Concept explainers
(a)
Interpretation:
The pKa value for a protonated
Concept introduction:
The stability of a charged species depends on the groups attached to the positively charged atom. The electron withdrawing group increases the concentration of positive charge on the nearby atom. While, the electron donating group decreases the concentration of positive charge on the nearby atom. This increases the stability of nearby positively charged atom. In general, cations are stabilized by electron-donating groups near the positive charge.
(b)
Interpretation:
The pKa value for a protonated amine (R3NH+) depends on the number of alkyl groups attached to N, as shown below. This order disagrees with what we would predict using charge stability. The reason for the discrepancy is to be explained.
Concept introduction:
The stability of a charged species decreases as the effective electronegativity of an atom bearing a positive charge increases. The electron donating group decreases the concentration of positive charge on the nearby atom. This increases the stability of nearby positively charged atom. In general, cations are stabilized by electron-donating groups near the positive charge. Bulky group around the cation, reduces the solvation process. This decreases the stability of the ion and increases acidity.
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Organic Chemistry: Principles and Mechanisms (Second Edition)
- но HO но он The pK, of ascorbic acid (vitamin C) is 4.17, showing that it is slightly more acidic than acetic acid (CH3CO0H, pKa 4.74). (a) Show the fou r different conjugate bases that would be formed by deprotonation of the four different OH groups in ascorbic acid. (b) Compare the stabilities of these four conjugate bases, and predict which OH group of ascorbic acid is the most acidic. (c) Compare the most stable conjugate base of ascorbic acid with the conjugate base of acetic acid, and suggest why these two compounds have similar acidities, even though ascorbic acid lacks the carboxylic acid (COOH) group.arrow_forwardThe pKa of ascorbic acid (vitamin C, page 55) is 4.17, showing that it is slightly more acidic than acetic acid (CH3COOH, pKa 4.74).Compare the stabilities of these four conjugate bases, and predict which OH group of ascorbic acid is the most acidicarrow_forwarda) Identify the acidic proton for each of the following molecules: HO OH SH H t t NH₂ b) Rank the compounds in order of increasing acidity using pka values. c) In each case, draw the structure of the conjugate base.arrow_forward
- Draw the products of each proton transfer reaction. Label the acid and base in the starting materials, and the conjugate acid and base in the products. (c) + H2SO4arrow_forward(i) Draw the dissociation reaction for a carboxylic acid in water and define the Ka for this reaction. Write the equation that relates pKa to Ka. (ii) A deprotonated carboxylic acid can be drawn in two resonance forms. Draw the two forms and explain what the term “resonance” means. (iii) Draw an energy profile for the above dissociation reaction and describe how the profiles for a strong and a weak acid would differ.arrow_forwardRank the following structures in order of increasing basicity. NH₂ NH₂ vergren NH₂ A) | < || < ||| B) || < ||| < | C) III < | < || D) | < ||| < || E) III < ||arrow_forwardWhat is the conjugate acid of each of the following? What is the conjugate Dase of eacn? (a) NH Parts of the formula in your answer are transposed. Your answer appears to be missing a charge. Conjugate acid (b ) (CH₂)₂NH \table[[chemPad, (9) Help], [xlx =larr|l, Greek -],[(CH),NH,N What is the conjugate acid of each of the following? What is the conjugate base or eacn (UTIL SOLES- (a) NH3 Conjugate acid Conjugate base (b) (CH3)2NH Conjugate acid Conjugate base chemPad XX→→ chemPad XX→ NH₂ NH 2 NH4 NH 4 Parts of the formula in your answer are transposed. Your answer appears to be missing a charge. chemPad XX→ (CH4)2NH2 (CH_4)_2NH_2 chemPad XX→= Greek (CH₂)2N (CH_2) 2N Help Greek Help Greek X Help Greek juur Helparrow_forwardWhat is the increasing order of basicity among the following compounds ? I NH OH | < | < III < IV OIV < III < II < 1 I < III < II < IV OII < | < ||| < |V || < ||| < | < IV II NH III NH OH IV OH NHarrow_forwardArrange the following substances in order of increasing stability of conjugate base. 1. H₂Se II. H₂S III. H₂ Te || < ||| < | ||| < | < || | < ||| < || O II < | < || O I < || < ||| ||| < || < |arrow_forwardArrange the following compounds in decreasing order of acidity * |- CICH2CH2CH2COOH Il - CH3CH2CHCICOOH III – CH3CHCICH2COOH III > I> || O I > II > || O I > I| > II III > || >|arrow_forwardThe presence of a pi bond also makes a compound a base. With this in mind, draw the conjugate acid of ethylene, CH2=CH2.arrow_forwardThe ammonium ion (NH4* , pKa = 9.25) has a lower pKa than the methylammonium ion (CH;NH3*, pKa= 10.66). Which is the stronger base, ammonia (NH3) or methylamine (CH3NH2)? Explain.arrow_forwardarrow_back_iosSEE MORE QUESTIONSarrow_forward_ios
- Organic Chemistry: A Guided InquiryChemistryISBN:9780618974122Author:Andrei StraumanisPublisher:Cengage Learning