Edited February 3, 201312 yr by John Cuthber

I realised LDA was a bad example after I posted it. Regardless, phenyl lithium has a pKa somewhere in the 40's (IIRC). I wouldn't expect the sodio derivative to be more basic.

I couldn't find data for cyclohexyl sodium, but I suspect it's nearer 50 than 40.

Of course, these numbers are a bit suspect anyway.

 

The point remains that a solution of butyl lithium in cyclohexane probably won't chew holes in your skin much faster than saturated caustic soda.

The point remains that a solution of butyl lithium in cyclohexane probably won't chew holes in your skin much faster than saturated caustic soda.

 

Agreed. The OP is a little ambigious (as you noted before), though I suppose it could be an issue of misusing the term, 'corrosive,' without realising that it is not the same as asking about acid/base strength.

Yes, sorry

 

I wrote down the wrong formula and I have a PhD too. I am ashamed as a thief!

 

C₆H₁₁^-Li⁺ have to be right, (I hope this time)

 

Any way, over 14 values, basicity depend on the solvent used that is different from the water. The absolute value has little importance. In the scale that I have found this is the strongest base.