Explain each of the following facts with a mechanistic argument.

(a) When butyl methyl ether (1-methoxybutane) is treated with HI and heat, the initially formed products are mainly methyl iodide and 1-butanol; little or no methanol and 1-iodobutane are formed.

(b) When the reaction mixture in part (a) is heated for longer times, 1-iodobutane is also formed.

(c) When tert-butyl methyl ether is treated with HI, the products formed are tert-butyl iodide and methanol.

(d) Tert-butyl methyl ether cleaves much faster in HBr than its sulfur analog, tert-butyl methyl sulfide.

(e) When enantiomerically pure (S)-2-methoxybutane is treated with HBr, the products are enantiomerically pure (S)-2-butanol and methyl bromide.