[1] Concentrated sulfuric acid (H₂SO₄) and saturated aqueous sodium bicarbonate (NaHCO₃) are provided as solutions, not as pure compounds. Therefore, it is more useful to list their concentrations in the table rather than their MW. The concentrations of these reagents are approximately 18 and 1 M, respectively. BACK TO PROCEDURE

[2] Although an odor is not normally regarded as a "hazard" unless it is foul ("stench"), make an exception for the odor of isopentyl acetate (banana oil). Although its banana-like odor is not particularly unpleasant at first, most students do not enjoy long-term exposure to this odor. BACK TO PROCEDURE

[3] Molar equivalents are described in the Calculations appendix. BACK TO PROCEDURE

[4] This reflux operation is identical to the one performed in Experiment 3. You should pass a slow stream of water through the condenser, while heating the flask with a ceramic heater mounted on top of a stirring motor and lab jack.

Your solution will probably become colored as it is heated. This is frequently observed when reactive organic compounds are refluxed with a strong acid. Keep in mind, however, that your desired product, isopentyl acetate, is not colored. So expect colored impurities, but don't chase after them. BACK TO PROCEDURE 

[5] Your apparatus should look something like the drawing shown at right (you will use the monkey bars instead of a ring stand) (Note: this would be a good time to watch the 18 minute video on extractions and separatory funnel procedures put out by MIT on YouTube). Use an Erlenmeyer flask large enough to hold the liquid that you will drain into it. A 250 mL flask will definitely hold all of the liquid in a 250 mL funnel. Note: never fill a separatory funnel more than half way (also a good rule-of-thumb for other lab glassware). Notice that a separatory funnel consists of several parts: tapered stopper (teflon or glass), funnel, stopcock + washer (or spring clip). All of these parts are needed. The stopcock + washer should be adjusted so that they fit snugly in place and will not allow liquid to leak around them.

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[6] Extracting and washing refer to identical operations with different goals. Extract always means that a desired compound (in this case, isopentyl acetate) will be moved from its current location (reaction mixture + water) into an extraction solvent (diethyl ether). Wash always means that an undesired compound (acetic acid + sulfuric acid) will be moved from its current location (diethyl ether) into the wash solution (aqueous base).

Padias p. 119-121 describes the chemical reactions and solubility changes that enable seemingly identical extraction and washing operations to achieve their intended purposes. Draw a chart like that in Figure 3-8 inside your notebook (left hand page) that shows how the four compounds in this experiment - acetic acid, isopentyl alcohol, isopentyl acetate, and sulfuric acid - will behave during your workup procedure. BACK TO PROCEDURE

[7] Warning: Residual acetic acid and sulfuric acid will react vigorously with NaHCO₃ and release lots of gas. Don't mix your layers until the gas evolution appears to have stopped, then mix them cautiously (and vent the funnel frequently). After each wash, drain the aqueous layer into a new flask so that you can test its pH with pH paper. You should continue washing the ether layer with fresh portions of wash solution (and draining these washes into different containers) until a basic or neutral wash layer is obtained. BACK TO PROCEDURE

[8] The endpoint for week #1 will vary from student to student. Fast workers will be encouraged to distill some or all of their ether solution. Most students will simply store this solution until week #2.

Because banana oil and diethyl ether both produce objectionable vapors, these solutions must be stored in the cabinets underneath the fume hoods (the cabinet vents to the hood). Place your solution in the (clean DRY) round bottom flask that you will use for the distillation, cap the flask with a Teflon or glass stopper, and rest this flask inside a beaker (choose a beaker that will keep the flask upright). Place a piece of paper inside the beaker with your NAME, LAB DAY, and FLASK CONTENTS. BACK TO PROCEDURE

[9] Your apparatus should look something like the following drawing (Padias Figure 3-13 does not come as close, but it correctly shows the boiling flask immersed in a Thermowell heater and a collection flask attached to the vacuum adaptor).

A standard metal clamp is used to support the boiling flask. Two plastic clamps are used to attach the condenser at each end, and another clamp is used to attach the collection flask to the vacuum adaptor.

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[10] Gas chromatography is described in Padias p. 167-175. You will not be asked to perform a quantitative analysis of your data. If you are not familiar with the basic principles of chromatography then read Padias p. 150-151. BACK TO PROCEDURE

[11] NMR (or FT-NMR) is the most powerful characterization tool available to organic chemists. See Solomons & Fryhle, chapter 9.1-9.10 and Padias p. 75-93 for detailed descriptions of this all-important research tool. BACK TO PROCEDURE