Tetramethyl guanidine conjugate acid pKa around 12 is much stronger base than N,N-dimethylacetamide conjugate acid pKa around 0.5? I need a very good explanation of this. I would greatly appreciate it?
Tetramethyl guanidine conjugate acid pKa around 12 is much stronger base than N,N-dimethylacetamide conjugate acid pKa around 0.5? I need a very good explanation of this. I would greatly appreciate it?
Look at the structure of tetramethyl guanidine.....we call this a nitrogen superbase ! If this molecule accepts a proton and acts as a base ,,,we get an enormous amount of RESONANCE stabilization. The resonance structures that you draw out will show that all 3 nitrogen atoms partake in delocalization of the positive charge. Protonation of the amide nitrogen would cause a loss of resonance stabilization...... assuming protonation did occur,,,,,the positive Nitrogen would also be flanked by a carbonyl group which would also act as a destabilizing factor. Draw this out to convince yourself.
Here's another simple way to think about it. Methyl groups are electron donating groups, and help a molecule become a better lewis base (electron donor). The amide has a carbonyl group, and fewer methyl / electron donating groups. Carbonyl groups as you know from aromatic additions are electron withdrawing groups, which make compounds better lewis acids.
This site uses cookies to help personalize content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies and terms of service.