Question

R-OH + NaOH --> no reaction
Ph-OH + NaOH --> Ph-ONa + H-OH
..why??

Answer 1

R -->aliphatic (Electron releasing group)
Ph --->Electron withdrawing group which makes OH group more acidic.

Making it more acidic implies Ph-OH is stronger acid than R-OH and as we know strong bases react with strong acids only

Answer 2

R-OH is acidic too, nai? so, why doesnt it react? ..weak acids also react with strong bases!

Answer 3

Nope R-OH is not at all acidic. The best way to analyse the acididty of a compund is how stable would the compound be when it loses the H atom.
In case of Ph-Oh, after losing H, it comes
\[Ph-O^-\]
Since Ph has electron withdrwaing effect, therefore it pulls the negative charge and thus stabilises the compound formed.

But in Case of R-OH, it becomes
\[R-O^-\]

Since R is electron releasing group, it further increases the negative charge on oxygen, making it unstable and hence reducing the ability to give off H and thus less acidic than Ph-OH