Introduction to the Laboratory

Laboratory is an integral part of your organic chemistry course. In the laboratory, you will observe some of the properties described in class. You will also learn the basic techniques of working with organic compounds that are employed by organic chemists. The emphasis in lab will be on understanding results rather than obtaining products. Ten percent of your overall grade will be based on lab: attendance, notebook (yellow pages), short reports, quizzes, and technique. In addition, approximately 10% of each exam will be based on material from the laboratory.

Schedule. Laboratory meets weekly on Mondays and Tuesdays. Most of the meetings begin with a briefing session. Every student is expected to be present and working during the assigned period. If additional time is needed to complete labs, students must obtain permission from the instructor to work in the lab. Unsupervised work on weekends or in the evening is prohibited.

Experiments. Each student is expected to prepare before coming to lab by reading the assigned background information. Students are expected to work individually unless directed otherwise.

Laboratory Equipment. All students will share a large pool of microscale glassware. It is essential that all glassware be cleaned and dried before leaving the lab. In addition, the lab workspace must also be cleaned. Students will alternate cleaning the balance area and the small room next to the lab. Failure to follow these procedures will result in points being deducted from the final grade.

Laboratory Data and Reports. Each student must have a notebook for keeping laboratory observations and data in duplicate. The Prelab and Lab work sections described below should be written in your lab notebook. The yellow carbon copies will be turned in for grading.

    Prelab

    (This section should be completed before you start the experiment.)

  1. Introduction. Write a brief sentence or two describing what you expect to learn or accomplish. Give a literature reference for the procedure. (Where did you get the procedure to follow? Give page number and authors or the URL for online sources!)
  2. Reaction summary. This section includes a balanced equation and a mechanism for each chemical reaction that took place.
  3. Table of Reagents and Products. Include compound name, molecular weight, structure, amount used (in grams or mL and MOLES), and pertinent data (i.e., melting point, solubility, density, concentration).

    4. Lab Work

  4. Data and Observations. This section of the lab notebook contains what you did and what you saw. Do not simply copy the experimental procedure from the lab manual; that will be a certain method for losing points on the lab. Be sure to report the exact amount of chemicals used. The balances in the lab give more than one decimal place; report all the decimal places. Sometimes it will be easier to weigh liquids than to measure them by volume. Observations include such things as color, smell (be careful here), viscosity, and physical state (solid or liquid). Be sure to keep track of the reaction times for each step carried out. Always measure the mass of the final product you isolate. State how the product was characterized. Measured physical properties should be included in your notebook when these observations are obtained.

    5. Results and Conclusions


  5. Yield data.
    1. Cite evidence that your product is the correct one. Compare physical data to literature values (mp, bp, spectroscopic data, etc.). Estimate product purity.
    2. Include all numerical data (units labeled), well-labeled calculations (especially percent yield), and graphs. Analyze the data. (Note: You may need to refer to your general chemistry textbook to review calculations for theoretical yield and percent yield. Do NOT calculate percent yield by dividing grams of product by grams of starting material.)
  6. Conclusions. Explain what impurity is removed in each purification step. Discuss any errors that may have caused your results to deviate from what was expected. Summarize what you learned. Include answers to questions assigned by your instructor in the text of your conclusions. Discuss more than just loss due to the physical limitations of the equipment. For instance, if you have less than a 100% yield there are more reasons than just "Some of the solid stuck to the flask and some passed through the filter paper."

Technique includes preparedness (possible quizzes), product yield, and product purity. You will lose points for yield and purity only in unusual circumstances; it is not worth your time to spend forever in lab trying to get every detail perfectly correct.

There are a few points you must keep in mind for all of the experiments.

  1. Keep a little of each intermediate for analysis.
  2. Do not discard any intermediates or products; vials will be set up for their collection.
  3. Keep an accurate record of all lab work in your notebook.
  4. Be careful about pouring chemicals down the sink; when in doubt, ASK!
  5. Do not store products in conical vials; use storage vials or petri dishes instead.
  6. Do not leave thermometers in the aluminum blocks. We will not monitor temperature this way, and it’s an easy way to break the thermometers.
  7. Do not turn the hotplates past 3 unless the instructor tells you otherwise.