Is NH3 more basic than OH?
Started by seraphkz
You are correct. Nitrogen and Oxygen are in the same row and the trend is that the less electronegative atom is more willing to donate electrons making it more basic.
Your question isn't entirely clear. Are you refering to ROH, .OH, or :OH-?
Are you referring to carboxylic acid derivatives or free NH3 and OH- in solution? Amides (RCOO-NH2) are the strongest base in the CA derivs, more so than (RCOO-OH, obviously since that is carbolxylic acid). But rather than looking at electronegativity (which refers to electrons in a bond), ionize your species and examine the leaving group.
Strongest Base(worst leaving group): NH2- > OR- > OH- > RCOO- > Cl- :Weakest base(best leaving group)
Add a proton to each of those anions and you have a list of acids in order of weakest(NH3) to strongest (HCl).
In free solution OH- will take up protons before NH3.
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pKa of NH4 (as NH4Cl) is 9.25
pKa of H2O is 15.7
Therefore, OH(-) is a stronger conjugate base than NH3.
Or, if you want to look at trends along the periodic table (in order of electronegativity)
CH3- > NH2- > OH-
Or put another way, all else being equal (two anions compared, for example) Oxygen holds its electrons more tightly than does Nitrogen, and is a poorer Lewis base.
No, electronegativity is relative when 2 atoms are in a bond, and it specifically refers to an atom, not ions. That is, in H-F, the electrons in the bond are more "tightly held" by F-atom as opposed to H-atom because F-atom is more electronegative. Saying one ion(OH- or NH2-) is more electronegative than another is ambiguous.
