Chem2O6 - 1996/97

Assignment #1 Due: October 10, 1997

1. Convert the following line structures into molecular formulas.

Epinephrine, Aspirin, and Folic Acid

2. Draw all possible structures for compounds with the molecular formula C4H9N.

3. (a) A series of organic molecules is drawn below. Each one can behave as a Bronsted acid toward an appropriate base. Below that is a list of bases. For each "acid", identify ALL of those bases which are strong enough to produce a mixture of the acid and its conjugate base in which at least 50% exists as the conjugate base (for an equimolar mixture of acid and base). Draw the structure of the conjugate base form for each acid.

organic acids and bases

(b) In most cases, acid-base reactions must be carried out in a polar solvent like water, an alcohol, or an ether. Why? Could you carry out all of the above deprotonation reactions in methanol or water? If no, identify which ones wouldn't work, and explain why.

4. Using the table of pKa's in the front of Ege's book, determine Keq for the following reaction:

4-nitrophenol + ammonia

5. The compound methylcyclohexane exists in solution as two rapidly interconverting CONFORMERS which are shown below. You should construct a molecular model to illustrate to yourself how this occurs; it involves only C-C bond rotations.

axial and equatorial methylcyclohexane

(a) Which conformer will predominate at 25 oC?

(b) Calculate the equilibrium constant at 25 oC, for the equilibrium as written above.

(c) Calculate the percentages of A and E present at 25 oC.

(d) Calculate the temperature at which the mixture would consist of 48% A and 52% E.

6. Depending on reaction conditions, bromine can react with alkenes in two ways:

propene + bromine

Using the table of average bond energies on p.67 of the textbook, estimate Hr for the two possible reactions, and identify which of the two is more exothermic.

7. The following two compounds are converted to alcohols upon treatment with NaOH in water. In both cases, the rate of the reaction depends only on the concentration of the organic halide, and is independent of [NaOH].

(a) Identify the products expected from these reactions. Using one of the compounds, draw the reaction coordinate diagram for the reaction, and draw structures for all energy minima and maxima. Identify the transition state for the rate determining step.

(b) One of the compounds reacts much faster than the other. Identify which one you would expect to be more reactive, and explain why.

Make sure that your answers are STAPLED TOGETHER and labelled with:

Your NAME & STUDENT NO.
Your LAB-SECTION/GROUP/TA

Assignments are due at 5pm on Friday, October 10 (in your DropBox in ABB - the one corresponding to your tutorial section). Late assignments will receive a grade of ZERO, unless a medical slip is filed with the Dean's Office.

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02oct97; wjl