Describe the nucleophilic reactions of ethers with $HX$ and provide examples.

(N/A) Reactivity of ethers with $HX$:
$(i)$ Ethers are the least reactive among all functional groups.
$(ii)$ Ethers react with excess hydrogen halides $(HX)$ under vigorous conditions to produce alcohols and alkyl halides.
$R-O-R + HX \xrightarrow{\Delta} RX + ROH$
$(iii)$ The order of reactivity of hydrogen halides $(HX)$ with ethers is $HI > HBr > HCl$.
$(iv)$ Ethers react with concentrated $HI$ or $HBr$ at high temperatures to cleave the $C-O$ bond,forming an alcohol and an alkyl halide.
$(b)$ Ease of $C-O$ bond cleavage and product formation:
$(i)$ In symmetrical dialkyl ethers,cleavage of the $C-O$ bond by $HX$ yields identical products.
$(ii)$ In alkyl aryl ethers $(R-O-Ar)$,the alkyl-oxygen $(R-O)$ bond is cleaved,resulting in the formation of $RX$ and $ArOH$ (phenol).
The $Ar-O$ bond is more stable and stronger than the $R-O$ bond due to partial double bond character. The weaker $R-O$ bond breaks,and the nucleophile $X^-$ attacks the alkyl group to form $RX$,while $H^+$ adds to the phenoxide oxygen to form $ArOH$.