# Usage of ammine vs amine in nomenclature

In the nomenclature of complex salts we use ammine for NH3 instead of amine.

I thought this was to differentiate between ammine ligand and amine in organic ligand (like en).

However, Wikipedia cites the usage has historical reasons. So why exactly do we use ammine instead of amine?

• I always remember it because it directly derives from ammonia (with a double-m). Whereas the amines are only modified versions of ammonia, they no longer can dissociate to liberate it. – Jan Dec 15 '15 at 22:08

(Will do more research into ammines come February.)

# Premise

Ammonia is spelled with two 'm's. The more natural derivative of the word in a linguistic sense would also have the same number 'm's. Thus whichever predates the other, ammine complexes or amines, would claim the throne.

In a structural sense, when awknowledgement of the first ammine complex came it was literally in a solution of ammonia (see more below).

# Etymology of ammonia and amine

Our travels begin in sunny Ancient Egypt. One important deity of the time was Amun, the god of wind and air along with his wife-in-mythology Amaunet. At the beginning of the Middle Kingdom of Egypt (c. $2055-$$1650 BC), he was annointed patron saint of Thebes. Later Amon become part of a trinity, along with gods Re and Ptah. This coincided with Thebes restored as capital city due to pharaoh Ahmose I (c. 1539-$$1514$ BC).

Eventually Amon would become the god of gods. This is when he also goes by Amon-Re (or Ra), after uniting with sun god Re.$^{\text{[a]}}$

Egypt's glory shone far beyond its borders. Ancient Greeks adopted their own version of Amon. There he would be called Ammon, with two 'm's.

As it so happens, near one of Amun's temples in then-Egypt is a depository of $\ce{NH4Cl}.$ From this háls ammôniakós (Greek for 'salt of Amun') we can easily extract $\ce{NH3}.$

$$\ce{NH4Cl(s) ->[t^\circ] NH3(g) +HCl(g)}.$$

It makes sense for the option with two 'm's to outdate amine. Etymonline agrees (in ~ English):

ammonia (n.) $-$ $1799$, modern Latin, coined $1782$ by Swedish chemist Torbern Bergman ($1735$$-$$1784$) for gas obtained from sal ammoniac [----];

amine (n.) $-$ "compound in which one of the hydrogen atoms of ammonia is replaced by a hydrocarbon radical," $1863$, from ammonia + chemical suffix -ine (2).

Note: has been expanded upon under 'Amine in chemical literature' further down.

# The why

Why ammine for coordination compounds and not amine? It is probably because the study of metal ammines predates any knowledge of amines. Indeed, in $1798$ Tassaert$^{[1]}$ reported on 'ammoniacal solutions of cobalt(II) chloride [which when] allowed to stand overnight yield an orange-colored crystalline product containing six molecules of ammonia'$^{[2]}$. The compound in question was $\ce{CoCl3*6NH3}$. These and similar compounds were dubbed metal ammines$^{\text{[b]}}$.

Note that at the end of $18^{\text{th}}$ century organic chemistry had not yet developed. The crucial and accidental evidence against vitalism$^{\text{[c]}}$ came in $1828$ when the German chemist Wöhler artificially synthesised an organic compound $-$ urea $-$ an amide with two amine qroups!

$$\ce{AgNCO + NH4Cl-> AgCl + NH4NCO \\ NH4NCO ->[t^\circ]NH_3 + HNCO <=>\underset{urea}{CO(NH2)2}}$$

