During the next weeks of lab, you and a partner will be assigned the task of determining the identity of an unknown organic compound and then proving the identity of that compound to your instructor. This lab will require you to work independently and to use deductive reasoning as you zero in on the unknown that you have been given.

The following information will be helpful as you search for the identity of your unknown:

1. Elemental analysis indicates that the unknown contains carbon, hydrogen and oxygen.
2. The unknown may also contain halogen or nitrogen atoms in addition to the atoms above.
3. Analysis indicates that the molecule does not possess any other type of atom.
4. The only nitrogen containing functional group that any of the molecules may possess is nitro.
5. If the unknown contains an nitro, ether or a carboxylic ester functional group, then it also
contains some additional functional group that is not an ether, ester, halide, or nitro.

0. Successfully identify two unknowns with similar characteristics using the computer program, Simulated QUALitative ORganic chemistry (SQUALOR). You may work with your partner during this stage, but each student must solve two unknowns. Therefore, if you work with a partner you will need to solve four unknowns.

Other laboratory assignments will be completed during this time. You may use the SQUALOR program at any time when the building is open. You should bring your laboratory notebook to document the process you used to identify the simulated unknown.

You will not be assigned an actual unknown compound until you and your partner submit the solutions for all of your SQUALOR unknowns.

1. Upon correctly solving the SQUALOR problems, you may request an actual unknown. Once you have received a sample, you may begin by doing the following in no particular order.

• Read Laboratory Manual handout pp. 483-487.

  Carefully determine melting point (if solid) or boiling point (if liquid). Care in this step can save you much frustration later down the road. It is strongly advised that a known compound be tested first in order to insure the validity of the technique you are using.

  This is probably the single most important step in the entire process since it is almost impossible to correctly identify your unknown if you have incorrect melting point or boiling point data. Do not rush this step. Be sure that you are performing the experiments correctly by running experiments with useful known compounds (by useful, if you believe that your molecule is an organic liquid with a boiling point in the mid-100's, then you should seek a known organic liquid with a boiling point in the mid-100's to validate the technique you are using).

• Determine solubility characteristics (pp. 487-490) in common solvents.
  
  
• Obtain the infrared spectrum of your unknown. Search the IR spectrum for important group frequencies. This particular step may be done outside of normal laboratory hours (see General Notes, below). In many cases it is more useful to perform this test as a final proof of structure. Once you believe you know the identity of the unknown, search for its spectrum in an IR Spectrum Atlas and compare with your unknown.

1. Read pp. 499-504.
   
   
2. Select the tests that will help you to verify (or rule out) possible functional groups. You will probably need to perform only a few of these tests, in light of the data which you have already obtained. It is important to first perform the tests on known compounds so that you will know what a negative and a positive result look like. Choice of the knowns you use is important. For example, if you wish to distinguish the difference between a 1° alcohol and a 3° alcohol, be sure that you use an actual 1° alcohol as one of your knowns and an actual 3° alcohol as the other.
   
   
3. Before performing any classification test (or derivative reaction, as described below), you are REQUIRED to do the following five preparatory steps.
   
   
   1. Look in a minimum of two sources to get more than one explanation of the test/reaction you wish to perform (recording this information in your lab book)
   2. Write a step-by-step checklist/flowchart explaining exactly how you will perform the test. Don't leave anything vague in this checklist.
   3. Write a description of the purpose of the test/reaction. For example, under exactly what conditions does a positive result occur? Are there false positives? etc.?
   4. Suggest knowns that will useful to verify the test for a known positive and known negative.
   5. Provide a "grocery list" of chemicals needed. Sometimes you will need to make your own solutions, sometimes the solutions will have been prepared for you.

   Your instructor/lab assistant will not provide any help until these steps have been completed.

3. After completing one or more classification tests, you should know what class of molecule you have been given. Now that you have classified your unknown, you are ready to determine its actual identity as follows.

1. Find the appropriate table at the back of the lab text (pp. 523-534) for your class of unknown. For example, if you have an aldehyde, turn to the aldehyde table on page 525.

   Using the table, list any of the compounds whose melting/boiling points come fairly close to your sample. Your unknown IS FOUND IN THESE TABLES and, thus, it is likely to be one of the ones you just listed.

2. Read pp. 505-506 (up through the important safety note).
3. Using the table in the book as a guide for selection of appropriate derivatives, prepare two derivatives from your unknown. The procedures for preparation of the derivatives are found in your lab manual (pp. 506-517) as well as in many of the other books in the lab. As in step 2c, you must fulfill the five required preparatory steps for each derivative reaction before performing the experiment.
4. Determine the melting points of your derivatives carefully.
5. Comparing the melting point of the derivatives to the table, unambiguously identify the unknown.

4.Complete the lab summary, organize your notes and give your final oral report to your lab instructor. Congratulations! You did it!

GENERAL NOTES

Reagents
Since many chemicals are used in this lab and not all students will use the same chemicals we are not placing reagents under the hood. Instead you will find the reagent on one of the wall shelves in the laboratory. We have organized the lab carefully so that one can find any compound in just a few seconds. IT IS ESSENTIAL that the reagents are returned to the SAME LOCATION immediately after you are finished with it.

Safety
It is important to treat all materials used in this laboratory with the utmost caution. Individual unknowns should be treated as though they are highly toxic materials which may beabsorbed through the skin (since some of them actually are). Of course, any contact with chemicals must be immediately treated and reported to the instructor or teaching assistant. Use of safety glasses is - as always - mandatory. The use of protective gloves is highly desirable.

Environment
No materials used in this laboratory may be emptied down the drain. All organic waste must be placed into the appropriate receptacles in the hood. Try to work with small quantities in order to preserve your supply of unknown and to produce as little waste as possible.

Extra hours
Several simple procedures may be performed outside of the normal laboratory hours. In particular, the use of all manuals found in the laboratory, the use of the FT-IR, crystallization of solids (followed by their filtration), and determination of melting points (not boiling points) may be performed whenever the laboratory is not in use if another qualified student or instructor will be present for the duration of the experimentation. No procedures other than those explicitly listed above may be performed outside of the regular laboratory hours without the advance expressed permission of the instructor. No student is authorized to perform any laboratory work (including cleaning glassware, etc.) alone at any time. Students found working alone in the laboratory may be prohibited from use of the lab for the remainder of the semester with their laboratory grade reduced accordingly.

Chemical purity
NEVER put a pipet into a reagent bottle (unless the bottle has a dropper on its side for that purpose). Instead, pour a little of the liquid into a small beaker and remove liquid from the beaker. DO NOT RETURN left over liquid to the bottle; dispose of it in the organic waste.