njl
National Hazard
Posts: 609
Registered: 26-11-2019
Location: under the sycamore tree
Member Is Offline
Mood: ambivalent
|
|
How come amines only form salts with the H+ cation?
Title, really. Ammonium chloride is formed when Ammonia is protonated by the acidic hydrogen from Hydrogen Chloride. In aqueous solutions this can be
represented as H+ protonating NH3 to for NH4+, with the positive charge balanced by a negative Cl- ion in solution. But why can't a compound like
Lithium chloride act in the same way (forming NH3Li+ and Cl-)? Is it because Lithium is bulkier than Hydrogen?
|
|
|
outer_limits
Hazard to Others
Posts: 139
Registered: 3-3-2020
Member Is Offline
Mood: hybridized
|
|
Hydrogen cation needs only 2 electrons to fill its 1s orbital and it exist in solution as H3O+ ions. When something undergoes a protonation it uses
it's own free pair of electrons to grab the hydrogen from hydronium ion.
Lithium as cation has already its 1s orbital filled. In order to create a stable compound you would have to fill 2s and 2p which will require to add 8
electrons.
[Edited on 6-8-2020 by outer_limits]
[Edited on 6-8-2020 by outer_limits]
|
|
|
DraconicAcid
International Hazard
Posts: 4278
Registered: 1-2-2013
Location: The tiniest college campus ever....
Member Is Online
Mood: Semi-victorious.
|
|
You can also form a salt by reacting ammonia with CH3Br. NH3 + CH3Br --> NH3CH3(+) Br(-)
Also, Cu(2+) + 4 NH3 --> [Cu(NH3)4](2+)
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
|
|
|
clearly_not_atara
International Hazard
Posts: 2694
Registered: 3-11-2013
Member Is Offline
Mood: Big
|
|
Ammonium is not a "salt" or traditionally understood metal complex. It is a covalently bonded molecular ion. Lithium forms much weaker covalent bonds
with nitrogen because the difference in electronegativity is much larger. Thus the preferred configuration is Li(NH3)6+ which is made possible by much
longer-range monopole-dipole interactions.
[Edited on 04-20-1969 by clearly_not_atara]
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