First pivotal trace of amines pops up in $1842$, $44$ years after Tassaert's discovery of coordination chemistry. Russian chemist N. N. Zinin uses dihydrogen sulfide to reduce nitrobenzene$^{[3]}$$^{\text{[d]}}:$$\ce{C_6H5NO2 + 3H2S ->[NH3]\underset{aniline}{C6H5NH2} + 3S + 2H2O}.$$On Zinin's research, co-founder of amine chemistry A. W. von Hofmann declares^{[4]}, If Zinin had done nothing more than to convert nitrobenzene into aniline, even then his name should be inscribed in golden letters in the history of chemistry. Aliphatic amines were simultaneously and independently synthesised in 1849 by chemists Wurtz of France and Hofmann of Germany. Both could be credited with the discovery of ethylamine. Hofmann's method allowed for the additional preparation of secondary and tertiary amines.^{[3]} Wurtz treated ethyl isocyanate with potassium hydroxide; Hofmann applied heat to solutions of alkyl halogenides and ammonia.^{[3]}$$\tag{Wurtz}\ce{C2H5N=CO + H2O->[KOH]C2H5NH2 + CO2}\tag{Hofmann, I}\ce{R-I + NH3->[t^\circ]R-NH2*HI}\tag{Hofmann, II}\ce{2R-I + NH3->[t^\circ]R2-NH*HI + HI}\tag{Hofmann, III}\ce{3R-I + NH3->[t^\circ]R-N*HI + 2HI}$$For quaternary amines, Hofmann used the following scheme:$$\tag{Hofmann, IV}\ce{R3N + RI->R4-N*I}.^{[3]}$$But because ammine was already reserved, they went with amine.^{[5]} Furthermore, if you think about it, the naming is rather successful. Well, at least for primary amines.^{\text{[e]}\ \text{[f]}}$$\text{metal ammines contain the complete}\ \ce{NH3->} \text{keep the}\ m\\ \text{pr. amines have one less hydrogen or}\ \ce{-NH2->} \text{lose the}\ m$$# Amine in chemical literature In 1834, German chemist Liebig optained a dirty white or buff-coloured amorphous substance by heating ammonium thiocyanate.^{[5]\ [6]\ [7]\ [8]\ [9]\ [10]\ [11]}$$\tag{$\alpha$}\ce{KSCN + NH4Cl ->[t^\circ] NH4SCN + KCl}\tag{$\beta$}\ce{NH4SCN <=> \underset{thiourea as thione}{S=C(NH2)2} <=>[t^\circ] \underset{thiourea as thiol}{HS-C(NH)NH2}}\tag{$\gamma$}\ce{\underset{thiourea as thiol}{HS-C(NH)NH2} ->[t^\circ] NH3 + HNCS \\ \underset{thiourea as thiol}{HS-C(NH)NH2} ->[t^\circ] H2S\ \ \ + \underset{cyanamide as aminonitrile}{N#C-NH2}}\tag{$\delta$}\ce{\underset{cyanamide as aminonitrile}{N#C-NH2} <=> \underset{cyanamide as diimine}{HN=C=NH}}$$He named the product melam without any admitted etymology other than his own fantasy. Indeed, Liebig mentions in his original paper^{[5]\ [6]}, [These designations] are, if you like, grasped from the air (i.e. pure inventions), and serve the purpose just as well as if they were derived from the colour or one of the properties. Liebig proceeded to boil melam with a solution of potassium hydroxide and ammonia. This yielded melamine.^{[5]\ [6]\ [7]} Neither the structure of melam nor melamine were known to Liebig at the time.^{[5]} Melamin(e) was most likely derived by Liebig as melam + -in(e).^{[5]}$$^\text{[g]}$

A few years before $1849$, Liebig had predicted the existance of amines.$^{[5]}$$^\text{[h]} Liebig called them compound-ammonias^{[5]}. The word amine itself was used already in 1853$$^{[12]}$ in the works of French chemist Gerhardt. Often times this was put in parentheses as an alternative name. For example$^{[12]}$,

• méthyl-ammoniaque (méthylamine),

• amyl-ammoniaque (amyl-amine).

Acceptance of the word amine was not immediate. Besides having to distinguish between amines and metal ammines, amides were too an obstacle. The restriction to retain amine for ammonia [where any] hydrogen atom [has been] successively replaced by hydrocarbon radicals was generally accepted in $1863$.$^{[5]}$

# TL; DR

$$\text{Amun in Greek}+\text{nearby }\ce{NH4Cl}\ \text{depository}\ce{->[Tassaert dibs on ammine in 1798][\text{vitalism until a.l. 1828}]}\text{amine in 1863}$$

## Extra information

• $\text{[a]}$ According to some texts, the unification as Amon-Ra goes back to the reign of Mentuhotep II ($2055-$$2004 BC). Amon's (or Amon-Ra's) importance declined, then increased again during Amenemhet I (1985-$$1956$ BC), fell and rose to national prominence with Ahmose I.$^{[13]}$

• $\text{[b]}$ Most of the early work was done with ammonia, and thus the resulting class of complexes were already then known as metal ammines$^{[14]}$. Developments in naming specific compounds are summarised in this diagram:

$$\text{after discoverer}\ce{->[\text{m.c.l.}]}\text{basis on colour}\ce{->[\text{m.c.l.}]}\text{count number of ammonias only}\ce{->[\text{m.c.l.}][Werner's coordination theory 1893]}\text{premodern}$$

where $\text{m.c.l.}$ is short for many compounds later. Some examples of such practice is included the table$^{[14]}$ below.

