# Can sugars dissolve in liquid ammonia?

Can monosaccharides and disaccharides dissolve in liquid ammonia due to hydrogen bond formation?

My rationale is that these sugars may be able to form hydrogen bond with ammonia ($$\ce{NH3}$$).

• Welcome to Chemistry SE! Adding your rationale as to what brought you to this presumption as well as literature precedents would increase the chances of a positive, descriptive answer here. – z1273 Mar 18 at 12:34
• Do you mean liquid ammonia or aqueous ammonia (ammonium hydroxide solution)? – Waylander Mar 18 at 12:51
• Liquid ammonia. – Soduthanthanakka Mar 18 at 12:53

Can sugars dissolve in liquid ammonia?

Yes, according to Ref.1, liquid ammonia is used to extract sugars in sugar-beet chips:

5.88 kilograms of sugar-beet chips having a moisture content of 5.4 percent and a saccharose content of 68 percent (calculated on the dried substance) are treated in an autoclave of 50-litre capacity with 18 kilograms of liquid ammonia. [...] The extracted pulp, after driving off the ammonia, contains only 1.2 percent of saccharose, which constitutes 0.4 percent of the total sugar.

Accordingly, 99.6% of sugar in sugar-beet chips are isolated in one extraction using liquid ammonia as the solvent. However, it was noted that the saccharose is not present as such in the solution, but is in the form of a compound of saccharose with ammonia. These ammonia-saccharose compounds can be obtained in a well crystallized form, which are composed of $$\pu{1 mol}$$ of saccharose and $$\pu{2 mol}$$ of ammonia and even those of other compositions Ref.1). I assume this is analogous to hydration by water molecules in aqueous solutions.

The high solubility of sugar in liquid ammonia seemingly due to H-bonding capabilities similar to water. This is evident by sucrose solubility in nonaqueous solvents such as morpholine (with a $$\ce{N-H}$$ bond) and N-methylmorpholine (without a $$\ce{N-H}$$ bond), which are $$39.8$$ and $$\pu{0.37 g}$$ in $$\pu{100 g}$$ of solution, respectively at $$\pu{85 ^\circ C}$$ (Ref.2). This difference in solubility is analogous to sucrose solubility in water and methanol, which are $$210$$ and $$\pu{1 g}$$ in $$\pu{100 mL}$$ of solution, respectively at $$\pu{25 ^\circ C}$$ (Wiki, and Ref.3). Further, sucrose is insoluble in diethyl ether.

References:

1. Georg Hingst, Werner Emte, "Process for recovering sugar from natural products containing it," US Patent 1958, 2,829,985 (Patent Application, 1955, US2829985A) (PDF).
2. Oleg K. Kononenko, Karl M. Herstein, "Nonaqueous solvents for sucrose," Ind. Eng. Chem. Chem. Eng. Data Series 1956, 1(1), 87–92 (DOI: https://doi.org/10.1021/i460001a017) (PDF).
3. Z. Bubník, P. Kadlec, "Chapter 5: Sucrose solubility," In Sucrose: Properties and Applications; M. Mathlouthi, P. Reiser, Eds.; Springer: Boston, MA, 1995, pp. 101-125 (ISBN: 978-1-4613-6150-3).
• Regarding the first reference: Bad Segeberg is the place of residence for Georg Hingst, so you would want to strike that. – njuffa Mar 18 at 21:18
• @ njuffa: Thanks for the notation. I thought it is the name of second author. I'll change it. – Mathew Mahindaratne Mar 18 at 21:38
• I admit I have never heard about this extraction on industrial level. – Poutnik Mar 19 at 8:29