Ammonolysis Explained

In chemistry, ammonolysis (/am·mo·nol·y·sis/) is the process of splitting ammonia into NH2- + H+. Ammonolysis reactions can be conducted with organic compounds to produce amines (molecules containing a nitrogen atom with a lone pair, :N),^[1] or with inorganic compounds to produce nitrides.^{[2] [3]} This reaction is analogous to hydrolysis in which water molecules are split. Similar to water, liquid ammonia also undergoes auto-ionization, ,^[4] where the rate constant is k = 1.9 × 10^-38.^[5]

Organic compounds such as alkyl halides, hydroxyls (hydroxyl nitriles and carbohydrates), carbonyl (aldehydes/ketones/esters/alcohols), and sulfur (sulfonyl derivatives) can all undergo ammonolysis in liquid ammonia.

Organic synthesis

Mechanism: Ammonolysis of Esters

This mechanism^[6] is similar to the hydrolysis of esters, the ammonia attacks the electrophilic carbonyl carbon forming a tetrahedral intermediate. The reformation of the C-O double bond ejects the ester. The alkoxide deprotonates the ammonia forming an alcohol and amide as products.^[7]

Of haloalkanes

On heating a haloalkane and concentrated ammonia in a sealed tube with ethanol, a series of amines are formed along with their salts.^{[8] [9]} The tertiary amine is usually the major product.^[10]

This is known as Hoffmann's ammonolysis.^[11]

Of alcohols

Alcohols can also undergo ammonolysis when in the presence of ammonia. An example is the conversion of phenol to aniline, catalyzed by stannic chloride.^[12]

ROH + NH3 A ->[\ce{SnCl4}] RNH2 + H2O

Of carbonyl compounds

The reaction between a ketone and ammonia results in an imine and byproduct water. This reaction is water sensitive and thus drying agents such as aluminum chloride or a Dean–Stark apparatus must be employed to remove water. The resulting imine will react and decompose back into the ketone and the ammonia when in the presence of water. This is due to the fact that this reaction is reversible:^[13]

R2CO + NH3 <=> R2CNH + H2O .

Inorganic synthesis

Ammonolysis can be used to synthesize nitrides (and oxynitrides) by reacting various metal precursors with ammonia, some options include chemical vapor deposition, treating metals or metal oxides with ammonia gas,^[14] or liquid supercritical ammonia (also known as "ammonothermal" synthesis, analogous to hydrothermal synthesis).^[15]

M + NH3 -> MN + 3/2 H2

MO2 + 4/3 NH3 -> MN + 2 H2O + 1/6 N2

The products of these reactions may be complex, with mixtures of oxygen, nitrogen, and hydrogen that can be difficult to characterize.^[16]

Notes and References

1. Stevenson . Arthur C. . September 1948 . Ammonolysis . Industrial & Engineering Chemistry . en . 40 . 9 . 1584–1589 . 10.1021/ie50465a006 . 0019-7866.
2. Jayatunga . Benthara . Karim . Md Rezaul . Lalk . Rebecca . Ohanaka . Okey . Walter R. L. Lambrecht . Lambrecht . Walter . Zhao . Hongping . Kash . Kathleen . Metal–Organic Chemical Vapor Deposition of ZnGeGa2N4 . Cryst. Growth Des. . 2020 . 20 . 1 . 189–196 . 10.1021/acs.cgd.9b00995 . 213595512 .
3. Reichert . Malinda D. . White . Miles A. . Thompson . Michelle J. . Miller . Gordon J. . Vela . Javier . Preparation and Instability of Nanocrystalline Cuprous Nitride . Inorganic Chemistry . 2015 . 54 . 13 . 6356−6362 . 10.1021/acs.inorgchem.5b00679. 26091284 .
4. Fernelius . W. Conard. . Bowman . Glade B. . 1940-02-01 . Ammonolysis in Liquid Ammonia. . Chemical Reviews . en . 26 . 1 . 3–48 . 10.1021/cr60083a002 . 0009-2665.
5. Pleskov . V.A . 1935 . Acta Physiochim.
6. Rangelov . Miroslav A. . Vayssilov . Georgi N. . Yomtova . Vihra M. . Petkov . Dimiter D. . 2005-02-24 . Theoretical study of the o-OH participation in catechol ester ammonolysis . Organic & Biomolecular Chemistry . en . 3 . 5 . 737–744 . 10.1039/B417285J . 15731858 . 1477-0539.
7. Hori . Kenzi . Ikenaga . Yutaka . Arata . Kouichi . Takahashi . Takanori . Kasai . Kenji . Noguchi . Yoshiyuki . Sumimoto . Michinori . Yamamoto . Hidetoshi . 2007-01-29 . Theoretical study on the reaction mechanism for the hydrolysis of esters and amides under acidic conditions . Tetrahedron . en . 63 . 5 . 1264–1269 . 10.1016/j.tet.2006.11.039 . 97011776 . 0040-4020.
8. Web site: Clark . Jim . Haloalkanes and ammonia . www.chemguide.co.uk.
9. Web site: Ashenhurst . James . 2017-05-26 . Alkylation of Amines . Master Organic Chemistry . en-US.
10. Werner . Emil Alphonse . 1918-01-01 . The preparation of ethylamine and diethylamine . . en . 113 . 899 . 10.1039/CT9181300899 . 0368-1645.
11. Book: Dhingra, Anand . The Sterling Dictionary Of Chemistry . 1999-12-01 . Sterling Publishers Pvt. Ltd . 978-81-7359-123-5 . 194 . en.
12. Hamada . H. . Matsuzaki . T. . Wakabayashi . K. . 1980-04-01 . Liquid-phase ammonolysis of phenols with metal chloride catalysts . Nippon Kagaku Kaishi; (Japan) . Japanese . 4.
13. Strain . Harold H. . February 1930 . Ammonolysis of Ketones . Journal of the American Chemical Society . en . 52 . 2 . 820–823 . 10.1021/ja01365a058 . 0002-7863.
14. Blanton . Eric W. . He . Keliang . Shan . Jie . Kash . Kathleen . 2017-03-01 . Characterization and control of ZnGeN2 cation lattice ordering . Journal of Crystal Growth . en . 461 . 38–45 . 10.1016/j.jcrysgro.2017.01.008 . 0022-0248. 1610.03512 . 2017JCrGr.461...38B . 99518345 .
15. Häusler . Jonas . Schnick . Wolfgang . 2018-08-14 . Ammonothermal Synthesis of Nitrides: Recent Developments and Future Perspectives . Chemistry – A European Journal . en . 24 . 46 . 11864–11879 . 10.1002/chem.201800115 . 29476648 . 0947-6539.
16. Pandey . Shobhit A . Zhang . Chi . Ibrahim . Daniah H. . Goldfine . Elise A . Wenderott . Jill K. . dos Reis . Roberto . Paul . Rick L. . Spanopoulos . Ioannis . Kanatzidis . Mercouri . Michael Bedzyk . Bedzyk . Michael J. . Dravid . Vinayak P. . González . Gabriela B. . Haile . Sossina M. . 2021-09-14 . Hidden Complexity in the Chemistry of Ammonolysis-Derived "γ-Mo 2 N": An Overlooked Oxynitride Hydride . Chemistry of Materials . en . 33 . 17 . 6671–6684 . 10.1021/acs.chemmater.1c00617 . 240539182 . 0897-4756.