Introductory Organic and Biochemistry

Quiz: Alcohols and ethers.

Ouellette 2/e Ch 8-9.

Answer key
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Remember to emphasize reasons, not just answers.

1. Draw the structure of 5-bromopent-3-ene-1-ol.

2. Consider the following ether: CH3CH2CH2-O-CH2CH3.

a. Name the ether in the common name form, naming the alkyl groups attached to the ether O.

b. Name the ether in the form alkoxy alkane.

c. What is the nominal bond angle at the O? Explain.

3. You have an organic chemical with (exactly) one O atom in its molecular formula. You add some to water, and the pH of the resulting solution is below 7. What type of compound is this? (That is, what functional group does it contain?)

4. Draw the major organic product of mild oxidation of 2-hexanol.

5. We skipped the material on reactions of ethers. But of course, they do undergo one common reaction that is typical of all organic compounds. Write a balanced equation for this reaction of diethyl ether.

a. Draw a non-alcohol isomer of 3-hexanol.
b. Is it possible to have a cyclic isomer of 3-hexanol (with any functional group)? Explain.
c. Which of the compounds from part a (the given alcohol or the non-alcohol isomer you drew) has the higher boiling point? Explain.

7. Give an example of how you could convert a primary alcohol to a tertiary alcohol with the same C skeleton, using a series of two common reactions. Use specific chemicals (of your choice) for the alcohols.

I strongly encourage you to complete all of the questions above and check yourself on those before doing the remaining questions.

a. Give an example of a secondary alcohol. Show structure.
b. Name the compound you drew in part a. (IUPAC preferred. If it has a common name, maybe include that, too.)
c. Give an example of a common reaction of the compound you drew in part a. Choose a reaction that is specific for the major functional group. [Give major organic reactant(s) and product(s), and major conditions. Need not be balanced, or show all detail.]
d. Name the (major organic) product from part c.
e. Compare the boiling points of the (major organic) reactant and product from part c. Explain.

9. The oxidation of alcohol by chromic acid (Jones reagent) can be used to quantitatively measure alcohol. This is because the reaction involves a color change, from the orange Cr(VI) to the green Cr(III). Thus the appearance of the green color, which can be measured quantitatively, is a measure of how much alcohol is present. In fact, this is the basis of some measuring devices for alcohol, including some "breathalyzers".

The balanced equation for the oxidation of ethanol by chromic acid (with the dichromate ion being the key Cr(VI) species) is:
3 CH3CH2OH + 2 Cr2O72- + 16 H+ --> 3 CH3COOH + 4 Cr3+ + 11 H2O

A typical approach would be to make a calibration curve, using samples of known alcohol concentration. One then makes a graph of "amount of green color" vs "weight per cent of alcohol". Real samples are then analyzed, and the result read from the graph.

In each of the following parts you are asked how well this method would work for an alcohol other than ethanol. In each case, tell whether the method would basically work. If a modification of the method is required, describe it, as best you can. (The modifications are quantitative. You need not do the calculations, but tell quite specifically what the modifications are, in terms of chemistry.)

(Don't worry about other issues, such as sample preparation; just consider the chromic acid oxidation step.)

a. 1-butanol
b. 2-butanol
c. t-butanol (2-methyl-2-propanol)

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Last update: August 20, 2011