\begin{array}{|c|c|c|c|} \hline \mathbf{Complex} & \mathbf{Colour} & \mathbf{Name} & \mathbf{Present}\ \mathbf{formulation}\\ \hline \ce{CoCl3*6NH3} & \text{yellow} & \color{gold}{\text{luteo}}\text{cobaltic chloride} & \ce{[Co(NH3)6]Cl3} \\ \ce{CoCl3*5NH3} & \text{purple} & \color{purple}{\text{purpure}}\text{ocobaltic chloride} & \ce{[CoCl(NH3)5]Cl2} \\ \ce{CoCl3*4NH3} & \text{green} & \color{green}{\text{praseo}}\text{cobaltic chloride} & trans\text{-}\ce{[CoCl2(NH3)4]Cl} \\ \ce{CoCl3*4NH3} & \text{violet} & \color{violet}{\text{violeo}}\text{cobaltic chloride} & cis\text{-}\ce{[CoCl2(NH3)4]Cl} \\ \ce{CoCl3*5NH3*H2O} & \text{red} & \color{pink}{\text{roseo}}\text{cobaltic chloride} & \ce{[Co(NH3)5(OH2)]Cl3} \\ \ce{IrCl3*6NH3} & \text{white} & \color{gold}{\text{luteo}}\text{luteoiridium chloride} & \ce{[Ir(NH3)6]Cl3} \\ \hline \end{array}

An attentful reader ought to notice that $\ce{CoCl3*6NH3}$ is yellow and $\ce{IrCl3*6NH3}$ is white. But they both have the same prefix -luteo. At first it did indeed mean yellow but later the same scheme was adopted to notate an equal number of ammonias. Crazy but it is true!$^{[14]}$ You can probably see that proper nomenclature could not get there soon enough.

• $\text[c]$ In chemistry, vitalism was the idea that compounds found inside living things are fundamentally different from inorganic chemistry. Such organic molecules were believed to be impossible to synthesise outside an organism.

To captivate how little of organic chemistry was understood in the first half of the 18th century, Wöhler stated in $1835$$^{[5]}$,

[Organic chemistry is] like a primaeval forest of the tropics, full of the most remarkable things.

Proponents of vitalism had a hard time accepting the evidence. They argued that the process was achievable since carbamide is simply a waste product. However, luckily notable progress followed.$^{[15]}$

• M. Berthelot $-$ natural fat ($1854$ doctoral thesis)
• H. Kolbe, E. Frankland $-$ acedic acid ($1861$)
• A. Butlerov $-$ sugars ($1861$, see Formose reaction)
• ${\text{[d]}}$ Aniline had been successfully separated in $1826$ by German merchant and chemist O. Underderben. Note, however, that this was not a synthesis $-$ he used dry destillation of indigo.$^{[5]\ [16]}$

• ${[\text{e}]}$ This was very much intentional. Wurtz recognised in $1849$ that methylamine and ethylamine could be regarded as ammonia in which one equivalent of hydrogen is replaced by methyl or ethyl.$^{[5]}$

• $\text{[f]}$ Classification of primary, secondary, and tertiary amines was introduced by Gerhardt in $1856$.$^{[17]}$

• $\text{[g]}$ Some authorities$^{[18]}$ claim melamine as having come from mel(am) $+$ amine. This is wrong since amines were unknown at that time.$^{[5]}$

• $\text{[h]}$ From Zinin to Liebig, amines were probably grouped as alcaloïdes artificiels (French for artificial alcaloids) because the structure had not yet been proposed.$^{[19]}$

# Refrences and bibliography

• $[1]$ B. M. Tassaert, Ann chim. phys., 28, 92 (1798).

• $[2]$ Fred Basolo, Ralph G. Pearson. Mechanisms of Inorganic Reactions. (1958). (page 2)

• $[3]$ Michele Giua. Storia della Chimica. (1962) (pages 342$-$344)

• $[4]$ A. W. von Hofmann. Ber. Deut. chem. Ges. (1880). 13,. 449$-$450.

• $[5]$ W. E. Flood. The Origins of Chemical Names (1963) (pages xxii, 33$-$35, 37$-$38, 137$-$138)

• $[6]$ J. von Liebig. 'Uber einige Stickstoff $-$ Verbindungen'. Justus Liebigs Annalen der Chemie, 10, 1, 1$-$47 (1834).

