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Chem 109 A

Chem 109 A. Chapter 2 E-mail: benzene4president@gmail.com Web-site: http://clas.sa.ucsb.edu/staff/terri/. Ch.2. 1. Show the equation using Kekule structures for the reaction between ammonium ion (NH 4 + ) and methoxide ion (CH 3 O - ). a. Label the conjugate pairs

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Chem 109 A

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  1. Chem 109 A Chapter 2 E-mail: benzene4president@gmail.com Web-site: http://clas.sa.ucsb.edu/staff/terri/

  2. Ch.2 1. Show the equation using Kekule structures for the reaction between ammonium ion (NH4+) and methoxide ion (CH3O-). a. Label the conjugate pairs b. Circle the stronger acid c. Calculate the approximate Keq d. Which direction does the equilibrium lie?

  3. Ch. 2 • As acid strength ↑ • Ka ↑ • pKa↓ • conjugate base strength ↓

  4. Ch.2 2. Show the equation using Kekule structures for the reaction between acetate ion (CH3COO-) and protonated ethanol (CH3CH2OH2+). a. Label the conjugate pairs b. Circle the stronger acid c. Calculate the approximate Keq d. Which direction does the equilibrium lie?

  5. Ch. 2 • 3. What is the resulting pH if 5 moles of ammonia were mixed with 5 moles of ammonium chloride (pKa = 9.4)? What is the pH if the molar ratio was 1:10 or 100:1 respectively?

  6. Ch.2 4. For the following pairs predict the stronger acid. Explain your reasoning. a. HF orHCl b. H2SorH2O c. HF or H2O d. CH3OH or CF3OH e. CH3(CH2)2CH(Cl)OH or CH3CH(Cl)(CH2)2OH • CH3OH orHCO2H • HC≡CH or H2C=CH2 • CH3NH2or CH3NH3+

  7. Ch. 2 • Comparing Relative Acid Strength • Are the acidic hydrogens on the same element? • 1. No • A. Same period elements => acid strength increases with increasing electronegativity • B. Different period elements => acid strength increases with increasing atomic radius 2. Yes A. Formal charge => Acid strength increases with increasing charge B. Hybridization => Acid strength increases with increasing s character • C. Resonance => Acid strength increases with withdrawing electrons via delocalization • D. Induction => Acid strength increases with withdrawing electrons due to induction

  8. Ch. 2 • 5. Predict the stronger base. • A. NH3or PH3 • B. CH3O- or CF3O- • C. CH3OCH3or CH3COCH3 • D. CH3O- or CH3NH-

  9. Ch. 2 • 5. What pH would allow the following to dissolve best in water verses hexane? • A. Aliphatic carboxylic acid • B. Aliphatic amine • C. Aliphatic alcohol

  10. Ch. 2 • 6. You are planning to synthesize a compound and one of the by-products is hydroxide. If you wanted to maintain a pH of 4.2 would it be better to use a formic acid (pKa = 3.75)/formate buffer or acetic acid (pKa = 4.76)/acetate buffer?

  11. End of Chapter 2

  12. Ch. 3 1. Give the following a systematic name and common name (if possible):

  13. Ch. 3 2. Draw the following compounds and assign a systematic name: a. sec-butyl iodide b. isoheptane c. tert-butyl isopentyl ether d. pentyl alcohol e. cyclobutyldimethylamine

  14. Ch. 3 3. What is more soluble in water? a. Methanol or ethanol b. Propylamine or trimethylamine

  15. Ch. 3 4. What has a higher boiling point? a. butane or pentane b. pentane orneopentane c. ethanol or dimethyl ether d. butylamineordimethylethylamine e. flourocyclohexaneorbromocyclohexane

  16. Ch. 3 5. Determine if the following alcohols primary, secondary or tertiary: a. 2-methyl-2-pentanol b. 3-ethyl-1-hexanol c. cyclopropanol

  17. Ch. 3 6. Determine if the following amines primary, secondary or tertiary: a. Cyclopentanamine b. N,N-diethyl-2-butanamine c. butylisobutylpentylamine

  18. Ch. 3 7. Draw the conformations of pentane considering rotation about the C2-C3 bond. Label the structures relative energy/stability. Draw an energy diagram that corresponds with your drawings.

  19. Ch. 3 8. Draw the two chair conformers for bromocyclohexane and determine which isomer is more stable. Explain your reasoning.

  20. Ch. 3 9. Which geometric isomer is more stable; cis or trans 1,3-dimethylcyclohexane?

  21. Ch. 3 10. Draw the chair conformers for 1-isopropyl-3-methylcyclohexanol. Which structure is more stable?

  22. Ch. 3

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