rganic Chemistry Jasperse Acid- Practice Problems A. Identify each chemical as either an acid or a base in the following reactions, and identify conjugate relationships. -You should have one acid and one base on each side -You should have two conjugate pairs 1. CH 3 CH 2 H + NaH CH 3 CH 2 Na + H 2 2. CH 3 CH 2 NHLi + CH 3 H CH 3 CH 2 + CH 3 Li 3. CH 3 CH 2 C 2 H + CH 3 MgBr CH 3 CH 2 C 2 MgBr + CH 4 4. CH 3 H + H 3 + H 2 + CH 3 H 2 + 5. CH 3 CH 2 NH 3 + + CH 3 H CH 3 CH 2 + CH 3 H 2 + B. Choose the More Basic for Each of the Following Pairs (Single Variable). You can use stability to decide. 6. NH 3 Na 7. NaH H 2 Keys: 1. Charge 2. Elecronegativity 3. esonance 8. NH 9. Na 10. Ph Ph 11.
C. ank the basicity of the following sets: Multiple Variable Problems 12. CH 3 MgBr CH 3 CH 3 13. H 14. Na H Na 15. NH H D. Choose the More Acidic for Each of the Following Pairs: Single Variable Problems 16. NH 3 NH4 17. H 2 H 18. H CH3 19. H 20. H H 21. NH2
E. ank the acidity of the following sets: Multiple Variable Problems 22. H H 2 H HF 23. NH 3 H H 2 H H 24. H NH 3 25. 26. He H H F. Draw arrow to show whether equilibrium favors products or reactants. (Why?) 27. H + H 2 + H H H Keys: 1. Charge 2. Elecronegativity 3. esonance 28. H + NH + G. For the following acid-base reaction, a. put a box around the weakest base in the reaction b. put a circle around the weakest acid c. draw an arrow to show whether the equilibrium goes to the right or left. (4pt) 29. H + Na +
Acid- Chemistry (Section 1.13-18) Chem 341 Jasperse Ch. 1 Structure + Intro 12 Acidity/Basicity able Entry Class Structure Ka Acid Strength Strength Stability 1 Strong Acids H-Cl, H 2 S 4 10 2 Cl, H S 2 Hydronium H 3 +, H + cationic 10 0 H 2, H neutral 3 Carboxylic Acid H 10-5 4 Ammonium Ion (Charged) H N 10-12 N Charged, but only weakly acidic! Neutral, but basic! 5 Water HH 10-16 6 Alcohol H 10-17 H 7 Ketones and Aldehydes! H 10-20! 8 Amine (N-H) (ipr) 2 N-H 10-33 9 Alkane (C-H) CH 10-50 3 (ipr) 2 N Li CH2 Quick Checklist of Acid/ Factors 1. Charge 1. Cations more acidic than neutrals; anions more basic than neutrals 2. Electronegativity e 2. Carbanions < nitrogen anions < oxyanione < halides in stability 3. esonance/conjugation x 3. resonance anions more stable than anions without resonance t When neutral acids are involved, it s best to draw the conjugate anionic bases, and then think from the anion stability side. he above three factors will be needed this semester. he following three will also become important in rganic II. 4. Hybridization 5. Impact of Electron Donors/Withdrawers 6. Amines/Ammoniums
Chem 341 Jasperse Ch. 1 Structure + Intro 13 More Detailed Discussion of Acid/ Patterns/Factors to remember 1. Charge Factor: central atom being equal, cations are more acidic than neutrals (H 3 + > H 2, NH 4 + > NH 3 ), and anions more basic than neutrals (hydroxide > water). 2. Electronegativity Factor: Acidity H-C < H-N < H- < H-X (halogen) Anion Stability Basicity Electronegativity Why: All neutral acids produce an anion after losing an H he more stable the anion Z - that forms, the more acidic the parent H-Z will be. (he Product Stability/eactivity principle). he anion stability correlates the love for electrons (electronegativity). Summary of Key elationships: ANIN SABILIY and the ACIDIY of a neutral acid precursor. ANIN SABILIY and the BASICIY of the anion (inverse relationship) ANIN BASICIY and the ACIDIY F HE CNJUGAE ACID are inversely related (the stronger the acidity of the parent acid, the weaker the basicity of the conjugate anion) KEY: WHEN HINKING ABU ACIDIY AND BASICIY, FCUS N HE SABILIY F HE ANIN. 3. esonance/conjugation: Anion resonance is stabilizing, so an acid that gives a resonance-stabilized anion is more acidic. And an anion that forms with resonance will be more stable and less basic. xygen Series Examples: Acidity: sulfuric acid > carboxylic acid > water or alcohol Anion Basicity: Anion Stability: S H H S < > < > Note: esonance is normally useful as a tiebreaker between oxygen anions, nitrogen anions, or carbon anions