5-Amino-1-pentanol

5-Amino-1-pentanol is an amino alcohol with a primary amino group and a primary hydroxy group at the ends of a linear C5-alkanes. As a derivative of the platform chemical furfural (that is easily accessible from pentoses), 5-amino-1-pentanol may become increasingly important in the future as a building block for biodegradable polyesteramides and as a starting material for valerolactam — the monomer for polyamides.

Occurrence and preparation
The complete hydrogenation of furfural (furan-2-aldehyde) yields tetrahydrofurfuryl alcohol (2-hydroxymethyltetrahydrofuran), which undergoes ring expansion upon dehydration to give dihydropyran. Dihydropyran reacts with ammonia in a reductive amination under ring opening to produce 5-amino-1-pentanol.



Product yields of up to 85% can be achieved with a continuous process using a nickel-hydrotalcite catalyst.

Similarly, the hemiacetal 2-hydroxytetrahydropyran that is formed from dihydropyran with hydrochloric acid can be converted to 5-amino-1-pentanol by reductive amidation with ammonia and hydrogen upon water elimination.



Properties
5-Amino-1-pentanol forms white crystalline clumps at solidification temperatures around 35 °C, which dissolve in water, ethanol, and acetone. The aqueous solution (500 g-l−1) reacts strongly alkaline (pH 13.2 at 20 °C).

Reactions
Amino alcohols such as 5-amino-1-pentanol have been studied for their suitability of absorption of carbon dioxide.

5-Amino-1-pentanol dehydrates when heated over ytterbium(III) oxide (Yb2O3) to give 4-penten-1-amine (I). Also formed piperidine (II), 2,3,4,5-tetrahydropyridine (III), and 1-pentylamine (IV).



Being bifunctional, 5-amino-1-pentanol reacts in a polycondensation reaction with esters of dicarboxylic acids (or their cyclic acid anhydrides, such as succinic anhydride) to give polyesteramides. These polymers have been investigated as biodegradable plastics, e.g. absorbable sutures. During the reaction, the succinic anhydride reacts initially with the nucleophilic amino group to form an ω-hydroxycarboxylic acid, which is subsequently polycondensed with carbodiimides, such as the hydrochloride of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimides (EDC-HCl).



In a dehydrogenation, catalyzed by rhodium and ruthenium complexes, valerolactam, the δ-lactam of 5-aminopentanoic acid, is formed from 5-amino-1-pentanol in high (94%) yield.



Valerolactam could be of relevance for polyamide 5. Polyamide 5 has garnered little attention so far but is of interest due to its ferroelectricity.