Pka,conjugate and ph checking
Heya guys there was just some stuff which I wanted to check.
3 aminophenol at ph1 the amino end protonated
Ph10: the phenol bit ionised and amino end deprotonated
ph7: zwetterion with both ends ionised?
I went looking around for some Pka values for an amine and ester. For amine I got around 30 and ester(in general) I got 25. Does this make sense?
If I wanted to draw a equation for a conjugate acid/base for 3-aminophenol at ph8.0 would this be right?
C6H4(NH2)(OH)+NaOH---> C6H4(NH3+)(OH-) + OH-
cheers guys/gals
3 aminophenol at ph1 the amino end protonated
Ph10: the phenol bit ionised and amino end deprotonated
ph7: zwetterion with both ends ionised?
I went looking around for some Pka values for an amine and ester. For amine I got around 30 and ester(in general) I got 25. Does this make sense?
If I wanted to draw a equation for a conjugate acid/base for 3-aminophenol at ph8.0 would this be right?
C6H4(NH2)(OH)+NaOH---> C6H4(NH3+)(OH-) + OH-
cheers guys/gals
(edited 12 years ago)
Original post by Medifield
Heya guys there was just some stuff which I wanted to check.
3 aminophenol at ph1 the amino end protonated
Ph10: the phenol bit ionised and amino end deprotonated
ph7: zwetterion with both ends ionised?
I went looking around for some Pka values for an amine and ester. For amine I got around 30 and ester(in general) I got 25. Does this make sense?
If I wanted to draw a equation for a conjugate acid/base for 3-aminophenol at ph8.0 would this be right?
C6H4(NH2)(OH)+NaOH---> C6H4(NH3+)(OH-) + OH-
3 aminophenol at ph1 the amino end protonated
Ph10: the phenol bit ionised and amino end deprotonated
ph7: zwetterion with both ends ionised?
I went looking around for some Pka values for an amine and ester. For amine I got around 30 and ester(in general) I got 25. Does this make sense?
If I wanted to draw a equation for a conjugate acid/base for 3-aminophenol at ph8.0 would this be right?
C6H4(NH2)(OH)+NaOH---> C6H4(NH3+)(OH-) + OH-
Remember at pH = pKa then you will have 50% protonated/deprotonated
Phenol pka ~ 10
Hence phenol at pH 10 = 50% phenoxide and 50% phenol. Amino group as normal.
pka R-OH2+ ~ -2
pka R-NH3+ ~ 8
hence at pH 1, amino group protonated, OH group as normal.
pH 7 you will have your normal molecule.
Your pka values for amine and ester are correct, be sure you know which proton is deprotonated in an ester (forms an enol/enolate depending on conditions).
You should be able to tell your equation is wrong instantly as the charges don't balance. While OH is a strong enough base to deprotonate phenol, at pH 8 the concentration of OH is very low and the vast majority of your molecule will be unchanged.
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