• $[7]$ Bernard Bann, Samuel A. Miller. 'Melamine And Derivatives Of Melamine'. Chemical Reviews, 58 (1), 131$–$172. (1958)

• $[8]$ Klaus Bretterbauer, Clemens Schwarzinger. 'Melamine Derivatives – A Review on Synthesis and Application'. Current Organic Synthesis, 9, 342$-$356 (2012).

• $[9]$ Michihiro Ohta, Shinji Hirai, Hisanaga Kato, Vladimir V. Sokolov, Vladimir V. Bakovets. 'Thermal Decomposition of $\ce{NH4SCN}$ for Preparation of $\ce{Ln2S3}$ ($\ce{Ln}$ = $\ce{La}$ and $\ce{Gd}$) by Sulfurization'. Materials Transactions, vol. 50, No. 7, 1885$-$1889 (2009).

• $[10]$ Zerong Daniel Wang, Motoko Yoshida, Ben George. 'Theoretical study on the thermal decomposition of thiourea'. Computational and Theoretical Chemistry, vol. 1017, 91$–$98 (2013).

• $[11]$ A. Kawasaki, Y. Ogata. 'Kinetics of the formation of melamine from dicyandiamide'. Tetrahedron, vol. 22, 1267$-$1274 (1965).

• $[12]$ M. Charles Gerhardt. Traité de chimie organique. First edition. (1853) (pages 8, 134, 210$-$211, 277, 396$-$397, 427, 463, 545, 551, 611, 613, 616$-$619)

• $[13]$ Seppo Zetterberg. Maailma ajalugu. (2015). (pages 41$-$43)

• $[14]$ Fred Basolo, Ronald Johnson. Coordination Chemistry. (1964) (pages 4$-$13)

• $[15]$ H. Karik. Üldine keemia. Handbook for students. (1987) (page 223)

• $[16]$ Alex Nickon, Ernest F. Silversmith. Organic Chemistry: The Name Game. (1987) (page 305)

• $[17]$ M. Charles Gerhardt. Traité de chimie organique. Fourth edition. (1856) (page 592)

• $[18]$ The American Heritage Dictionary of the English Language: Fourth Edition. 2000. https://web.archive.org/web/20081201105219/http://www.bartleby.com:80/61/24/M0202400.html (Jan 3, 2017)

• $[19]$ Encyclopædia Universalis. 'Amines'. http://www.universalis.fr/encyclopedie/amines/ (Jan 2, 2017)

• Please by all means criticise, correct and add as you see fit! This is by no means complete but shouldn't be far off from the probable answer. If someone has access and can understand A. Werner, Neuere Anschauungen auf den Gebieten der Anorganischen Chemie, Third edn., Vieweg, Braunschweig, 1913, pp. 92–95 it might provide extra insight. – Linear Christmas Dec 3 '16 at 21:13

HISTORY

• AMINE

PRIMARY, SECONDARY, AND TERTIARY

The qualifiers primary, secondary, and tertiary were first applied to the classification of the organic amines in 1856 by the French chemist, Charles Gerhardt, in volume four of his famous Traité de chimie organique in order to distinguish between amines resulting from the first (primary), second (secondary), and third (tertiary) stages in the progressive substitution of the three hydrogen atoms of the ammonia molecule (NH3) by various alkyl radicals:1 One might call the nitrogen compounds primary, secondary or tertiary according as they represent the ammonia type with substitution of one, of two, or of three atoms of hydrogen [1]

• AMMINE

Werner published his coordination theory in 1893, which postulated that single atoms or molecules could be joined and grouped around a central atom. It is said that in the middle of night in late 1892, Werner woke up suddenly after visualizing the solution for the structure of coordination complexes in a dream. Throughout the remaining night and the next day he wrote down the details of his coordination chemistry, which he published in his legendary paper: On the constitution of inorganic complexes" ... "To validate his theory, Werner had to work for nearly 25 years and in the process, he prepared more that 8000 compounds. in 1907, Werner prepared a compound, an ammonia-violeo salt, predicted by his coordination theory. [2]

Werner assigned the violeo salt the cis configuration by preparing them by treating the carbonato complex with conc. HCl. $\ce{[Co(NH3)4(NO2)2]X}$ ..." [3]

BIBLIOGRAPHY

[1] Jenssen, W.B. J. Chem. Educ., 2012, 89 (7), pp 953–954.

[2] Mahanti, S. "Alfred Werner. Founder of coordination chemistry" http://www.vigyanprasar.gov.in/scientists/alfred_werner.pdf Last accesed 3 Dec., 2016.

[3] Panda, B.K. Indian Journal of Science, 2013, 3(6), 25-31.