Question

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.

Short answer

Short Answer: To convert furan to hexamethylenediamine, follow these steps: (1) hydrolyze furan with hot KMnO4 in an alkaline environment to obtain muconic acid, (2) hydrogenate muconic acid using Pd or Pt catalysts and H2 to produce adipic acid, and (3) reduce adipic acid with LiAlH4 in ethereal solvents to obtain hexamethylenediamine.

Step-by-step solution

Understand the structures of furan and hexamethylenediamine.

Furan is an aromatic heterocyclic compound containing an oxygen atom. Its molecular formula is C4H4O. Hexamethylenediamine, on the other hand, is a diamine with the molecular formula (CH2)6(NH2)2. It contains two amine groups (-NH2) on either end of a six-carbon chain.

Perform hydrolysis of furan to produce muconic acid.

First, we need to break the aromaticity and add carboxylic acid (-COOH) functional groups to furan. This can be done by hydrolyzing furan using hot potassium permanganate (KMnO4) in an alkaline environment (e.g., NaOH). The reaction yields muconic acid (C6H6O4), a dicarboxylic acid with two carboxylic acid functional groups on both ends of the molecule.

Convert muconic acid to adipic acid.

Next, we need to reduce the two double bonds present in muconic acid. This can be achieved using metal catalysts like palladium (Pd) or platinum (Pt) on a support like carbon, and hydrogen (H2) in a high-pressure environment. The reaction will produce adipic acid (C6H10O4), a dicarboxylic acid with six carbons in the chain.

Convert adipic acid to hexamethylenediamine.

Finally, to obtain hexamethylenediamine, we need to change the two carboxylic acid functional groups (-COOH) present in adipic acid to amine groups (-NH2). This can be done through a reduction reaction. A common reagent used for this reaction is lithium aluminum hydride (LiAlH4) in ethereal solvents like diethyl ether or tetrahydrofuran (THF). The reaction yields hexamethylenediamine (C6H16N2). In summary, to convert furan to hexamethylenediamine, the proposed reagents and experimental conditions include hydrolysis with hot KMnO4 in an alkaline environment, followed by hydrogenation using Pd or Pt catalysts and H2, and finally reduction with LiAlH4 in ethereal solvents.