In each of the following reactions, a new ring is formed. Use curved arrow notation to explain the formation of the new ring.
a. `1,4-` Dibromobutance `(0.1 mol)` is treated with sodiuk suplhile `(0.1 mol)` in aqueous ethabnol.
b. `1-` Choloro `-2` (`2-` hyddroxyphenyl) ethane is treated with aquencous sodium hydroxide.
c. `o-` Methoxybenyl bromide reacts faster than `p-` nitrobenyzl bromide with ethanol to form an ether product. Explain why.
d. Explain the formation of the two products in the following reactions:

e. What mass of propene obtained from `34.0gm` of `I-` iodopropane on heating with ethanolic `KOH`, if the yield is `36%` ?
f. The nucleophilic substitution of primary alkyl chlorides with sodium acated acetate is catalysed by sodium iodide. Explain why.

Explanation

The electron-dontaing group `(-OCH_(3))` by resonance increases the stabiliy of benzyl of benyl carbonium ion, whereas the electron-withdrawing group [`(NO_(2))` group] by resonance decreases the stablity of benzyl carbonium ion. Hence, reaction `(1)` is faster than `(2)` with ethanol to give ether by `SN^(-1)` mechanism.
d.
Two products are formed due to allylic rearrangements.
e. `CH_(3)CH_(2)CH_(2)I underset(KOH)overset("Ethanolic")(rarr) CH_(3) CH = CH_(2)`
`Mw = 170 gm, Mw = 42 gm`
`170 gm` of iodopropane gives `42gm` of propene.
`34gm` of iodopropane gives `(42xx34)/(170) = 8.4gm`
If the yield is `36%` then `Wt`. of propene `= (8.4xx34)/(100)`
`= 3.024gm`
f. `R-Cl+CH_(3) - COONa rarr R - O - overset(O)overset(||)(C)-CH_(3) + NaCl`
This reaction is `SN^(2)`. Nuclophile is `CH_(3)COO^(@)`
But in alkyl chloride, `(C-Cl)` is a strong bond and is difficult to break. But in the presence of `Nal, (R-Cl)` is converted to `(R-I)` (Finkelstein reaction) and therefore, in `(R-1)` the `(C-1)` bond is weak, which can e easily cleaved. So `SN^(2)` reaction is cataysed in the presence of `Nal`.
`R - Cl + Nal rarr R - I + NaCl`