Indicate which of each pair of compounds is likely to be more acidic and why? (h) EtO2C CO2Et EtO2C CO2Et (i) O2N OH O2N OH (j) H3C C(=O) OH H3C C(=O) NH2 (k) Ph-C=C-CH3 Ph-C=C-H (l) O O (m) this C atom C=O this C atom
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(h) EtOzC COzEt is likely to be more acidic than EtOzc_ "COzEt because the presence of the carbonyl group (C=O) in EtOzC COzEt makes it more acidic by stabilizing the negative charge on the oxygen atom after losing a proton. Show more…
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Q1. For the following pairs of acids choose the stronger acid and the correct explanation. Fill in the chart to answer the question (Concept: The more stable the conjugate base the more the equilibrium is shifted to the products which makes the acid more acidic. Look for the differences between the pairs of molecules. How is the charge on the conjugate base stabilized?) 1) CH3OH or 2) CH3NH 3) CH3OH or 4) CH3SH a) Because induction is transmitted through sigma bonds, the closer the electronegative atom is to the acidic atom or group, the more acidic the molecule is b) Since a negatively charged atom farther on the right of the periodic table is more electronegative than the atom on the left of the periodic table, the acid with that obtains a negative charge on the more electronegative atom is more acidic. - no other factors are involved c) An sp carbanion is a weaker base than an sp3 amide ion. (this is the one you need to memorize) d) As the acid functional group becomes more sterically hindered by adjacent alkyl groups, the acidity of the compound decreases because of poor solvation of the conjugate base which causes the equilibrium is to be shifted more to the reactants. Or alkyl groups are electron donating and destabilize the negative charge on the on the conjugate base. e) Because induction is transmitted through sigma bonds, increasing the electronegativity of the atom adjacent to the negatively charged region of the conjugate base decreases its basicity and increases the acidity of the acid f) Resonance of the negative charge of the conjugate base onto electronegative atoms is more stabilizing than resonance onto less electronegative atoms. g) A larger negatively charged atom is more stable than a smaller negatively charged atom because the charge on the larger atom is spread over a larger volume, is more polarizable and has a lower charge density. Thus the stronger acid will have the charge of the conj. base on the larger atom. (no other factors considered). h) Delocalization of the negative charge onto more atoms stabilizes the conjugate base and shifts the equilibrium to products making it a stronger acid. (for both acids, the conj. base anion resonance occurs on atoms of equal electronegativity) i) As the hybridization of the conjugate base changes from sp3 to sp2 to sp, the basicity of the conjugate base decreases, and the acidity of the acid increases.
Alkendra S.
Which of the above substances would you predict to be the strongest acid? Why? All of them are equally acidic because they all have a hydrogen atom. NH3, H2O, and HF are all equally acidic because the element they're bonded to is electronegative, therefore weakening the bond with hydrogen. None of them can serve as acids. HF is the most acidic because F is the most electronegative, weakening the H-F bond enough that the H+ ion is easily donated. Which of the above substances is most basic? Why? NH3 and H2O are equally basic because they each have a lone pair of electrons and nitrogen and oxygen can accommodate the positive charge that would be created when bonding with an H- ion. NH3 is the most basic of the substances because it has a lone pair of electrons and nitrogen's electronegativity is low enough to accommodate a positive charge when NH4- is formed. NH3, H2O, and HF are equally basic because they all have a lone pair of electrons that can be used to form a bond with an H-ion. None of these substances can serve as a base. Which of the substances would you classify as neutral? Why? Only H2O is neutral because it can just as easily serve as an acid and donate an H- ion or serve as a base and accept an H- ion. None of these substances are neutral because they are all either acidic or basic. CH4 and H2O are both neutral because CH4 is neither acidic nor basic and H2O can serve equally as either an acid or a base. Neutrality doesn't exist anymore.
Nicole S.
Q1. For the following pairs of acids, choose the stronger acid and the correct explanation. Fill in the chart to answer the question (Concept: The more stable the conjugate base, the more the equilibrium is shifted to the products, which makes the acid more acidic. Look for the differences between the pairs of molecules. How is the charge on the conjugate base stabilized?) 1) CH3OH or 2) CH3NH3 3) CH3OH or 4) CH3SH 5) F 6) Br 7) OH 8) OH 10) OH 11) OH 12) NH2 13) OH 14) OH 15) OH 16) OH 17) OH 18) NH2 a) Because induction is transmitted through sigma bonds, the closer the electronegative atom is to the acidic atom or group, the more acidic the molecule is. b) Since a negatively charged atom farther on the right of the periodic table is more electronegative than the atom on the left of the periodic table, the acid that obtains a negative charge on the more electronegative atom is more acidic. - no other factors are involved. c) An sp carbanion is a weaker base than an sp3 amide ion. (this is the one you need to memorize) d) As the acid functional group becomes more sterically hindered by adjacent alkyl groups, the acidity of the compound decreases because of poor solvation of the conjugate base, which causes the equilibrium to be shifted more to the reactants. Or alkyl groups are electron-donating and destabilize the negative charge on the conjugate base. e) Because induction is transmitted through sigma bonds, increasing the electronegativity of the atom adjacent to the negatively charged region of the conjugate base decreases its basicity and increases the acidity of the acid. f) Resonance of the negative charge of the conjugate base onto electronegative atoms is more stabilizing than resonance onto less electronegative atoms. g) A larger negatively charged atom is more stable than a smaller negatively charged atom because the charge on the larger atom is spread over a larger volume, is more polarizable, and has a lower charge density. Thus, the stronger acid will have the charge of the conjugate base on the larger atom. (no other factors considered) h) Delocalization of the negative charge onto more atoms stabilizes the conjugate base and shifts the equilibrium to products, making it a stronger acid. (for both acids, the conjugate base anion resonance occurs on atoms of equal electronegativity) i) As the hybridization of the conjugate base changes from sp to sp2 to sp3, the basicity of the conjugate base decreases, and the acidity of the acid increases.
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