Chemistry Lab Manual

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Chemistry 3373F Lab Manual
2008
Modified 11/07

Table of Contents

Chem 3373 Laboratory Schedule for Fall 2008.............................................................................2 The Benzoin Condensation of Benzaldehyde ..............................................................................3 Synthesis of Dilantin and Related Compounds (two weeks).........................................................6 Synthesis of an Alkaloid: Pseudopelletierine (two weeks) ............................................................9 Synthesis of 5,5-dimethyl-1,3-cyclohexanone ............................................................................11 Diels-Alder Syntheses of Polycyclic Compounds ......................................................................13 The Fischer Indole Synthesis: Preparation of 2-Phenylindole ...............................................16

Chemistry 3373f, Fall 2007

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Chem 3373 Laboratory Schedule for Fall 2008

Date (Week of) September 15 September 22 September 29 October 6 October 20 October 27 November 3 November 10 November 17 November 24

Activity Check-In and begin benzoin condensation Dilantin and related compounds continue dilantin lab pseudopelletierine, finish dilantin lab finish pseudopelletierine 5,5-dimethyl-1,3-cyclhexanone Diels-Alder Reactions Fischer Indole Synthesis, lab checkout Possibly a Written Laboratory Final Exam, other activity, review session, or nothing at all -

Report Due benzoin dilantin and others pseudopelletierine dimedone Diels-Alder Fisher Indole (submitted in lecture).

Generally, before you will be allowed to begin the lab, you must have in your notebook a drawing showing each separate reaction to be performed and then below the reaction in columns list the chemicals and reagents to be used, molecular weight, equivalents, mmol, wt, density (where applicable), mL (where applicable), bp (where applicable), mp (where applicable). There should also be a row for the product. Your lab report should be quite brief. It should consist of a copy of your lab notebook, copies of your spectra along with interpretive comments, and a detailed reaction mechanism. The notebook should show the calculation of the percent yield, mp, etc, and the procedure. Neatness counts. The procedure does not need to be in complete sentences. Each spectra will have a neatly computer made structure using a program such as chemdraw or one of the free alternatives (see the course website under links), your name and your lab section. In this lab you will turn in the products you make, and quality and quantity (as determined visually and by NMR) count. The initial plan is to have the demonstrators prepare the 1H NMR samples from the bulk material that you submit to them. The 1H NMR spectra will be provided to you the following week. The reports will be due one week after that.

Chemistry 3373f, Fall 2007

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The Benzoin Condensation of Benzaldehyde

Aromatic aldehydes, in the presence of catalytic cyanide ion, dimerize to form the corresponding α-hydroxyketone (acyloin). This reaction, which is reversible, is known as the benzoin condensation. This “condensation” is a bit of a misnomer since it is not actually a condensation reaction since no water or alcohol is produced but two species do come together. Cyanide acts as a catalyst and has three different roles in this process as shown in the mechanism below. Addition of the cyanide ion to create a cyanohydrin effects an umpolung of the normal carbonyl charge affinity, and the electrophilic aldehyde carbon becomes nucleophilic after deprotonation:

A strong base is now able to deprotonate at the former carbonyl C-atom:

A second equivalent of aldehyde reacts with this carbanion; elimination of the catalyst regenerates the carbonyl compound at the end of the reaction:

Then

Chemistry 3373f, Fall 2007

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The cyanide ion catalysis works only for aromatic aldehydes presumably...
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