

This reaction sequence proceeds as follows:
1. Formation of A (Grignard Reagent): Ethanol is converted to ethyl iodide via reaction with red phosphorus and iodine. Subsequently, ethyl iodide reacts with magnesium in dry ether to yield ethylmagnesium iodide (A), a highly reactive Grignard reagent.
2. Formation of B (Addition to Aldehyde): Ethylmagnesium iodide (A) undergoes addition to formaldehyde (HCHO), forming a magnesium alkoxide intermediate (B). This reaction elongates the carbon chain.
3. Formation of C (Acidification): Acidification of intermediate (B) protonates the alkoxide, resulting in propanol (C).
4. Formation of D: Propan-1-ol (n-propyl alcohol) is the final product, with no further reaction occurring.
Conclusion: The primary product, D, is n-propyl alcohol.
The correct order of the rate of reaction of the following reactants with nucleophile by \( \mathrm{S_N1} \) mechanism is:
(Given: Structures I and II are rigid) 