Organic Chemistry Laboratory Final Exam Study Guide PDF

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chem 3106 lab study guide summer II 2018...

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Organic Chemistry Laboratory Final Exam Study Guide To prepare for your final exam, it is a good idea to do the following; re-read all on-line notes associated with each experiment, read through the notes you took during each prelab lecture, read through the techniques/standard experimental apparatus at the beginning of the lab notebook and review all of your old quizzes. In the document below is a list of topics that a well-prepared student SHOULD be able to answer or explain. Make sure you get all of your questions answered and understood well before the final exam. Two minutes before the final exam is scheduled to begin is not the time to ask questions. Following is a partial list of topics covered over the duration of the class. It is not complete. Disclaimer: This study guide is to aid you in your studies. If something is or is not present on this study guide it does not mean it will or will not appear on the final exam. Reaction Mechanisms • •

Understand and be able to work through the mechanisms explained this semester in lab. Know the terminology stated in each reaction (ex. nucleophile, electrophile, radical, etc.)

General • • • • • • •

Know the names of all glassware. Know relevant safety procedures. Know how to safely dispose of chemicals and other lab waste. Know general lab techniques. Know proper notebook techniques. Know proper weighing techniques. Know what procedure should be done to accomplish specific goals such as purification of solids, purifications of liquids, functional group analysis, separation of solids, separation of liquids, and material identification.

Safety • • • •

What are some of the terms used to describe the potential dangers of a chemical compound? What is a flash point and what is it used for? What is a flammable material? Inflammable? Combustible? What is a corrosive material? Mutagen? Teratogen? Carcinogen? Lachrymator? Irritant? Toxic? Pyrophoric? Hygroscopic? Oxidizers? Reactives? ShockSensitive?

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Give two examples for each of the above terms. What is a MSDS and why is it important? How do you read an MSDS to know what is important about the material? What are some precautions taking when working with highly reactive chemicals? What are PPE? Give at least two examples and why they are useful.

Melting Points • • • • • • • •

Thermometer safety. What properties should an ideal melt point/range contain? What effects if any does soluble impurities have on melt point / range? Insoluble impurities? Is melting point a physical or chemical property and why? How does the following factors influence melting point? Molecular weight, polarity, hydrogen bonding, branching Should a melting point/ range be taken fast or slow? If given a series of mixed melting points, be able to identify composition. If given a melting point range and the literature value, be able to assess the purity of the sample.

Infrared Spectroscopy • • • • • • • •

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Define the main regions of interest in the IR. What are the frequency ranges and groups are represented in each region? Understand how the identify a functional group based on the peak location, shape or intensity. Explain in simple terms how an infrared works. Explain the Electromagnetic spectrum What is wavenumber and how is it calculated? Understand the relationship between wavenumber and energy. Is a larger wavenumber higher or lower in energy? Frequency? Be able to recognize the IR spectrum of the following functional groups: terminal alkyne, alkyne, nitrile, carboxylic acid, alcohol, primary amine, secondary amine, alkane, carbonyl, ketone, ester, ether linkage. Be able to select the proper IR if given a structure. (Pick at least five from the experiments) Be able to select the proper structure if given an IR spectrum. (check your organic chemistry book if you do not know)

Thin-Layer Chromatography & Column Chromatography • • • •

What is TLC (thin-layer chromatography)? Know how to calculate Rf. How is the purity of a reaction mixture determined using TLC? How is the identity of a product in a reaction mixture determined using TLC?

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Given a set of TLC plates or Rf values, be able to determine reaction outcomes. If F is a starting material and four syntheses were run, what does each plate indicate? Given two structures predict which how to determine which will have a lower Rf. Given 2 Rf’s predict how you would determine which compound is more polar. How are TLC and column chromatography similar and differ? (i. e. capillary vs. gravity used for separation) What are the various layers in column chromatography and explain their purpose? Why were the solvents introduced into the column in a particular order? What concept or process allow for separation in column chromatography? (Hint: review all note dealing with separation) What is a mobile phase? Give an example What is a stationary phase? Give an example Be able to write structures of all chemicals used in the experiments.

Distillation/Refluxing • • • • • • •

Why is placement of thermometer important? How to properly read a thermometer? Know names of each piece of glassware. What is a theoretical plate and why is it important? What is reflux and why is it performed? (page 23 in your lab book) Be able to write structures of all chemicals used in this experiment? What is a major safety concern when refluxing? (Hint: formation of peroxide)

Recrystallization • • • • • • • •

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What is the purpose of recrystallization? Be able to take weight by difference. What are the properties of a good recrystallization solvent? What is percent recovery and how is it calculated? What error(s) affect only purity or percent recovery or both? (Review notes, data sheet and quiz) If given an experimental action, be able to predict the effect on purity or percent recovery. Is it possible to have percent yield greater than 100%? Why? When doing recrystallization, why should the solvent be added until the entire solid dissolves and no more? What happens if additional solvent is added? What happens if not enough solvent was added? Why should the product be allowed to crystallize slowly and not plunge directly into ice water?

Separation of Acidic Substances (Extractions; an example) • What is the difference between liquid-liquid extractions and solid-liquid extractions?

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What type of extraction is used in the separation of an acidic substances experiment? o In the first extraction of benzoic acid (BA) and 2-naphthol (look up structures), why do we use NaHCO3? o In the second extraction of BA and 2-naphthol, why do we use NaOH? Explain partitioning. Explain what drives a compound to move from one phase to another. If given a series of structures, be able to predict the highest solubility in a given phase. o What would happen if you extracted a solution containing both a strong and weak acid with NaOH? (Basic General Chemistry between strong acids and bases) S.A. + S.B. ---------à฀ W.B. + W.A. W.B. +W.A. –x-> S.A. + S.B. Looking at pKa values, what makes a reaction proceed to the right? What is the purpose of the HCl? What product forms once NaHCO3 has been added? What product forms once NaOH has been added? Know the solubility changes from benzoic acid (BA) to sodium benzoate. What would cause a low % recovery for BA? What would cause a higher % recovery for 2-Naphthol? Know safety about using concentrated NaOH and HCl. If given a set of pkas, be able to predict if the reaction will proceed in the forward direction or not.

Gas Chromatography (GC) • • • • • • •

Explain chromatography. Explain how GC works. What properties dictate the relative retention time of a series of chemicals? Be able to predict the impact on retention time by changing column temperature, flow rate, sample size, and column length. If given a GC trace, be able to calculate the retention time and percent composition of any peak. Be able to read a GC and understand the composition of a sample. What unique safety concerns are associated with a GC?

Percent Yield • • •

Be able to calculate theoretical maximum amount of product (theoretical yield) and limiting reagent (theoretical yield) for any reaction. What is meant by percent error? What is the difference between theoretical yield, percent yield, and percent error? How would you define these in a reaction?...