What are the strong acids?
This is a helium hydride ion (HeH+). It is technically* the strongest acid in existence.
Now you may be thinking something along the lines of: “Wait a minute, I thought helium was a noble gas and so didn't bond with anything!”
I hate to tell you this but what you learnt in school was wrong.
Helium hydride is formed in the decay of tritium and many believe that it is found in the interstellar medium (the matter that is found between star systems in galaxies), although, none has been observed there.
It is also possible that it was the first compound in the universe because when the universe became cool enough for ions to form, only hydrogen and helium (and a little lithium) were present. These ions of helium hydride would later cause the formation of the first stars.
So how is it the strongest acid in existence?
To find the acidity of helium hydroxide, the proton affinity test is used, this measures the amount of energy released when the substance reacts with a proton. The lower the amount of energy released, the stronger the acid.
Helium has the lowest known proton affinity and therefore helium hydride is the strongest known acid. It is in fact so reactive that it can not actually be measured with the normal pH scale.
Helium hydride still remains a bit of a mystery to scientists. It is tough to spot via spectroscopy and should be seen easily given that current models suggest that there should be lots of it. The other compounds suggested by the models have been found so why not helium hydride? Maybe it isn't quite as stable as we thought.
Because helium hydride is so integral to our understanding of how the first stars were formed, if it has different properties to what we think now it would cause us to have to rewrite our ideas of how the first stars and galaxies appeared.
As I said in another scientific answer, if anything is wrong, please tell me and I will correct it.
Why do phenol not react with hydrophobic acid?
Phenols can't be dehydrated by treatment with acid and can't be converted into halides by treatment with .
This is because Phenols do not give protonation reactions readily.
Phenols resemble aryl halides in that the functional group resists displacement. Unlike ROH, phenols do not react with to give aryl halides,
These observations are related to shorter and stronger C-O bond in phenols as compared to alcohols and as a result, C-O bond in phenol is “not” cleaved easily.
Also, remember that cleave of C-O bond in alcohols require protonation or similar electrophilic attachment on basic oxygen of alcohol which converts a strongly basic and hence poor leaving group -OH into a better leaving group.
This is primarily owing to
(a) In phenols, even the basic character of oxygen is decreased as the lone pair of oxygen is involved in resonance with the benzene ring and also C-O bond acquires partial double bond character.
(b) sp2 carbon of phenol cannot undergo nucleophilic substitution by simple SN2 because of no possibility of back side attack .
(c) Phenyl cations are very less stable hence even SN1 is ruled out. Phenyl cation is less stable than even a primary carbocation. Because the positively charged carbon of a phenyl cation is constrained within a six-member ring, this intermediate is even further destabilized by angle strain. The phenyl cation is therefore even less stable than the vinyl cation. [Aromatic diazonium salts, on the other hand, form phenyl cations upon releasing N2 due to increased entropy factor).