Chem 212Survey of Organic and BiochemistrySpring 2005

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Exam 2: Ch. 6-10

19 April 2005

Instructions:

1. If you leave the room for any reason you may not return to continue the exam.

2. No books or notes of any kind are permitted. You may borrow a model kit.

3. Put all your answers on this exam paper. If you want something graded which is written on scratch paper, you must indicate so in the regular space for the answer.

Good Luck!

  1. (5 pts) Mark each stereocenter in the following molecules with an asterisk (*), and then write the number of possible stereoisomers underneath each structure

2. (6 pts) Assign priorities to the groups in each set (1=highest, 4=lowest):

  1. –C(CH3)3–CH=CH2–CH=C(CH3)2–CH2CH2OH

1324

  1. –CHO –COOH–C≡C–H–NH2

3241

  1. –CH2CH2Br–CBr3–OH–Br

4321

  1. (4 pts) For each of the following tetrahedral centers with priorities shown, assign the chirality designation as either R or S:
  1. (5 pts) Assign the chirality (R or S) for each of the chiral centers in the following molecules.
  1. (8 pts) Predict the products for the following reactions, and (using the table provided) predict the side (products or reactants) favored at equilibrium. Also indicate which of the starting materials is acting as an acid and which as a base.
  1. H2O + HCO3-  HO- + H2CO3

acid base base acid

pKa = 14 pKa = 6.37 Reactants favored

  1. HPO42- + H2S  H2PO4 + HS-

base acid acid base

pKa = 7.04 pKa = 2.12 Reactants favored

  1. HSO4- + H2PO4-  SO42- + H3PO4

acid base base acid

pKa = 1.04 pKa=2.12 Reactants favored

  1. (4 pts) Without a calculator, convert the given pKa values into Ka values, or the given Ka values into pKa values:
  2. pKa = 4 Ka = 10-4 (= 0.0001)
  1. pKa = -2 Ka = 102 (= 100)
  1. Ka = 1000000 (i.e. Ka = 106) pKa = -6
  1. Ka = 0.01 (i.e. Ka = 10-2) pKa = 2
  1. (3 pts) Which will be the more acidic solution in each case?
  2. 0.20 M pyruvic acid (pKa = 2.49) or 0.20 M Phosphoric acid (pKa = 2.10)

more acidic

  1. 0.10 M benzoic acid (Ka = .000065) or 0.10 M lactic acid (Ka = .00084)

more acidic

  1. 0.10 M carbonic acid (Ka = .00000043) or 0.10 M boric acid (pKa = 10)

Carbonic acid solution is more acidic; the Ka = 4.3 x 10-7, which is larger than the Ka for boric acid, 1 x 10-10

8. (5 pts) Write the formula for:

  1. The conjugate base of H3O+ H2O
  1. The conjugate base of HPO42- PO43-
  1. The conjugate acid of HSO4- H2SO4
  1. The conjugate base of NH3 NH2-
  1. The conjugate acid of trimethylamine (CH3)3NH+
  1. (7 pts) Classify each of the following amines as primary, secondary, tertiary or quaternary, and also indicate whether they are heterocyclic and/or aromatic.


10. (4 pts) Draw the structure of each of the following amines:

11. (6 pts) Draw the structure of the products:

12. (3 pts) Draw the product or products:

  1. (4 pts) Give the structures of the following compounds:

(12 pts) Give the products of the following reactions:

  1. Draw the enol form of each of the following ketones, or if such a form does not exist, write “No Enol”


  1. The following molecule can form an enol, which can then form a different carbonyl structure. Draw these two structures.

17. (6 pts) Draw the structure of each of the following:

  1. (4 pts) Complete the equations for these reactions:
  1. (2 pts) Draw the structure of a gamma-Lactone
  1. (3 pts) Draw the structure of three carboxylic acids that are intermediate in acidity between 2,2-difluorooctanoic acid and 4-bromooctanoic acid, and rank all of the compounds from most to least acidic

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