Editing Amine (section)

==Physical properties==
[[Hydrogen bonding]] significantly influences the properties of primary and secondary amines. For example, [[Methylamine|methyl]] and [[Ethylamine|ethyl]] amines are gases under standard conditions, whereas the corresponding [[Methanol|methyl]] and [[Ethanol|ethyl]] alcohols are liquids. Amines possess a characteristic ammonia smell, liquid amines have a distinctive "fishy" and foul smell.

The nitrogen atom features a [[lone electron pair]] that can bind H<sup>+</sup> to form an [[ammonium ion]] R<sub>3</sub>NH<sup>+</sup>. The lone electron pair is represented in this article by two dots above or next to the N. The water [[solubility]] of simple amines is enhanced by [[hydrogen bonding]] involving these lone electron pairs.  Typically salts of ammonium compounds exhibit the following order of solubility in water: primary ammonium ({{chem|RNH|3|+}}) > secondary ammonium ({{chem|R|2|NH|2|+}}) > tertiary ammonium (R<sub>3</sub>NH<sup>+</sup>). Small aliphatic amines display significant solubility in many [[solvent]]s, whereas those with large substituents are lipophilic. Aromatic amines, such as [[aniline]], have their lone pair electrons [[conjugated system|conjugated]] into the benzene ring, thus their tendency to engage in hydrogen bonding is diminished. Their boiling points are high and their solubility in water is low.

===Spectroscopic identification===
Typically the presence of an amine functional group is deduced by a combination of techniques, including mass spectrometry as well as NMR and IR spectroscopies. <sup>1</sup>H NMR signals for amines disappear upon treatment of the sample with D<sub>2</sub>O.  In their [[infrared spectrum]] primary amines exhibit two N-H bands, whereas secondary amines exhibit only one.<ref name=OChemSmith3E />  In their IR spectra, primary and secondary amines exhibit distinctive N-H stretching bands near 3300&nbsp;cm<sup>−1</sup>.   Somewhat less distinctive are the bands appearing below 1600&nbsp;cm<sup>−1</sup>, which are weaker and overlap with C-C and C-H modes.  For the case of [[propyl amine]], the H-N-H scissor mode appears near 1600&nbsp;cm<sup>−1</sup>, the C-N stretch near 1000&nbsp;cm<sup>−1</sup>, and the R<sub>2</sub>N-H bend near 810&nbsp;cm<sup>−1</sup>.<ref>{{cite journal |last1=Smith |first1=Brian |title=Organic Nitrogen Compounds II: Primary Amines |url=https://www.spectroscopyonline.com/view/organic-nitrogen-compounds-ii-primary-amines |website=Spectroscopy |series=Spectroscopy-03-01-2019 |date=March 2019 |volume=34 |pages=22–25 |access-date=12 February 2024}}</ref>