Will a triple bond away from the donating Hydrogen affect acidity?
There was a molecule with 2 triple bonds N=c-ch2-c=n (the = are triple bond) and another molecule CH3CH3. Which is more acidic?
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Answer by Peter B
Any feature in the molecule which can stabilize the conjugate base will make the acid stronger. Look for electron withdrawing groups (EWG) to add stability to the conj. base. In this case the CH3CH2- has no stability features at all (pKa ~50). Whereas the nitrile groups are EWG and help move the minus charge from the C to each of the two N atoms (through conjugation). Prove it to yourself by drawing 3 resonance forms for the anion (conj. base). (By the way the pKa is about 11.2 almost as acidic as phenol!)
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