At one time, a raw material for the production of hexamethylenediamine was the pentose-based polysaccharides of agricultural wastes, such as oat hulls. Treatment of these wastes with sulfuric acid or hydrochloric acid gives furfural. Decarbonylation of furfural over a zinc-chromium-molybdenum catalyst gives furan. Propose reagents and experimental conditions for the conversion of furan to hexamethylenediamine.

Furan is a five-membered ring heterocyclic compound containing an oxygen atom, and its structure can be represented as follows: Furan: C_4H_4O Hexamethylenediamine, on the other hand, is a linear, aliphatic compound with two amine groups at the terminal positions and is represented as: Hexamethylenediamine: H_2N(CH_2)_6NH_2

The transformation of furan to hexamethylenediamine can be achieved in two main steps: 1. Hydrogenation: Reduction of the aromatic ring to form a cyclic hexane structure. 2. Amination: Conversion of the six carbon cyclic structure to hexamethylenediamine by introducing amine groups at the terminal positions.

For each of the two reactions identified in step 2, we need to propose suitable reagents and experimental conditions. 1. Hydrogenation: Furan can be hydrogenated using a strong reducing agent like H_2 in the presence of a metal catalyst, such as palladium (Pd) or platinum (Pt) supported on carbon, or Raney nickel, under high pressure (e.g. 10 bar) and at elevated temperature (e.g. 100-150 °C). Reaction: C_4H_4O + 2H_2 ⟶ C_4H_8O 2. Amination: The hydrogenation product, tetrahydrofuran (C_4H_8O), can be aminated using a strong Brønsted-Lowry base like ammonia (NH_3) in the presence of a dehydrating agent such as phosphorus pentoxide (P_4O_10). The reaction can occur at high temperature (e.g. 250-350 °C) and under high pressure. Reaction: C_4H_8O + 2NH_3 + 2H_2 ⟶ H_2N(CH_2)_6NH_2 In summary, furan can be converted to hexamethylenediamine by hydrogenating the aromatic ring followed by aminating the obtained cyclic structure, using H_2 (in the presence of a metal catalyst) and NH_3 (in the presence of a dehydrating agent), under high temperature and pressure.