Question

of the following acids, which one would be least likely to donate urs proton due to the unstable conjugate base?

1. which is the donatable hydrogen for each of the given structures?

2. what is the hybridization of the atom to which the donatable hydrogen is attached?

3. do any of the atoms identified in question 2 have a positive charge? if so explain why this is not a good thing and makes the hydrogen more donatable as opposed to less?

4. based in your answer from question 3, identify te structures that would be eleminited due to posotove charge

5. compair the remailing structures. what is the hybridization of the atoms to which the donatable hydrogen is connected?

7. if the hybridization is different, identify the structure that is eleminated firsr ans provide valid reasoning for its elimination. identify the final and structure least likley to donate its proton ans provide valid reasoning for it.

Of the following acids, which one would be least likely to donate its proton due to the unstable conjugate base produced? SeEmone Acid a) b)x d) Reasoning Spz Question 1: Which is the donatable hydrogen for each of the given structures? Question 2: What is the hybridization of the atom to which each of the donatable hydrogens is attached? Question 3: Do any of the atoms identified in question 2 have a positive charge? If so, explain why this is not a good thing and makes the hydrogen more donatable as opposed to less? Question 4: Based on your answer to question 3, identify the structures that are eliminated due to the presence of the positive charge. Question 5: After narrowing down the possibilities, compare the structures remaining. What is the hybridization of the atoms to which the donatable hydrogen is connected? Question 6: Are the hybridization of the atoms in the remaining structures the same or different?

Answer 1

Given acids and there respective pka's: а CH3 H3C нсм pka=-6 -CH₂ pka= 45 - CH₂ b ~ NH3 HzCYCH pka= 10 NH2 pka= 35 1) a) the proton attached to carbonyl oxygen is donatable. b) The proton attached to ammonium ion nitrogen. c) The proton attached to sp2 carbon d) -NH2 proton 2) a) sp2 oxygen; b) sp3 Nitrogen; c) sp2 carbon; d) sp3 nitrogen 3) a and b have positive charge. a) carbonyl oxygen is already an electronegative atom and it is bearing positive charge makes it easy to donate proton and get neutral. b) The nitrogen is also an electronegative and hence after donation of proton the nitrogen becomes neutral and hence it is more stable. 4) structure a and b.

5) Structure c contains sp2 carbon and the proton attached to terminal sp2 carbon are more donatable. In structure d the sp3 nitrogen has protons which can be donated. 6) in C there is another sp2 carbon and rest of other carbons are sp3. In d there all carbons are sp3. 7) We need to eliminate first the structure d, because pka of N-H is 35 whereas pka of sp2 C-H is 45 means N-H proton can be easily donated making structure d more acidic. Thus the last remaining structure is c). The alkene in c. is least likely to donate proton as the resulting conjugate base after donation is carbanion and it is very unstable.